FILE COPY

DO NOT REMO’ L ~ , * < ,« . .. . NBSIR 77-1272

Intermediate Standards for

Solar Domestic Hot Water

Systems/HUD Initiative

Developed for Use in the HUD/States Solar

Domestic Hot Water Initiative Program

Solar Energy Program

Office of Housing and Building Technology

Center for Building Technology, IAT

National Bureau of Standards

Washington, D. C. 20234

July 1977

Prepared for Department of Housing and Urban Development

Office of Policy Development and Research

Division of Energy, Building Technology and Standards

Washington, D. C. 20410

NBSIR 77-1272

INTERMEDIATE STANDARDS FOR

SOLAR DOMESTIC HOT WATER

SYSTEMS/HUD INITIATIVE

Developed for Use in the HUD/States Solar

Domestic Hot Water Initiative Program

Solar Energy Program

Office of Housing and Building Technology

Center for Building Technology, IAT

National Bureau of Standards

Washington, D. C. 20234

July 1977

Prepared for Department of Housing and Urban Development

Office of Policy Development and Research

Division of Energy, Building Technology and Standards

Washington, D. C. 20410

AU Of

‘

U S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director
5
ACKNOWLEDGEMENTS

The preparation of the original document (HUD/FHA 4930.2) has been a joint effort of members

of the Solar Energy Program Team at the National Bureau of Standards, Center for Building

Technology. Team members include:

Office of Housing and Building Technology

Robert Dikkers

David Waksman

John Holton

Kenneth DeCorte

William Niessing

Thermal Engineering Section

Elmer Streed

James Hill

John Jenkins

Dennis Jones

Michael McCabe

Mark Hannifan

Materials and Composite Section

Larry Masters

Leopold Skoda

Elizabeth Clark

Paul Brown

Jean-Noel Andre

McClure Godette

Mechanical System Section

James Kao

Building Services Section

Robert Beausoliel

Grover Sherlin

Structures Section

William Greene

Architectural Research Section

Richard Crenshaw

Office of Building Standards and Codes Services

James Harris

Robert Eisenhard

Program for Fire Control - Construction

(Center for Fire Research)

Daniel Gross

William Walton

Edward Budnick

Typing, Editing, and Preparation by

Rita Whalen

Mary Lou Miller

Leslie Suddueth

The principal authors of this Solar Domestic Hot Water Standard are:

Michael McCabe Elmer Streed

John Holton

i
PREFACE

The "Intermediate Standards for Solar Domestic Hot Water Systems" are based on the

"Intermediate Minimum Property Standards for Solar Heating and Domestic Hot Water Systems"

4930.2 (S/MPS) and are intended for use in the HUD/States Hot Water Initiative Program.

In developing this document, references in the S/MPS to heating and combined heating and hot

water applications have been deleted. Some language has been changed and additional commentary added to make this document more useful. All such changes have been identified by a heavy line in the margin.

The HUD/States Hot Water Initiative Program is a program providing financial assistance to homeowners to install solar domestic hot water systems. The program currently is being

offered in the states of New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut,

New Jersey, Pennsylvania, Delaware, Maryland, Florida, and 13 counties in New York.

These standards consider only aspects of planning and design that are different from con- ventional hot water systems by reason of the solar systems under consideration. To the

greatest extent possible, they are based on current state-of-the-art practice and on nationally recognized standards including the HUD Minimum Property Standards (MPS) and the HUD

"Interim Performance Criteria for Solar Heating and Combined Heating/Cooling Systems and

Dwellings." These standards assume a level of building design and construction quality

equivalent to local code requirements or the MPS whichever is applicable.

The text makes occasional reference to the MPS which refers to the original underlying HUD

standards, the "Minimum Property Standards for One and Two Family Dwellings" 4900.1, the

"Minimum Property Standards for Multifamily Housing" 4910.1, and the "Minimum Property

Standards for Care Type Housing" 4920.1. The reference is to the same paragraph in all these

documents unless otherwise noted. For purposes of the Hot Water Initiative, the references

to the "Minimum Property Standards for One and Two Family Dwellings" 4900.1 will be the

applicable reference. Reference to MPS 4910.1 and 4920.1 is not essential but has been

retained in some instances for fullest explanation of a particular point.

In general, the Chapters and Divisions in this document are organized to parallel the

Chapters and Divisions contained in the MPS. Within Divisions, however, these standards

do not follow the numbering of the MPS, but rather list the solar topics sequentially. It has been found that this method allows the presentation of these new topics in a manner

that is clearly related to the MPS and yet is not made cumbersome. Not all chapters or divisions in the MPS have topics which require coverage for solar energy use; for example,

there are no such topics in Chapter 2, Generally Acceptability Criteria, nor in Division 512,

Furnishings

.

An example will help to illustrate the organization of this document:

Consider hail loads as they relate to solar collectors. Hail loads

are not a subject in the MPS, but would be covered in Chapter 6,

Division 1, General Structural Requirements if they were. In these

standards they are located in Chapter 6, Division 1, Section S-601-7.

For comparison, plumbing construction is covered in Chapter 6,

Division 15, Section 615-5 of the MPS. In these standards it is also

located in Chapter 6, Division 15, but in Section S-615-12.

MPS MPS Solar Supplement

Hail loads none S-601-7

Plumbing 615-5 S-615-12

It has frequently been found useful to include a commentary on a particular standard. The

commentaries are not mandatory, but are intended to give further explanation and guidance

to users of the standards on topics which may have special consequences in solar installations.

Several appendices are includes which give additional information for assistance in use of

the standards. Appendix A presents the calculation procedures to be used to verify the thermal

performance of solar domestic hot water systems proposed for the HUD/States Hot Water Initiative

Program. Appendix C, "Illustrated Definitions," is presented in the "Intermediate Minimum

Property Standards for Solar Heating and Domestic Hot Water Systems" 4930.2, or in the HUD

publication, "Solar Hot Water and Your Home" and is not included here.

ii
The format developed for these standards has been structured to convey information in a number of categories as follows

:

S - the prefix used on all sections (for solar) to distinguish them from

existing MPS sections

BOLD FACE TYPE - to present standards and commentaries applicable to

MULTIFAMILY HOUSING ONLY

Conventional type - to present standards applicable to one and two family

dwellings, multifamily housing and care type housing

Italics - to present commentari.es applicable to one and two family dwellings,

multifamily housing and care type housing

SI CONVERSION UNITS

In view of the present accepted practice in this country for building technology, common

U.S. units of measurement have been used throughout this document. In recognition of the

position of the United States as a signatory to the General Conference of Weights and

Measures, which gave official status to the metric SI system of units in 1960, assistance

is given to the reader interested in making use of the coherent system of SI units by

giving conversion factors applicable to U.S. units used in this document.

Length

1 in = 0.0254 meter (exactly)

1 ft = 0.3048 meter (exactly)

Area

1 in^ = 6.45 x 10”^ meter^

1 ft^ = 0.09290 meter^

Volume

1 in-^ = 1.639 x 10

-

^ meter^

1 gal (U.S. liquid) = 3.785 x 10“ ^ meter^

Mass

1 ounce-mass (avoirdupois) = 2.834 x 10” ^ kilogram

1 pound-mass (avoirdupois) = 0.4536 kilogram

Pressure or Stress (Force/Area)

1 inch of mercury (60°F) = 3.377 x 10 pascal

1 pound-force/inch^ (psi) = 6.895 x 10^ pascal

Energy

1 foot-pound-force (ft*lbf) = 1.356 joule

1 Btu (International Table) = 1.055 x 10^ joule

1 kilowatt-hour = 3.600 x 10^ joule = 3.412 x 10^ Btu

Power

1 watt = 1 x 10^ erg/second

1 Btu/hr = 0.2929 watt

Temperature

t° C = 5/9 (t» F - 32)

Heat

9 -1

1 (Btu*in)/(h*ft^*F) = 1.442 x 10 W/(m*K) (thermal conductivity)

1 Btu/lbm .°F = 4.184 x 10^ J/(kg*K) (specific heat)

1 langley = 4.184 x 10^ J/m2 = 1 cal/cm^ = 3.69 Btu/ft^

iii
GENERAL TABLE OF CONTENTS

Chapter 1 General Use. . . 1-1

Chapter 2 General Acceptability Criteria (Not used) 2-1

Chapter 3 Site Design 3-1

Chapter 4 Building Design 4-1

Chapter 5 Materials 5-1

Chapter 6 Construction 6-1

Appendix A Method for Predicting the Thermal Performance

of Active Solar Domestic Hot Water Heaters A-l

Appendix B Materials Tables B-l

Appendix C (Not Used) C-l

Appendix D Definitions D-l

Appendix E Referenced Standards E-l

Appendix F Abbreviations F-l

iv
'I

S-100

I

S-101

S-101-1

S-102

CHAPTER 1

General Use

APPLICATION

These "Intermediate Standards for Solar Domestic Hot Water Systems/HUD

Initiative" shall be used in conjunction with MPS 4900.1, "Minimum Property

Standards for One and Two Family Dwellings," MPS 4910.1, "Minimum Property

Standards for Multifamily Housing," and MPS 4920.1, "Minimum Property Standards

for Care Type Housing." Furthermore, the solar components must provide for the

collector of solar energy, conversion of the solar energy to thermal energy,

and distribution, storage and control of the thermal energy so obtained. Insofar

as applicable, these standards apply to active and passive solar energy systems

that utilize building elements, mechanical subsystems or combinations thereof.

Commentary: MPS 4900.1 , MPS 4910.1 , and 4920.1 are available from HUD offices

,

and are sold by the Superintendent of Documents, U.S. Government Printing

Office, Washington, D.C. 20402.

VARIATIONS TO STANDARDS

NEW MATERIALS AND TECHNOLOGIES

These standards are intended to encourage the use of new or innovative designs,

technologies, methods or materials in solar applications. These features include designs, methods of construction, systems, subsystems, components, materials

and processes which do not comply with the MPS and this document, and whose

acceptance cannot be determined by other provisions of these standards. Alternatives, nonconventional or innovative designs, methods, and materials shall

demonstrate, however, equivalent quality to these standards in operating effectiveness, structural soundness, durability, economy of maintenance or operation,

and usability. Variations shall be made in accordance with Section 101-4 of MPS.

Commentary: One basis for design, fabrication, construction, and acceptance of

new and innovative solar systems, subsystems, components, materials, and processes is the "Interim Performance Criteria for Solar Heating and Combined

Heating/Cooling Systems and Dwellings, " January, 1975, available from GPO,

Stock Humber 0324-01043 , price $1.90.

PRODUCT AND DESIGN MODIFICATIONS

Variations from approved designs shall be submitted to HUD for review.

Commentary: It is recognized that product or design changes may occur. These

changes may affect the performance of the system or its components.

1-1
-
CHAPTER 2

GENERAL ACCEPTABILITY CRITERIA

| (not used)

2-1

CHAPTER 3

SITE DESIGN

TABLE OF CONTENTS

Page

S-300 GENERAL

S-301 PROPOSED SITE

S-301-1 Site Surroundings

S-303 LAND USE

S-303-1 Solar Equipment Location and Arrangement

S-303-2 Site Hazards

S-304 LOTS, YARDS AND BUILDING SETBACK DISTANCE

S-304-1 Projection into Yard Area

S-304-2 Usable Outdoor Area

S-304-3 Snow and Ice

S-309 SERVICES

S-309-1 Maintenance

S-311 DRAINAGE

S-311-5 Drainage Swales and Gutters

S-311-7 Downspouts

S-312 PLANTING DESIGN

S-312-3 New Plant Material

3-2

3-2

3-2

3-2

3-2

3-3

3-3

3-3

3-3

3-3

3-3

3-3

3-4

3-4

3-4

3-4

3-4

3-1
CHAPTER 3

S-300

S-301

S-301-1

S-303

S-303-1

SITE DESIGN

GENERAL

The provisions of this chapter are applicable to solar domestic hot water

(DHW) systems. This chapter is intended to be used in conjunction with the

Minimum Property Standards (MPS) Chapter 3.

PROPOSED SITE

SITE SURROUNDINGS

Solar buildings and solar system components shall be located and designed in

such a manner as to harmonize with the surrounding community.

Commentary: Solar system components may include elements which are large

and visually dominant when viewed from off-site. If not carefully designed

and located, such elements can produce a detrimental effect on the overall

quality of a residential area.

LAND USE

SOLAR EQUIPMENT LOCATION AND ARRANGEMENT

Solar buildings and site located solar equipment shall be arranged and

located to relate well to:

a. The natural topography.

Commentary : The location of the solar collector should he planned to avoid

pockets where frost can collect or unprotected ridges where winds can he more

extreme in order to avoid heat losses due to lew temperatures and high winds.

b. The climate.

Commentary: The location of the solar collector should he planned to take

into account prevailing winds in order to avoid excessive heat losses due to wind and to drifting snow which impair the collection of solar energy. For

specific requirements on tilt and orientation see S-61S-2. 1. 2 and C-8, C-9 in

Appendix.

c. Attractive on-site and off-site views.

Commentary : Components of the solar system may he large and could block

attractive views from the building.

d. Existing and proposed site elements such as vegetation, fences, landforms

and buildings.

Commentary: Proper relationship of a solar collector to site elements can minimize the shading of the collector and reduce air flow over the collector

Location of the solar building in the northern portion of the site can help

to minimize the possibility of shading solar collector surfaces by future

off-site development.

e. Existing and proposed pedestrian and vehicular circulation systems.

Commentary: Proper location of solar equipment in relation to pedestrian

circulation may reduce tampering and vandalism.

3-2
I

S-303-2

S-304

S-304-1

I S-304-2

I

S-304-3

S-309

S-309-1

f. Existing and proposed surrounding buildings and facilities.

Commentary: The location and orientation of the solar collector should

consider physical and chemical air borne waste from nearby facilities such

as incinerators and factories which might have an impact on the efficiency

of the solar collector. (See S-515-1 . 5)

SITE HAZARDS

Special considerations must be given to assure that elements of the solar

system do not create unnecessary safety hazards to users.

Commentary : Hazards which require special attention include the reflection

of sunlight which creates visual distraction, the projection of sharp edges

which influence the movement of people near free-standing collectors, and the

proximity of solar components to recognized architectural hazards such as exterior overhangs, stairs, ramps, landings, doors, etc.

LOTS, YARDS AND BUILDING SETBACK DISTANCE

PROJECTION INTO YARD AREA

The projection of solar collectors into yards shall conform to those restrictions placed on open balconies, bay windows and uncovered porches in

applicable codes and standards.

USABLE OUTDOOR AREA

Components of the solar system shall not impinge on the requirements for

usable outdoor area as specified in applicable codes and standards.

Commentary: Reasonable outdoor open space must be maintained for livability

service, emergency access, isolation of fire and protection of adjacent

property

.

SNOW AND ICE

In areas which have a snow load of 20 pounds per square foot or greater

required by local codes, provisions shall be made over entrances and locations

of pedestrian and vehicular ways to restrain or deflect sliding snow and ice masses which may slide off elevated solar system components.

Commentary: Solar system components may often include smooth slippery

surfaces located in elevated positions at steep angles. These elements

may heat up rapidly and loosen masses of snow or ice which may slide-off.

Means should be provided to prevent a hazard to people or property. Methods

such as deflectors, restraints, low friction materials, or design of "safe

fall" areas (pedestrian or vehicular ways spaced away from the building)

should be considered.

SERVICES

MAINTENANCE

Solar energy components located on the site shall be accessible for cleaning,

adjusting, servicing, examination, replacement or repair without trespassing

on adjoining property.

Commentary: Components should not be located unnecessarily under buildings

or roads or in other places which are difficult to reach. Storage tanks in

particular are large and may need periodic replacement or inspection.

3-3
Solar collectors on roofs over 3 stories must have access provided

FOR CLEANING AND MAINTENANCE,

COPMENTARY: THE USE OF PORTABLE LADDERS IS NOT CONSIDERED TO BE

ADEQUATE UNDER THESE CIRCUMSTANCES,

S-311 DRAINAGE

S-311-5 DRAINAGE SWALES AND GUTTERS

Gutters or other means of controlling runoff shall be provided on solar collectors when the soil is of such a nature that excessive erosion or expansion may occur as a result of increased runoff.

S-311-DOWNSPOUTS

S-311-7 .In addition to method of disposal of 311-7.1 of the MPS, downspouts may

be discharged into an acceptable non-potable water storage tank if it is

part of the solar system.

Commentary: Current MPS requires that the water from a downspout empty into

available storm sewer or on a splash block. When downspouts are used as part

of a solar system, it is acceptable for it to empty into a storage tank provided consideration has been given to the quality of the water and its effect

on the solar system. (See S-515-2. 3)

S-312 PLANTING DESIGN

S-312-3 NEW PLANT MATERIAL

S-312-3 .

Plant material should be selected and located to prevent the unwanted reduction

of thermal output of a solar collector from shading, sap or other by-products

of plants.

3-4
CHAPTER 4

BUILDING DESIGN

TABLE OF CONTENTS

Page

S-400 GENERAL 4-2

S-402 ACCESS AND CIRCULATION 4-2

S-402-1 General 4-2

S-402-10 Solar Energy Equipment 4-2

S-405 FIRE PROTECTION 4-2

S-405-1 General 4-2

S-405-4 Fire Resistance Requirements 4-2

S-405-6 Exits 4-3

S-405-7 Firestopping 4-3

S-405-12 Roof Coverings 4-3

4-1
CHAPTER 4

BUILDING DESIGN

S-400 GENERAL

The provisions of this chapter are applicable to solar domestic hot water

(DHW) systems. This chapter is intended to be used in conjunction with

the Minimum Property Standards (MPS) Chapter 4.

S-402 ACCESS AND CIRCULATION

S-402-1 GENERAL

S-402-1.

1

The design and installation of the solar domestic hot water systems shall

not impair the normal movement of occupants of the building or emergency

personnel.

Commentary; Special consideration should be given to the effect of the

CONFIGURATION OF ROOF-MOUNTED COLLECTORS ON FIRE EXITING, FIRE FIGHTING OR

EMERGENCY RESCUE,

S-402-10 SOLAR ENERGY EQUIPMENT

Solar energy equipment shall be accessible for routine maintenance without

disassembling any major structural or mechanical element. Sufficient space

or clearance shall be provided based upon solar equipment sizes and potential maintenance equipment sizes to permit examination, replacement,

adjusting, servicing and/or maintenance. See Section S-600-5.

Commentary: Accessibility for repair and maintenance should reflect the

expected life of the equipment and the frequency of routine maintenance

required. An element with a shorter maintenance cycle or life expectancy

should be more accessible than one with a long maintenance cycle or life

expectancy

.

S-405 FIRE PROTECTION

S-405-1 GENERAL

S-405-1.1 The incorporation of solar systems into the living unit shall not increase

the fire hazard or interfere with the means of safe egress in the event of

a fire.

S-405-4 FIRE RESISTANCE REQUIREMENTS

S-405-4.1 Integrated Construction

The incorporation of solar subsystems shall not reduce the fire resistance

ratings required by applicable codes and standards.

Commentary: Roof-mounted collectors which are an integral part of the roof

construction shall not reduce the required fire resistance rating of the

roof assembly.

S-405-4.

2

Penetrations

Penetrations through fire-rated assemblies shall not reduce the fire

resistance ratings required by applicable codes and standards.

4-2
S-405-6 EXITS

Components of the solar system shall not be located in such a way as to interfere with the primary or secondary means of occupant egress

Commentary : The location of solar equipment on a roof shall not reduce

the usability of that roof for access or egress. Solar system components

located remote from the building but near a means of egress shall not block

the means of egress if a fire occurs in the solar system component.

S-405-7 FIRESTOPPING

Major solar system components that are integral parts of assemblies which

normally require firestopping shall be firestopped on all sides. Firestopping shall be wood blocking of minimum 2 inch nominal thickness or of

noncombustible materials providing equivalent protection. Firestopping

may be included as an integral part of the component where the component as installed provides equivalent protection.

Commentary: It is the intent of the section to prevent solar system components from reducing the effectiveness of firestopping. For example, in the case where a solar collector is an integral part of a wood framed watt which

would normally be firestopped between studs, firestopping shall be required

in the wall above and below the solar collector.

S-405-12 ROOF COVERINGS

Installation of solar collectors or system components on or as an integral

part of the roof shall not reduce the fire retardant characteristics of the

roof covering below the level specified hy applicable codes and standards.

4-3
'
CHAPTER 5

MATERIALS

TABLE OF CONTENTS

Page

S-500 GENERAL 5-2

S-500-1 Applicable Standards 5-2

S-500-2 Exceptions and Re-Statements 5-2

S-500-3 Suitability of Alternate or Special Materials 5-2

S-501 GENERAL REQUIREMENTS 5-3

S-501-1 General 5-3

S-501-2 Labeling 5-3

S-501-3 Safety 5-3

S-501-4 Documentation of Performance 5-3

S-515 MECHANICAL - SOLAR POWERED EQUIPMENT 5-4

S-515-1 General Provisions 5-4

S-515-2 Collectors 5-5

S-515-3 Energy Transport System 5-21

S-515-4 Mechanical Supporting Devices 5-22

S-515-5 Valves 5-23

S-515-6 Pumps and Fans 5-23

S-515-7 Thermal Storage Units 5-24

S-515-8 Heat Transfer Fluids 5-25

S-515-9 Heat Exchangers 5-27

S-515-10 Gaskets and Sealants 5-28

S-515-11 Insulation/Thermal and Moisture Protection 5-29

S-515-12 Catch Basins ..... 5-30

S-515-13 Organic Coupling Hoses 5-31

5-1
CHAPTER 5

S-500

S-500-1

S-500-2

S-500-2 .

S-500-2.

S-500-3

MATERIALS

GENERAL

The provisions in this chapter are applicable to solar domestic hot water

(DHW) systems. This chapter is intended to be used in conjunction with

the Minimum Property Standards (MPS) . Materials provisions (Chapter 5)

of the MPS are applicable in addition to the items explicitly discussed

in this document.

dommentary : Conditions of potentially deleterious exposure of materials

used in solar systems and particularly in solar collectors vary widely with

the design and operating characteristics of the system and collectors . The

performance of materials in the context of the overall normal and no-flow

characteristics of system and collectors should be considered as primary

factors in material selection .

APPLICABLE STANDARDS

Except as modified herein, materials, equipment and installation shall

be in accordance with the standards and nationally recognized model codes

cited within the body of this document; the current applicable editions

and titles of referenced standards and codes are contained in Appendix E. State and local codes which deviate from nationally recognized codes or standards in order to satisfy local conditions may be accepted by HUD if

such deviations are identified and substantiated with satisfactory engineering data.

EXCEPTIONS AND RE-STATEMENTS

Exceptions

Exceptions to the cited standards are included in this document where

deemed appropriate by HUD.

Re-statements

Certain requirements that are already covered in the referenced standards

are re-stated in this document to emphasize the need for implementing these

requirements in HUD construction.

SUITABILITY OF ALTERNATE OR SPECIAL MATERIALS

Alternate or special materials or products, other than those contained

herein may be used when found acceptable by established HUD procedures

and Division 513 of MPS and Section S-101 of this document.

5-2
DIVISION 1

S-501 GENERAL REQUIREMENTS

S-501-1 GENERAL

Materials installed shall be of such kind and quality as to assure that

the solar energy system will provide a) adequate structural strength,

b) adequate resistance to weather, moisture, corrosion and fire, c) ac- ceptable durability and economy of maintenance and market acceptance.

S-501-2 LABELING

Mandatory labeling requirements, where applicable, are contained herein

for specific materials and products.

Commentary: Installation, operation and maintenance information re- quirements are specified in S-600-3.

S-501-3 SAFETY

S-501-3.1 Protection of potable water and circulated air

No material, form of construction, fixture, appurtenance or item of

equipment shall be employed that will introduce toxic substances, impurities, bacteria or toxic chemicals into potable water and air circulation systems in quantities sufficient to cause disease or, harmful

physiological effects.

Commentary: This situation is of concern not only as it pertains to ducts

,

piping, filters and joints but also to storage areas, such as rock beds.

In addition, the growth of fungus, mold and mildew is possible when collectors are applied to a roof surface over the water tight membrane. If

the collectors are in contact with the membrane or held away from the mem- brane to allow for drainage, the shaded membrane area can support the

growth of mildew and other fungus in some warm, moist climates. Special

design considerations should be included to avoid this problem in climates

where it can occur.

S-501-4 DOCUMENTATION OF PERFORMANCE

Documentation of satisfactory long term performance under in-use condition

of systems, components, or materials may be used to demonstrate compliance

with the standards listed in this chapter.

5-3
DIVISION 15

S-515

S-515-1

S-515-1 .

1

S-515-1.

2

S-515-1.

3

S-515-1.

4

S-515-1.

5

S-515-1.

6

S-515-1.

7

S-515-1.

8

MECHANICAL - SOLAR POWERED EQUIPMENT

GENERAL PROVISIONS

Fire Safety

Assemblies and materials used in the solar systems shall comply with the

nationally recognized codes for fire safety under all anticipated operating

and no flow conditions.

Effects of External Environment

The domestic hot water (DHW) system and its various subassemblies shall

not be affected by external environmental factors prevalent at the site

to an extent that will significantly impair their function during their

intended design life.

Temperature and Pressure Resistance

Components shall be capable of performing their functions for their intended design life when exposed to the maximum and minimum temperatures

and pressures that can be developed in the system.

Materials Compatibility

All materials which are joined directly to or in contact with other materials

shall have sufficient chemical compatibility with those materials to prevent

deterioration that will significantly impair their function during their

intended design life. Provisions shall be made to allow for differences

in the expansion and contraction of joined materials due to expected

temperature fluctuations.

Airborne Pollutants

Materials exposed to airborne pollutants while in service, such as ozone, salt spray, sulfur dioxide, oxides of nitrogen and/or hydrogen chloride,

shall not be affected by those pollutants to an extent that will significantly impair their function during their intended design life.

Chemical Decomposition Products

Materials shall not be affected by chemical decomposition products ex- pelled from components under in-use conditions to an extent that will

significantly impair their function during their intended design life.

Abrasive Wear

Exterior materials shall not be affected by abrasive wear caused either

by cleaning or by natural factors such as wind blown sand to an extent

that will significantly impair their function during their intended

design life.

Soil Corrosion

Materials installed in corrosive soil shall be either of a material unaffected

by such soil or shall be isolated from it by a protective coating. The

coating and its application shall conform to AWWA C-203.

5-4
S-515-1.9 Corrosion by Leachable Substances

Sutistances that can be leached by moisture from any of the materials within

the system which may be exposed to moisture shall not cause corrosive deterioration of any other materials to an extent that will significantly

impair their function during their intended design life.

S-515-1.10 Leakage

Leakage from assemblies or subassemblies which contain heat transfer fluids

shall not significantly impair the function of other components which may

come in contact with the leaking heat transfer fluid or create a safety

hazard.

S-515-2 COLLECTORS

S-515-2.1 General

Collectors shall perform their function for their intended design life.

. Commentary : In addition to their primary function of collecting solar

energy , collector panels can be used as the roofing membrane. They can also

be mounted over a roofing membrane or mounted remotely . The primary function

of a roofing membrane is to prevent the entrance of water into the structure.

When collector panels are designed to fulfill this function, leakage at joints

must be considered in the design.

When collectors are mounted over a roofing membrane, consideration should

be given to the growth of fungus, mold, and mildew between the roofing

membrane and the collector and to potential problems in reroofing under

collectors. Also, it is possible, due to extreme temperature differentials

,

to cause the formation of ice dams which could in turn back water under

shingles or other roofing materials, causing rapid deterioration. Consideration should be given to the methods of applying non-integral collectors to roof structures and to the choice of waterproofing membrane.

S-515-2. 1.1 Labeling and Technical Data Sheets

Collectors shall be labeled to show the manufacturer's name and address,

model number, serial number, and collector weight (dry). Technical data

sheets shall also be provided which include collector efficiency as measured

according to S-615-2.2, maximum allowable operating and no-flow temperatures

and pressures, minimum allowable temperatures, and the types of fluids which

can and cannot be used.

Commentary: Other data related to the installation and operating conditions or characteristics is desirable such as the pressure drop across the

collector.

S-515-2. 1.2 Thermal Stability

Collectors shall not exhibit a change in the product of FR

Ta (intercept) or Fr Ul (slope) that would result in a 10% or greater decrease in thermal

efficiency for the proposed system design operating conditions when evaluated

in accordance with the following testing procedure.

Testing Procedure :

The parameters F^ xa and Fr shall be determined in accordance with the

test procedure described In ASHRAE Standard 93-77 both before and after exposing

the collector panel assembly to the Exposure Test described below. Both the

before and after collector thermal performance tests (ASHRAE Standard 93-77)

shall be performed utilizing the same test facility under similar climatic

conditions

.

5-5
Exposure Test:

A. Test specimen shall consist of a complete air or liquid collector panel

assembly.

B. Pre-exposure preparation :

(1) Air collectors shall be sealed and capped with a pressure relief

device set to a value within 10% of the collector manufacturer's

maximum recommended operating pressure. The inlet shall be equipped

with a means to allow the admission of dry air if internal pressures

of less than one (1) atmosphere occur.

(2) Liquid collectors intended for use in all systems (with or without

draindown) shall be completely filled with clean tap water, following

which the inlet shall be sealed and the outlet provided with a pressure

relief valve set to a value of within 10% of the manufacturer's

recommended maximum operating pressure.

(3) Liquid collectors limited to use in systems that draindown when not

operating shall be completely filled with clean tap water, following

which the water shall be allowed to gravity drain for 15 minutes with

the collector mounted at a 45° tilt angle. The collector inlet

shall then be sealed and the outlet provided with a pressure relief

valve set to a value of within 10% of the manufacturer's recommended

operating pressure.

C. Exposure conditions

Exposure conditions shall consist of 30 days of cumulative exposure to a minimum daily incident solar radiation flux of 1500 Btu/ft^.day as measured in the plane of the collector aperture. The exposure conditions

shall include at least one consecutive four-hour period with a minimum

flux of 300Btu/ff2-hr. In water filled specimens, this must occur after

water boilout has occurred. The average ambient temperature shall be 80°F

or higher during the 300Btu/ff2 -hr exposure time. The collector shall

be mounted to a rack at a tilt angle such that the incident solar radiation during solar noon is within + 10° of the normal to the plane of the

aperture

.

D. Data records

(1) The exposure conditions including insolation, ambient temperature,

wind velocity, and precipitation shall be recorded to enable determination of the average daily values. Values shall be recorded every

30 minutes during the 300 Btu/ft^'hr exposure.

(2) A regularly scheduled weekly visual inspection shall be made and a record of changes in the physical construction or appearance of the

collector kept.

(3) The results of the pre-test and post-test thermal performance shall

be plotted on the same graph for comparison purposes.

Commentary: The purpose of the "no-flow" test is to identify3 in a short

period of time3 potential problems with collector materials or construction.

The 30 days do not necessarily have to be consecutive but the test should be

performed on a continuous basis until the solar radiation levels have been

achieved for 30 cumulative days. It is recognized that other heat transfer

fluids exist which may be preferred by the manufacturer or designer.

If the test is conducted in a manner other than that prescribed, the collector

specification shall state the specific conditions used during the test and

identify the pertinent limitations regarding collector array installation

5-6
S-515-2.1.3

and operation. The above exposure test procedure is based upon draft ver- sions of a test method in preparation by ASTM.

Outgassing of Materials

Outgassing products or condensates on the cover plate surfaces shall not

contribute to a decrease in thermal performance greater than that specified

after exposure as described in S-515-2. 1.2.

Commentary: Outgassing from components inside the collector could lead to condensation on the underside of the collector cover plate (s) which may

reduce the transmittance of the cover plate (s)

.

S-515-2. 1.4 Flashing

a. Flashing for collector panel supports that penetrate the primary roof

membrane shall be designed to prevent the penetration of water or melting snow for the life of the roof system.

b. Flashing systems shall be designed to permit minor repairs without

disturbing the roof membrane, collector supports, or collector panels.

c. In general, flashing for roof penetrations shall comply with applicable

Sections of 507-5 and 507-8 of the MPS.

Commentary: Suggested practices for flashing used on no-slope or lew slope

roofs and roof penetrations are provided in the National Roofing Contractors

Association's "A Manual of Roofing Practice3 " 1970.

S-515-2.2 Cover Plates

S-515-2.2.1 General

The materials used as glazing for cover plates must meet the following

requirements based on materials properties as well as safety considerations.

The safety requirements are made with respect to the physical location of

the glazing and the exposure risk of persons nearby.

S-515-2. 2.1.1

Commentary : Appendix table B-l lists properties of a number of materials

that have been used for cover plates.

Structural Requirements

All glazing materials shall be of adequate strength and durability to withstand the loads and forces required by Section S-601 of this document.

S-515-2. 2 J.. 2 Types of Applications

Applications include windows which act as cover plates for solar collectors,

both integral with dwelling construction and freestanding components.

a. Glazing materials other than those specified in b or c below, shall

meet the intent of the requirements for glazing in MPS Section 508-8.3.

Commentary: Consumer Product Safety Act, Part 1201 , was published in

the Federal Register January 6, 1977 and will become effective on

July d, 1977 (except for fire retardant glazing required by ordinance

for which the effective date is January 6, 1980). This standard contains

mandatory safety standards for architectural glazing materials.

5-7
S-515-2.2.

S-515-2.2.

S-515-2.2.

S-515-2.2.

Film- type glazing materials for the outermost cover plate, if unsupported,

may be unacceptable if they can be deflected under load, e.g. , a person's

hand pushing against the glazing, may present an opportunity for

exposure of the film (and the person's hand) to hot surfaces such as

the absorber plate. Also, there is a probability of exposure to impact

which may result in tearing of the film.

b. Glazing materials with slopes less than 45° which extend below 6' 0"

(from ground level) shall be safety glazed or otherwise protected

against impact of falling bodies.

Commentary: This commonly refers to glazing on which children may

climb or against which a passerby may fall.

c. Glazing panels which are an integral part of a roof or rack-mounted

system on a roof, not routinely accessible by the occupant, shall meet

the requirements of Section S-601.

Cormentary: Annealed glass or films may be acceptable ,

2 Codes and Standards

Materials used as glazing for cover plates shall comply with MPS Section

508, Section S-601 of this document and applicable sections of local

building codes and national standards.

3 Materials Performance

3.1 Thermal Stability

After testing as described in S-515-2.1.2, there shall be no cracking, crazing,

warping, sagging, or buckling of the cover plate(s) that will result in premature failure or degradation in collector performance greater than the

design limits.

3.2 Ultraviolet Stability

Documentation shall be provided that the cover plate(s) is resistant to degradation by UV radiation that would significantly impair its function during its

design life. In lieu of other documentation, the transmittance of the cover plate (s) as measured by ASTM E 424-71 shall not significantly change after

exposure using any one of the three aging procedures described below. The com- putation of solar transmittance based on the spectrophotometric method in

E 424 shall be standardized on air mass 2.

For collectors with multiple covers, the tests below shall be performed with

the cover plates in their design configuration.

Commentary: In the absence of other documentation, a change in cover plate

transmittance of more than 10% is considered significant.

Aging Procedure 1

Expose components or materials to simulated solar radiation (such as xenon

arc radiation) for a period of 2000 equivalent sun hours. The exterior

surfaces of components which are exposed to rainfall in service shall be

subjected to a water spray for a period of 5 minutes during each 60 minutes

of the light exposure. For components not exposed to rainfall under normal

operating conditions, the water spray shall not be included in the procedure.

5-8
Aging Procedure 2

Expose components or materials to concentrated natural solar radiation using

machines such as those referenced in ANSI Z97. 1-1975, paragraph 4.3.2 for a period of 2000 equivalent sun hours. The exterior surfaces of components

which are exposed to rainfall in service shall be subjected to a water spray

for a period of 8 minutes during each 60 minutes of sunlight exposure. For components not exposed to rainfall undet normal operating conditions, the

water spray shall not be included in the procedure.

Aging Procedure 3

Expose components and materials to solar radiation outdoors for twelve

months. The average daily flux of the solar radiation, as obtained by

averaging the daily fluxes over the twelve month period of outdoor exposure,

shall be at least 1,500 Btu/ft2.

S-515-2.2.3.3 Glass

Where safety glazing is used, it shall meet the requirements of the MPS,

Section 508, as specified in S-515-2.2.1.2 of this document .

S -515-2. 2. 3. 4 Other Materials

Cover plate materials other than glass shall conform to the requirements

of MPS, Section 513 and the intent of S-515-2.2.3.3.

Commentary : Appendix Table B-l lists a number of materials that have

been used for cover plates.

S-515-2.3 Absorber Plate

S-515-2 .3.1 General

Materials used for absorber plates shall not degrade to an extent that

collector performance would be reduced below allowable design limits.

S-515-2. 3. 2 Materials Performance

S-515-2. 3. 2.1 Thermal Stability

Any deformation that occurs in the test described in S-515-2. 1.2 shall not

result in premature failure or degradation in collector performance greater

than the design limits.

Commentary: In addition to buckling, sagging, and warping that can be produced

in the thermal stability test, consideration should be given to the possibility

that repeated boilout cycles can lead to deformation or rupture of the

absorber plate.

S-515-2. 3. 2. 2 Erosion/Corrosion

Flow rates shall be maintained below the values listed in Tables S-515-2. 3.

2

and 2.3.3 to prevent erosive wear.

5-9
Commentary : The variables which have an important impact on the rate of

erosion/corrosion are:

1) the quantity and size distribution of solids in suspension

2) the flow rate

3) the pipe diameter

4) the oxygen content of the fluid

5) the angle of the change of flow direction

6) the internal surface condition of the pipe

7) the temperature

8) partial obstructions in flow passages which create localized areas of

highly turbulent fluid flow

S-515-2 . 3 . 2 . 3 Compatibility with Transfer Medium

a. The absorber plate or flow conduits shall not be pitted, corroded, or otherwise degraded by the heat transfer medium to an extent that will

result in failure during its design life. In lieu of other documentation

for metals, modifications of tests listed in Table S-515-2. 3.1 shall be

used to demonstrate compliance with this requirement. For materials

other than metals, documentation shall be provided to demonstrate compliance

with S-515-1.4 and this requirement.

Commentary: Two types of heat transfer liquid, aqueous and non-aqueous

may be used in the collector system. Generally, corrosion is associated

with aqueous transfer media. However, corrosion could also occur in non- aqueous media under one or more of the following conditions:

1) if the liquid is initially agressive to the containment material

2) if liquid decomposition generates corrosive products

3) if water is initially present in the liquid or contaminates the liquid

once in use.

b. Metallic absorber plates or flow conduits in direct contact with heat

transfer liquids in open systems shall generally be used in accordance

with the acceptable conditions listed in Table S-515-2. 3. 2 where

applicable. Generally unacceptable conditions listed in this table shall

be avoided. Documentation shall be provided to demonstrate that materials

applications not explicitly covered in Table S-515-2. 3. 3 meet the intent

of S-515-1.4 and S-515-2 . 3 . 2 . 3a.

Metallic absorber plates or flow conduits in direct contact with heat

transfer liquids in closed systems shall generally be used in accordance with the acceptable conditions listed in Table S-515-2. 3. 3 where

applicable. Generally unacceptable conditions listed in this table shall

be avoided. Documentation shall be provided to demonstrate that materials

applications not explicitly covered in Table S-515-2. 3. 3 meet the intent

of S-515-1.4 and S-515-2. 3. 2. 3a.

Commentary: Tables S-515-2. 3. 2 and S-515-2. 3. 3 are intended to provide

general guidelines for the selection of metals or alloys for use in

solan collectors . Various alloys of the same base metal may be expected

to show significant variability in resistance to corrosion. Small

concentration changes in a number of chemical species may significantly

change the corrosion behavior of a given material at a given temperature.

A complete description of this behavior is not possible in this context.

Therefore, generally unacceptable use conditions as stated should be

avoided unless it has been demonstrated that the metal or alloy performs

suitably in the anticipated use condition. Adequate performance is

anticipated for normal operation in generally acceptable use conditions.

The stated generally acceptable use conditions are directed toward normal

operation. Under the conditions of stagnation, where high temperatures

may be encountered, different behavior may occur. It is recommended that

specific tests be carried out to ensure adequate materials performance

in these conditions.

5-10
SAE' Report J447a (1964) , Prevention of Corrosion of Metals, provides

guidance in preventing corrosion in aqueous media, but its application

should be tempered by consideration of the special operating characteristics

of solar collectors, e.g., no-flow temperature effects.

Table S-515-2.3.1: Corrosion Test Methods*

Number Title Comment

NACE TM-01-71 Autoclave Corrosion Testing

of Metals in High Temperature

Water

Modify to reflect conditions

present in solar system

NACE TM-02-74 Dynamic Corrosion Testing of

Metals in High Temperature

Water

Modify to reflect conditions

present in solar system

NACE TM-02-70 Conducting Controlled Velocity

Laboratory Corrosion Tests

Modify to reflect conditions

present in solar system

NACE TM-01-69 (1972) Laboratory Corrosion Testing

of Metals for the Process

Industries

Describes factors to consider in corrosion testing

ASTM D1384-70 (1975) Corrosion Test for Engine

Antifreeze in Glassware

Modify to reflect conditions

present in solar system

ASTM D2570-73 Simulated Corrosion Testing

of Engine Coolants

Modify to reflect conditions

present in solar system

ASTM D2776-72 Corrosivity of Water in the

Absence of Heat Transfer

* Modification of test procedures developed for purposes other than

collector material testing shall adequately reflect all expected

collector conditions including no-flow conditions.

Commentary: Open and Closed Systems

Open systems are those in which air, in addition to that initially in the

transfer liquid, can be absorbed into the liquid by contact with the atmosphere or air entrapped in the system.

Closed systems are those in which the air initially absorbed in the transfer

liquid is not replaced to a significant extent. In a closed system, there

is no exposure of the liquid to the atmosphere except above the expansion

tank (in some cases a nitrogen blanket above the liquid in the expansion

tank may be used); there is no entrapped air in the piping or storage

systems and the expansion tank is isolated from the flaw path between the

collector and storage. In addition, liquid leakage requiring frequent make

up is avoided.

5-11
TABLE S-515-2.3.2 Generally Acceptable and Unacceptable Use Conditions for Metals

in Direct Contact with Heat Transfer Liquids in Open Systems

Generally Unacceptable Use Conditions Generally Acceptable Use Conditions 1 /

Aluminum

1.

When in direct contact with untreated

tap water with pH <5 or >9.

2.

When in direct contact with aqueous

liquid containing less electro positive

metal ions, such as Copper or iron or halide ions.

3. When specific data regarding the

behavior of a particular alloy are not

available, the velocity of aqueous liquid shall not exceed A ft/sec.

4. When in direct contact with a liquid

which is in contact with corrosive fluxes.

1. When in direct contact with distilled

or deionized water which contains

appropriate inhibitors and does not

contact copper or iron.

2. When in direct contact with distilled

or deionized water which contains

appropriate inhibitors and a means of

removing heavy metal ions obtained

from contact with copper or iron.

3. When in direct contact with stable

anhydrous organic liquids.

Copper

1. When in direct contact with aqueous

liquid containing high concentrations

of chlorides, sulfates or liquid which

contains hydrogen sulfide.

2. When in direct contact with chemicals

that can form copper complexes such as ammonium compounds.

1. When in direct contact with distilled,

deionized or low chloride, low sulfate

and low sulfide tap water.

2. When in direct contact with stable

anhydrous organic liquids

.

3.

When in direct contact with an aqueous liquid having a velocity greater than 4 ft/sec.—

4.

When in direct contact with a liquid

which is in contact with corrosive fluxes

.

5. When in contact with an aqueous liquid

with a pH lower than 5.

6. When the copper surface is initially

locally covered with a copper oxide film

or a carbonasceous film.

7 . When operating under conditions conducive

to water line corrosion.

Steel

1. When in direct contact with untreated

tap, distilled or deionized water with

pH <5 or >12.

1. When in direct contact with distilled,

deionized or low salt content water

which contains appropriate corrosion

inhibitors

.

5-12
TABLE S-515-2 .3.2 (Contd.)

Generally Unacceptable Use Conditions Generally Acceptable Use Conditions 1 /

2. When in direct contact with a liquid

which is in contact with corrosive fluxes.

3. When in direct contact with an aqueous

liquid having a velocity greater than

6 ft/sec. 2J

4. When operating under conditions conducive

to water line corrosion.

2. When in direct contact with stable

anhydrous organic liquids

.

3. When adequate cathodic protection of

the steel is used (practical only for

storage tanks)

.

Stainless Steel

1.

When the grade of stainless steel selected is not corrosion resistant in the

anticipated heat transfer liquid.

2.

When in direct contact with a liquid

which is in contact with corrosive

fluxes

.

1. When the grade of stainless steel se- lected is resistant to pitting, crevice

corrosion, intergranular attack and

stress corrosion cracking in the

anticipated use conditions.

2. When in direct contact with stable

anhydrous organic liquids

.

Galvanized Steel

1. When in direct contact with aqueous

liquid containing copper ions.

2. When in direct contact with aqueous

liquid with pH <7 or >12.

3. When in direct contact with aqueous

liquid with a temperature >55°C.

1. When adequate cathodic protection of

the galvanized parts is used (practical

only for storage tanks)

.

2. When in contact with stable anhydrous

organic liquids.

Brass and Other Copper Alloys

Binary copper-zinc brass alloys (CDA 2XXX series) exhibit generally the same behavior

as copper when exposed to the same conditions. However, the brass selected should

resist dezincification in the operating conditions anticipated. At zinc contents of

15% and greater, these alloys become increasingly susceptible to stress corrosion.

Selection of brass with a zinc content below 15% is advised. There are a variety of

other copper alloys available, notably copper-nickel alloys, which have been developed

to provide improved corrosion performance in aqueous environments.

'The use of suitable antifreeze agents and buffers is acceptable provided they do not promote

corrosion of the metallic liquid containment system. The use of suitable corrosion inhibitors for specific metals is acceptable provided they do not promote corrosion of other

metals present in the system. If thermal or chemical degradation of these compounds occurs,

the degradation products shall not promote corrosion.

2/

The flow rates at which erosion/corrosion becomes significant will vary with the conditions

of operation. Accordingly, the value listed is approximate.

5-13
TABLE S-515-2. 3. 3 Generally Acceptable and Unacceptable Use Conditions for Metals

in Direct Contact with Heat Transfer Liquids in Closed Systems

Generally Unacceptable Use Conditions Generally Acceptable Use Conditions 1

/

Aluminum

1. When in direct contact with untreated

tap water with pH <5 or >9.

2. When in direct contact with liquid

containing copper, iron or halide ions.

1. When in direct contact with distilled

or deionized water which contains

appropriate corrosion inhibitors.

2. When in direct contact with stable

anhydrous organic liquids

.

3.

When specified data regarding the behavior

of a particular alloy are not available,

the velocity of aqueous liquid shall not

exceed 4 ft/sec.

Copper

1.

When in direct contact with an aqueous liq^/l.

uid having a velocity greater than 4 ft/sec—

When in direct contact with untreated

tap, distilled or deionized water.

2.

When in contact with chemicals that can form copper complexes such as ammonium compounds.

2. When in direct contact with stable

anhydrous organic liquids.

3.

When in direct contact with aqueous

liquids which do not form complexes

with copper.

Steel

1 .

2 .

When in direct contact with liquid

2 y having a velocity greater than 6 ft/sec.—

When in direct contact with untreated

tap, distilled or deionized water with

pH <5 or >12.

1. When in direct contact with untreated

tap, distilled or deionized water

with pH >5 or <12.

2. When in direct contact with stable

anhydrous organic liquids

.

3. When in direct contact with aqueous

liquids of pH > 5 or <12.

Stainless Steel

When the grade of stainless steel

selected is resistant to pitting,

crevice corrosion, intergranular attack

and stress corrosion cracking in the

anticipated use conditions.

2. When in direct contact with a liquid 2. When in direct contact with stable

which is in contact with corrosive fluxes. anhydrous organic liquids.

1. When the grade of stainless steel selected 1. is not corrosion resistant in the anticipated heat transfer liquid.

5-14
TABLE S-515-2.3.3 (Contd.)

Generally Unacceptable Use Conditions

1 / Generally Acceptable Use Conditions —

Galvanized Steel

1. When in direct contact with water with 1. When in contact with water of pH >7 pH <7 or >12. but <12.

2. When in direct contact with an aqueous

liquid with a temperature >55 °C.

Brass and Other Copper Alloys

Binary copper-zinc brass alloys (CDA 2XXX series) exhibit generally the same behavior

as copper when exposed to the same conditions. However, the brass selected shall

resist dezincification in the operating conditions anticipated. At zinc contents of

15% and greater, these alloys become increasingly susceptible to stress corrosion.

Selection of brass with a zinc content below 15% is advised. There are a variety of

other copper alloys available, notably copper-nickel alloys, which have been developed

to provide improved corrosion performance in aqueous environments

.

1 /The use of suitable antifreeze agents and buffers is acceptable provided they do not

promote corrosion of the metallic liquid containment system. The use of suitable corrosion

inhibitors for specific metals is acceptable provided they do not promote corrosion of

other metals present in the system. If thermal or chemical degradation of these compounds

occurs, the degradation products shall not promote corrosion.

2 /The flow rates at which erosion/corrosion becomes significant will vary with the conditions

of operation. Accordingly, the value listed is approximate.

5-15
Commentary: Corrosion

Corrosion is a very complex phenomenon in which many parameters are of

importance . In the case of the corrosion of metals likely to be used in

the liquid containment system, parameters of importance are:

the composition of the metals or alloys

the composition of the water, i.e. the concentrations of salts and

dissolved gases and heavy metal ions

- the temperature

the flow rate and the possibility of erosion-corrosion

- system design factors, particularly the presence of galvanic cells or differential aeration cells

- the presence of additives or their decomposition products

Galvanic cells result from contact between dissimilar metals while differential aeration cells are areas where a metal is in contact with the

liquid which has a variable dissolved oxygen content.

1. Water Composition

Water composition has an important effect on corrosion. The composition

of tap water varies substantially from one geographic area to another.

Even within a given area, water composition will vary depending on its source (surface vs. well water) and the time of year. The major variables

include: pH, gas content (Og, COg) , chloride content, sulfate content,

solids content ( organic matter) , and conductivity. Because of variation

in water, similar variations in the type and severity of corrosion may

be expected.

la. pH

The pH of the transfer liquid will have an important impact on cor- rosion rates. However, the optimum pH range to achieve minimum cor- rosion of a given material, will change with temperature [1], Because

varying temperatures occur within a solar heating system and the temperature at a given point will change with time, care must be taken

to optimize the pH range. It should be noted that the pH of a system

immediately after filling is not necessarily the equilibrium pH.

lb. Og Content of Aqueous Media

Generally, corrosion of metals such as Cu and carbon steel will de- crease with a decreasing amount of Og in aqueous media. In the

absence of Og, measurable corrosion of Cu and steel does not occur. In a closed system, where Og will be depleted, the corrosion rate

will become negligible . Corrosion inhibitors should not be necessary

in a completely closed containment system composed of Cu or steel,

if the proper pH is maintained. However, the probability of a closed

system remaining closed is uncertain since the eventual intrusion

of oxygen cannot be discounted. Therefore, the use of corrosion

inhibitors or oxygen scavengers should be considered.

Oxidizing species such as dissolved oxygen act to stabilize the

passivity of the protective film on stainless steel. When stainless

steel is used in the absence of such species, it may be necessary to specify a grade which will provide adequate resistance to corrosion

attack under these conditions.

11] R. M. Diamant, "The Prevention of Corrosion," Business Books Ltd.,

London, 1971.

5-16
The corrosion of At may continue even in the absence of oxygen since an alternative corrosion process can occur. In this process, anodic

dissolution of Al is accompanied by the evolution of molecular

hydrogen. However, this reaction is expected to be negligible if the

pH is maintained between 5 and 7 in the absence of aggressive ions.

lc. Chlorides

Chloride concentration should be kept to a minimum since the presence

of chlorides in water accelerates corrosion of most metals. Therefore, the metallic collector components selected should be compatible

with the chloride level anticipated in the heat transfer liquid. Aside

from its initial presence in water, there are several potential sources of chloride in a solan unit:

- Residual chloride from pickling treatment of metallic components.

This may also be a source of sulfate; white this is a rather unlikely source of these ions, cane should be taken that the components

of the system are thoroughly cleaned before assembly.

- Chloride from the decomposition of nan-metallic components in the

system.

- Chloride from flux used in soldering or brazing components during

installation.

2. Temperature

The temperature is an important consideration with regard to selection of

containment materials . Corrosion in aqueous media generally increases

rapidly with temperature until the boiling point is approached. In systems

open to the atmosphere, the corrosion rate will tend to decrease due to a sharp decrease in the solubility of oxygen in water at these temperatures.

However, in a pressurized system, from which the dissolved oxygen cannot

escape , corrosion may continue at an accelerated rate.

3. Copper in a Recirculating System

In "once through" systems , copper pipe is usually only connected downstream from iron pipe. Residential plumbing is an example of this. This

practice is carried out because small amounts of copper tend to go into

solution. When these copper ions contact more active metals such as Zn or Al, and to a lesser extent , Fe , they are reduced to copper metal which

subsequently deposits on the metal surface. When this occurs, a galvanic

cell ^s set up and rapid corrosion initiates. Ho such effect is anticipated

for systems utilizing copper and stainless steel. The presence of a dielectric pipe joint between Cu and Al or Fe will not alleviate this

problem. Similar action may be expected if Fe deposits on Al.

4. Galvanizing

Galvanizing has long been used to protect iron or steel from corrosion.

Zinc is more active than iron and, when the two are in electrical contact

,

will corrode preferentially . Thus, the iron is cathodically protected.

The rate of corrosion of zinc is generally lower than that of iron, so a relatively thin coating may last for quite a long time. However,

there are data indicating that at elevated temperatures approaching 158°F

(70°C), this effect is reversed and the iron corrodes rather than the

zinc. \2]

[2] G. Butler and H. C. K. Ison, "Corrosion and its Prevention in Waters,"

Reinhold Publishing, N.Y., 1966.

5-17
In addition, the corrosion rate of zinc itself increases rccpidly in the

temperature range between 131 and 194°F (55 and 90°C). Accordingly, the use of galvanized steel above 131°F (55°C) should be considered with cane.

5. Stainless Steel

While stainless steel is generally regarded as corrosion resistant, it may

be susceptible to intergranular attack, pitting, crevice corrosion or

stress corrosion cracking. The corrosion resistance of stainless steel

varies greatly with the grade used and the thermal treatment. Therefore,

the grade of stainless steel selected should be resistant to corrosion

when exposed to the anticipated heat transfer liquid.

6. Galvanic Coupling

Contact between dissimilar metals in the liquid containment system should

be avoided when aqueous heat transfer media are to be used. However,

physical separation of dissimilar metals may not always ensure against

galvanic corrosion (see commentary on copper in a recirculation system).

7. Stress Corrosion

Collector components may be subject to substantial residual stresses re- sulting from their fabrication. In addition, thermal cycling during operation may introduce applied stresses. Typical collector designs and

operating conditions may be such that it is virtually impossible to avoid

residual or applied stresses.

Some metals and alloys are susceptible to stress corrosion when stressed

in the presence of contaminants commonly present in water, aqueous fluids, or in the atmosphere. Therefore, the metals used in collectors should be

limited to those which are not susceptible to stress corrosion when in

contact with the anticipated heat transfer liquid.

8. Expression of the Results of Corrosion Measurements

Corrosion may be localized in the form of pitting, crevice corrosion,

intergranular attack, stress corrosion, or erosion corrosion or it may

be uniform. Localized corrosion is generally more destructive since it

results in perforation in far shorter periods. Therefore, the type of

attack observed should be reported. The measurement technique used in

evaluating the severity of attack should also be consistent with the type

of attack observed. For example, weight loss measurement would not be

completely adequate to assess the degree of damage caused by localized

corrosion. Weight loss measurement may be meaningful when the degree of

localization of attack is described. However, results should also include

pit density, maximum depth of penetration Op rate of penetration measure- ment where appropriate.

ASTM standards G 1-72, G1 6-71, and G 46-76 provide recommended practices

relating to corrosion test evaluation.

S-515-2.3.2.4 Ultraviolet Stability

Organic absorber plates shall not degrade to an extent that will

significantly impair their function during their design life when exposed

to UV radiation.

Commentary: Organic absorber plates can crack, embrittle, soften, fade, or undergo other changes that could result in premature failure.

5-18
S-515-2.4

S-515-2.4.

S-515-2.4.

S-515-2.4.

S-515-2.4.

S-515-2.4

Absorptive Coatings

1 General

Materials used for absorptive coatings shall not degrade to an extent that

collector performance will be reduced below allowable design limits.

Commentary: Appendix Table B-2 lists some characteristics of absorptive

coatings currently in use. Absorptive coatings are generally of two types

,

selective or nonselective . A nonselective coating has an absorptance to emittance ratio near unity whereas in a selective coating, the ratio is

higher. A selective coating has a high absorptance (a) over the solar

spectrum (.3 to 2.0 ym) with low emittance (z) to reduce thermal radiative

heat losses.

For coatings applied by an electroplating process, as are many selective

coatings, the substrate finish, plating geometry, bath composition, and

current density may influence the properties necessary for optimum solar

applications

.

2 Materials Performance

2.1 Thermal Stability

After testing as described in S-515-2.1.2, there shall be no evidence of

checking, cracking, blistering or flaking of the absorptive coating that

will significantly impair its function. ASTM methods D 660-44 (1970),

D661-44 (1975), D714-56 (1974) and D772-47 (1975) shall be used to evaluate the above properties.

2.2 Ultraviolet Stability

Documentation shall be provided that the absorptive coating is not adversely

affected by UV radiation to an extent that will significantly impair its

function during its intended design life. In lieu of other documentation,

the absorptive coating shall not exhibit checking, cracking, blistering, or flaking after testing using any one of the three aging procedures described

in S-515-2. 2. 3. 2 in its design configuration.

Commentary: The above tests shall be performed with a cover plate between

the absorptive coating and the light source (if so designed) to simulate

in-service conditions. The cover plate shall be of the same type and con- figuration as used in an actual collector.

In the absence of other documentation, a change in absorptive coating a or z of 107o is considered significant.

.2.3 Moisture Stability

Documentation shall be provided that the absorptive coating is not adversely

affected by moisture with which it comes in contact to an extent that will

significantly impair its function during its intended design life. In lieu

of other documentation, the absorptive coating shall not exhibit checking,

cracking, blistering or flaking after testing for 30 days according to ASTM D 2247-68 (1973).

Commentary: Moisture is not expected to come in contact with absorptive

coating in collectors which have a desiccant or in evacuated tube collectors

.
S-515-2 .4.2.4 Compatibility With Heat Transfer Medium

S-515-2.

5

S-515-2. 5.

S-515-2. 5.

S-515-2. 5.

S-515-2.

6

S-515-2. 6.

S-515-2. 6.

S-515-2. 6.

S-515-2. 6.

When absorptive coatings are in direct contact with the heat transfer

medium documentation shall be provided to show that they are not affected

by the medium to an extent that would significantly impair their function

during their design lives. In lieu of other documentation, the absorptive

coating shall exhibit no checking, cracking, blistering or flaking or signs

of erosion after immersion in the fluid transfer medium for 100 hours at the

maximum service temperature according to ASTM D1308-57 (1973).

Collector Enclosure

1 General

Collector enclosure materials shall be in accordance with applicable

sections of Division 5 and 6 of the MPS.

Protective coatings, where used, shall be in accordance with Section 509-7

of the MPS.

2 Materials Performance

2.1

Thermal Stability

After testing as described in S-515-2. 1.2, there shall be no cracking or warping of the collector enclosure materials to an extent that would

result in premature failure or degradation in collector performance

greater than the design limits.

Reflective and Antireflective Surfaces

1 General

Changes in reflective and antireflective surfaces due to in-use exposure

shall not result in a decrease in collector performance below the design

limits.

2 Materials Performance

2.1 Thermal Stability

After testing as in S-515-2. 1.2, there shall be no cracking, crazing,

delamination or change in reflectance properties of the surfaces to an extent that would result in premature failure or degradation in collector

performance greater than the design limits.

2.2 Ultraviolet Stability

Documentation shall be provided that the reflectance properties of the

surfaces will not be adversely affected by UV radiation to an extent that

will significantly impair their function during their design life.

In lieu of other documentation, the reflectance, as measured for air mass 2 by ASTM E 424-71, method A, shall not decrease by more than 10%

after exposure using any one of the three aging procedures described

in S-515-2. 2. 3. 2.

5-20
S-515-3

S-515-3.1

S-515-3. 1.

S-515-3.1.

S-515-3.

2

S-515-3. 2.

S-515-3. 2.

S-515-3. 2.

S-515-3. 2.

ENERGY TRANSPORT SYSTEM

This section covers materials used to transport the heat transfer

medium to a heat exchanger or storage facility and also those necessary

components used to return the heat transfer medium from the heat exchanger

or storage facility to the collector subsystem.

Applicable Standards for Liquid Systems

1 Compliance with MPS

Materials used in the transport system shall be in accordance with Sections

515-3.2, 515-5.1, 515-5.2 and 515-6.4 of the MPS where applicable.

2 Other Standards

Materials used for transporting liquids shall be shown to be in compliance

with applicable standards.

Commentary: Examples of some standards that may be useful are given in

Appendix Table B-4. Most of the standards for piping shown in Appendix

Table B-4 are the standards normally considered by the model plumbing codes,

designers may use other ANSI, ASTM, or Federal Standards or Specifications

that may be more appropriate to their particular design.

Materials Performance for Liquid Systems

1 Thermal Stability

Components comprising the transport system shall not be damaged by normal

thermal expansion and contraction of piping materials under in-use con- ditions. Proper pipe hangers and supports and fittings shall be used to allow normal movement of piping. See Appendix Table B-4.

2 Chemical and Physical Compatibility

a. Materials comprising the transport system shall have sufficient chemical

and physical compatibility with organic materials in the system, such

as sealants and gaskets, to which they are joined or in contact to prevent significant deterioration.

b. Materials comprising the piping or transport system shall have sufficient

chemical and physical compatibility with the heat transfer liquid to prevent significant corrosive wear and deterioration. (For metals,

see S-515-3. 2. 5)

3 Erosion/Corrosion

Materials comprising the transport system shall be in conformance with

S-515-2 .3.2.2.

4 Joints Between Dissimilar Metals

Dissimilar materials joined to form the transport system shall be electrically

isolated from each other unless documentation is provided to demonstrate

that the joints are sufficiently compatible to prevent corrosive wear and

deterioration during their design lives.

5-21
S-515-3.

2

S-515-4

S-515-4.

1

S-515-4.

3

Commentary : Care must be taken to avoid short circuiting of dielectric

couplings. For example - dielectric couplings used to isolate dissimilar

metals which are buried in soil may be ineffective because of contact of the

metals with ground water, or dielectric couplings may be short circuited

through pipe supports connected to metal structures.

.5 Metals

Metals used in the transport system which are in direct contact with heat

transfer liquids shall be used in accordance with the generally acceptable

conditions listed in Tables S-515-2.3.2 or S-515-2.3.3 where applicable.

Generally unacceptable conditions listed in these tables shall not be used.

Documentation shall be provided to demonstrate that material usages not

covered in the tables meet the intent of S-515-1.4 and S-515-3. 2. 3.

MECHANICAL SUPPORTING DEVICES

General

Mechanical supporting devices including support devices for roof, wall, or remote mounted collectors shall be designed and constructed of materials in

accordance with Section 500 of MPS.

Pipe and Duct Hangers

Pipe and duct hangers, used to support insulated pipes or ducts, shall be

designed to avoid damaging the insulation material.

Commentary : If pipe or duct hangers are installed over the insulation

material} metal surface plates should be used to avoid damaging the insulation.

5-22
S-515-5 VALVES

S-515-5.1 Applicable Standards

S-515-5.

2

Valves shall be shown to be in compliance with applicable standards. Valves

manufactured to other standards not listed but fulfilling the requirements of

a particular solar heating system design shall be evaluated in accordance with

Sections 513 and 613 procedures and shall be acceptable to the HUD field office

Commentary: Examples of standards that may he useful are given in Appendix

Table B-4. Standards for valves usually present pressure-temperature ratings.

Appendix Table B-5 presents these ratings as an example for ball valves

,

Federal Specification WW-V-35a-l975. National standards do not cover all

valves useful to solar heating system design. Valves not covered by standards

may be acceptable to HUB if a history of successful usage can be demonstrated

by the valve manufacturer or solar heating system designer.

Material Performance

Valve materials shall be compatible with the heat transfer liquid as re- quired in S-515-1.4 and S-515-3.2.

S-515-6 PUMPS AND FANS

S-515-6.1 Applicable Standards

a. Centrifugal, rotary and reciprocating pumps shall be in compliance with

the requirements of the Hydraulic Institute [1].

Ccrmentary : A Hydraulic Institute Standard defines the product, material, process or procedure with reference to one or more of the following : nomenclature

,

composition, construction, dimensions, tolerance, safety , operating characteristics, performance, quality, rating, testing and service for which designed [2]

b. Fans shall comply with the applicable standards of the AMCA or HVI and

shall be tested, rated and labeled accordingly.

S-515-6.

2

Material Performance

Pump materials shall be compatible with the heat transfer liquid as re- quired in S-515-1.4 and S-515-3.2.

[1] Hydraulic Institute, 1230 Keith Building, Cleveland, Ohio 44115

HYDRAULIC INSTITUTE STANDARDS FOR CENTRIFUGAL, ROTARY & RECIPROCATING PUMPS,

thirteenth edition, 1975. Library of Congress Card No. A56-4036

5-23
S-515-7 THERMAL STORAGE UNITS

Thermal storage units are defined as any container, space or device which

has the capacity to store thermal energy or transfer media (liquid or solid) containing thermal energy for later use.

S-515-7 .

1

General

Thermal storage units shall be of sufficiently durable material to fulfill

the heating storage requirements of the system for the intended design

life of the storage unit.

S-515-7.

2

Applicable Standards

Applicable standards for thermal storage materials are presented in Appendix

Table B-6. The thermal performance of storage units can be evaluated using

ASHRAE Standard 94-77.

S-515-7.

3

Labeling

Pressurized thermal storage containers shall be labeled in accordance with

515-1.2 of the MPS. In addition, labels shall list the maximum operating

pressure and temperature and minimum operating temperature.

S-515-7.

4

Materials Performance

S-515-7. 4.1 Contamination

Thermal storage tank materials, including any interior protective coatings

and the heat storage medium used, shall not impart toxicity, undesirable

tastes, or odors to either air or water intended for human consumption.

For liquid system, the requirements of the U. S. Public Health Service

Drinking Water Standards shall apply.

S-515-7. 4.

2

Materials Compatibility

a. Materials comprising the thermal storage system shall not cause corrosive wear and deterioration which results in premature failure

or degradation in storage performance greater than the design limits.

b. Metals used in the thermal storage system which are in direct contact

with heat transfer liquid shall be in accordance with the generally

acceptable conditions listed in Tables S-515-2.3.2 or S-515-2.3.3,

where applicable. Generally unacceptable conditions listed in these

tables shall not be used. Documentation shall be provided to demonstrate that material usages not covered in the tables meet the intent

of S-515-1 . 4 and S-515-7 . 4 . 2a.

5-24
S-515-8 HEAT TRANSFER FLUIDS

S-515-8.

1

S-515-8. 1.

S-515-8.

2

S-515-8. 2.

S-515-8. 2.

General

The heat transfer fluid shall be of sufficient stability to perform its

intended heat transfer functions for the intended life of the fluid. The

heat transfer fluid shall not cause premature failure or degradation in

performance exceeding the design limits as specified in Section S-615-1.1.2

for those parts of the solar energy system with which it comes into contact

Commentary : Appendix Table B-7 presents a partial listing of properties

of several types of heat transfer liquids.

1 Labeling

The provisions of the Federal Hazardous Substances Act (1971) shall apply

to heat transfer fluids. In addition, heat transfer media classified

as combustible shall be labeled as such.

Emergency first aid instructions shall be included on the label of toxic

heat transfer fluid containers. A technical data sheet shall be provided

with all heat transfer fluids which contains the following information:

Service temperature range

Viscosity over service temperature range

Freezing point

Boiling point

Flash point

Auto ignition temperature

Specific heat over service temperature range

Vapor pressure over service temperature range

Instructions for inspection, treatment and disposal of fluid

Emergency first aid instructions.

For toxic fluids, a list of the chemical components of the fluid shall be

available expressed in mg. /liter. This list shall include any substances

which comprise more than 0.10% of the medium.

Toxic and Combustible Fluids

1 General

Heat transfer fluids which require special handling (e.g., toxic, com- bustible, corrosive, explosive, etc.) shall not be used unless the systems

in which they are used are designed to avoid unnecessary or unreasonable

hazards; see Section S-615-10.1.

2 Flash poifit

Temperatures attained by fluids in solar systems under operating and no flow conditions shall not exceed a temperature which is 100°F below the

flash point of the fluid. In no case shall a liquid with a flash point

below 100°F or a flammable gas be used. Flash point shall be determined

by the methods described in NFPA No. 321, Basic Classification of Flammable

and Combustible Liquids.

5-25
S-515-8 . 2

.

S-515-8 .

3

S-515-8. 3.

S-515-8. 3.

S-515-8. 3.

Commentary: NFPA No. 321 (1973) defines Flammable Liquids as those with

flash points below 100-° F and Combustible Liquids as those with flash points

at or above 100°F. This section prohibits the use of flammable liquids

(flash point below 100°F) and permits the use of combustible liquids

(flash point at or above 100°F) under prescribed conditions. In common

,

non-technical usage, the term flammable liquid frequently refers to any

liquid with a flash point, including liquids classified as combustible.

3 Atmospheric Concentration of Toxic Materials

The concentration of the vapor of the heat transfer medium in the building's

interior atmospheric environment shall not exceed l/10th the threshold

limit value (TLV) for that particular medium in an 8-hour period.

Commentary: The TLV is primarily concerned with industrial exposures

.

Because routine household exposure could be for much longer time periods,

the 1/1 Oth value of the TLV is recommended. TLV's are under continuous

review; a list of currently adopted values is published by the American

Conference of Government Industrial Hygienists

.

Materials Performance

1 Changes in the Heat Transfer Fluid

Except when such changes are allowed by the design of the system, the

heat transfer fluid shall not freeze, give rise to excessive precipitation,

give rise to sludge, asphaltic or resinous deposits or coatings, otherwise

lose its homogeneity, boil, change pH or undergo changes in viscosity outside the design range when exposed to its intended service temperature and

pressure range and other intended operating conditions.

Commentary: Some organic fluids may degrade by oxidation in open systems

and thereby be unacceptable for use in such systems while providing

satisfactory service in closed systems.

2 Chemical Compatibility

Heat transfer fluids designed to be used in contact with component materials

shall not cause deterioration in the component which results in premature

failure or degradation in collector performance greater than the design

limits . Inhibitors in the concentration used shall be compatible with

all components in the system with which they come in contact.

Commentary: Guidance is given in Section S-515-2. 3. 2. 2 and S-515-2. 3. 3. 3.

3 Thermal Stability

The heat transfer fluid shall not degrade at temperatures up to the

maximum service temperature or cause deterioration of the system components

which results in premature failure or degradation in system performance

greater than the design limits .specified in Section S-615-1.1.2.

Commentary : This maximum temperature will generally be reached under

"no-flow" conditions. Appendix Table B-7 includes data for a number of

typical transfer liquids. Some fluids may decompose somewhat at elevated

temperatures . For example, ethylene glycol can degrade to form organic

acids. Buffers are usually included with such liquids to control the

pH. It may be desirable, if fluids decompose with time , to change the

fluids periodically.

5-26
S-515-9 HEAT EXCHANGERS

S-515-9.1 General

When nonpotable liquid is used in a solar energy system to transfer

heat to domestic (potable) hot water, the design of the heat exchanger

shall be such that either a minimum of two walls or interfaces are maintained between the non-potable liquid and the potable water supply or protection is provided in such a manner that equivalent safety is provided

Commentary: Double wall heat exchanger designs are one way of meeting

the intent of this criterion. When double wall heat exchanger designs

consisting of two single wall heat exchangers in combination with an intermediary potable heat transfer liquid are used, leakage through one of the walls would result in a single wall configuration. Although this

design is considered to meet the intent of this criterion, there are several other designs that avoid this problem.

The use of single wall configurations which solely rely upon potable

water pressure to prevent contamination is not considered to be an acceptable solution. Similarly, extra thick single walls are not

considered to meet the intent of this criterion.

For approval of other than double wall designs, the procedures described

in S-101 should be utilized.

Potable water as defined by the Public Health Service Drinking Water

Standards is considered suitable for systems with single wall exchangers

as long as its quality is maintained to the Public Health Service Drinking

Standards.

S-515-9.

2

Applicable Standards

Heat exchangers shall be in compliance with the applicable standards

given in S-515-9. 2.1 and S-515-9. 2. 2. Exchangers manufactured to other

standards not listed but fulfilling the requirements of a particular

solar heating system design may be acceptable.

S-515-9. 2.1 Tubular Heat Exchangers

Tubular heat exchangers shall be in compliance with the appropriate

requirements of TEMA.

S-515-9. 2.

2

Heating Coils

Forced circulation air-heating coils shall be in compliance with the

requirements of ARI Standard 410.

S-515-9.

3

Material Performance

Heat exchanger material shall be compatible with the heat transfer fluid

as required in S-515-1.4 and S-515-3.2.

5-27
S-515-10 GASKETS AND SEALANTS

S-515-10.1 Applicable Standards

Caulking and sealants shall be in accordance with 507-6 of the MPS, where

applicable. Gaskets which seal pressurized systems shall withstand the

maximum service pressure when tested in accordance with ASTM D 1081-60 (1974).

Commentary: Since gaskets and. sealants used in solar systems may not be

adequately covered by existing specifications. Appendix Table B-8 is

included to serve as a guide in selecting specific sealing materials.

S-515-10.

2

Materials Performance

S-515-10. 2.1 Thermal Stability

Gaskets and sealants included in the test described in S-515-2.1.2 shall

not exhibit cracking, loss of elasticity, outgassing, or loss of adhesion

sufficient to impair their function at the completion of the test.

Commentary: A potential problem with sealants and gaskets used in collectors

is that during no-flow conditions outgassing may occur with the outgassing

products being deposited on the interior surface of the cover plate. Such

deposits can reduce the transmittance of the cover plate.

S-515-10. 2.

2

Chemical and Physical Compatibility

a. Gaskets and sealants shall be chemically and physically compatible

with the substrates to which they are joined.

Commentary : Compatibility of gaskets and sealants with substrates may

be evaluated in the process of testing materials for compliance with

the Federal Specifications listed in Appendix Table B-8.

b. Documentation shall be provided to show that gaskets and sealants in

direct contact with the heat transfer fluid are not degraded by the

fluid. In lieu of other documentation, gaskets and sealants which

are in direct contact with heat transfer fluid shall not exhibit significant expansion, cracking, loss of elasticity or loss of adhesion

when immersed for 100 hours in the heat transfer fluid at the maximum

service temperature. ASTM D 471-75 or F 146-72 shall be used as a guide in performing these tests.

S-515-10. 2.

3

Ultraviolet Stability

Gaskets and sealants that are normally exposed to UV radiation in service

shall not be adversely affected by such radiation. Documentation shall be

provided demonstrating that such materials are capable of withstanding

exposure to sunlight for their design lives without functional impairment.

Commentary : Data obtained under ambient environmental exposure conditions

will be accepted if data obtained under in service conditions is unavailable.

Gaskets of ethylene propylene diene monomer (EPDM) rubber or silicone rubber

are examples of materials that may be appropriate for these applications.

5-28
S-515-11 INSULATION/THERMAL AND MOISTURE PROTECTION

S-515-11. 1 General

These requirements apply to both fixed and movable insulation installed

in conjunction with or as an integral part of the solar system. Materials

used for insulation shall be of sufficient proven effectiveness and durability under the expected operating conditions to assure that required

design conditions concerning heat losses, sound control and fire rating

are attained. Insulation in contact with the ground shall not be adversely

affected by soil, vermin or water. Insulating materials shall be in accordance with 507-3 of the MPS and S*-607-3. Insulating materials for air

ducts shall be in accordance with S-515-3.1. Materials used for waterproofing shall be in accordance with Section 507-1 of the MPS. Materials

used for vapor barriers shall be in accordance with Section 507-2 of the

MPS.

Commentary: When movable insulation is used in passive systems, design

considerations should be given to ensure protection of the insulation

from structural damage, degradation due to weather or other degrading

factors

.

S-515-11. 1.1 Flame Spread Classification

The flame spread classification index for all insulation materials shall

not exceed the following values:

Plastic Foam 25

Loose Fill Insulation 50

Other Insulation Material 150

The ASTM E84 flame spread test method shall be the basis for evaluating

the surface burning characteristics of the insulation materials. Where

fibrous blankets with facings are to be used, the surface burning characteristics of the complete faced insulation blanket shall be measured.

Commentary: Wo single test is sufficient to provide a full estimate of

performance of a product in a fire. Plastic foams and loose fill insulation are difficult to evaluate in ASTM E -84. The requirement of

Flame spread classification of 25 maximum for plastic foams and 50 for

loose fill insulation will provide as much safety assurance as is possible

with current test methods. Such a classification shall not be construed

as the equivalent of "noncombustible . " Many insulation materials, including those consisting of cellulose, plastic foam and fibrous glass

(containing organic binder) are combustible materials which will bum and

release heat, especially when exposed to continuous large fire sources.

S-515-11. 1.2 Flame Resistance Permanency

Chemical retardant insulations shall retain their flame resistance throughout their service lifetime. The procedures and equipment specified in

ASTM C739-73, Section 10.4, "Flame Resistance Permanency" shall be used

in judging the effect of aging on the permanence of any flame retardants

used during manufacture.

5-29
S-515-11.2 Materials Performance

S-515-11 .2.1 Collector Insulation

S-515-11.2. 1.1 Thermal Stability

Collector insulation shall not degrade at the maximum service temperature

to an extent which results in premature failure or degradation in collector

performance greater than the design limits specified in Section S-615-1.1.2

After testing as described in S-515-2.1.2, there shall be no swelling

or other dimensional changes in the collector insulation, outgassing or physical changes resulting in the decrease in thermal performance in excess of that permitted in the test.

Commentary: Organic materials found in insulation have been known to evolve from oolleotor insulation during system operation, leaving a ooating on the cover plates which impairs collector performance. Normally,

the insulation nearest the absorber plate is exposed to temperatures

higher than insulation near other parts of the collector. It may be

possible to use one type of insulation adjacent to the absorber plate and

another type in areas of the collector which will not be exposed to extreme temperatures . Fiberglass insulation with binders can be preheated to expel volatiles prior to use in collectors . If such pretreatment is used, the upper temperature limit becomes somewhat higher.

S-515-11. 2.

1

Pipe or Duct Insulation

Pipe or duct insulation shall be stable at the maximum temperature to which it will be exposed in service.

Commentary : General practice for the use and protection of pipe

insulation is described in the ASHRAF Handbook of Fundamentals.

S-515-11. 2.

3

Storage Subsystem Insulation

If insulation whose thermal properties are affected by water is used,

the insulation shall be protected in accordance with S-515-11. 1.

S-515-12 CATCH BASINS

S-515-12 .General

Catch basins shall be of adequate size and construction to fulfill their

intended functions and be constructed of materials in accordance with

Section 515-5 of MPS.

S-515-12.

Materials Performance

S-515-12. 2.1 Materials Compatibility

Catch basin materials which are jointed to or in contact with other

materials shall have sufficient chemical and physical compatibility

with those materials to prevent deterioration.

S-515-12. 2.

Coating

The catch basin coating, when used, shall not be significantly deteriorated

during its design life by weathering or by the transfer medium with

which it comes in contact.

5-30
S-515-13 ORGANIC COUPLING HOSES

S-515-13.1 Materials Performance

S-515-13. 1.1 Thermal StabilityOrganic coupling hoses included in the test described in S-515-2.1.2

shall not exhibit cracking, loss of elasticity, or embrittlement at the

completion of the test that will significantly impair their function.

Commentary : The selection of coupling hoses ccnd clamps is quite critical.

Many failures have been noted due to the clamping of hoses with screw or

spring-type clamps , exposing the hose to high temperatures which tend to vulcanize the area beneath the clamp, causing it to lose resiliency and

begin to leak. Further tightening of the clamps will temporarily stop

leakage but further vulcanizing will occur with the end result being a hard non-resilient ring under the clamp which can no longer be tightened

to prevent leakage. Silicone rubber hose is one of the few materials

which have been tested and tend to maintain their resiliency with no tendency to take a thermal set. The silicone rubber hoses, however,

tend to be so pliable that screw-type clamps with perforated bands should

not be used as it is possible to extrude the material through the perforations in the band. If this material is used, smooth band clamps

should be utilized.

S-515-13. 1.2 Ultraviolet Stability

Organic coupling hoses which are exposed in service to UV radiation shall

not be adversely affected by the radiation. In lieu of other documentation,

organic coupling hoses shall not exhibit significant cracking, loss of

elasticity or embrittlement after 500 hours exposure as described in

ASTM D750-68 (1974).

S-515-13. 1.3 Compatibility with Heat Transfer Fluid

Documentation shall be provided to demonstrate that organic coupling

hoses which are in direct contact with heat transfer fluids are not

significantly degraded by the fluids. In lieu of other documentation,

the hoses shall not exhibit cracking, loss of elasticity or embrittlement that will significantly impair their function when tested for 100

hours at the maximum service temperature according to ASTM D471-75 or F146-72

.

Commentary: SAE Standard J20e (1974) covers coolant system hoses for

automobiles . For solar systems using glycol liquids, this SAE Standard

may be applicable for demonstrating compliance with S-515-13. 1 . 3. It

is expected, however, that hoses in solar systems will be exposed to more strenuous conditions than automobile hoses.

S-515-13. 1.4 Compatibility with Piping Materials

Organic coupling hoses which are used to join piping shall be compatible

with the piping.

S-515-13. 1.5 Ozone Degradation

Documentation shall be provided to demonstrate that organic coupling

hoses which are exposed in service to the environment are not significantly

degraded by ozone in the air. In lieu of other documentation, the hoses

shall exhibit no cracking or loss of elasticity that will significantly

impair their function when tested for 100 hours to an ozone atmosphere

of 50+5 pphm/volume at 23°C according to ASTM D1149-64 (1970)

.

5-31

CHAPTER 6

CONSTRUCTION

TABLE OF CONTENTS

Page

S-600 GENERAL 6-3

S-600-1 Labeling 6-3

S-600-2 Alternate Construction 6-3

S-600-3 Installation, Operation and Maintenance Manual 6-3

S-600-4 Replacement Parts 6-4

S-600-5 Maintainability of Systems and Subsystems 6-4

S-600-6 Safety and Health Requirements 6-5

S-601 GENERAL STRUCTURAL REQUIREMENTS 6-7

S-601-1 General 6-7

S-601-2 Design Dead Loads 6-7

S-601-3 Design Live Loads 6-7

S-601-4 Wind Loads 6-8

S-601-5 Snow Loads 6-9

S-601-6 Seismic Loads 6-9

S -601-7 Hail Loads 6-11

.S-601-8 Dynamic Loads 6-14

S-601-9 Thermal Distortion 6-14

S-601-10 Collector Cover Plates 6-14

S-601-11 Connections of Collector Frames and/or Other Support Structures . . . 6-14

S-601-12 Storage Tanks 6-14

S-607 THERMAL AND MOISTURE PROTECTION 6-16

S-607-2 Waterproofing, Dampproofing and Vapor Barriers 6-16

S-607-3 Insulation 6-16

S-615 MECHANICAL 6_17

S-615-1 Thermal Design 6-17

S-615-2 Collectors | 6-20

6-1
Page

S-615-3 Mechanical Supporting Devices 6-24

S-615-4 Valves 6-24

S-615-5 Pumps and Fans 6-24

S-615-6 Mechanical Vibration Isolation 6-24

S-615-7 Thermal Storage . 6-25

S-615-8 Heat Transfer Fluids 6-28

S-615-9 Waste Disposal .... 6-28

S-615-10 Plumbing 6-29

S-615-11 Auxiliary Energy System 6-33

S-615-12 Heat Exchangers . 6-33

S-615-13 Air Distribution 6-33

S-615-14 Controls and Instrumentation 6-34

S-615-15 Chimneys and Vents 6-35

S-615-16 Mechanical Ventilation 6-35

6-2
CHAPTER 6

CONSTRUCTION

S-bOO GENERAL

The provisions of this chapter are applicable to solar domestic hot water

(DHW) systems. This chapter is intended to be used in conjunction with

the Minimum Property Standards (MPS) . Building construction provisions

(Chapter 6) of the MPS are applicable in addition to the items explicitly

discussed in this document.

S-600-1 LABELING

Solar domestic hot water (DHW) systems, subsystems, and components snail

be labeled or given clear indication ot their operating temperatures,

pressures, flow direction and filled weight as appropriate in accordance

with 515-1.2 of the MPS.

Commentary: Labeling requirements for specific material and products are given in Chapter 5 of this document.

S-600-2 ALTERNATE CONSTRUCTION

Alternate or special methods of construction other than those contained

herein, may be used when found acceptable by established HUD procedures

and Division 613 of MPS and Section S-101 of this ducument.

S-600-3 INSTALLATION, OPERATION AND MAINTENANCE MANUAL

Manuals shall be provided to describe the installation, operation and

maintenance of the DHW systems.

A complete manual as described in S-600-3.1, 3.2, and 3.3 shall be provided to the installer or maintenance contractor. A simplified owners manual shall be provided to the building occupant which shall include

as a minimum: system description including a schematic diagram; owner maintenance procedures; and a tabulation of appropriate pressure, temperature and flow information that is indicative of system performance.

The owners manual shall also include the names and addresses of manufacturers of all the primary components of the system.

Commentary : It is suggested that each manufacturer of a subsystem should

provide installation, operating and maintenance manuals for each subsystem

he provides, and that he show typical systems using his and other subsystems to complete the whole. The installer, who is responsible for the

complete installation and therefore for the complete system should assemble

all the manuals from the subsystem manufacturers into a complete manual

pertinent to the system. He should add any other information needed for

an understanding of the complete system and its functioning. Control

sequences are determined almost entirely in the field and should be described for the specific installation.

S-600-3.1 Installation Instructions

The manual shall include physical, functional and procedural instructions

describing how the subassemblies of the DHW systems are to be installed.

6-3
S-600-3 .

2

S-600-3.

3

S-600-4

S-600-5

S-600-5 .

1

S-600-5.

2

These instructions shall include descriptions of both system interconnections

and connections with the dwelling and site.

thintenance and Operation Instructions

The manual shall completely describe the DHW system, its breakdown into

subsystems, its relationship to external systems and elements, its performance

characteristics and its required parts and procedures for meeting specified

capabilities.

The manual shall list all parts of the systems, by subsystem, describing

as necessary for clear understanding of operation, maintenance, repair

and replacement, such characteristics as shapes, dimensions, materials,

weights, functions, and performance characteristics. The manual shall

include a tabulation of those specific performance requirements which are dependent upon specific maintenance procedures. The maintenance procedures

including ordinary, preventive and minor repairs, shall be cross-referenced

for all subsystems and organized into a maintenance cycle. The manual shall

fully describe operating procedures for all parts of the system including

those required for implementation of specified planned changes in mode of

operation. The instructions shall provide warning against hazards that could

arise in the maintenance of the system and shall fullv describe precautions

that shall be taken to avoid these hazards.

Maintenance Plan

The manual shall include a comprehensive plan for maintaining the specified

performance of the DHW system for its design service lives.

The plan shall include all the necessary ordinary maintenance, preventive

maintenance and minor repair work, and projections for equipment replacement, and shall include important pressure, temperature and flow information as checkpoints throughout the system to assist in troubleshooting.

REPLACEMENT PARTS

Parts, components, special tools and test equipment required for service,

repair or replacement shall be commercially available or available from

the system or subsystem manufacturer or supplier.

Commentary: This provision is intended to preclude long periods of system

down-time due to the need for the repair or replacement of parts.

MAINTAINABILITY OF SYSTEMS AND SUBSYSTEMS

Service Complexity

The DHW systems and subsystems shall be capable of being serviced with a minimum amount of special equipment by a trained service technician

using a maintenance manual and common tools.

Commentary: On larger collector installations it may be desirable to make

PROVISIONS FOR SUPPLYING ELECTRICAL POWER AND WATER FOR MAINTENANCE PURPOSES,

Access for System Maintenance

All individual items of equipment and components of the DHW systems

which may require periodic examination, adjusting, servicing and/or maintenance shall be accessible for inspection, service, repair, removal or replacement without dismantling of any adjoining major piece of equipment

or subsystem.

6-4
S-600-6

S-600-6.1

S-600-6.

2

S-600-6.

3

S-600-6.

4

S-600-6.

5

S-600-6.

6

Commentary : It is recommended that individual collectors in an array he

replaceable or repairable without disturbing non-adjacent collectors in

the array.

Accessibility as a function of component life is an important consideration.

Some manufactured collector systems and many individually designed systems

are done in such a way that sequential installation is necessary . This can make it very difficult to replace an individual collector without disturbing

the entire array.

SAFETY AND HEALTH REQUIREMENTS

General

The incorporation of solar systems into the living unit shall not create

an environment which is more hazardous to the occupants than that of a conventional living unit. Materials and the construction used in installation of solar systems shall be in accordance with the fire protection

provisions of S-405.

Combustible Liquids

The storage, piping and handling of combustible liquids shall be in

accordance with the Flammable and Combustible liquids code NFPA No. 30.

Protection From Heated Components

Components of solar systems which are accessible, located in areas normally

subjected to occupant traffic and which are maintained at elevated temperatures shall either be insulated to maintain their surface temperatures at

or below 140°F at all times during their operation or suitably isolated.

Any other exposed accessible components that are maintained at temperatures above 140°F shall be identified with appropriate warnings.

System Component Clearances

Combustible solids adjacent to solar equipment or an integral part of a solar component shall not be exposed to elevated temperatures which may

cause ignition.

Commentary: Heating of cellulosic materials as well as other combustible

materials over an extended period of time may result in the material reaching and surpassing its autoignition temperature. The most commonly accepted

ignition temperature of wood is 392°F. However, studies have indicated

that wood may ignite when exposed to a temperature of 21 2°F for prolonged

periods of time. The ignition temperature of plastics may be above or below those of cellulosic materials. Clearances for HVAC equipment, ducting and piping are discussed in NFPA No. 89M. Where applicable, clearances

specified by a nationally recognized testing laboratory may be used.

Protection Against Over-Pressure and Over-Temperature

The total system shall be protected against excessive pressures and temperatures. Pressures shall be limited as specified in S-615-14.

Personal Safety

Where access for service of cleaning of solar subsystems requires a person

to balance on a narrpw or (steeply) sloping surface, provisions shall be

made for securing a life-line, guard-rail or other personal protective

device.

6-5
S-600-6 .

Growth of Fungi, Mold or Mildew

S-600-6.

S-600-6.

Components and materials used in the DHW system shall not promote the

growth of fungi, mold or mildew in accordance with applicable codes,

the test specification of Section 10, UL 181-74 and MPS, Appendix D,

Section E.

Cormentary : Special consideration should be given to the presence of

fungi in air handling systems since such micro-organisms are frequently

allergenic.

Protection Against Vermin or Rodents

Solar energy systems (including piping, fixtures, appliances and other

equipment) shall not contribute to the entry or growth of vermin of

rodents. Maintenance of physical barriers, minimization of concealed

spaces conducive to harboring vermin or rodents, provisions of access for

cleaning shall be in accordance with applicable codes such as Section 2.13

of the National Standard Plumbing Code .

Protection of Potable Water Supply

The design and installation of the solar system its subsystems and components shall be accomplished in such a manner as to provide complete protection of the potable water supply. Such installations shall be in

accordance with Chapter 10 of the National Standard Plumbing Code and

other applicable codes (see Section S-615-10)

6-6
DIVISION 1

S-601 GENERAL STRUCTURAL REQUIREMENTS

S-601-1 GENERAL

This section contains those supplemental requirements to Chapter 6 of the MPS

needed to cover solar systems which utilize conventional structural materials

(materials covered by the current MPS edition). Unless specifically

modified herein, the requirements of MPS Chapter 6, apply in addition to the supplemental requirements in this section.

All structural design for solar systems and their mounting structures shall

be based on generally accepted engineering practice. All loading shall be

in accordance with ANSI A58.1 except as shown otherwise in this document

or MPS.

S-601-2 DESIGN DEAD LOADS

In calculating the dead loads for solar systems, the weights of the transfer

liquid in the collector, liquid in storage tank, and liquid in other subsystems and components shall be included, except when using dead load to resist uplift or overturning.

Commentary: Liquids are normally present in systems in which they are the

heat transfer medium and thus are a long term sustained toad where creep

is a consideration. They a iso effect seismic forces in a fashion simitar

to any other dead load. However, it is possible to remove liquid, thus

they should no be counted on to resist uplift.

S-601-3 DESIGN LIVE LOADS

S-601-3.

1

Roof Mounted Solar Systems

Resistance to design live roof loads prescribed in Table 6-1.2 of MPS 4900.1

(Table 6-1.3 of MPS 4910.1 and 4920.1) shall not be required for collector

panels that are mounted on roofs but do not form an integral part of the

roof if adequate access is provided for service and maintenance personnel.

For collectors which form an integral part of the roof, resistance to the

design live roof loads listed in Table 6-1.2 shall be required.

Commentary: The design live loads contained in Table 6-1.2 of MPS 4900.1

constitute minimum loading requirements needed primarily for human safety.

The roof will need to be repaired from time to time; therefore , it must

support the workman making the repairs, regardless of the wind and snow

loading requirements. This is not the case for accessible roof-mounted

collectors; they do not need to support workmen when being repaired. Hence,

they need only to sustain the required environmental loading (wind, snow

and hail).

S-601-3.

2

Maintenance Loads

All components of the solar energy systems which must support maintenance

personnel shall resist a single concentrated load of 250 lbs. distributed

over a 4 sq. in. area, acting on the installed component in the most critical locations. Special allowance shall also be made for heavy maintenance

equipment, if used.

6-7
S-601-4

S-b01-4.

S-601.4.1.

S-601-4. 1.

S-601-4. 1.

S-601-4. 1.

S-601-4.

S-601-4.

S-601-4.

S-601-4.

WIND LOADS

Flat Plate Collectors Mounted on Roofs and Walls

Wind loads on flat plate solar collectors shall be those specified for

roofs and walls in Section 601-6 of the MPS or as modified in paragraphs

S-b01-4.1.1, .2, .3, and .4 below.

1 Flat plate collectors that are mounted with their cover plates and back

surfaces flush with the surface of the roof shall resist the wind loads

that would have been imposed on those areas of the roof covered by the

collectors.

2 Flat plate collectors mounted at an angle or parallel to the surface of

the roof on open racks shall resist any uplift load caused by the impingement of wind on the underside of the collector. This wind load is in

addition to the equivalent roof area wind pressure and suction loads, and

shall be determined by utilizing accepted engineering procedures which

may include wind tunnel testing. Equivalent roof area wind loads are those wind loads that would have been applied to the areas of the roof

occupied by the collectors. Equivalent roof area wind loads shall be

applied to the outer cover plate of the collectors.

3 In calculating design wind loads for flat plate collectors mounted on roofs,

the internal pressure coefficients, C listed in Table 11, ANSI A58.1

shall be taken as zero for the wind pressure within a collector. Collectors

that form an integral part of the roof structure shall resist the internal

pressures from the inside of the building just as any other roof member.

4 Wind loads on flat plate collectors mounted at an angle to a vertical wall

shall be the same as those required for equivalent roof eave area as stipulated in section 6. 5. 3. 2. 4 of ANSI A58.1. Wind loads on flat plate

collectors mounted parallel to, or integral with vertical walls shall be

the same as those required for exterior walls.

Other Types of Solar Collectors Mounted on Roofs and Walls

Wind loading on other types of solar collectors shall be determined using

the results of accepted engineering procedures including the MPS and ANSI

A58.1 or physical simulation which may include wind tunnel testing.

Roof Wind Loads

Roof loading due to wind effects on flat plate collector and concentrating

collector support structures and/or enclosures must be included not only

in the design of the roof support framing, but also in the design of all

structural elements influenced by these loads.

Ground Mounted Collectors

Wind loading on ground-mounted flat plate collectors and their support

structures shall be determined in the same manner as that for roof-mounted

flat plate collectors. Where flat plate collectors are mounted on open

racks, equivalent roof area wind loads shall be those given for nonenclosed structures as given in section b.6, ANSI A58.1, taking into

account local terrain characteristics.

Exposed Storage Tanks

Wind loads on exposed storage tanks shall be determined in accordance with

ANSI A58.1.

6-8
S-601-5

S-601-5.1

S-601-5. 1.

S-601-5.1.

S-601-5.1.

S-601-5.

2

S-601-5.

3

S-601-6

S-601-6 .

1

S-601-6.

2

SNOW LOADS

Flat Plate Solar Collectors Mounted on Roofs and Walls

Snow loads acting on flat plate solar collectors or caused by their installation shall be those required for roofs as specified in Section 601-5 of MPS

or as modified in paragraphs S-601-5. 1.1, .2, and .3 below.

1 Flat plate collectors that are mounted with their cover plates and back

surfaces parallel to the surface of a roof, and those that are mounted at

an angle to the surface of a roof, on open or closed racks in a saw-tooth

arrangement shall support the snow loads that would otherwise have been

imposed on areas of the roof covered by the collectors. Where collectors

are mounted with their cover plates forming steep slopes, shedding of snow from the collector may cause snow to accumulate at the base of the collector

or other hazardous conditions which shall be considered in the design of

the roof.

2 Flat plate collectors mounted at an angle to the surface of a wall, and

supported by the wall, shall be designed to support the same snow loads

as an equivalent roof eave area.

3 Consideration shall be given to the potential local accumulation of snow under fiat plate collectors.

Roof Loading

A single or multiple saw-tooth array of collectors may cause severe drifting between each mounted collectors (and under open racks) in addition to the snow load on the cover plates. These unusual snow loads must be determined on the basis of local snow conditions.

Other Types of Solar Collectors

Snow loads on other types of solar collectors shall be determined as specified in the applicable portions of ANSI A58.1 and by accepted

engineering procedures.

SEISMIC LOADS

General

Seismic design requirements for the mechanical and electrical components

of solar energy systems are covered in this section. Architectural and

structural components shall be designed in accord with MPS Sec. 601-9.

The requirements of this section shall apply to the erection, installation,

relocation, or replacement of, or addition to, any mechanical or electrical

component of, a solar system. If elements of the solar energy system are attached to any existing structural element, or if parts of any existing

structural element are modified or replaced with parts different in size

and weight, the element, as well as its connections to the building shall

be re-designed to comply with the seismic design requirements of Section

601-9 of MPS.

Mechanical and Electrical Components

For those buildings required to be designed for earthquake by section 601-9

of the MPS, mechanical and electrical components of solar energy systems

shall resist seismic forces as specified for parts and portions of buildings

in the latest edition of the Uniform Building Code (UBC) [1]. The value of

Cp used in the UBC to establish the seismic force shall be taken from table

S-601-6.

fl] The Uniform Building Code is published by the International Conference

of Building Officials, Whittier, California.
The design of all connections between the mechanical or electrical com- ponents and the structural frame shall allow for anticipated movements of

the structure. The details of the connections shall be made a part of the

contract documents.

Commentary : Mechanical or electrical components of a solar system are subjected to seismic forces generated by their mass and may also be influenced by interaction with elements of the structural system.

TABLE S- 601-6

Part of System Direction of

Force

Value of C -

p y

Storage tanks, pressure vessels

boilers , furnaces , absorption

air conditioners, other equipment

using combustible or high temperature energy sources, electrical

motors and motor control devieeb,

heat exchangers

any

direction

0.12 when resting on ground

0.20 when connected to, or housed, elsewhere

in the building.

Flat plate and concentrating

solar collectors

any

direction

0.20

Tranfer liquid pipes larger

than 2 l/2 in. in diameter

any horizontal

direction 0.12

— For flexible and flexibly mounted equipment and machinery, appropriate values of C shall be determined by a properly documented dynamic analysis, or by dynamic testing,

using appropriate excitation spectra approved by HUD. Consideration shall be given

to both the dynamic properties of the equipment and machinery and to the building or structure in which it is placed.

2/ When located in the upper portion of any building where the H^^/D ratio is 5:1 or

GREATER THE CP VALUE SHALL BE INCREASED BY 50%

Where Hm = height in ft, of the part of the system above the base level of

N THE BUILDING

D = The dimension of the structure in feet in a direction parallel to

THE APPLIED FORCE

6-10
S-601-7 HAIL LOADS

The cover plates, lenses, and reflector surfaces of solar collectors shall

be protected against or resist the perpendicular impact of a single hailstone of the magnitude stipulated below falling at its terminal velocity.

Hail size: D= 0.3d

in which D = hail stone diameter, inches

d = mean annual number of days with hail taken from Figure

S-601-7 [1].

Terminal velocities for various hail sizes are given in Table S-601-7. [2].

Compliance with this provision shall be based on documented past hail loading performance or testing using the procedures described in NBS Building

Science Series BSS 23 [3] or analytical procedures acceptable to HUD.

Commentary: The correlation of hail size with mean annual number of days

with hail was determined using data relating the probability of occurrence of hail particle size to the number of days with hail (tabulated in

Ref. [4], and limited statistical information relating the local area covered by a hailstorm} and the regional area for which statistical data

is compiled. The hail size indicated has a 5% probability of being ex- ceeded in any one year (estimated 20 year recurrence interval) . The hail

requirements in this section are based on available information which does

not contain physical test data. Therefore, local hailstone loading performance should be considered in implementing the requirements of this

section.

The impact from the vertical terminal velocity is used as a measure of the

effect of hail falling with or without horizontal wind. It is possible

that a larger impact could occur on surfaces sloped from 30 0 to 00° if the

maximum particle diameter occurred simultaneously with a high horizontal

wind velocity perpendicular to the surface. It may be overly conservative

for particles over 1.5 " impacting on near vertical surfaces. However, due

to the lack of information on this phenomenon and the low probability of

its occurrence, it is assumed that the terminal velocity gives the best measure of -impact force consistent with the present state of the art.

The loadings specified in this section to determine collector performance

closely parallel those that conventional asphalt shingles and built up

roofing are expected to withstand for all but the mid-continent hail belt.

[1] Baldwin, J. L., Climates of the United States , U.S. Dept, of Commerce,

Washington, D.C. (1973).

[2] Mathey, R. C., Hail Resistance Tests of Aluminum Skin Honeycomb Panels

for the Relocatable Lewis Building, Phase II , NBS Report 10193,

National Bureau of Standards, Washington, D.C. (1970).

[3] Greenfield, H. , Hail Resistance of Roofing Products , Building Science

Series 23, National Bureau of Standards, Washington, D.C. (August 1969).

[4] Storm Data , U.S. Dept, of Commerce, National Oceanic and Atmosphere

Administration, Environmental Data Service (monthly periodical).

6-11
6-12

from:

Baldwin,

J.

L.,

Climates

of

the

United

States

,

U.S.

Department

of

Commerce,

Washington,

D.C.,

1973.
TABLE S-601-7

Values of weight and terminal velocity in free fall computed for smooth ice spheres.

Diameter Weight Terminal

in gm lb Velocity

ft/sec

1/2 0.98 0.002 51

3/4 3.30 0.007 62

1 7.85 0.017 73

1 1/4 15.33 0.034 82

1 1/2 26.50 0.058 90

1 3/4 42.08 0.093 97

2 62.81 0.138 105

2 1/4 89.43 0.197 111

2 1/2 122.67 0.270 117

2 3/4 163.28 0.360 124

3 211.98 0.467 130

from: Mathey, R. C., Hail Resistance Tests of Aluminum Skin Honeycomb Panels for the

Relocatable Lewis Building, Phase II , NBS Report 10193, National Bureau of

Standards, Washington, D.C., 1970.

6-13
S-601-8 DYNAMIC LOADS

Dynamic Loads resulting from sun tracking solar collectors or other moving

equipment shall be taken into account in the design of the dwelling frame.

S-601-9 THERMAL DISTORTION

Thermal distortion of the mechanical or structural components of the solar

system shall not cause premature failure or degradation in system performance

greater than the design limits.

Thermal distortion of the solar system, including that occurring during

periods of stagnation, shall not cause damage to the system or the supporting

dwelling structure.

Commentary: Expansion coefficient data for cover and absorber plate materials

is listed in Appendix Tables B-l and B-3.

S-601-10 COLLECTOR COVER PLATES

Deflection or local distress of cover plates resulting from the maximum design

loading shall not allow the cover plate to become separated from the unit nor

result in degradation in collector performance greater than the design limits.

This shall be demonstrated by analysis or physical simulation.

Commentary: Since wind can come from any direction, there will be maximum

pressure ( inward) loading for units mounted on the windward side of an installation and maximum suction (outward) loading for those mounted on the

leeward side (unless shielding is provided) . Depending on the installation,

suction loading can, and often does, exceed pressure loading; hence, cover plate retainers must be adequately designed to prevent them from being

separated from the collector frame or induce failure of the cover plate by

suction loading.

S-601-11 CONNECTIONS OF COLLECTOR FRAMES AND/OR OTHER SUPPORT STRUCTURES

When collector frames and/or other support structures are mounted on walls,

roofs, or other weather resistant surfaces, distortion of the frame from

imposed loading shall not cause penetrations or separations of these surfaces such that moisture leaks occur through the weather resistant surfaces.

S-601-12 STORAGE TANKS

S-601-12 .

Design and Fabrication

Storage tanks shall be designed and fabricated to standards embodying

principles recognized as good engineering design and fabrication practice

for the materials used. These standards shall include those listed in

appendices C and E of the MPS and others as approved by HUD.

Tanks containing soil or rock like materials shall be designed for lateral

pressures in accordance with accepted principles of soil mechanics.

S-601-12.Testing

Each liquid storage tank shall be tested in accordance with section S-615-10.10

to prove that leakage does not occur. Storage tanks designed to contain

only dry heat storage material need not be leak tested unless a safety hazard

can result from a storage tank failure.

S-601-12.

Environmental and Vehicular Loading

In addition to meeting the design, fabrication and test requirements, stipulated in the preceeding paragraphs of this section, storage tanks shall

meet the following loading requirements.

6-14
S-601-12 .3.1 Above Ground

Unsheltered storage tanks shall resist loads resulting from snow, wind, hail,

thermal, and seismic loading. Sheltered (completely enclosed) tanks need

only resist seismic loading.

S-601-12. 3. 2 Underground

Underground tanks shall resist soil and hydrostatic loads and foundation

loads transmitted to them; and they shall be anchored to prevent flotation

resulting from flooding or high ground water level when the tanks are empty.

For sites subject to commercial traffic or heavy truck traffic, storage tanks

shall resist the wheel loads transmitted to them as specified in AASHTO H20-44,

with no impact. For areas subject to other vehicular or human traffic, the

pertinent loads stipulated in section 601-4.3 of MPS 4910.1 or 4920.1 shall

be resisted.

Commentary: The criterion specifies the level of vehicular traffic for

which burned components should be designed in cases where heavy vehicular

traffic is anticipated to occur in service for purposes of access. The

H20-44 truck is considered to be representative of load levels associated

with heavy vehicles such as trucks for repair} maintenance, moving, and

delivery of fuel.

6-15
DIVISION 7

S-607

S-607-2

S-607-2.

1

S-607-3

S-607-3.

1

THERMAL AND MOISTURE PROTECTION

WATERPROOFING, DAMPPROOFING AND VAPOR BARRIERS

Waterproofing of Exterior Storage Tanks, Pipes and Ducts

Underground thermal storage tanks, pipes and ducts, and unsheltered above

ground thermal storage tanks, pipes and ducts shall be waterproofed to stop water seepage into the iomponents and insulation. See Section 607-2

of MPS and 1972 ASHRAE Handbook of Fundamentals Chapter 17.

INSULATION

Areas of Application

Materials used for thermal insulation shall be in accordance with

S-515-11 and may be applied to the following areas: walls, roofs,

ceilings, floors, pipes, ducts, vessels and equipment exposed to the

external environment.

Exposed plastic foam (untreated or fire-retardant treated) , Kraftasphaltic vapor barrier on mineral and organic fiber insulations, and

non-fire-retardant treated loose fill insulation shall not be permitted

in habitable areas unless fully protected from the interior of the

building by a thermal barrier of 1/2 inch gypsum wallboard having a finish

rating of not less than 15 minutes or other approved material having an equivalent finish rating as determined by ASTM E-119. Thermal barriers

shall be installed in a manner guch that they will remain in place for a minimum of 15 minutes under the same test conditions.

Installed insulation and vapor barriers shall not make contact with re- cessed light fixtures, motors, fans, blowers, heaters, flues, and chimneys.

Thermal insulation shall not be installed within 24 inches of the top or within 3 inches of the side of a recessed electrical fixture enclosure,

wiring compartment or ballast unless labeled for the purpose. To retain

loose fill insulation from making contact with other energy-dissipating

objects, a minimum of 2 inches of air space should be provided and assured

by the use of blocking.

Commentary: Although a degree of material combustibility is allowed, the

intent is to allow insulating materials which are not more combustible

(or flammable) than earisting construction and insulation materials, and

to preclude any increased fire hazard due to the retention of heat from

energy dissipating objects. In areas where occupants are likely to be

engaged in normal activities, the insulation should perform its intended

function without the increased risk of ignition, rapid flame spread, and

heat and smoke generation. Insulation in concealed spaces may be a particuiar fire problem due to its susceptibility to smoldering and its

inaccessibility for fire fighting.

All solar system piping, ducts, heat exchangers, and storage tanks containing

heated fluids should be insulated to the following minimum insulation values:

Thermal Storage Tanks R-ll

Pipes 1" and less in diameter R-4

Ducts, Pipes over 1" and less than 4"

in diameter, and Heat Exchangers

R-6

For maximum efficiency, the complete domestic hot

insulated to the above values.

water system should be

6-16
DIVISION 15

S-615 MECHANICAL

S-615-1 THERMAL DESIGN

S-615-1.

1

General

The solar energy system shall be capable of collecting and converting solar

energy into thermal energy. Solar thermal energy shall be used, in combination

with a conventional auxiliary energy source and other components such as thermal

storage to meet the standards and requirements for domestic hot water set forth

in Section 615 of the MPS. The system shall be capable of dissipating thermal

energy where this function is included in the design.

Commentary: The prediction of system performance should reflect the cumulative

degradation in components resulting from environmental or system wear and

deterioration. The residential domestic hot water load is generally considered

constant throughout the year for purposes of system design.

S-615-1.

2

Back-up

The thermal energy contribution provided by solar energy shall be backed up 100 percent with an auxiliary thermal energy subsystem which will provide the same degree of reliability and performance as a conventional system.

Commentary : The uncertainty in the availability of solar energy during inclement weather requires complete hack-up of the solar energy contribution to meet

hot water requirements.

S-615-1.

4

System Capacity - Domestic Hot Water Heating

S-615-1. 4.1 Auxiliary Energy Subsystem

The auxiliary energy domestic hot water heating subsystem shall meet the minimum

requirements for storage, draw and recovery shown in Tables S-615-7.1 or S-615-7 . 2.

Commentary: There are benefits if the back-up method is designed to minimize

the use of a utility supplied, on-line, auxiliary energy service during peak

load conditions. The minimum acceptable hot water storage is listed in the

MPS but generally solar energy DEW systems have a larger storage capacity than

the MPS requirements

.

Attention to energy conservation measures for auxiliary energy subsystems

utilizing fossil fuels is particularly beneficial with solar DEW systems as combustion inefficiencies and stack losses can extract large penalties in

overall energy consumption. Recent studies [7] of gas-fired storage heaters

have identified potential 35% reduction in fuel consumption by the addition

of insulation, changed thermostat set point, baffling, forced draft, flue

dampers, and electric ignition.

S-615-1. 4.

2

Solar Energy System

a. Determination of the average annual energy requirements for solar hot water

heating applications shall be based on average monthly conditions as the

maximum analytical simulation time interval to compare solar energy system

performance with the load.

[1] A. D. Little, Inc., "Study of Energy Saving Options for Refrigerators and Water

Heaters, Volume 2: Water Heaters," FEA Contract CO-04-50228-00, May 1977

6-17
S-615-1.

7

S-615-1.8

S-615-1.

9

b. Minimum daily usage of hot water shall be as indicated in Table S-615.1.

Commentary: The design shall allow for the higher requirement where the

\potential increase in use exists.

c. Minimum hot water supply temperature shall be 140°F except for Housing for

the Elderly and Care Type Housing. For Housing for the Elderly and Care

Type Housing, temperatures are specified in Section 615-6.1 of MPS 4910.1

and 4920.1 respectively. An average source water temperature of 55°F shall

be used for design purposes if local temperatures are unknown.

Commentary : A residential DHW design temperature of 140°F is required by

the MPS and is necessary to meet some appliance operating temperatures

.

Energy cut-off devices which deflect the solar heated liquid from entering

storage prevent the storage tank and hence the delivery piping from

exceeding the required, temperature. Storage may be allowed to go to higher

temperatures if means are provided to blend, cold water with the delivery

stream to achieve the required temperature.

Local source water temperature can vary from 45 to 75°F with climate,

region, and season. For guidance, a table of source water temperatures

is presented in Appendix A, Table A-l.

d. The solar energy contribution shall be determined as a percentage of the

dwelling average annual DHW energy requirements . Analytical simulations

or correlations based upon simulations which include the effect of load,

solar system performance and climatic conditions shall be utilized to predict the average monthly and annual energy contribution to be provided by

solar energy and auxiliary energy.

Commentary: One acceptable method of predicting performance is presented

in Appendix A. Parametric studies have shown that a solar energy contribution of between 50 and 80% of the DHW load is generally optimum when cost

benefits hare been considered.

Protection Against Blockage of Fluid Flow

The entire heat transport system shall be protected to prevent contamination

by foreign substances that could impair the flow and quality of the heat

transfer fluid beyond acceptable limits.

Commentary: The heat transfer fluid passages in solar collectors and some heat exchangers may have small cross sections in which blockage by dirt,

scale, pieces of gasket material, pieces of packing or other foreign matter

in the heat transfer fluid could occur.

S-Y-S.imSHiIlUiSIfi

The shutdown of the solar heating or domestic hot water system in one unit

OF A MULTI-FAMILY DWELLING SHALL NOT INTERFERE WITH THE FUNCTION OF THESE

SYSTEMS IN ANY OTHER UNIT.

COWENTARY: THIS IS TO PERMIT THE SHUTDOWN OF EQUIPMENT IN AN INDIVIDUAL

DWELLING UNIT FOR REPAIRS WITHOUT IMPAIRING THE OPERATION OF THE EQUIPMENT

IN OTHER DWELLING UNITS THAT ARE CONNECTED TO THE SAME CENTRAL SYSTEM.

Excess Collected Energy

Provisions for dumping excess thermal energy shall be provided when required

for safe operation of the system.

Commentary : For systems in which it is not practical to shut the collection

system down, the excess energy can be transfered to the external environment

using a heat exchanger or alternate methods.

6-18
Table S-615-1 Daily Hot Water Usage (140°F) for Solar System Design

Category One

and

and Two Family Units U

Apartments up to 70 Units

Apts, of U

20-200 Units

Apts, of 2J

over 200 Units

No. of People 2 3 4 5 6 — —

No. of Bedrooms 1 2 3 4 5 — —

Hot Water/Unit

(gal/day)

40 55 70 85 100 40 35

1/ Assumes 20 gal. per person for first 2 people and 15 gal. per person for additional

family members*

2/ From: R. G. Werden and L. G. Spielvogel: "Part II Sizing of Servic Water Heating

Equipment in Commercial and Institutional Buildings," ASHRAE Transactions, Vol. 75,

PII, 1969 p. iv.1.1.

6-19
S-615-2 COLLECTORS

S-615-2. 1 General Provisions

S-615-2. 1.1 Design Flow Rates

When an array of solar collectors is connected by manifolds, the design

shall assure, or provision shall be incorporated in the manifolds and/or

collectors to balance the flow rate through each collector. The variation

shall not exceed + 20% of the design flow range.

Commentary : An available method of balancing air and liquid EVAC equipment

is described in the National Standards for Field Measurement and Instrumentation: Total System Balance , Vol. 2, No. 12173 (Associated Air

Balance Council 2146 Sunset Blvd. , Los Angelesy California 90026). The

method describes procedures and measurements, but does not establish

standard balance values.

S-615-2. 1.2 Tilt and Orientation

The collector shall be installed in a mount capable of maintaining tilt

and azimuth to within + 10° of design conditions.

Commentary: A fixed collector tilt angle equal to the latitude for domestic

hot water applications is typically used. This angle will tend to maximize

the year-round performance of domestic hot water heaters. However, deviations

of ± 10° from this value, when using conventional flat plate collectors

facing south, will have little effect. Size or performance corrections should

be made for deviations greater than +_ 10 ° , see Appendix A.

Conventional flat plate collector azimuth should be such that the effective

aperature generally faces south. However, deviations to the east or west by

up to 20° may not result in a significant decrease in incident radiation.

Weather conditions such as morning or evening fog may influence the deviation

from south. Size or performance corrections should be made for deviations

greater than +_ 20° , see Appendix A.

If the optimum orientation will seriously interfere with building design

requirements, or will impose extensive additional structural provisions

,

tradeoffs for less optimum orientation or relocation of the collector where

the optimum orientation can be utilized should be considered.

The orientation of concentrating type collectors is a function of the collector acceptance angle design and may require tracking within specific limits.

S-615-2. 1.3 Shading

Shading of collectors shall be considered during the design so that shading

by trees, adjacent collectors or other obstructions is accounted for.

Commentary: On east and west exposures during the entire year, and on south exposures during the winter, the solar altitude may be low enough

to cause direct shading and a resultant loss in collection capability

.

A practical design goal is to limit the reduction in collected useful

thermal energy during the month of peak load to less than 5%.
S-615-2.1.4 Dirt Retention

The cover plate(s) shall not collect or retain dirt to an extent that would

significantly reduce its ability to transmit sunlight.

Commentary : The possible collection and retention of dirt by the cover plate

and the effect of retained dirt on collector performance may be significant.

The retention of dirt may depend on the surface characteristics and tilt angle

of the collector. Rainfall and snow melt are generally sufficient to keep

the collector cover plates clean. If periodic scrubbing is necessary for

cleaning, the cover plates should be resistant to damage by abrasion re- sulting from the scrubbing. If the collector is ventilated, provisions should

be made for exclusion of dust by appropriate filters.

S-615-2.1.5 Cleaning

In designs where the interior surfaces of collector glazing and cover plates or absorber surfaces are not protected against accumulation of

dust or dirt, provisions shall be made to allow cleaning of these surfaces

as frequently as necessary to prevent a significant deterioration of collector performance.

Commentary: On active collectors that are not hermetically sealed or provided with air filters and in passive installations which may have

large air plenums behind glazed surfaces or combine solar collection with

view provisions, accessability for periodic cleaning is essential to con- tinued high solar transmittance. Selective absorber surfaces must be

kept clean as dust accumulations can change their emittance characteristics

.

S-615-2.1.6 Ice Dams and Snow Build Up

The design of solar buildings and systems shall prevent the formation of ice

dams and snow build up.

Cormentary: In very cold climates, water flowing off a warm collector

may freeze on cold surfaces immediately below it (such as exposed eaves),

thereby forming an ice dam which can cause water to back up under roofing

or into the collector itself. This may be moderated by methods such as elimination of the cold surface or provision of an impervious surface such

as continuous flashing. Snow sliding off a collector may pile up at the

bottom and cover part of the collector. This would have a tendency to reduce the efficiency of the collector and increase the possibility of

thermal breakage of glass in the collector. This may be moderated by

methods such as the provision of space below the collector for snow pile

up or by the installation of heating cables.

S-615-2.1.7 Mud Splash

The design of solar buildings and systems shall minimize the possibility

of mud splash on collector surfaces.

Cormentary: Water running off collectors located close to the ground can

cause mud splashing to coat portions of the collector and reduce its efficiency. Remedies to this include: easy access for cleaning, position of

collectors elevated sufficiently to avoid splashing, or provisions of

gutters or splash free material at the base of the collector.

S-615-2.1.8 Protection Against Thermal Shock and Pressure

Collectors shall not be damaged or adversely affected by extreme temperature

and pressure that could occur by thermal shock resulting from sudden environmental or fluid flow changes during operation.

6-21
Commentary: Thermal shook could result from the passage of hot fluid through

a cold oolleotor or oold fluid through a hot oolleotor during start-up. The

designer should either assure that the materials used in the oolleotor oan withstand the extreme temperatures and pressures or provide temperature and

pressure relief from thermal cycling or shook. See Section S-615-14.1.3.

S-615-2 . 1.

9

Moisture Build-up Control

Means shall be provided to prevent moisture build-up in collectors to an extent that would reduce collector performance below allowable design limits.

Commentary: Moisture build-up in the oolleotor oan soak insulation and reduce its effectiveness, leaoh alkalies out of fiberglass insulation and hasten

its degradation, lead to chemical attack on absorber plates and cause con- densation on cover plates.

Depending on the design, the likelihood of condensate forming on the interior

surface Is) of the cover plate (s) may be high. Desiccants in breather tubes or breather plugs can be used to maintain a dry environment. The desiccants

should be located in such a way that they are not in contact with the collector plate and it is desirable that they be capable of regeneration by

solar energy as the collector builds temperature.

One additional potential problem with collectors is that, in industrial

atmospheres, the introduction of pollutants in condensate solution may cause permanent etching of the underside of the cover plate (s)or chemical attack

of the absorber over a period of time. Such etching can permanently reduce

the transmittance. When this possible condition exists, design considerations

must be given to avoid the problem.

S-615-2.1.10 Access to Components

If routine maintenance or repair of collector components is anticipated,

the collector shall be designed to permit easy access to those components.

Commentary: Some materials such as rubber hoses, joint sealants, exterior

coatings, etc. may have to be replaced periodically. Also, in some geographic locations, the cover plates may have to be cleaned occasionally.

If materials in the collector are likely to be replaced, repaired or maintained within the design life of the collector, it is important to provide

easy access to those materials.

S-615-2. 1.11 Openings

All openings in the collector enclosure shall be protected to prevent the

entry of insects and vermin.

S-615-2.

2

Collector Thermal Performance

S-615-2. 2.1 General

This section is intended to cover component and integral collectors which

can be flat plate, concentrating, reflector aided, fixed or tracking types.

S-615-2. 2.

2

Collector: Component

This type collector can be characterized as a component for an active solar

system requiring the use of powered mechanical equipment to move the heat

transfer fluid (liquid or gas) through the collector. The collector thermal

performance shall be based upon the slope- intercept method of expressing

efficiency for the range of operating conditions including solar power density,

heat transfer fluid temperature, ambient temperature, wind, solar radiation

incident angle, and flow rates to be used in the design.

6-22
Commentary: The collector performance characteristics can he measured using

the ASERAE te8t method 93-77 [2] for rating solar collectors or any other

method demonstrated to have an overall limit- of-error of less than +5%. This

method provides sufficient efficiency versus operating condition data to con- struct a curve normalized for insolation and temperature difference between

ambient and heat transfer fluid temperature. Curves for typical flat black

and selective coated absorber panels with one and two covers are shown in

Appendix A for air and water collectors . Collectors with other geometric,

optical or thermal characteristics may require additional tests to fully

describe their thermal performance for all environmental and operating conditions. The operating electrical power is recorded and reported during all tests.

S-615-2.2.3 Collector: Combined With Storage

This type of combined component system can be characterized as an active

system with integral construction and operation of the components such

that the solar radiation collection and storage phenomena cannot be measured separately in terms of flow rate and temperature changes. The

system thermal performance is determined by the short term (1 to 3 days)

collection and storage of thermal energy obtained from solar radiation and

the amount of useful energy delivered to the load from storage for part

and full load conditions. Experimental performance data, in terms of heat

collected and stored or delivered to load, shall be provided for the design

conditions including insolation, heat transfer fluid temperature,

ambient temperature, wind, solar radiation incident angle, and flow, rates. The daily and average test period electrical operating requirements are reported with system performance.

Commentary: Although a consensus test method to rate and evaluate these

systems does not exist, the efficiency in terms of converting incident

solar energy into useful thermal energy can be measured and reported as

a function of the specified operating conditions.

S-615-2.2.5 Passive: Component (.Thermo syphon) Systems

This type collector can be characterized as one in which the collector is a separate component to collect, convert and transfer the thermal energy.

The thermal performance of individual collector panels can be obtained

from procedures described in Section S-615-2.2.2 active collectors. System

performance is obtained from measurements of incident solar energy and hot

water delivered to the load for extended periods to determine monthly averages.

Commentary: A tnermosyphon water heating system is an example of the application of a passive component type collector where tne hot water circulation

results from the cnange in density of the fluid with temperature

.

The movement of a heat transfer fluid by natural convection is achieved by

relatively low pressure differentials. Pipe sizing for minimum pressure

drop is essential. It is necessary that pipe or duct size, shape, distance,

and elevations be considered in predicting the performance based upon

individual collector panel test data. Design considerations and equipment

performance data is available [2].

[1] ASHRAE Standard 93-77, "Methods of Testing Solar Collectors Based on Thermal Performance," American Society of Heating, Refrigerating and

Air-Conditioning Engineers, 345 East 47th Street, New York, N.Y. 10017.

[2] Baughn, J. W. and Dougherty, D. A., "Experimental Investigation and

Computer Modeling of Solar Natural Circulation System," Proceedings of

the 1977 American Section of ISES Annual Meeting, Orlando, Florida.

6-23
S-615-3 MECHANICAL SUPPORTING DEVICES

S-615-3.1 Pipe Hangers and Supports

Pipe hangers and supports shall be installed in accordance with the prevailing model plumbing code having jurisdiction in the area.

S-615-4 VALVES

Gate valves or similar valves that open to nearly full pipe bore shall be

used for shut off valves. Globe ball or similar valves shall be used for

flow control.

S-615-5 PUMPS & FANS

S-615-5.1 Applicable Standards

a. Pumps shall be installed in accordance with the requirements of the

Hydraulic Institute . [1]

b. Fans shall be installed in accordance with the recommendations of the

ASHRAE Guide or applicable manuals of NESCA and SMACNA.

c. All moving machinery shall be protected and guarded to comply with the

current safety standards of ANSI B15.1 if such machinery is exposed to other than maintenance personnel.

S-615-6 MECHANICAL VIBRATION ISOLATION

S-615-6.1 General Requirements

All operating mechanical equipment shall be isolated by suitable piping

or duct connections and where necessary by isolation pads or foundations

to prevent transmission of noise or vibration. The dwelling shall be

free of objectionable sound as required in HUD circular 1390.2, Noise

Abatement and Control.

Equipment conforming to other sound level criteria referenced in these

standards shall also be acceptable.

I5J Hydraulic Institute Standards for Centrifugal , Rotary and Reciprocating

Pumps , Thirteenth Edition, 1975. The Hydraulic Institute, 1230 Keith

Building, Cleveland, Ohio 44115.

6-24
S-615-7

S-615-7.1

THERMAL STORAGE

General

This section applies to sensible heat type thermal energy storage devices

using gas or liquid as the heat transfer fluid and liquid as the heat storage

medium. The storage medium can be contained in a separate enclosure, stored

at more than one temperature, or can be a part of the building structure.

Commentary: Some typical storage subsystem arrangements are shown in Appendix

A. The interaction between storage temperature and collector operating

efficiency must be considered in the design and operation of the thermal

storage unit. Designs which enhance storage temperature stratification, control the storage fluid mixing, and which use utility supplied, on-line energy

during non-peak load conditions are desirable.

/

S-615-7. 2 Applicable Standards

Thermal storage shall comply with the design standards of MPS Section 615

and the applicable recognized standards given in MPS Appendix E.

S-615-7. 3 Thermal Storage Requirements

S-615-7. 3. 2 Domestic Hot Water Heating

The solar thermal energy storage for preheating domestic hot water shall

have a volume capacity not less than the number of gallons, storage capacity

shown in Tables S-615-7.1 or S-615-7. 2.

, Commentary : It is possible to operate a hot water storage container with

large temperature gradients permitting the auxiliary energy source to be

incorporated in the same container, or the auxiliary energy can be supplied

after the water has been removed from the solar heated container. It should

be noted that developing effective stratification in a tank reduces its total

heat storage capacity as compared to an unstratified condition. Actual

system draw rates should be checked against this reduced capacity. Several

1 and 2 tank system configurations are described in Appendix A.

S-615-7. 3.4 Thermal Energy Loss

The thermal energy loss from storage containers located outside the heated

dwelling shall not exceed 10% of the maximum operating thermal energy capacity

over an average 24 hour winter design day.

Commentary: Calculations of the thermal loss from tanks, piping, and valves can be performed using average fluid and ambient temperatures and thermal

insulation conductivity valves with procedures described in the ASHRAE

Handbook of Fundamentals. Section S- 607- 3.1 contains guidance on insulation

valves.

S-615-7.4 Tank Drainage

Each tank shall be provided with means of emptying the liquid. Each tank

located above grade or floor level shall be provided with a valved pipe at

its lowest point to permit emptying the tanx. Each buried tank shall have

provisions for utilizing a pump or siphon or other means to allow emptying.

6-25
S-615-7 .

5

Tank Filling

Tanks of large capacity should have an indicator or other means for determining that the tank is full. Tanks should have overflows with outlets located

so that spillage will not run into the building structure or damage the

premises. Tanks that do not contain potable water but require make up water

from the potable water system shall be filled by way of an air gap or other means acceptable to the administrative authority having jurisdiction.

S-615-7. 6 Inlet and Outlet Location

The inlet and outlet piping or ducts for thermal storage shall be located

in the container to prevent thermal "short circuiting" of the fluid flow.

Commentary: The collector performance is a function of the fluid temperature,

therefore, the storage- to-collector fluid outlet should be located in the

coldest portion of the container such as the lower 5% of a vertical liquid

tank. The inlet should be located in the warmest portion of the storage

volume but in the case of electric auxiliary below the heating element. Inlets

and outlets of liquid containers should be installed to provide flow parallel

to the top and bottom of the tank, respectively, to minimize mixing.

S-615-7. 7 Auxiliary Energy Input

Auxiliary energy heating elements or the inlet of heat transferred from auxiliary energy sources to the inside of storage devices shall be located in the

warmest practical area of the container.

Cormentary: In designs where it is possible to add auxiliary energy to storage,

the configuration should be designed to maintain the collector inlet temperature

as low as possible. In single tank systems very inefficient collector operation

will result if auxiliary heat is introduced at the bottom of the tank. Any

possible stratification in the tank will be destroyed and hot water will be

circulated to the collector resulting in inefficient operation. On retrofit

installations, it may be necessary to disconnect the lower electric heating

element.

S-615-7. 9 Protection Against Maximum Temperature, Pressure and Vacuum

Thermal storage shall be protected against maximum temperature, pressure and vacuum in accordance with the provisions of S-615-74.1.

Commentary: During extended periods with no draw, solar DHW systems can supply

thermal energy to such an extent that dangerously high temperatures may be

reached in storage tanks. To avoid this, thermostatically controlled valves or other methods may be used to prevent undesired collector heat from entering

storage. Such provisions may require collectors to be stagnation tolerant or provide heat dumping capability in the collector circulation loop. In any

case, maximum tank temperature should be limited to 180°F.

6-26
Table S-615-7.1 Direct Fired Water Heater Capacities. \J

PVXZ OAT i elect: " OIL SELECT." OlL (HE EiacT

.

OIL CAS ELECT."' UIL

lumber of Bedrooms i 5 —3 —

Storage (gal)

1 to Input (Btuh 1-1/2 or kv) Bath* Draw ( gph

)

Recovery

(gph)

2027K

43

23

202.5

30

10

3070K

89

! 59

3036k

60

30

303.5

44

14

3070K

89

59

3036k

60

30

404.5

58

18

3070K

89

59

- —

Ifuaber of Bedrooms 2 3 4 5 Storage (gal)

Draw (gph)

Recovery

(gpW)

30

36 k

60

30

40

4.5

58

18

30

70K

89

59

40

56K

70

30

50

5.5

72

22

30

70K

89

59

40

38k

72

32

50

5.5

72

22

30

70K

89

59

50

47K

90

40

66

5.5

88

22

30

70K

89

59

lumber of Bedrooms 3 4 '3 '6

Storage ( gal

)

40 50 30 50 66 30 50 66 30 50 80 40

3 to Input (Btuh 3-1/2 or kv) 38k 5.5 70K 38k 5.5 70K 47K 5.5 70K 50K 5.5 70K

®*ths Draw (gph) 72 72 89 82 88 89 90 88 89 92 102 99 Recovery

! gpFT"*' | 32 22 59 32 22 59 40 22 59 42 22 59

Kote: Storage capacity, input and the recovery requirements indicated in the Table are typical and may vary with each Individual manufacturer. Any combination of these requirements to produce the

1 hour draw stated will be satisfactory. Recovery is based on 100 P water temperature riae.

Example: Por a 3-b«droom, 2 bath residence there are three choices as follows: A 40 gal storage/30 gph recovery gas heater: a 50 gal storage/22 gph reoovery electric heater; or a 30 gal storage/59 gph recovery oil heater; or an equivalent combination which will produce at least a 70 gph total draw.

Table S-615-7.2 Indirect Fired Water Heater Capacities. 2/

NUMBER OF BATHROOMS 1 to 1-1/2 2 to 2-1/2 3 to 3-1/2 NUMBER OF BEDRR0MS 2 3 4 3 4 5 3 4 5 6 TANK TYPE INDIRECT BOILER-CONNECTED WATER HEATER CAPACITIES

(180 F BOILER WATER - INTERNAL OR EXTERNAL

CONNECTION)

I-W-H rated gal in 3 hr

100 F degree rise

40 40 66 66 66 66 66 66 66 66

Manufacturer rated gal. in 3 hr 100 F deg rise

49 49 75 75 75 75 75 75 75 75 1

1 - I Tank capacity in gals. 66 66 66 66 66 82 66 82 82 82

TANKLESS TYPE INDIRECT BOILER- CONNECTED WATER HEATER CAPACITIES

(200 F BOILER WATER - INTERNAL OR EXTERNAL

CONNECTION)

I-W-H rated gpm. 100 F deg rise

2.75 2.75 3.25 3.25 3.25 3.75 3.25 3.75 3.75 3.75

1 Manufacturer rated, draw

in 5 min. 100 F deg rise

15 15 25 25 25 35 25 35 35 35

Note: Heater capacities and inputs are minimum allowable. Variations in tank size are permitted when

recovery is based on 4 gph/kw @ 100 F rise for electrical, AGA recovery ratings for gas heaters,

and IBR ratings for steam and hot water heaters.

1/ From HUD MPS (4900.1 and 4910.1) Table 6-15.2.

2/ From HUD MPS (4900.1 and 4910.1) Table 6-15.3.

6-27
S-615-8

S-615-8 .

1

S-615-8.

1

S-615-8.

S-615-8.

S-615-9

S-615-9.

S-615-9.

2

HEAT TRANSFER FLUIDS

Toxic and/or Combustible Fluids

. 1 General

Requirements for handling non-potable heat transfer fluids are discussed

in Sections S-615-9, Waste Disposal; S-615-10, Plumbing; and S-615-12,

Heat Exchangers, of this document.

.2 Detection of Toxic and/or Combustible Fluids

If toxic or combustible heat transfer fluids are used, means shall be provided

for the recognition of leaks and thus the warning of occupants when leaks occur.

Commentary: These substances may be treated in a manner similar to antifreeze

and gases when providing for tell-tale indicators. For instance, antifreeze

agents, such as ethylene glycol, may be treated with non-toxic dyes which distinguish them clearly. Furthermore, if any such materials are to be stored

on the premises, they should be stored in containers which are labeled in

accordance with the Federal Hazardous Substances Act andbe protected from easy

opening by children e.g., childproof lids. Safe storage locations should be

provided.

.3 Identification

Drains and other designated fluid discharge or fill points in solar systems

at which toxic, combustible, high temperature or high pressure fluids may

be discharged shall be labeled with a warning describing the identification

and hazardous properties of the fluid, instructions concerning the safe

handling of the fluid, and emergency first aid procedures.

Commentary: The original fluid containers will frequently be discarded after

the system is charged which could result in no record of the fluid's properties being retained. The system drain is the point at which the owner or

service personnel are most likely to contact the heat transfer fluid and

permanent labeling should be retained at that point. Identification may be

provided by attaching a tag containing the required information such as may

be supplied, by the heat transfer fluid manufacturer.

WASTE DISPOSAL

Catchment

Systems utilizing other than air or potable water as a heat transfer fluid

shall provide for the catchment and/or harmless removal of these fluids

from vents, drains or re-charge points as approved by local administrative

code authority. Potable water shall be discharged to suitable drainage

systems connected to the building or site drains. See MPS Section 615-9.

Provision of Containment for Discharge Treatment of Toxic and/or Combustible

Fluids

Adequately sized and protected receptacles shall be provided when toxic and/or

combustible fluids are used in order to collect and store the overflow from:

pressure relief valves, liquids drained from the system when it is being serviced, and identifiable leakage. Provisions of MPS Section 615-4.4 (Section

615-4.5 in MPS 4920.1) shall be applied.

Commentary: When a toxic heat transfer fluid is used (see Section S-515-8 . 2)

,

a catch basin must be provided. It must be sufficiently large to accept dilution as required by MPS Section 615-9 before disposal.

6-28
If the diluted medium is biodegradable through conventional sewage treatment, the diluted medium is to be flushed into the sanitary sewer system

(not the storm sewer system). Consideration should be given to the effect

of flushing solar systems on the "Basic Design Loading" for sewage treatment, Section CS 603, HUD Handbook 4940. 3, Minimum Design Standards for

Community Sewage Systems .

S-615-10 PLUMBING

S-615-10 . 1 Handling of Nonpotable Substances

Potable water supply shall be protected against contamination in accordance

with the prevailing model plumbing code having jurisdiction in the area, in

addition to the recruitments which follow.

S-615-10. 1.1 Separation of Circulation Loops

Circulation loops of subsystems utilizing non-potable heat transfer fluids

shall either be separated from the potable water system in such a manner that

a minimum of two walls or interfaces is maintained between the non-potable

liquid and the potable water supply or otherwise protected in such a manner

that equivalent safety is provided.

Commentary : Double wall heat exchanger designs are one way of meeting the

intent of this criterion. When double wall heat exchanger designs consisting

of two single wall heat exchangers in combination with an intermediary potable

heat transfer liquid are used, leakage through one of the walls would result

in a single wall configuration. \ Although this design is considered to meet

-dshe intent of this criterion, there are several other designs which avoid

this problem.

The use of single wall configurations which solely rely upon potable water

pressure to prevent contamination is not considered to be an acceptable

solution. Similarly, extra thick single walls are not considered to meet

the intent of this criterion

For approval of other than double wall designs, the procedures described

in S-101 should be utilized.

S-615-10. 1.2 Identification of Nonpotable and Potable Water

In buildings where dual fluid systems, one potable water and the other

non-potable fluid, are installed each system may be identified either by

color marking or metal tags as required in ANSI A13. 1-1956 [1] or other

appropriate method as may be approved by the local administrative code

authority. Such identification may not be required in all cases.

S-615-10. 1.3 Backflow Prevention

Backflow of nonpotable heat transfer fluids into the potable water system

shall be prevented in a manner approved by the local administrative code

authority

.

Commentary: The use of air gaps and/or mechanical backflow preventers

are two possible solutions to this problem. The following are some recognized

standards that may be acceptable to the local administrative code authority:

Complete titles are given in Appendix E.

[1] Scheme for the Identification of Piping Systems, ANSI A13.1 - 1956.

6-29
Air gaps

Backflow preventers

- ANSI-All 2. 1 .

2

- FCCCHR Chapter 10

IAPMO PS 31-74

AWWA C506-69

A.S.S.E. 1011

A.S.S.E. 1012

A.S.S.E. 1013

A.S.S.E. 1015

A.S.S.E. 1020

ANSI-All 2. 1.1

S-615-10.2 Pipe Sizing

Pipe sizing shall be in accordance with recognized methods.

S-615-10 3 | ExP ans i°n and Contraction

t

j Provisions for expansion and contraction without undue strain or distortion

shall be made as required by means of offset branches, expansion compensators,

or flexible pipes. Piping shall be adequately supported to prevent undue

strain on the flexible pipes and branches.

S- 615- 10 . 4 Protection Against Maximum Temperature, Pressure and Vacuum

Systems shall be protected against maximum temperature, pressure and vacuum

in accordance with the provisions of S-615-14.1.

S-615-10. 5 System Drainage

Liquid systems shall be designed so that complete isolation and drainage

of all system components, piping, or storage tanks can take place in a reasonable length of time for maintenance purposes. See S-615-7.4, Tank

Drainage.

S-615-10. 6 Protection from Scalding

S-615-10.

S-615-10.

7

7.1

All domestic hot water systems shall be equipped with means for limiting

temperature of the hot water for personal use at fixtures to 140°F.

Commentary: For further discussion, see Section S-615-1.4.2c.

Provision of Valves and Fittings

Shutoffs

All domestic water heaters and water heating systems shall be va-lved to provide shutoff from the cold water supply systems.

S-615-10. 7. 2 Water Hammer Arresters

When a liquid is used as the transfer fluid in a solar energy system and

quick-closing

v

alves are employed in the design, the piping system shall be

able to control or withstand potential "water hammer". Water hammer

arresters shall be in compliance with local codes.

S-615-10. 7. 3 Air Bleeds

When liquid heat transfer fluids are used in solar heating systems, the

systems shall be provided with suitable means for air removal.

6-30
S-615-10.8 System Cleaning

After completion of piping tests and after all equipment has been installed,

the entire liquid systems shall be thoroughly flushed to remove sediment,

dirt and loose scale, etc. Strainers shall be cleaned or replaced. During

the flushing of the system, the collectors must be disconnected or bypassed

to preclude passage of debris through the collectors.

S-615-10.9 Expansion Tanks

Adequate provisions for the thermal expansion of solar heat transfer and

storage liquids that would occur over the service temperature range shall

be incorporated into the solar heating system design.

Expansion tanks shall be sized in accordance with the recommendations of

1976 ASHRAE Systems Handbook.

S-615-10.10 Leak Testing

S-615-10.10.1 Pressurized Tanks and Systems

Those portions of heating systems which contain liquid heat transfer fluids

and are not directly connected to the potable water supply shall not leak

when pressures of not less than 1-1/2 times their design pressure are imposed for a minimum of 15 minutes [1], The pressure shall be gradually

applied and sustained for a sufficient length of time to permit examination

of all pipe joints for leakage. Those portions of the system using

domestic hot water shall not leak when tested in accordance with the code

having jurisdiction in the area where the system is used. In areas having

no building code, a nationally recognized model code shall be used [1].

S-615-10.10. 2 Non-Pressurized Tanks

Non-pressurized tanks shall be tested visually for leaks by filling tanks

with water.

Commentary: A hydrostatic test pressure of i -i/2 times design pressure

is considered a standard test pressure . for pressurized system [2], For

most applications, clear water is used. The temperature of the water

should be no lower than that of the ambient atmosphere. Otherwise, sweating will result and proper examination will be difficult. In environments

where freezing may occur, antifreeze or hydrocarbons may be added to keep

the water from freezing. Bleeder valves or petcocks should be provided

at the highest point or points in the system to permit venting of all air

in the piping during the filling operation [2], Automatic vents must be

protected from freezing.

S-615-10.11 Discharge of Liquids

Relief valves shall be piped to discharge to locations acceptable to the

local administrative code authority having jurisdiction.

S-615-10 . 12 Location of Exposed Piping

Piping and equipment shall be located so as not to interfere with normal

operation of windows, doors, or other exit openings and so as to prevent

damage to piping, equipment, or injury to persons.

[1] The BOCA Basic Plumbing Code, Southern Standard Plumbing Code, The

Uniform Plumbing Code, and The National Plumbing Code.

[2] Piping Handbook, Remo C. King and Sabin Crocker, McGraw-Hill Book

Company, 5th Edition.

6-31
S-615-10.13 Underground Piping

Underground water service piping shall be installed in accordance with

the provisions of Section 615-5.3 of MPS. Underground heat distribution

piping shall be installed in accordance with Section 615-5.3 (k) of MPS.

S-615-10.14 Treatment of Water

When make-up water is of such a quality that excessive corrosion or scaling is known to exist, a suitable water treatment system as recommended

by the Water Quality Foundation shall be provided.

Commentary: The use of small water passages in collectors and heat ex- changers makes them susceptible to plugging and any size water passage

may be subject to reduction in heat transfer from the precipitation of

salts or corrosion products.

S-615-10.15 Freeze Protection

For systems subject to freezing of the heat transfer fluid, freeze protection by draining, circulation of an anti-freeze agent or other means

shall be provided.

Commentary: Some methods of freeze protection (i.e . , the circulation of heat

transfer fluid from storage) are generally considered to be effective only

when used in locations with moderate climatic conditions where freezing is an infrequent occurrence. Consideration should be given to the probability of

power failure occurrence when selecting a freeze protection method that is

dependent on electrical power for its operation. The use of heat tapes for

freeze protection is not recommended because of their fire hazard potential.

S-615-10.15.1 Draindown Freeze Protection

In draindown systems, if drainage of heat transfer fluid to the thermal

storage tank is intended, the storage tank shall be sized adequately to accommodate it. See S-615-7.3.1 and S-615-10.2. System designs incorporating automatic drainage of heat transfer fluid to storage to prevent

freezing of the fluid in solar collectors shall not be constructed of

materials which corrode in the presence of air or shall be suitably protected .

Commentary : One means of preventing corrosion during system drainage would

be by introducing an inert gas such as nitrogen.

S-615-10.15. 2 Draindown Venting

In draindown systems, provisions for venting of collector panels and manifold

lines shall be provided as required to allow refill of the collector system

without air entrapment.

Commentary: Operation and maintenance of draindown venting must be com- patible with venting for normal operations . Draindown venting may employ

either venting to the atmosphere or pressurized methods with valves and

holding tanks which automatically accomplish the refilling and venting.

6-32
S-615-11 AUXILIARY ENERGY SYSTEMS

S-615-11.1 Applicable Standards

S-615-11. 1.1

|

Domestic hot water systems shall comply with the design standards of MPS

Section 615 and the applicable recognized standards given in MPS

Appendix E.

S-615-11.

2

System Interconnection

The interconnections of the auxiliary energy system to the solar energy system

shall be made in a manner which will not result in excessive temperature or pressure in the auxiliary system or in bypassing of safety devices of the

auxiliary system.

S-615-12 HEAT EXCHANGERS

S-615-12.1 Sizing

a. A heat exchanger when used in conjunction with the solar collector and

storage shall be evaluated for its effectiveness in transferring heat from

the collector to storage. The heat exchanger effectiveness is expressed by:

e c “ < Ac

p >c

(t

o ‘ t i )/(Ac

p

) min (t

o ~

where

C . = (me ) . = the minimum fluid capacitance rate of collector (C ) or min p mxn t . c storage (C s ) C = (me ) = fluid capacitance rate in the flow circuit between storage

^ S and the collector heat exchanger

C

c = (me ) = fluid capacitance rate in the flow circuit between collector

^ C and the collector heat exchanger

t = storage temperature (°F)

t = collector outlet temperature (°F)

t^ = collector inlet temperature (°F)

e = effectiveness of the collector - storage heat exchanger m = flow rate of the working fluid (lb/h)

Cp = fluid specific heat (Btu/lb’°F)

Commentary : Diagrams of typical locations and a discussion of heat exchangers

are presented in Appendix A. Calculation methods for heat exchangers performance are described in the 1972 ASHRAE Handbook of Fundamentals. A minimum effectiveness value of 0.7 is a typical value that is used.

S-615-12.

2

Protection Against Maximum Temperature, Pressure and Vacuum

Heat exchanger shall be protected against maximum temperature, pressure and vacuum in accordance with the provisions of S-615-14.1.

S-615-13 AIR DISTRIBUTION

S-615-13.

1

1

Applicable Standards

Design of all solar domestic hot water systems using air collectors shall be

in accordance with applicable recommendations of the 1976 ASHRAE Systems

Handbook and manuals of NESCA and ARI. Installation shall comply with NFPA

Standards 90B, 31, and 54.

Commentary: Duct work should be designed for the shortest practical run and elbows should be kept to a minimum. Constrictions should be avoided.

S-615-13.

2

Dust and Dirt Prevention

Duct and fan systems shall be protected against accumulation of deposits

of dust or dirt that could reduce flow and efficiency. Air filters are required on the outlet side of rockbed storage in active systems.

6-33
S-615-14 CONTROLS AND INSTRUMENTATION

S-615-14. 1 Fail-Safe Controls

The control subsystem shall be designed so that in the event of a power

failure, or a failure of any of the components in the subsystem, the temperatures and/or pressures developed in the DHW system will not be damaging

to any of the components of the systems and the building or present a danger

to the occupants. The safety devices shall meet the requirements of Section

515-6.4 of MPS and be demonstrated to be adequately safe and protected for

the intended application.

S-615-14. 1.1 Automatic Pressure Relief Devices

Adequately sized and responsive pressure relief devices shall be provided

in those parts of the energy transport subsystem containing pressurized

fluids. A pressure release device shall be provided in each portion of

the system where excessive pressures can develop. Each section of the system

shall have a pressure relief device so that no section can be valved off or otherwise isolated from a relief device. Automatic pressure relief devices

shall be set to open at not more than the maximum pressure for which the subsystem is designed.

Relief devices shall drain to locations in accordance with Section S-M'5^9.1.

Commentary : Care should he taken in the design and layout of the fluid

transport system to prevent conditions in which locally excessive pressures

are developed as a result of flow restrictions. Precautions must be taken

to assure that heat transfer liquids do not discharge on asphalt base roofing materials or other types of roofing or locations which may be hazardous3 cause structural damage s building finish discoloration, or damage to plant

materials .

S-615-14. 1.2 Vacuum Relief

The solar energy system, including collectors, pipes, tanks, and heat

exchangers shall be protected against possible collapse by design or by

provision of vacuum relief valves.

Commentary: System components may be subjected to collapse if heating

system leakage were to occur or if the system were drained without venting.

S-615-14. 1.3 Collector Thermal Shock

Automatic flow control valves shall be provided for collectors unable to withstand temperature shock.

S-615-14. 2 Identification and Location of Controls

Main shutoff valves and switches shall be conspicuously marked and placed

in a readily accessible location, in the same manner as electrical ser- vice panels, in accordance with Section 240.24 of NFPA 70, and MPS, Section

616.

S-615-14. 3 Indirect Water Heaters

Indirect domestic water heater installations shall include operating

controls for the heat source, of the type recommended by the boiler

manufacturer. The installation shall be made in accordance with the

boiler manufacturer’s instructions.

6-34
S-615-14.4 Efficient Operation (Active Systems)

Automatic control of the heat transfer fluid circulation between the

collector and storage or load shall be used to limit operations to con- ditions when useful energy can be collected. Designs utilizing collector

flow as a fail-safe method shall employ override controls as required.

Commentary: The collector circulation in liquid systems is normally

limited to conditions when the absorber plate temperature is greater

than the storage or load temperature by a At of 10°F for start-up and

a At of 3°F for shut-down. A larger At may be used for air systems

depending upon the circulating fan electrical power requirements

.

Sensors should be located to accurately and reliably measure the heat

transfer fluid properties used in the control process. The collector

temperature sensor used to initiate operation of the circulator is

normally located in the upper portion of the collector to insure that

it senses heated fluid. The storage sensor is normally located below

the heating element in resistance heated auxiliary single tank systems

and in the lower portion of the preheat tank for two tank systems.

Sensors should either be intrusion type or mechanically mounted to the

surface for intimate thermal contact and resistance to corrosion,

vibration or environmental effects. Lead wire insulation should provide abrasion and environmental protection.

S-615-15 CHIMNEYS AND VENTS

S-615-15.1 Termination Height of Chimneys and Vents

Termination height of chimneys and vents shall be in accordance with

NFPA 211.

Commentary : The presence of solar equipment may introduce building com- ponents that are elevated above the roof surface, thus producing wind

disturbance at a higher level. The standards of NFPA 211 will provide for

proper clearance and separation.

S-615-16 MECHANICAL VENTILATION

S-615-16.

1

Air Discharge Openings

Air discharge openings through roofs or exterior walls shall not be

located such that their exhaust will cause the deposition of grease, lint,

condensation or other deleterious materials on solar optical components.

6-35

APPENDIX A

METHOD FOR PREDICTING THE THERMAL PERFORMANCE

OF DOMESTIC HOT WATER HEATERS

Applicable to the HUD/States Solar

Domestic Hot Water Initiative Program

Table of Contents

1. Summary of Operation and Design of Solar Water Heaters

1. Introduction

2. System Descriptions

3. System Design Factors Affecting Thermal Performance

2. Prediction Method

1. Summa ry of the Prediction Method

2. Basis of the Prediction Method

3. Procedure

1. Selection of Reference Collector Area, A £

2. Adjustments for Collector Characteristics and/or

Heat Exchanger Modifiers

3. Adjustments for Orientation

4. Adjustments for Storage Heat Capacity

5. Adjustments for Cold Water Makeup Temperature

6. Example Problem

3. Supplementary Information

1. Modified Collector Performance Characteristics, F'(xot), F'UL

K K

2. Heat Exchanger Effectiveness, e

riA

4. References

5. Nomenclature .

Page

A2

AA3

A- 12

A- 16

A- 16

A-17

A- 18

A-18

A-19

A-21

A-21

A-21

A-22

A- 34

A- 34

A- 39

A-48

A-49

A-l
1 . SUMMARY OF OPERATION AND DESIGN OF SOLAR WATER HEATERS

1.1 INTRODUCTION

The comparison of solar water heating with other applications of solar energy, such

as space heating, illustrates major design differences. The influence of changes in

ambient temperature on the demand for hot water is considerably less than in the case of space heating and cooling. As ambient temperatures change, the requirements

for heating and cooling in a dwelling undergo large variations, thereby requiring

installation of large collector and storage facilities with a sizable auxiliary

energy supply. Hot water demand, however, is not greatly affected by weather changes.

Moreover, the comparatively low operating temperature of a solar collector for

domestic hot water heating results in a significantly smaller heat loss than from

a collector used for air-conditioning, where overall temperature difference as high

as 140°F (78°C) between collector and ambient may be involved. The output of a solar

water heater is, therefore, primarily dependent on solar radiation intensity and

duration. The requirements for hot water storage are, accordingly, dependent mainly

on the hot water use pattern.

The quantity of energy required for domestic hot water is a function of at least the

following five factors:

a. local makeup water temperature

b. desired hot water temperature

c. quantity of water used daily

d. daily use schedule

e. storage and line losses

Average monthly makeup water temperature for 14 U.S. cities varies from 32°F (0°C)

to 81°F (27.2°C) during a year, as indicated in Table A-l. Therefore, assumption

of a nominal value of 55°F (13°G) may not be optimal for sizing of solar energy

subsystems. Calculated average daily domestic hot water heating loads for single

family detached residence in these 14 cities ranged from 50,000 to 108,000 Btu's

for January and from 50,000 to 82,000 Btu's for July, as shown in Table A-2.

A complete understanding of the solar hot water system requires detailed knowledge of each of the system components. The basic parts of the solar water heater

are the solar collector, storage tank, circulating system, and auxiliary energy

supply. Other components such as a heat exchanger, expansion tank, and differential

temperature controller are commonly used in active systems.

Considerations for freeze protection, corrosion resistance, and overheating have

resulted in the use of various heat transfer fluids, drain-down methods, and failsafe devices to meet long term durability and reliability requirements. A solar

energy system is usually designed for average weather conditions and seldom provides

100% of the energy requirements. For extended conditions of low incident solar

radiation, auxiliary energy sources back up the solar energy system to meet the

total requirement.

The system designs used to meet the thermal performance, durability/reliability,

back up and particular building integration needs have resulted in a variety of

system configurations and components. Some of the basic approaches used to date to provide hot water heating for residential applications are illustrated in Figures

A-l through A~8. Section 1.2 provides a brief description of these systems. A

summary of the features, limitations, and general comments for the eight types of

systems is presented in Table A- 3.

A-2
City Source^" Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1. Phoenix Ri, Re, W 48 48 50 52 57 59 63 75 79 69 59 54

2. Miami W 70 70 70 70 70 70 70 70 70 70 70 70

3. Los Angeles Ri, W 50 50 54 63 68 73 74 76 75 69 61 55

4. Albuquerque W 72 72 72 72 • 72 72 72 72 72 72 72 72

5. Las Vegas W 73 73 73 73 73 73 73 73 73 73 73 73

6. Denver Ri 39 40 43 49 55 60 63 64 63 56 45 37

7. Ft. Worth L 56 49 57 70 75 81 79 83 81 72 56 46

8. Nashville Ri 46 46 53 66 63 69 71 75 75 71 58 53

9. Washington, DC Ri 42 42 52 56 63 67 67 78 79 68 55 46

10. Salt Lake City W, C 35 37 38 41 43 47 53 52 48 43 38 37 11. Seattle Ri 39 37 43 45 48 57 60 68 66 57 48 43

12. Boston Re 32 36 39 52 58 71 74 67 60 56 48 45

13. Chicago L 32 32 34 42 51 57 65 67 62 57 45 35 1

H1^ New York City Re 36 35 36 39 47 54 58 60 61 57 48 45

1. Data from Handbook of Air Conditioning System Design , p. 5-41 through 5-46 McGraw Hill Book Company, New York (1965). Abbreviations: C-creek, L-lake,

Re-reservoir, Ri-river, W-well.

Table A-l Monthly Temperature (t^) in °F at Source for City Water in 14 Selected Cities

LOCATION JANUARY JULY

1 . Phoenix 92 77

2. Miami 50 50

3. Los Angeles :< 90 66

4. Albuquerque 68 68

5. Las Vegas, Nevada 67 67

6. Denver 101 77

7. Ft. Worth oo 61

8. Nashville 94 69

9. Washington, D.C. 98 73

10. Salt Lake City 105 87

11. Seattle 101 80

12. Boston 108 80

13. Chicago 108 75

14. New York City 104 82

Table A-2 Average Daily Service Hot Water Heating Loads

' for a Single Family Detached Residence for 14

Selected Cities in January and July (Btu x 10^)
1.2 SYSTEM DESCRIPTIONS

System 1 - Direct Heating with Single Tank

This system circulates potable water through the collector and utilizes one storage

tank. Efficient operation is dependent upon developing thermal stratification in the

storage tank and, consequently, the auxiliary heating source (normally an electric

coil) is located in the upper portion of the tank. Solar heated water enters near

the center and is removed near the bottom as illustrated in figure A-l. A threeway mixing valve is used to limit the outlet water temperature to the desired maximum. Valves for relief, balancing, venting and direction control are used. The

control starts the circulator when the upper portion of the collector is warmer

than the lower portion of the storage tank. This type of system can operate effectively in a freeze resistant mode in a moderate climate by pumping heated water

through the collector or by the use of heating tapes on the collector and piping

during freezing conditions. By depending on these provisions, however, serious

damage can result if power is lost.

System 2 - Direct Heating with Preheat Tank and Separate Auxiliary Tank

This system circulates potable water through the collector similar to system 1 but utilizes a preheat tank in addition to an auxiliary tank. Operation of the

system is not dependent upon thermal stratification in the auxiliary tank and thus,

the use of electric, gas, or oil auxiliary energy does not significantly influence

the solar energy contribution to the load. Thermal stratification in the preheat tank

are beneficial, however. The circulator is initiated when the upper portion of the

collector is warmer than the lower portion of the preheat tank. Flow and safety

requirements are similar to system 1. The system is shown in Figure A-2.

System 3 - Direct Heating with Preheat Tank and Automatic Draindown

This system employs similar features and operating characteristics to system 2 but incorporates draindown provisions for freeze protection. The system must be

properly plumbed and vented to completely drain all portions of the collector

and exterior lines. The control system uses an exterior mounted

thermostatic switch to activate normally closed valves which will open when the

temperature decreases to 36°F or if the power is lost. The collector and piping

must be corrosion resistant or the system must self-pressurize with an inert gas

to minimize oxidation effects. The system is shown in Figure A-3.

System 4 - Vented or Low Pressure Draindown

Another type of draindown system, shown in Figure A-4, operates with the preheater

tank open or at very low pressure. The collector is mounted above the preheater

tank and is drained when the circulation stops. A vent must be located at the top

of the collector to admit air or inert gas when draining and to expel air or inert

gas when the collector is filling. The pre-heat tank may contain a heat exchanger

so water can move to the auxiliary tank using line pressure. Alternatively, the

heat exchanger may be replaced by a pressure pump to move water to the auxiliary tank

while maintaining service pressure. The circulator operation is controlled in the same manner as other systems.

System 5 - Indirect Heating with Antifreeze Loop and Heat Exchanger

The systems shown in Figures A-5a and A-5b are closed loop with an antifreeze as the

heat transfer fluid and the storage tank operated at normal domestic water

pressures. If a toxic fluid is used, present standards require a double-walled

heat exchanger because of contamination considerations. The heat exchanger may

be in-line counter flow, tank wrap around or an internal tank type. The importance

of stratification for efficient operation is the same as described for system 1. In addition to the vent, relief and check valves, an expansion tank is required

to accommodate fluid volume changes with temperature.

A-4
System 6 - Indirect Heating with Air Collector and Air/Water Heat Exchanger

Replacement of the liquid collector with an air collector offers a particular

advantage in freezing climates by simplifying the control system and reducing the

danger of destructive damage. Other problems which are minimized such as corrosion,

leaks, and boiling must be traded off against increased duct size and use of electrical power for the blowers. A small pump is used to transfer the potable water through

the heat exchanger which is located within the building envelope for freeze protection

A preheat tank system can be used as shown in Figure A-6 with gas, oil or electric

auxiliary heat or a one tank system with electric auxiliary may be used as shown in

system 1.

System 7 - Thermosyphon

The thermosyphon hot water heating system utilized the change in density of water

with temperature to cause the circulation of hot water from the collector to storage.

As shown in Figure A-7, the storage tank must be located above the collector so the

circulation occurs only when solar energy is absorbed. No control system is

necessary when gravity flow is used and the control system for a pressurized or draindown system usually becomes too complicated to justify. Properly designed

thermosyphon systems produce a temperature rise of about 15°F and peak flow rates of

about 15 lbm

/hr*ft2. The estblishment and maintenance of a significant temperature

gradient in the preheat tank is necessary for efficient operation. Properly sized

pipes with minimal flow resistance are essential to satisfactory operation. Thermosyphon systems are usually located in climatic regions in which there is little or no danger of freezing. If there is any possibility of a freeze, the preheat tank,

the collectors, and all exposed piping should be drained manually.

System 8 - Combined Collector and Storage

The use of plastic bags or tubes filled with water and with a transparent cover, shown in Figure A-8, can be used as a source of hot water on a daily basis. The unit

is normally manually filled in the morning and the hot water is drawn off in the

early evening because the night time heat loss is large. The system is not pressurized and should be capable of being completely drained if used in a freezing climate.

A5
Table A3

Summary of the Features, Limitations and General Comments for Various

Types of Residential Solar Water Heater Types

System Types Features Limi tations General Comments

1. Direct heating, single

tank (Fig. A-l) Circulate potable water

Storage located below

collector

Simple temperature control

to operate pump

Has full main pressure

Not amenable to use of antifreeze or corrosion

inhibitors

Simple reliable low operating cost Efficiency related to use profile and storage tank stratification

2. Direct heating, pump circulation, preheat

tank and mixing

valve (Fig. A-2)

Mixing valve controls

outlet water temperature

Same as No. 1

Collector and piping must withstand high pressure

or high temperature

Not amenable to use of antifreeze or corrosion

inhibitors

Provides maximum use of solar energy

3. Direct heating, pump circulation, drainable (Fig. a-3)

Non-freezing by draining

freeze protection effective

with power failure

Loss of water in collector for each drain-down

Susceptible to corrosion

or must be flushed with

inert gas

Requires dralndown valve

A. Direct heating, pump circulation, vented

(Fig. A-4)

Non-freezing by draining

and venting to storage

No loss of water in collector

Susceptible to corrosion

or must be flushed with

inert gas

Requires pressure pump and control

5. Indirect heating,

circulating type

(Fig. A-5)

Provides freeze protection

and corrosion inhibitor Exposure to no- flow conditions can damage

heat transfer fluid

Requires double wall heat exchangers for toxic heat transfer fluid Requires two pumps

6. Indirect Heating Air Collector (Fig. A-6Freeze protection not required if fluid loop

in protected area Potable water used in fluid loop Fluid leakage minimized

Electric power for blower operation may be greater

than pump Heat exchanger penalty

greater than liquid

System reliability, durability

and maintenance more readily

predictable. Collector can

be used either with preheat

tank or single tank with

temperature gradient

7. Thermosyphon (Fig. A-7) No electrical energy for circulator required Control hardware not required or minimal

Direct heating of potable

water

Usually used in non-freeze

climate

Storage tank located above collector

Collector and piping sized

and configured for low pressure drop to not impede natural fluid flow

8. Collector-Storage

Combined (Fig. A-8) No automatic circulating

or control hardware

Direct heating of potable water

Manual operation to fill and drain Overnight storage not practicalThe system is usually easily

removed for maintenance

Readily adaptable to retrofit

sites

A-6
LEGEND

A7
A-8

Figure

A-2.

System

2

-

Direct

Heating

with

Preheat

Figure

A-3.

System

3

-

Direct

Heating

with

Preheat

Tank

and

Separate

Auxiliary

Tank

Tank

and

Automatic

Draindown
FILL

Figure

A-4.

System 4-

Vented

or

Low

Pressure

Figure

A-5a.

System

5aIndirect

Heating

with

AntiDraindown

System

freeze

Loop

and

External

Heat

Exchanger
^FILL 0) M

0)

M 00 < § *3

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A- 10
A-ll

Figure

A-8.

System

8

-

Combined

Collector

and

Storage
1.3 SYSTEM DESIGN FACTORS AFFECTING THERMAL PERFORMANCE

Figures A-l to A-8 show a number of different system configurations available

using solar energy to heat hot water for residential applications. Of the eight

system types described, simplified methods for predicting thermal performance are available only for those systems containing two storage tanks. These are defined

as systems 2, 3, 4, and 6. Section 2.0 will describe the method for sizing solar

collectors for these systems, based on the f-chart correlations of references [4]

and [5]. However, since single tank active systems such as systems 1 and 5 are

also available, some means of performance evaluation is required. Detailed computer

simulations using the TRNSYS [7] code are available for these systems. At present,

there are no general evaluation procedures available for systems 7 and 8.

This section includes the results of the detailed computer studies of thermal performance of a reference solar DHW system located in Madison, Wisconsin using TRNSYS.

The numerical results are applicable to the similar climatic region of New England,

however, the qualitative results should be applicable for all climatic regions. The

purpose of this study was to evaluate the effects on system thermal performance of

the following design options for the storage subsystem:

° single tank vs. double tank configuration

° stratified vs. mixed tank performance

° nominal vs. improved insulation

The reference solar DHW system is described in Table A-4 and consisted of a direct

heating system with a 41.4 sq. ft. flat plate, single glazed, non-selective collector

facing south at a tilt angle equal to the latitude. The storage tank options

considered include a single 80 gallon storage/auxiliary tank as shown in Figure A-l

and a double tank system comprised of an 80 gallon preheat and an 80 gallon auxiliary

tank, as shown in Figures A-2 , A-3 , and A-4.. The tank heat loss coefficients of

0.13 and 0.071 Btu/hr°F ft2 correspond to glass fiber insulation thicknesses of

1 1/2 and 3 inches (R-7 and R-13)A/ respectively. The hot water load of 70 gallons

per day was assumed heated from 55°F to 140°F. Tank ambient conditions of 60°F were

assumed. Figure A-9 defines the hourly draw profile used for the study.

The results of the study for solar energy systems supplying about 50% of the energy

requirements are summarized in Table A-5. The data represents a complete year's

simulation. The results of runs 1A, IB, and 1C show the effect of reducing tank heat

loss coefficient on system performance for a two tank, non-stratif ied system. Run 1C

represents a limiting case with no storage heat loss, runs IB and 1A are for systems

with 3 and 1 1/2" (R-13 and R-7) of insulation, respectively. Examination of the

results for the storage tank with R-7 insulation (representative of current insulation

levels in electric storage heaters) reveal that twice as much heat was lost from the

auxiliary tank as from the preheat tank and that the tank heat loss was equivalent to 38% of the solar energy collected. Since many of the fossil fuel hot water systems

installed in residences have even less insulation, the performance of a solar BHW

system using existing poorly insulated storage tanks will be even more unsatisfactory.

Two ways of improving the system performance are to increase the insulation thickness

on each tank and, since the capacity of the auxiliary tank normally has little affect

on collector efficiency, to reduce the size of the auxiliary tank, consistent with

requirements

.

—

1 / 2 Heat loss coefficient in Btu/h ,0 F’ft = reciprocal of

insulation thickness is based on thermal conductivity

for density of 1.5 lb/ft^.

"R" value. Glass fiber

of 0.25 Btu-in/h-°F*ft z

A- 12
TABLE A4

DESCRIPTION OF REFERENCE SOLAR DHW SYSTEM

USED FOR DETAILED COMPUTER SIMULATIONS

IN MADISON WISCONSIN

SYSTEM DESCRIPTION

0 Direct Heating Type Circulating Potable Water in the

Collector (Systems 1, 2, 3, and 4)

COLLECTOR DESCRIPTION (Flat Plate, Single Glazed, Non-selective)

° Area: 41.4 ft^

° Orientation: 43° Tilt (equal to latitude), 0° Azimuth

° Cover Transmittance = .90

° Collector Plate Absorptance = .95

° Collector Loss Coefficient = 1.207 Btu/h - °F*ft^

° Capacitance Rate (C c /Ac

) = 10.28 Btu/h* °F* f

t

2 c STORAGE DESCRIPTION (Either One or Two Storage Tanks)

° Capacity: 80 Gallons each (20 in. diameter x 63 in. height)

° Stratification: Fully mixed or thermally stratified

0 Heat Loss Coefficient: U = 0.13 or 0.07 or 0. Btu/h ,0 F*ft^

LOAD DESCRIPTION

0 Daily Draw: 70 Gallons

° Draw Profile: Figure A-9

° Cold Water Temp: 55°F

0 Hot Water Temp: 140°F

A-13
Collector Efficiency

>3- vO

COm

-a-

.534 .529 .303 .513 .508

M M «

§ 0 H CO O'

0) —00 00

co »

m o

O hJ w O'

CO

.377 .213 1 o

.321

00

iH .405 .135 .075

Storage

Heat

Loss

Fraction

Total .190 .115 1 o

.182 .104 .136

CM

00o o

Aux. Tank .127 .076 1 o

r-» CM

.072 .136 .082 .047

Preheat Tank .063 .039 1 o

.055 .032 1 o

1o

1o

Solar

Fraction of Total .500 COU> .586 .557 00

r-H NO .327 .600 .614

Total

Energy

Reqd

.

10 6

Btu

21.78 19.96 17.69 21.74 20.90 20.87 19.45 18.80

Storage

Tank

Configuration

Heat

Loss

Coefficient

Btu/hr°F

ft^

.130 .071 1 o.130 .071 .130 .130 .071

Preheat

Tank

Stratification non-strat

.

non-strat

.

u

cfl MU

CDc

8

stratified stratified

non-strat

.

stratified stratified

No.

tanks CM CM CM CM - iH - iH

Run

No. VT IB 1C 2A 2B 3A 3B 0E

A-14
NORMALIZED

HOT

WATER

USAGE

Runs 2A and 2B were simulations for a two tank system in which the preheat storage

tank stratified, for R-7 and R-13 insulation, respectively. Similar to the results

for the unstratified two tank system, increasing the tank insulation thickness

increased the solar fraction of the load by reducing the heat loss. Note that in

each case there was a slight reduction in collector efficiency with increased preheat tank insulation due to the increased water temperature in the better insulated

tank. A comparison of runs 1A with 2A and IB with 2B show the increase in perfor- mance due to stratification in the two tank system. The primary effect of stratification is to reduce the collector inlet temperature and thus increase collector

efficiency; however, a slight reduction in preheat tank heat loss also occurs.

The major effects of stratification on system performance occur in the single tank

systems. Examination of run 3A reveals the extreme performance penalty resulting

from non-stratified operation with a single tank system. In this system, the entire

tank would be at the delivery temperature of 140°F which would make the collector

operate very inefficiently. It is very probable that single tank systems using

gas or oil for the auxiliary heat source would operate in this manner since these

tanks are constructed with the energy input at the bottom of the tank and free

convection circulation of the heated water would prevent stratification. The major

improvement in single tank system performance occurs in run 3B due to stratification and

results in increased efficiency of the collector and reduced storage tank losses,

It is anticipated that stratification will occur in single tank systems only when

the auxiliary energy source is located in the upper portion of the tank, for example,

with an electric hot water tank having the lower heater element disconnected. Run

3C shows that a well insulated, single tank, stratified storage system will have the

best overall performance in terms of the fraction of the total load provided by

solar and minimum heat loss.

In summary, the storage tank design options can have a major impact on the thermal

performance of a solar DHW system. In general, the best performance will occur in

single tank, stratified systems that are well insulated, although two tank stratified

systems with equivalent insulation thickness perform nearly as well. Since

stratification is a phenomena that may not occur even in single element electric

storage tanks unless the piping connections are specifically located to promote

stratification, it may be safer to use a two tank system where the lack of stratification does not result in as severe a performance penalty. If a one tank system

is selected, the manufacturer should specify that stratification will occur in the

tank for the range of operating conditions anticipated and present test data for

verification. In two tank systems, the auxiliary tank should be kept as small as practical to reduce losses and in all systems adding insulation to all storage tanks

to R-13 (the equivalent of 3 inches of fiberglass) provides considerable benefits.

Figure A-9 Assumed Hourly Hot Water Consumption

A- 15
2 . PREDICTION METHOD

2.1 SUMMARY OF THE PREDICTION METHOD

In this prediction method, a determination is first made of the collector area

required, Are f , to provide 50% of the domestic hot water load for a reference DHW

system and load located in a selected city. If necessary, adjustments are then made

to this collector area to account for the differences between the reference system

and the actual system under consideration. The collector area modified by the adjustment

multipliers gives the final minimum collector area required for the actual system, Areq.

2.1.1 Description of the Reference System

Reference system characteristics are described in Table A-6 and system configuration

is shown in Figure A-2 and A-3.

2.1.2 Systems Which Cannot be Analyzed

The following systems described in section 1.2 cannot be evaluated by this method:

a. Single tank systems (Fig. A-l and A-5), see section 1.3 for guidance

b. Thermosyphon systems (Fig. A-7), see reference [8] for guidance

c. Combined collector and storage (Fig. A-8)

2.1.3

Steps in the Analysis Procedure

a. Determine reference collector area (Are f) from Table A-7 for the city that most

closely represents the project location. Further explanation is given in

section 2.3.1.

b. Determine the appropriate representative city (MIAMI, TALLAHASSEE, ANNAPOLIS, or BOSTON) to be used in the adjustment analysis if adjustment is necessary. The

climatic zones map, Figure A-ll, may be useful in making this determination.

c. Adjustment to the reference system area (Aref) is done by multiplying the reference system collector area by the necessary adjustment factors as follows:

Areq = Aref x X X x

where: Areq = the required collector area

the reference collector area

the area adjustment factor due to collector

characteristics and heat exchanger modifier.

This factor is determined from Figures A-12a

to A-15a and is described in section 2.3.2.

the area adjustment factor due to collector

orientation. This factor is determined from

Figures A-12b to A-15b and is described in

section 2.3.3.

the area adjustment factor due to storage

tank heat capacity. This factor is determined

from Figure A-16 and is described in section

2.3.4.

A-16
= the area adjustment factor due to makeup water

temperature. This factor is determined from

Figure A-17 and is described in section 2.3.5.

Adjustments for a single parameter variation factor give results that are in

agreement with the "f-chart" simulation. Adjustments for multiple parameter

variations give results that are within 10% of the results obtained by an "f-chart" simulation if small in magnitude (that is well within the range of

the graphs). If large variations to the reference systems require evaluation,

it is recommended that the "f-chart" simulation be employed using the actual

system characteristics.

An example of the effect of multiple variations is given in section 2.3.6.

d. For systems employing single tanks or different levels of tank insulation, the

factors presented in section 1.3 may assist in evaluation.

e. The actual collector area selected for installation should be the size offered

by the manufacturer that meets or exceeds the size determined in the preceding

steps a-d.

2.2 BASIS OF THE PREDICTION METHOD

The purpose of this prediction method is to provide an easy-to-use means of determining

the approximate collector area required for an active solar domestic hot water (DHW)

system that is capable of providing 50% of the annual energy used for hot water heating

for a family of four. An analysis is presented for each of four cities that have

been found to have climatic conditions representative of the eleven eastern states

participating in the HUD/States Solar Hot Water Initiative Program.

This method for collector sizing is based on computer simulations of a reference solar

domestic hot water system. These simulations are believed to provide reasonable

system performance prediction but are as yet unvalidated. Until validation using

actual systems operating in different climatic regions can be accomplished, this

sizing method must be considered useful for guidance purposes only.

The performance of a solar assisted DHW system is usually characterized by the fraction of energy provided by solar of the total energy required both to heat a specified

quantity of water from the cold water main temperature to the hot water delivery

temperature and to replace the storage tank heat losses. This definition of perfor- mance does not include the additional energy requirements due to combustion inefficiency and stack loss for systems using fossil fuel auxiliaries nor does it include

the additional energy required to operate the solar system pumps, blowers, controls,

or freeze protection system. However, in any analysis of DHW system energy requirements, these energy components must be included.

The collector array area required for a desired performance level of most solar DHW

systems is affected by the local climatic conditions, by the characteristics of the

solar system^ and the hot water load. Climatic factors affecting performance include

the available solar radiation, the daytime ambient temperature, the water supply

temperature, and to a limited extent, the wind. System characteristics affecting performance include the collector design, orientation, and shading, the method of providing

freeze protection and the storage tank configuration (one or two tank system). System

performance is particularly sensitive to such component characteristics as collector

efficiency, heat exchanger effectiveness (for those systems employing antifreeze for

freeze protection) and location and type of the auxiliary energy source and somewhat

less sensitive to component characteristics such as storage tank capacity and heat

loss. The hot water load characteristics affecting system performance include the

daily usage profile, total draw of the system, and the water delivery temperature.

A-17
i In this analysis, an active solar DHW system is sized to provide 50% of the annual

energy requirements to heat 70 gallons per day of hot water to a delivery temperature

of 140°F. The cold water main temperature, tm , is assumed constant at 70°F for the

locations in Florida and 55°F for all other locations. The normalized draw profile

shown in Figure A-9 is repeated every day. The collector array consists of a flat

plate collector with no losses due to shading and with no augmentation due to added

reflectors. The collector working fluid may be either air or liquid; however, the

storage medium is assumed to be water.

A reference solar DHW system has been defined and its annual performance evaluated

using the f-chart computer program for 26 locations in or near the eleven eastern

states participating in the HUD/States Solar Hot Water Initiative. The results are shown plotted in Figure A-10 and summarized for 50% solar contribution in Table A-7.

The collector area required for the reference solar DHW system for a 50% solar con- tribution is called the reference area (Are f) for that location. Based on these

results, four cities are selected as being representative of the 26 locations. The

effects of variations from the reference system have been examined using the f-chart

computer program for each of the four cities. In another location, a detailed simulation has been performed using the TRNSYS computer program to evaluate system changes

(tank stratification and tank insulation) that cannot be investigated using the

f-chart program. These results are described in section 1.3.

The reference hot water system is shown in Figure A-3 and described in Table A-6. In the reference system, a flat plate collector with single glazing and flat black absorber

coating is mounted at a tilt angle equal to the latitude and at an azimuth angle of zero

(due south). Storage capacity is 1.9 gal. per sq. ft. of collector. In this system,

water is circulated directly between the preheat storage tank and collector without any

intermediate heat exchanger. This arrangement is called a single loop system and is

typical of the draindown type of solar water heaters. In the f-chart code, the preheat

tank is assumed fully mixed (unstratified) and assumed to have an equivalent R-13 insulation level. The auxiliary tank is assumed to be an in-line heater with no storage

capacity or heat loss. Water is circulated between the collector and preheat storage

tank whenever useful thermal energy can be extracted from the solar collector. Whenever

there is a draw of hot water from the system, hot water is withdrawn from the

auxiliary storage tank and is replaced by solar heated water from the top of the

preheat storage tank. This water is in turn replaced by cold makeup water supplied

to the bottom of the preheat storage tank. Conventional energy is added to the aux- iliary storage tank by combustion of gas or oil or by electric immersion heaters to maintain the temperature of the water in this tank at the prescribed setting of 140°F.

2 . 3 PROCEDURE

2.3.1 Selection of the Reference Collector Area, A

re £

The collector area for the reference system (Aref) located at the project site is

first selected. Table a- 7 lists the collector area required for the reference solar

DHW system to provide 50% of the hot water energy in 26 locations in or near the

program area. Emphasized are the four representative locations used in the modification analysis. Figure A-10 may be used if contributions other than 50% are to be

evaluated. The climatic region map, Figure A-ll, is included to assist in selecting

the most appropriate representative location for a particular system evaluation at a project site. Information is provided in the following section to adjust the reference system collector area for the following variations.

° modification of the system to a double loop system with energy transfer

from the collector loop to the storage loop via a heat exchanger

° selection of a solar collector having different efficiency characteristics

(F (xa) and F U ) than the reference collector K f) K L

° orientation of the collector at a tilt angle and azimuth angle other than

the reference system (tilt angle = latitude, azinoth angle = 0°)

A-18
storage tank capacity different than 15 Btu/°F‘ft^c (1.9 gal/ft2 c )

cold water inlet temperature different than 70°F in Florida and 55 °F elsewhere

3. 2 Adjustments to Reference System Collector Area Due to Collector

Characteristics and/or Heat Exchanger Modifiers

The reference solar DHW system utilizes a single glazed flat plate collector array

with a non-selective black paint absorber coating. The reference system is a draindown type consisting of a single loop for energy transport between the collector

and preheat storage tank, therefore, no heat exchanger is required.

The collector area requirements for any combination of collector characteristics

and heat exchanger modifiers can be determined by multiplying the reference area

for that location by the corresponding (A/Aref) Cx

for that location and system.

The performance characteristics of a particular flat plate collector are usually

determined experimentally using the ASHRAE 93-77 test procedure (Ref 1) . These

characteristics consist of the intercept factor F^(xa) ri and the slope factor FR

U^.

The reference collector for this study has values for the intercept and slope

factors, respectively, of 0.85 and 1.20 Btu/hr* °F" ft^. These values were reported

by the NASA-Lewis Research Center (Ref 2) , for a test collector similar to a commer- cially available single glazed non-selective collector developed tinder a government

contract. The effect of applying a double glazing or selective coating to a collector is usually to reduce both the intercept and slope factors in some predictable manner; however, other factors such as the construction of the collector

absorber plate (i.e., tube spacing, absorber plate thickness and thermal conductivity

tube-to-plate joint conductance), the forced convection transfer coefficient

between the transport fluid and tube wall and the rear surface conductance all

combine to yield significant variations in performance between different collectors

of the same generic type. Therefore, it is important to have measured efficiency

data for the particular collector selected in the range of operating conditions

anticipated for the solar DHW system.

Many solar DHW systems are designed with a double loop energy transport system

with either a non-freezing liquid or air circulated through the collector and with

potable water used as the energy storage medium. In these systems, a heat

exchanger is required to transfer the energy from the collector loop to the

storage tank. The performance penalties associated with this heat exchanger can be determined by the heat exchanger modifier given by the following equation:

(me ) p min

= minimum

where: (me ) is the product of the collector loop mass flow rate and fluid

P c specific heat (Btu/h»°F);

(me ) is the product of the storage loop mass flow rate and fluid

P s specific heat (Btu/h-°F);

F U is the experimentally measured collector slope factor (Btu/h* °F* f t^) R L A is the collector array effective area (ft^);

c

Ej, is the heat exchanger effectiveness.

Single loop systems without a heat exchanger have a heat exchanger modifier

F'/Fr

= 1.0. The above expression is also valid for a single loop system having

a neat exchanger located within the preheat storage. In this case,

(mcp

) min = 0ncp) c and the numerical value for the heat exchanger effectiveness

eHX mus be based on free convection heat transfer between the heat exchanger

surface and the fluid in the tank.

•p'min

A- 19
It is desirable to be able to relate the performance of a solar DHW system having

any collector performance characteristic and heat exchanger modifier to the performance of the reference system. In the f-chart methodology, the collector efficiency characteristics and the collector heat exchanger modifier are combined into

two modified parameters.

The modified intercept factor is given by:

K

FR

(x0t) n

= F~

x Fr < Ta)n R

The modified slope factor is given by:

f;

fr

u

l

= f: xFru

l

K The use of the collector sizing information presented in this section requires specific

values for the collector parameters Fr (xa) n and FrUr and for the heat exchanger effectiveness erX

so that F^/Fr can be computed using the equation on the previous page.

Collector manufacturers using the ASHRAE 93-77 collector test standard report efficiency

as a function of the parameter inlet fluid temperature minus ambient temperature divided

by insolation; however, some manufacturers report efficiency data using either outlet

fluid temperature or average fluid temperature. Since the f-chart procedure utilizes

collector parameters based on a plot using collector inlet fluid temperature, it is

necessary to convert those manufacturers' test data to equivalent data using inlet

temperature conditions, otherwise errors in collector sizing can occur. For purposes

of illustrating this procedure, section 3.1 is provided. That section first describes

the required data and calculation procedure to convert collector efficiency data to an inlet fluid temperature basis, and then illustrates the calculation of the modified

collector characteristics F^ (ia) n and F^Ur for the double loop system containing a heat exchanger.

The required heat exchanger performance parameter "effectiveness" is frequently

not stated in heat exchanger manufacturers' catalogs. To facilitate calculation of

this parameter, section 3.2 describes several methods of calculating effectiveness

depending on the method used by the heat exchanger manufacturer to present performance data. In addition, that section provides a method for estimating heat

exchanger effectiveness if no performance data are available.

In this analysis, the f-chart computer program was run for the reference solar DHW

system and the required collector area was determined for a system providing 50%

solar for various combinations of the modified collector characteristics Fj^ (xa) n

and FrUr • The results are shown plotted for the locations characterized by the cities

of MIAMI, TALLAHASSEE, ANNAPOLIS, and BOSTON in Figures A-12a to A-15a respectively,

in terms of the ratio of collector area required to reference area (A/Aref) cx . These

curves may also be used for comparative performance and economic analysis of different

combinations of collector design and heat exchanger performance. IV

1/ These curves lend themselves to use in economic studies in which collector area

can be traded against heat exchanger area, since as the heat exchanger effectiveness

decreases (due to decreasing heat exchanger area) the required collector area

increases. This study is done by first plotting a point corresponding to the un- modified collector characteristics Fr (xa) n and FrUr on the curve for the appropriate

city and noting the corresponding A/Are f. Since the same heat exchanger modifier

Fr/Fr multiplies the FR

(xa) and FRU

L factors, the collector/heat exchanger combination would plot as a straight line passing through the previously plotted point

and having a slope of unity. The intersection of this line with the various contours

of A/Are f would give the required relationship between collector area and heat ex- changer modifier FR

/FR. Since most heat exchanger manufacturers offer a family of

heat exchangers of the same basic design but differing in size, a range of effectiveness vs. size can be determined and the FR

./F^ evaluated for each increment in size

thereby establishing the collector area required for each size heat exchanger.

Finally, knowing the collector cost per unit area and heat exchanger costs for each

size, the minimum cost combination of collector area and heat exchanger can readily

be determined.

A- 20
2.3.3 Adjustments to Reference System Collector Area Due to Collector Orientation

The optimum orientation of a collector for a solar DHW system is facing due south

(azimuth = 0 °) with tilt angle equal to the latitude at that particular location.

Frequently, optimum orientation of the collector is not possible, particularly

when retrofitting a solar system to an existing building where it may be desired

to take advantage of an existing roof slope or to avoid shading by an adjacent

structure or tree. Therefore, the f-chart program has been run for the reference

solar DHW system and the required collector area determined for a system providing

50% solar for various combinations of tilt angle and azimuth angle. The f-chart

methodology does not consider the difference between east facing and west facing

collectors; therefore, at locations having strongly anti-symmetric solar radiation

patterns with respect to solar noon, the results are not valid and the system

designer should orient the collector to take maximum advantage of the local

climatic conditions.

The area requirements for various collector tilt and azimuth angles are shown plotted

for the locations characterized by the cities of MIAMI, TALLAHASSEE, ANNAPOLIS, and

BOSTON in Figure A-12b to A-15b respectively, in terms of the ratio of required collector

area to reference system collector area (area at optimum tilt and azimuth angles)

.

Examination of these figures shows a substantial variation in collector area penalty

due to non-optimum orientation in the different climatic regions investigated. For

example, in the Southern Florida region for collectors tilted at 35° or less, the area penalties will not exceed 20% for any collector azimuth up to 90° . In contrast

to the South Florida region, in New England for collectors tilted within 20° of

optimum, the maximum azimuth angle is 40° to limit area penalty to 20%.

2.3.4 Adjustments to Reference System Collector Area Due to Preheat Storage Tank

Heat Capacity

The reference system performance is based on an assumed preheat storage tank thermal

capacitance of 15 Btu/°F*ft^c (approximately 1.9 Gal/ft^j.). The variation in

required collector area for a 50% solar contribution with preheat storage tank

capacity is shown in Figure A-16 for the four representative climatic regions.

Note that although Figure A-16 shows that increasing the storage tank size increases

system performance (the effect being more noticeable in colder climatic regions), in

reality at some value of storage tank capacity, the increase in tank heat loss

will offset the gain due to increased storage capacity and the net performance will

diminish. Unfortunately, the f-chart computer program is based on a hot water

storage tank having an unusually low heat loss rate in comparison with commercially

available storage tanks and, therefore, the optimum storage tank capacity cannot be

evaluated

.

2.3.5 Adjustment to Reference System Collector Area Due to Variations in Cold Water

Makeup Temperature

The reference system performance is based on a constant value of 70°F water supply

temperature in Florida and 55°F elsewhere. Figures A-17a and A-17b show the variation

in required collector area due to variations in water supply temperature for the

reference solar DHW system that provides 50% of the energy requirement. Examination

of these results suggest that in Florida, a colder water main temperature increases

the collector area requirements while the opposite is true in the New England region

and there is virtually no effect in the Mid-Atlantic region. Since the analysis

assumed a constant daily draw of 70 gallons and a fixed delivery temperature of 140°F,

the effect of reducing the water supply inlet temperature is to increase the total

energy required and this would imply that more collector area is required for a specified annual performance. Since the analysis results show this trend only for

the Florida region, there appears to be an offsetting influence related to climatic

region. A possible explanation is that with colder water supply temperature in a colder climatic region, the increase in collected energy (due to higher collector

efficiency as a result of lower water main supply temperature) is greater than the

increased load and a given system will perform better (i.e. a system with a fixed

collector area will provide an increased solar fraction of the load)

.

A-21
2.3.6 Example Problem

Determine the collector area required for a solar DHW system providing 50% of the

annual hot water energy requirement for a family of four located in LYNN, Massachusetts

(latitude = 42°) based on the following system schematic and design parameters:

Collector Description Collector Efficiency

FR<TM)n ‘ - 66

, Fr

Ul- .82 Btu/h- F-ft^ Collector Orientation

Tilt - 30° Azimuth - 45°

Storage Loop water

flow rate 1 gal/h*ft

specific heat • 1.0 Btu/lb*°F

density 62.4 lb/ft-*

Hot. Hater

Loop Pump

t t - 140°F

70 gal/day

Comparison of the specified design parameters with the reference system design parameters tabulated in Table A-6 indicate area correction factors are required for the

modified collector efficiency characteristics, collector orientation, cold water

makeup temperature, and possibly, for preheat storage capacity. As stated previously,

the area correction factors were developed specifically for single parameter variations from the reference system. However, since it is desired to evaluate systems

with more than one parameter differing from the reference system, the following

method gives reasonable results based on the limited number of cases that have been

checked.

From Table A-7, the reference system collector area requirement in LYNN is 51.0 sq. ft.

and from Figure A-ll the regional city representative of LYNN is BOSTON. The collector

area correction factors are calculated using the data from BOSTON as follows:

a. Modified Collector Efficiency (A/Are f)cx

The collector loop capacitance rate per unit collector area is determined for the

specified volumetric flow rate and properties of the glycol-water mixture as follows

C (me ) , lb H_0 — = =15 — x 8 33 — A A , , 2 gal “ 62.4 lb H o 0

c c h* f t G

2

55 lb glycol Btu , x r r.-H x .65 = 7.16

Btu

h*°F*ft

The storage loop capacitance is determined as:

(me ) = — 1.0 gal o n lb . Btu

2 X 8,33

gal

X 1,0

lb* °F 8.33

Btu

h*ft“ * h* °F* f

t

c c

The heat exchanger modifier factor FR

/FR

is calculated using the following:

1 FR

A Fo U R t ^ +

c R L

£HX

Cmin

- 1

A-22
substituting the specified values of FrUl , and C c /Ac and recognizing that

Cmin = C c .yields

FR(Ttx) n

= ( * 94 ><* 66 > = - 62

F^U

l

= ( . 94) ( . 82) = .77

From Figure A- 15a for BOSTON, the modified collector efficiency factor is:

(A/Aref )cx

= 1 ' 2 ^

b. Collector Orientation Factor (A/Aref) 0

The collector orientation factor is obtained from Figure A-15b for BOSTON by

entering the figure at the specified tilt angle of 30° and azimuth angle of 45°:

< A/Aref>0 i- 10

c. Gold Water Makeup Temperature Factor (A/Aref) t

Figure A-17 gives the area correction factor for BOSTON for a cold water inlet of

temperature of 45°F as:

< A/Aref>t ' 97

d. Storage Tank Capacity Factor (A/

A

re f)

g

Since the design parameters stated fix the preheat storage tank at 52 gallons

and the storage capacitance factors are given relative to a collector area which

is yet unknown, an iterative solution is required.

As a trial solution, calculate the collector area based on the previously calculated

adjustment factors for collector modified efficiency, orientation and cold water

temperature as follows:

Trial 1

A

req = (51.0) (1. 25) (1. 10) ( .97) = 68.0 ft

2

The storage capacitance parameter is:

Me 52 gal x 8.33 x 1.0 —E. = I SSl lb ‘ F

= 64 A ? c 68.0 ft

Btu

3 F-ft'

c c Figure A-16 gives the appropriate adjustment factor for BOSTON as:

< A/Aref)s

" 1 ' 19

A-23
Trial 2

A = (68.0) (1.19) - 80.9

req

MC

P = (52X8.33) = Btu

A

c - 80.9

-

* o p . ft

2 c (A/A

ref) s - 1.22

Trial 3

A

reqd

= ( 68 -°)< 1 - 22 ) = 83-0

MC

P _ (52.0) (0. 33) = „ Btu

A

c " 83.0

- 5 ‘ 0p . ft

2 c

/ a ^ Then ( —

j = 1.23 which is sufficiently close to the calculated value for the

'ref's

second trial solution so that no further trials are necessary. The required

collector area is:

A = 83.0 ft

2 req

e. Computer Program Results

The foregoing problem was calculated directly using the f-chart computer program

for the described solar DHW system and the required collector area, Areq

, was

78.5 ft 2 . Therefore, the approximate area is 6% greater than the exact area, which is deemed acceptable in light of the proposed application. Other sample

calculation runs with the approximate method resulted in +10% error in collector

area when compared with the computer predicted area. The parameters particularly

sensitive to these errors are the water inlet temperature and the storage capacity.

It is therefore suggested, when using multiple parameters and the modified collector

efficiency factor (A/Aref) cx exceeds a value of 1.5, that water temperature variation be limited to +10°F to 15°F from the reference value of 55°F and storage

capacity variation be limited to +5 Btu/°F*ft 2 c from the reference value of

15 Btu/°F-ft2c .

A-24
TABLE A-6 SOLAR DHW REFERENCE SYSTEM DESCRIPTION

System Diagram Figure A-2 or A-3

Collector description

o collector fluid = water

o single glazed

o flat black absorber

o Fr

U

l

= 1.20 BTU/hr *°F* ft 2 J

System description

o two tank (solar preheat and fired auxiliary tanks)

o collector orientation

tilt angle = latitude

azimuth angle = 0° (due south)

o storage heat capacity = 15 BTU/°F*ft^, or 1.9 gal/ft^

o storage tank insulation = R-13

o heat transfer fluid = water

Load Description

o draw = 70 gal/day

o delivery temperature = 140 °F

o water main temperature = 70°F in Florida, 55°F elsewhere

o draw profile (as shown in Fig. A-9)

per ASHRAE 93-77 Test procedure

A-25
f-chart Available Data (Reference [6])

Reference Area, ArP f (ft 2 ),

for 50% Contribution

y Call

imber

Location Latitude (°)

1 Albany, NY 42.4 44.0

4 Amherst, MA 42.1 53.0

5 J./Annapolis , MD 38.6 39.0

7 Apalachicola, FL 29.5 25.0

14 Blue Hill, MA 42.1 47.0

16 ^/Boston, MA 42.2 49.6

20 Caribou, ME 46.5 47.5

37 Gainesville, FL 29.4 26.4

48 Ithaca, NY 42.3 54.0

49 Jacksonville, FL 30.3 29.2

50 Key West, FL 24.3 24.1

61 Lynn, MA 42.3 51.0

66 3 /Miami, FL 25.5 24.1

70 Natick, MA 42.2 44.0

72 Newport, RI 41.3 41.5

73 New York, NY 40.5 54.0

80 Pensacola, FL 30.3 28.3

82 Philadelphia, PA 39.5 37.5

85 Portland, ME 43.4 38.5

100 Schenectady, NY 42.5 60.0

103 Silver Hill, MD 38.5 37.0

105 State College, PA 40.5 48.5

108 4/Tallahassee, FL 30.3 27.0

109 Tampa, FL 27.6 24.1

110 Trenton, NJ 40.1 37.5

113 Washington, DC 38.5 40.5

Participating States: Vermont, New Hampshire, Massachusetts, Connecticut,

Rhode Island, Pennsylvania, New Jersey, Delaware,

Maryland, Florida

New York Counties: Bronx, Duchess, Greene, Kings, Nassau,

New York, Orange, Queens, Richmond, Rockland,

Suffolk, Ulster, Westchester

1 / Representative location

2 / Representative location

3/ Representative location

4/ Representative location

for Middle Atlantic Region

for New England Region

for southern Florida

for northern Florida

Table A- 7 Required Collector Area for 50% Solar Domestic Hot

Water Contribution HUD/State Solar Hot Water Initiative

A-26
ANNUAL

SOLAR

FRACTION

OF

DHW

LOAD

16 20 3046 SO * 70 M 90

COLLECTOR AREA, A^.ft2

Figure A-10 Collector Area to Provide a Given Annual % of

Domestic Hot Water Load ( Reference System)

A-27
Figure A-ll Climatic Zones

from: G.T. Trewartha, "An Introduction to Climate"

I

A-28
AZIMUTH

ANGLE

(DEG.

FR

(T<,) n

Figure A-12a Collector Area Multipliers for F^ (xa)

and F'U for MIAMI, FL

n

K L

TILT ANGLE (DEG.)

Figure A-12b Collector Area Multipliers for Tilt and

Azimuth for MIAMI, FL (Lat. = 25°)

A-29
AZIMUTH

ANGLE

(DEG.)

.4 .5 .6 .7 .8 .9

;

(to)

Figure A-13a Collector Area Multipliers for F^ ( TOt ) n

and FR

UL

f °r TALLAHASSEE > ^

Figure A-13b Collector Area Multipliers for Tilt and

Azimuth for TALLAHASSEE, FL (Lat. = 30°)

A-30
AZIMUTH

ANGLE

(DEG.

FR

(TO)

n

Figure A-14a Collector Area Multipliers for F^ (xa)

and F’Ut for ANNAPOLIS, MD T3 I *

Figure A-14b Collector Area Multipliers for Tilt and

Azimuth for ANNAPOLIS, MD (Lat. =38°)
AZIMUTH

.ANGLE

(DEG.

FR

( TM>n

Figure A-15a Collector Area Multipliers for (tci) and F'u for BOSTON, MA

R L

TILT ANGLE (DEG.)

Figure A-15b Collector Area Multipliers for Tilt and

Azimuth for BOSTON, MA (Lat. = 42°)

A-32
Figure A-16 Collector Area Multiplier for Storage Heat Capacity

1. ANNAPOLIS

2. BOSTON

Figure A-17a Collector Area Multiplier for Water Main Temperature, t m

1. MIAMI

2. TALLAHASSEE

Figure A-17b Collector Area Multiplier for Water Main Temperature, t m

A-33
3. SUPPLEMENTARY INFORMATION

3.1 MODIFIED COLLECTOR PERFORMANCE CHARACTERISTICS, F^ (xa)n and F^

In this section, the procedure for calculating the modified collector performance

characteristics Fr (xot)n and F^UL used in Figures A-12a to A-15a is explained. The

procedure is for a liquid system containing a collector /storage heat

exchanger which is the most complex case, however, it is also applicable for air

collectors and for liquid systems which do not contain a collector/storage heat

exchanger

.

To calculate the combined performance characteristics, it is necessary to first

establish the performance characteristics for the collector alone, F^ (xa)n and frUl- Both of the characteristics are then corrected for the effects of the collector/

storage heat exchanger by the heat exchanger modifier factor, Fr which includes

Tr

corrections for both the heat exchanger effectiveness and capacitance rates. This step gives F' (xa) and F'U . K “ R L A worksheet is provided for these calculations.

3.1.1 Collector Performance Characteristics, FR(xa) n , FR

U^

The performance characteristics for the collector alone are determined from manufacturers data which may be presented in any of several forms, and which covers the

appropriate range of operational temperatures, insolation, tilt angle, and fluid

flow rates. For information purposes, a set of performance curves for a number of

typical collectors are presented in Figure A-21a and A-21b.A/ The collector perfor- mance efficiency curve must be plotted such that the y axis is the thermal efficiency

(q) and the x axis is the temperature difference between a reference fluid temperature (t*) and the ambient temperature divided by the incident solar radiation

[ (t*-ta ) /l t ] as shown below.

Thermal Efficiency

‘'"‘a /F-hr-ft*

U

K BCu The equation of the straight line fit of the experimental data, in the operating

range, is given by: y

= -mx + b where: -m = the slope of the straight line

b = the y axis intercept (value of y when x = 0)

1 / ASHRAE 93-77 defines the collector efficiency using the gross collector area whereas

previous data was generally reported using aperture area. Figures A-21a and A-21b

present data for several liquid collector types with the efficiency based upon gross area and aperture area, respectively. Calculations in this procedure can be performed ' with either area; however, the efficiency and area must be consistent in all

portions of the calculation.

A-34
Using ASHRAE 93-77 as the basis for reporting performance data, the reference

temperature t* in the plot of experimental data is the fluid inlet temperature. In this case the collector characteristics FR (toi)^ and Fr

Ut are obtained directly from

the efficiency graph as the value of the intercept and slope, respectively. However,

in some cases the data are based on other reference temperatures. The following

procedure describes the determination of FR

(xa) n and FrU^ for three different values

of reference temperature.

The following data are required:

values of slope m and intercept b for a straight line plot of efficiency data

temperature basis (either inlet, average, or exit fluid temperature)

the ratio of the collector capacitance rate to effective area C c /Ae for

the collector test. 1/

where C c = collector fluid capacitance rate (me.) Btu/h*°F

Ae = effective collector area used in efficiency tests

Case 1 t* = t^ (fluid inlet temperature)

then FR

(xa)n = b (the y axis intercept of the data line)

F U = m (the magnitude of the data line slope)

t in + ^t Case 2 t* = x (average of inlet and exit temperature)

then FR

(T°On= b x

1 +

mAg

IcT

and Vl * " *

1 + mAe

2C7

Case 3 t* = t _ (fluid exit temperature)

out

then F

R

(Tot)n = b x

1 C

fr

u

l x

l + ^e

c Figure A-19 has been provided to facilitate calculation of the adjusted test data. In this figure, the required FR

U, is obtained directly by entering the curve with

the measured value of slope m ana rising vertically to the intersection with the

appropriate value of the parameter Cc /Ag (noting that solid lines are for the case 3 situation and dashed lines for case 2). Since the term FR

(xa) n x m/b is

numerically equal to the value of FrUl , the required value of FR

(xa) n is obtained

by multiplying the previously determined FR

U^ by the ratio b/m in consistant

units

.

1 / Note that with liquid collectors, the C

c /A

e ratio can differ substantially

between the collector efficiency test and the proposed application without seriously

affecting the f-chart performance predictions. However, with air collectors, the

C c /Ag ratio and the series arrangement of collectors, i.e. the number of

collectors in series must be similar between the test and proposed application for

the f-chart procedure to be valid.

A-35
3.1.2 Collector Heat Exchanger Modifier Is

’ F

s Calculate the collector loop and storage loop capacitance rates and determine

the minimum capacitance rate. The loop capacitance rate is the product of the mass

flow rate, m (lb/h) and fluid specific heat, c (Btu/lb -0 F).

P

C = (me ) collector loop

c pc

C = (me ) storage loop

s p s The minimum capacitance rate C , is the lesser of C or C . min c s The effectiveness of the collector /storage heat exchanger, e is a function of the

particular heat exchanger design and size and capacitance rate of each loop. If a numerical value of is not known, section 3.2 describes procedures whereby values

can be calculated or estimated depending on information available from the heat

exchanger manufacturer.

The heat exchanger modifier is determined by first calculating the following

dimensionless parameters:

C

c x = 7—c

HX min

y —vw

c

where Ac = the effective area of the collector array

The heat exchanger modifier is then determined either from the following equation

or from figure A-20.

Fr

1 + y(x-l)

Note that for any solar DHW systems without a collector/storage heat exchanger,

The values for the modified collector performance characteristics are calculated

as follows:

F

p ( Ta >n MTa )n x

l

fr

fru

l

= fru

l x FTA-36
WORKSHEET - MODIFIED COLLECTOR PERFORMANCE CHARACTERISTICS, F' (xa) n and F'U

R L

PROJECT:

Collector Efficiency Data From Test

intercept, b = slope, m = (Btu/h* °F* f

t

2

) tin + t out reference temperature basis: 1. t in , 2.

^

, 3. t Qut

collector test area, A

g = (ft^)

collector volumetric flow rate =

Correction to t^n

basis (use Figure A-19 or the following steps)

Case 1: (no correction) F_(xa)

R n

F U

R L

Case 2: F_(xa) = b x

K n

i +

2C

fr

u

l

= m x

1 +^e

2C„

C

c mC

p /volumetric

A^ ^flow rate ) h°“y) (TM*J (Z?

tte

)

test area

where: for liquids, density = ^8.33 lb/galj x (gravity

C

) 3 for air, density = 0.75 lb/ft , at 70° and 1 atm. specific heat = 0.24 Btu/lb*°F

Case 3: = b x

F U = m x R L

A-37
WORKSHEET (Continued)

P Collector Heat Exchanger Modifier, —fr for single loop systems without a collector/storage heat exchanger,

li

f

rCapacitance Rate

C

c = (from above)

C = (calc, as for C above)

s c Snin ° ^esser °F C„)

Collector Array Area Ac

s

Btu/h* °F

ft' Collector Storage Heat Exchanger Effectiveness, e cs

y

=

e cs ^min ac (frul )

Fi

= from figure or

1 + y(x-l)

Modified Collector Performance Characteristics

fr ^ TOt ^ n

=! Fr( t “)• m

i\ 'A

A-38
3.2 HEAT EXCHANGER EFFECTIVENESS, eHX

In the evaluation of a double loop solar DHW system performance using the "f-chart"

method, the calculation procedure requires an explicit value for heat exchanger

effectiveness egy . This section describes two approaches to calculation of

effectiveness, based on different ways design data may be provided by a heat

exchanger manufacturer. In situations when no manufacturer design data is available, a method is described to estimate heat exchanger effectiveness.

Definitions

0 Overall conductance (AU)jjx for a heat exchanger is the product of the overall heat

transfer coefficient U (which depends on the thermal properties of each fluid, the

fluid mass flow rate and the heat exchanger geometry) and the associated heat

transfer surface area.

0 Effectiveness is the ratio of the actual rate of heat transfer in the exchanger

to the theoretical maximum rate of heat transfer that would occur only in a counterflow exchanger with infinite surface area.

0 Log-mean temperature difference At^g is the effective temperature difference

between the inlet and outlet fluids such that the product of At^ and (AU)^X

equals

the actual heat transfer rate.

The basic relationships are developed in the following paragraphs.

In the following schematic heat exchanger drawing, the hot stream with capacitance

rate Cg and inlet temperature tg and the cold stream with capacitance rate Cg and

inlet temperature t c j_ both enter a heat exchanger that has an overall conductance

( au)hx’

Heat Exchanger with

overall Conductance

(AU)hx

The actual heat transfer rate is given by

C

c

(t C, Out " t

Cj in

) (3.2.1)

^ th, in out^ (3.2.2)

^HX AtLM (3.2.3)

A-39
The maximum theoretical heat transfer rate would occur if the fluid having the minimum

capacitance rate were heated (or cooled) to the inlet temperature of the maximum

capacitance rate fluid, i.e.

if C

'min

=* C,'H

The effectiveness is given by

= fi ^c^c, out

t c, in^ mCH(th , in ^H, out^

Cmin^th, int c, in^ Snin^jh, in *" 0 , in^

c, out (3.2.4)

The log mean temperature difference is a complex function of the hot and cold fluid

inlet and outlet temperatures and depends on the heat exchanger flow arrangement.

The term At^ is defined in terms of a reference log mean temperature difference for

a counterflow heat exchanger (Atjj^) c f and a correction factor K as follows:

manufacturers

.

Example 1

Calculate the effectiveness of a counterflow heat exchanger located in the collector/

storage circulation loop. Assume the collector circulation loop flow rate is 2 gpm

and the storage loop flow rate is 6 gpm and that fluid leaves the collector at 120 °F and fluid leaves the storage tank at 100?F. The heat exchanger manufacturers performance data for the specific heat exchanger and fluid properties is given in the

following curve*:

(3.2.5)

(3.2.6)

and K depends on the particular heat exchanger flow geometry and the following dimensionless

temperature ratios and :

*ii., in *" 0 , in

(3.2.7)

R„ = *h , in fc h , out

t - t c, out c, in

(3.2.8)

Tabular or graphical values of (At.^)^ and K are usually provided by heat exchanger

A-40
Entering the above curve with 2.0 gpm (cold) and 6.0 gpm (hot), with a 120°F - 100° = 20°F At, the actual heat transfer rate is determined to be 11,000 Btu/h. The maximum

rate of heat transfer is:

^max ” Snin

TM ^min ( fch» in t c> in) + 2.0 gal s 8.33 lb x 60 min x 1.0 Btu x 20°F = 20,000 Btu/h.

min gal h lb°F

From the definition, the heat exchanger effectiveness is calculated as:

euv 11, M0

=

Qmax

= 20 ’ 000 .55

Example 2

Calculate the effectiveness of a two pass shell and tube heat exchanger transferring

heat between water and a heat transfer fluid. Water enters the heat exchanger at 110°F and 10 gpm and the heat transfer fluid enters the heat exchanger at 160 °F and

15 gpm. The properties of the heat transfer fluid are c = .65 Btu/lb'°F and

density = 55 lb/ft^. ^

The manufacturers data consist of the following:

2

° overall heat transfer coefficient U = 150. (Btu/h* °F* ft )

0 2 heat transfer surface area A = 30.0 ft

° a table of factors to convert the performance of a counterflow heat exchanger to the performance of the actual heat exchanger by the log mean temperature difference

correction factor K is shown as follows:

A-41'
R1 — . —

T0S .1 .15 .2 .25 .3 .35 .4 .45 .5 .6 .7 .8 .9 1.0

.2 .999 .993 .984 .972 .942 .908 .845 .71

.4 No correction ro- quired when K &

R foil in this arso.

.994 .983 .971 .959 .922 .855 .70

.6 .992 .980 .965 .948 .923 .840

.8 .995 .981 365 345 .916 .872 h© .988 .970 .949 .918 .867 .770

• 2.0 .997 .973 .940 .845 . 74o) 3.0 .977 .933 .835 4.0 .993 .950 .850 5.0 .982 .917 6.0 .968 .855 1.0 .930 10.0 .996 .880 12.0 .985 .720 14.0 .972 16.0 .958 18.0 .940 20.0 |j .915

Example of Heat Exchanger Log-Mean

Temperature Difference Correction Factor, K

Since neither of the fluid exit temperatures are known, it is necessary to use a trial find error procedure.

The capacitance rate for the heat transfer fluid (hot) is given by:

s. -(i5 SM8 - 33

lb H

20

gal

IB fluid

IB H

20

65

Btu \

lb *°F/

4295

Btu

h'°F

The capacitance rate for the water (cold) is given by:

C

c 10 8.33

lb H

2 0

g£l x 1.0

Btu

lb • °F

= 4998 Btu

h-°F

Assume the exit temperature of the water t is 130°F.

c, out The actual heat transfer rate is calculated from equation (3.2.1) as:

Q • C

c

(t

c, out

- t c in > 4998 <130-110) - 99960

^

t. . = t, , - Q - 160 - 99960 - 136. 7”F

h. out h, In

n

The reference log mean temperature difference for a counter flow heat exchanger is

calculated from equation (3.2.6) as:

* Atm*cf (160 - 130) - (136 . 7 - 110)

Toi / 160 - 130 \ 6

[ 136.7 - 110

j

28 ,3°F

Since the heat exchanger is not of the counter flow arrangement, a correction factor

K must be determined from the manufacturers supplied data, in this example

based on the computed values of and R

2 as follows from equations (3.2.7) and (3.2.8)

A-42
K = .90

*1 130 - no

160 - no = .4

R , 160 , - 136.7 _ "130 - no “ i - ib

K ili then determined from the Supplied table (by extrapolation) as:

Then from equations (3.2.3) and (3.2.5)

Q = (AU)^ x (At^)^ x K = (150) (30) (28.3) (.90) = 114615

^

“d ‘c, out110 + islr '132.9-F.

Since the original exit temperature of the water was estimated to be 130°F, the

procedure is repeated until the estimated water temperature and the calculated water

temperature are the same.

For this problem, the exit water temperature is then calculated to be

t c, out131. 2°F

The actual heat transfer rate is then

Q

= 4988 (131.2 - 110) = 105,960 Btu/h*

The maximum possible heat transfer rate would occur if the minimum capacitance rate

fluid (the hot fluid in this example) were cooled to the cold fluid inlet temperature.

' Cmin <l:

' 'h

, in

t . ) = 4295 (160 - 110)

c, in 214,750

Btu

h

The heat exchanger effectiveness is given by equation (3.2.4) as:

= 105,960 = HX 214,750 *

The heat exchanger effectiveness can be assumed to be a constant for a given heat

exchanger and fluid mass flow provided the thermal properties of the fluids do not

vary substantially and provided no change of phase occurs. Thus, the calculated

value of effectiveness based on an assumed set of inlet temperatures would still be

valid over a range of hot fluid and cold fluid inlet conditions usually found in

most solar heating applications.

For the case where there are no performance data available for the particular heat

exchanger, an estimate of effectiveness can be made from the data of reference [3] for

a range of different heat exchanger designs, provided the overall conductance (AU)hx

is known. Figure A-18 -shows the effectiveness of counter flow, parallel flow, and cross flow heat exchangers as a function of the ratio (AU) Hx/Cmin with the ratio

Cmin/Cmax as the parameter. For the cross flow arrangement usually found in the liquid

to air heat exchangers, Cmin is usually the air side capacitance rate and the parameter

Cmixed/Cunmixed shown in Figure A-18 for this arrangement is equivalent to Cmin /CmaxA-43
If the particular flow arrangement of a heat exchanger is unknown, the effectiveness

can be estimated by taking an average of the calculated effectiveness for the counter

flow and parallel flow arrangements for the given (au)TM/

C

. and C . /C design HX min min max

parameters.

For situations in which a heat exchanger consists of a coil of tubing submerged in a tank of water, Cmin is the capacitance rate of the fluid circulating through the

coil and C^ay is essentially infinite. Thus, the ratio ^min^^ax = 0 is used to determine effectiveness from any of the three arrangements shown since for C^-^/Cmay = 0,

the expressions for effectiveness as a function of (AU)^/CTn -; n for all flow arrangements reduce to the same expression.

Figure A-18 General Heat Exchanger Performance [3

]

A-44
(to)

•

(Btu/h

-"F-ft 2)

INDICATED SLOPE, m (Btu/h .°F*f

t

2

)

Figure A-19 Correction of FR

( TOl ) n

an<* FRULto t in Bas i®

A-45
e cs ^min

Figure A-20 Heat Exchanger Modifier

j|

A-46
EFFICIENCY

7]

(%)

EFFICIENCY

Figure A-21a Typical Thermal Efficiency Curves for Liquid

Collectors Based on Collector Aperture Area

tj - t a

Figure A- 2 lb Typical Thermal Efficiency Curves for Liguid

Collectors Based on Collector Gross Frontal Area

A-47
4. REFERENCES

1. ASHRAE Standard 93-77, "Methods of Testing Solar Collectors Based on Thermal

Performance .

2. Johnson, S. M. and Simon, F. F. , "Evaluation of Flat-Plate Collector Performance

Obtained Under Controlled Conditions in a Solar Simulator," Proceedings of

American Section ISES Meeting, Winnipeg, Canada, Vol. 2, August 1976.

3. Kays, W. M. and London, A. L. , "Compact Heat Exchangers," National Press, Palo

Alto, California, 1955.

4. Klein, S. A., Beckman, W. A., and Duffie, J. A., "Design Procedure for Solar

Heating Systems," Solar Energy, Vol. 18, pp. 113-127, 1976.

5. Klein, S. A., Beckman, W. A., and Duffie, J. A., "A Design Procedure for Solar

Air Heating Systems," Proceedings of American Section ISES Meeting, Winnipeg,

Canada, Vol. 4, August 1976.

6. "f-Chart Computer Program Version 1.2," Solar Engineering Laboratory, University

of Wisconsin, Madison, Wisconsin.

7. "TRNSYS Computer Program," Solar Engineering Laboratory, University of Wisconsin,

Madison, Wisconsin.

8. Baughn, J. W. and Dougherty, D. A., "Experimental Investigation and Computer

Modeling of Solar Natural Circulation System," Proceedings of the 1977 American

Section of ISES Annual Meeting, Orlando, Florida.

A-48
5. NOMENCLATURE

Ac - Collector area (aperture or gross basis) [ft^]

Are f - Collector area for reference system [ f

t

^

]

Areq - Collector area required to meet % of DHW load [ f 1 2

] (AU)hx _ Heat exchanger heat transfer factor [Btu/(h*°F)]

Cc = (mCp)

c - Fluid capacitance rate of the collector working fluid [Btu/(h*°F)]

Cmin = (TMC p) m-L n

” fluid capacitance rate [Btu/(h'°F)]

Cs = (me ) - Fluid capacitance rate of the storage loop [Btu/(h*°F)]

P s Cp - Fluid specific heat [Btu/(h ,0 F)]

FR

- Collector heat removal factor

FR

“ Combined form of the collector heat exchanger effectiveness (e c ) and the

collector heat removal factor (FR) m - Mass flow rate of the working fluid either air or liquid (lb/h)

M - Mass of thermal storage (lb)

NTU - Number of heat transfer units (dimensionless)

Rl , R2 - Heat exchanger temperature ratios

tm - Temperature of water main supply [°F]

t s - Temperature of domestic hot water supply [°F]

2 U - Heat loss coefficient (storage tanks and pipes) [Btu/(h*°F*ft )]

Ul - Collector heat loss factor [Btu/(h- °F* ft^)

]

eHX ~ Heat exchanger effectiveness

n - Thermal efficiency (ratio of the thermal energy removed from the collector, to the total incident solar radiation on the collector aperture area or collector

gross area

(xa) n

- Transmittance-absorptance product at normal incidence

A-49

APPENDIX B

Appendix

Table

B-l:

Properties

of

Typical

Cover

Plate coX

cd •H

3-1 <U

cd

2>3

0)u

tc 3 C -U 6 ri n) 3 4-1 u £ n) a) •H 3-4 P. X Q) B ' o. a) O H

TB 13

O

X

O

!fl (D

C <U

O P. '•-'COB C »—l

cd 4-1 c o

CU

O

C

O c o

<u 4-j X tC

•H

C

CO <U C H

<d 4-i H co c • ca • x t w ^

•H

X

0) I a q

rH (D CO w > CO O <U 4J X C X «d X

60

U

•H

U

X

<U

O

X

32X

X

4-4 -C

0)

C

C*3

X

B-l c

4-1 c o w

4-1 4-1 C CO

cd 3

4-1 PO

a 4-j CO Q) < «

CO

CU ~ X o I -3 0) cfl 60 U

cd

O

X

X

cd o 3 U u

CQ - X 4-j 0) * a)

4-J 32 C

<U CO 60 W C CO

cd

m

CO I

cd co

>> • cd o co

T3C

cd

COCO

<U

3-i SbCO

CJCOW

cd T3

<D

4-j c

a;

co

cu

3-< O3-4 CUp.

cdD.

COO

4-1 U

cuoo

3-i cd Xo

CO

3-i o

4-1

3-4 CU

4-1 cd

3E.

3-4 • <u m > r- oo x

<u - x ^

cdx

C 3

3-i

X

<U x cd <3 x x c

•H <3 >O CO

Clarkson,

C.

W.,

Herbert,

J.

S.,

"Transparent

Glazing

Media

for

Solar

Energy

Collectors,"

oaDer

presented

at

U.S.

Section-ISES

Meeting,

Ft.

Collins,

Colorado,

August

7.1-23,

1974.
Appendix Table B-2 : Characteristics of Absorptive Coating:

Property

Material

Absorptance U

a Emittancee a~e Breakdown

Temperature

°F (°C)

Comments

Black Chrome .87-. 93 .i ^9

Alkyd Enamel .9 .9 1 Durability Limited at High

Temperatures

Black Acrylic

Paint

.92-. 97 .84-. 90 -vl

Black Inorganic

Paint

.89-. 96 .86-. 93 'Ol

Black Silicone

Paint

.86-. 94 .83-. 89 %1 Silicone Binder

PbS/Silicone

Paint

.94 .4 2.5 662 (350) Has a High Emittance for Thicknesses >10pm

Flat Black

Paint

.95-. 98 .89-. 97 VL

Ceramic Enamel .9 .5 1.8 Stable at High Temperatures

Black Zinc .9 .1 9

Copper Oxide

over Aluminum

.93 .11 8.5 392 (200)

* Black Copper

over Copper

.85-. 90 .08-. 12 7-11 842 (450) Patinates with Moisture

Black Chrome

over Nickel

.92-. 94 .07-. 12 8-13 842 (450) Stable at High Temperatures

Black Nickel

over Nickel

.93 .06 15 842 (450) May be Influenced by Moisture

at Elevated Temperatures

Ni-Zn-S over

Nickel

.96 .97 14 536 (280)

Black Iron over Steel

.90 .10 9

U Dependent on thickness and vehicle to binder ratio.

G. E. McDonald, "Survey of Coatings for Solar Collectors", NASA TMX-71730, paper presented at Workshop on Solar Collectors for Heating and Cooling of Buildings, November 21-23, 1974, New York City.

G. E. McDonald, "Variation of Solar-Selective Properties of Black Chrome with Plating Time", NASA

TMX-71731 , May 1975.

S. W. Moore, J. D. Balcomb, J. C. Hedstrom, "Design and Testing of a Structurally Integrated Steel

Solar Collector Unit Based on Expanded Flat Metal Plates", LA-UR-74-1093, paper presented at U. S. Section-ISES Meeting, Ft. Collins, Colorado, August 19-23, 1974.

D. P. Grimmer, S. W. Moore, "Practical Aspects of Solar Heating: A Review of Materials Use in Solar Heating Applications", paper presented at SAMPE Meeting, October 14-16, 1975, Hilton Inn.

R. B. Toenjes, "Integrated Solar Energy Collector Final Summary Report", LA-6143-MS, Los Alamos

Scientific Laboratory, Los Alamos, New Mexico, November 1975.

G. L. Merrill, "Solar Heating Proof-of-Concept Experiment for a Public School Building", Honeywell

Inc., Minneapolis, Minnesota National Science Foundation Contract No. C-870.

D. L. Kirkpatrick, "Solar Collector Design and Performance Experience", for the Grover Cleveland

School, Boston, Massachusetts, paper presented at Workshop on Solar Collectors for Heating and Cooling of Buildings, November 21-23, 1974, New York City.

B-2
Appendix Table B-3: Properties of Typical Absorber Subst rate Mat or i; .Is 1/

Material

Property

Aluminum Copper Mild Carbon

Steel Stain less Steel

Elastic Modulus,

Tension

psi x 10^

10 19 29 28

Density

lbs/cu. in. 0.098 0.323 0.283 0.280

Expansion Coefficient

(68-212°F)

in/in/°F x 10 _6

13.1 9.83 8.4 5.5

Thermal Conductivity

(77-212°F)

Btu/hr-ft 2 - °F-ft

128 218 27 12

Specific Heat

(212 °F) Btu/lb • °F

0.22 0.09 0.11 0.11

1/ Typical valves: standard specifications or manufacturer's literature should be consulted for specific types or alloys.

B-3
App&ndix TabI* B-4:, Standards for Piping, Valves and Ducts

Description ANSI ASTM Federal Specifications

Other

Ferrous pipe & fittings

Steel pipe, black and hot dipped zinccoated (galvanized) welded and seamless

for ordinary use B125. 2-1972 A120-73 WW-P-406D-1973 WW-P-406D-1-1974 —

Steel pipe welded and seamless B125. 1-1972 A53-73 — ASME SA53

Nipples, Pipe, threaded — — WW-N-351b-1967

WW-N-351b [ 1 ]-1970 CS5-65

Pipe fittings: (bushings, locknuts and

plugs) iron, steel and aluminum (threaded) 125-150 lbs. ... WW-P-471B-1970

Malleable-iron threaded fittings, 150 and 300 lbs. B16. 3-1971 — WW-P-521F-1968 —

Unions, pipe, steel or malleable iron; threaded connection, 150 lbs. and 250

lbs. WW-U-531D ...

Standard Specification for Seamless

and Welded Ferritic Stainless Steel Tubing for General Service B125.14 A268-73

Standard Specification for Seamless

and Welded Austenitic Stainless Steel Tubing for General Service B125.15 A269-73

Nonferrous metallic pipe and fittings

. Copper pipe, seamless H26. 1-1973 B42-75 WW-P-377d-1962 ASME SB42

Copper pipe, threadless H26. 2-1973 B302-74a — —

Copper tube, seamless H23. 3-1973 B74-74b — ASME SB75

Copper tube, seamless, for refrigeration and general use H23. 5-1974 B280-75 WW-T-775a-1962 —

Copper water tube seamless H23. 1-1973 B88-75 WW-T-799D-1971 —

General requirements for wrought seamless copper and copper alloy tube H23. 4-1973 B251-75 — ASME SB251 Seamless brass tube H36. 1-1973 B136-74 WW-T-791A-1971 ASME SB135 Seamless rad brass pipe H27. 1-1973 B43-75 WW-P-351a-1963 ASME SB43 Bronze flanges and flanged fittings,

150 and 300 lbs. B16. 24-1971 — — —

Cast-bronze fittings for flared

copper tubes B16. 26-1967 — — —

Cast-bronze solder joint drainage

f ittings-DMV

B16. 23-1969

B16. 23a-1973 — — —

Cast bronze solder joint pressure

fittings B16. 18-1972 — — —

Cast branse threaded fittings,

125 and 25* lbs. *16.15-1971

WW-P 460b-1967 WW-P-460b-l-1972

Copper tube fittings, solder ends — — W*-T-725a-1973

Unions, brass or bronze, threaded pipe

connections and solder-joint tube connections WW-U-516B

Unfons, pipe, bronze or naval brass, threaded pipe connection 250 lbs. WW-U-516a-1967

T*A
Appendix Table B-4

:

c ont inued

Description ANSI ASTM

Welded Copper Tube — B- 447

Welded Copper Nickel Pipe and Tube — B-467

Welded Copper and Copper Alloy Tube — B-543

Welded Copper Alloy Water Tube — B-586

Welded Brass Tube — B-587

Welded Copper Alloy Pipe — B-608 Copper-silicon alloy seamless pipe

and tube H26. 3-1973 B315-75

Wrought copper and bronze solder-joint

pressure fitting B16. 22-1973 —

Wrought copper and wrought copper alloy

solder-joint drainage fittings B16. 29-1973 —

Aluminum-alloy seamless pipe and seamless

extruded tube H38.7 B241

Aluminum-alloy drawn seamless tubes H38.7 B310-74a

Aluminum-alloy drawn tubes for general

purpose application H38. 17-1974 B483-73

Aluminum-alloy extruded round coiled tubes

for general purpose application H38. 18-1974 B491-73

Wrought aluminum and aluminum alloy welding

fittings H38. 19-1974 B361-73

Pipe hangers and supports — —

Pipe hangers and supports, materials,

design and manufacture ___ —

Pipe hangers and supports, selection

and application — —

Polybutylene (PB) plastic hot-water

distribution systems (180°F Max.) — D3309-74

Plastic hot-water distribution systems: chlorinated poly (vinyl chloride) (CPVC) for water service (180°F Max.) D2846-73

Cold water service, clamps, hose, low pressure — —

Standard methods of testing rubber hose J2.5 D380-75

Standard method of test for sealability

of gasket materials Z193. 1-1970 F37-68

Standard method of test for fluid resistance of gasket materials ... F146-72

Federal Other

Spec l f i cat Ions

WW-H-171D-1970

MSS SP-58-1975 1/

MSS SP-69-1966 1!

NSF 14-1965

WW-C-440B(2)
Appendix Table B-4: continued

Description ANSI ASTM Federal Other Specifications

Valves

Standard for solenoid valves for use with volatile refrigerants and water ARI 760, 1975

Valves, pressure, reducing and regulating

for installation on domestic water

supply lines IAPM0 PS15-71 y

Water pressure reducing valves for domestic water supply systems ASSE 1003, 1970

Valves, automatic relief (For water

/

steam). ANSI 21.22 1971

Valves, cast iron gate, 125 & 250 lb; threaded and flanged WW-V-58a-1966

Combination check and relief valves IAPMO TSC-8-66 1/

Valves, ball WW-V-35a-1965

Valves, bronze, angle, check and

globe, 125 and 150 lb, threaded

and flanged or soldered WW-V-51d-1967

Valves, water heater drain ASSE 1005

Globe type logllghter valves,

angle or straight pattern IAPMO PS 10-66 y

Valves, electrically operated UL 429, 1955

Valves (125 pound bronze gate) MSS SP 37, 1969

Valves (150 pound corrosion reslatant,

cast, flanged) MSS SP 42

Valves (butterfly)

2/ MSS SP 67, 1966 -

Low velocity duct construction standards SMACNA

High velocity duct construction standards SMACNA

Fibrous glass duct construction standards SMACNA

Pressure sensitive tape standards

for fibrous glass duct SMACNA

Duct liner application standard SMACNA

Fire damper guide SMACNA

1/ International Association of Plumbing and Mechanical

California 90032 Officials, 5032 Alhambra Avenue, Los Angeles,

2JManufacturers Standardization Society of the Valve and Fitting Industry, 1815 North Fort Meyer Drive

Arlington, Virginia 22209

B-6
Appendix Table B-5: Temperature and Pressure Ratings for Ball Valves—

Size Temperature, Materials (Pressure in psi)

(inches) °F Bronze Iron Carbon Steel Alloy Steel

1/2 -20 to 100 200 and 400 1000 1000

150 400 850 850

200 150 and 400 700 700

TO 250 152/and 400 500 500

300 300 300 300

325 200 200 200

3/4 353 125 125 125

375 90 90 90

400 60 60 60

1 -20 to 100 400 720 720

150 400 710 710

200 400 700 700

TO 250 400 500 500

300 300 300 300

2 325 200 200 200

353 125 125 125

375 90 90 90

400 60 60 60

2-1/2 -20 to 100 220 275 275

150 205 255 255

TO 200 190 240 240

12 250 180 225 225

1/ These ratings for ball valves, presented in Federal Specification WW-V-35a-1975 , are intended for guidance and are not intended to be restrictive. Valves should not be used

for pressures and temperatures exceeding the manufacturer's rating.

2 / 15 pounds saturated steam temperature.

B-7
Appendix Table B-6: Thermal Storage Unit Containers^

Container

Usage Transfer Pressure

3/ Recommended—

Container Protective

Recommended

Coating

Above Below Media Conditions Standard Coating Standard

Material Ground Ground Air Liquid High Low 2/ Compliance Ext. Int. Compliance

Aluminum X X X X X X ANSI B96.1

1973

-

1

Concrete X X X X X X IAPMO PS

I

(1966)

X X Ext. MPS 609-7.3

Int. TTP-95A(3)

27 May 66

Earth X X X Vapor Barrier

Materials as per ASTM E154.68

Vapor Barrier

Covering of Solids Required

MPS 507.2.2

Plastics X X X X X MIL-T-52777 4/ 21 Feb 1974

- -

Steel X X X X X X AWWA D-100

(1967)

X X Ext. MPS

609- 7.4 5/ Ext. & Int. AWWA DIO

2

(1964)

Wood X X X X NFO 8 (1965) - -

1/ Thermal Storage Unit - any container, space

,

or device which has the capacity to store transfer media

(liquid or solid) containing thermal energy for later use.

2/ Low pressure systems are those subjected to atmospheric pressure only, i.e. vented.

3/ When applicable, ASME Boiler and Pressure Vessel Code, Section VIII may be used.

j4/ Refers to fiber reinforced polyester containers

5/ In lieu of interior galvanized, glass-lined or stone-lined tanks.
Appendix Table B-7 : Examples of Typical Heat Transfer Liquids

1 /

Water

50% Ethylene

Glycol/Water

50% Propylene

Glycol/Water

Silicone

Fluid Aromatics

Paraffinic

Oil

Freezing Point,

°F (°C)

32 (0) -33 (-36) -28 (-33) -58 (-50) -100 to -25

(-73 to -32) —

Boiling Point,

°F (°C) (at atm. pressure)

212 (100) 230 (110) — None 300-400

(149-204)

700 (371)

Fluid Stability Requires pH

or inhibitor

monitoring

Requires pH

or inhibitor

monitoring

Requires pH

or inhibitor

monitoring

Good Good Good

2/ Flash Point, ~

°F (°C) None None 600 (315) 600 (315) 145-300

(63-149)

455 (235)

Specific Heat

(73°F)

[Btu/ (lb* °F)

]

1.0 0.80 0.85 0.34-0.48 0.36-0.42 0.46

Viscosity

(cstk at 77°F) 0.9 21 5 50-50000 1-100 —

Toxicity Depends on inhibitor

used

Depends on inhibitor

used

Depends on inhibitor

used

Low Moderate —

1/ These data are extracted from manufacturers literature to illustrate the properties of a few types of liquid that have been used as transfer fluids.

2/ it is important to identify the conditions ot tests for measuring flash point. Since the manufacturers

literature does not always specify the test, these values may not be directly comparable.

B-9
B-10
APPENDIX D

DEFINITIONS

General: Abbreviations, terms, phrases, and words and their derivatives used in these

Intermediate Standards for solar application shall have the meanings given in this

Appendix. The terms defined herein apply only for The Department of Housing and Urban

Development (HUD) purposes and may differ in some respects from definitions prepared for

building codes or other purposes. Wherever possible, the meaning in common use in the

residential construction field is used.

Active Solar System : An assembly of collectors, thermal storage device (s), and transfer

liquid which converts solar energy into thermal energy, and in which energy in addition

to solar is used to accomplish the transfer of thermal energy.

Air Gap : An air gap in a potable water distribution system is the unobstructed vertical

distance through the free atmosphere between the lowest opening from any pipe or faucet

supplying water to a tank, plumbing fixture, or other device and the flood level rim of

the receptacle. (NSPC)*

Auxiliary Energy Subsystem : Equipment utilizing energy other than solar both to supplement

the output provided by the solar energy system as required by the design conditions, and

to provide full energy backup requirements during periods when the solar H, or DHW systems

are inoperable.

Backflow : The unintentional reversal of flow in a potable water distribution system

which may result in the transport of foreign materials or substances into the other

branches of the distribution system. (NBS)

Backflow Preventer : A device or means to prevent backflow.

Back Pressure : Pressure created by any means in the water distribution system on the

premises, which by being in excess of the pressure in the water supply main could cause

backflow. (NBS)

Back Siphonage : The backflow of possibly contaminated water into the potable water

supply system as a result of the pressure in the potable water system becoming unintentionally less than the atmospheric pressure in the plumbing fixtures, pools, tanks, or vats

that may be connected to the potable water distribution piping. (NBS)

Chemical Compatibility : The ability of materials and components in contact with each other

to resist mutual chemical degradation, such as that caused by electrolytic action or plasticizer migration.

Collector, Combined : The collector and storage are constructed and operated such that

they functionally perform as one unit and the thermal performance of the individual

components cannot be meaningfully measured.

Collector, Component : Collector that is not structurally integrated with the storage

or building. The collector performance can be thermally characterized as an individual

component with a moving heat transfer fluid.

Collector Efficiency (instantaneous) : The ratio of the amount of energy removed by the

heat transfer fluid per unit of aperture over a time period of 5 minutes or less to the

total incident solar radiation on the collector for the same time period under steady

state conditions (test method details described in ASKRAE 93)

.

Collector, Integral (Passive) : The collector is constructed and operated as part of the

building structure and heating system. The thermal performance is considered a part

of the building heating load and solar energy provides a significant fraction of the

building heat requirements

.

* Abbreviations in parentheses indicate the sources of the definitions used here.

(See Appendices E and F)

D-l
Collector Subsystem : The assembly used for absorbing solar radiation, converting it into

useful thermal energy, and transferring the thermal energy to a heat transfer fluid.

Components : An individually distinguishable product that forms part of a more complex

product (i.e., subsystem or system).

Contaminants (hazardous) : Materials (solids or liquids or gasses) which when added

unintentionally (or intentionally) to the potable water supply cause it to be unfit for

human or animal consumption. (ASSE 1013)

Control Subsystem : The assembly of devices and their electrical, pneumatic or hydraulic

auxiliaries used to regulate the processes of collecting, transporting, storing, and

utilizing energy in response to the thermal, safety, and health requirements of the building occupants.

Creep : A time-dependent deformation resulting from sustained loads which can be influenced

by local environmental factors such as, thermal atmosphere and/or cycling, and solar

radiation.

Cross Connection : Any physical connection or arrangement between two otherwise separate

piping systems, one of which contains potable water and the other either water of unknown

or questionable safety or steam, gas, chemicals, or other substances whereby there may be

a flow from one system to the other, the direction of flow depending on the pressure

differential between the two systems.

Design Life : The period of time during which an H, and DHW system is expected to perform

its intended function without requiring major maintenance or replacement.

Design Limits : The allowable range in design specifications.

DHW : Domestic hot water system.

DWV : Drain, W’aste, Vent.

Emittance : The ratio of the radiant energy emitted by a body to the energy emitted

by a black body at the same temperature.

Energy Transport Subsystem : That portion of the H, and DHW systems which contains heat

transfer fluids and transports energy throughout the system.

Failure: Inability to perform intended function.

Failure (structural) : Failure of a structure or any structural element is defined as one

of the following:

(a) Sudden, locally-increased curvature, major spalling, or structural collapse.

(b) The inability of the structure to resist a further increase in load.

(c) Structural deflections under design loads that cause significant performance degradation of the component or subsystem.

Flow Condition : The condition obtained when the heat transfer fluid is flowing through

the collector array under normal operating conditions.

H.; Heating system,

Heat Capacity : The amount of heat necessary to raise the temperature of a given mass

one degree.

Heat Transfer Medium : A medium, liquid, or air or solid, which is used to transport thermal

energy.

Laminated Glass : Consists of two or more sheets of glass held together by an intervening

layer or layers of plastic material.

D-2
MAP : Manual of acceptable Practices. A HUD Document providing information and guidance

to assist in the use of the MPS.

Maximum "Flow" Temperature : The maximum temperature that will be obtained in a component

when the heat transfer fluid is not flowing through the system.

Maximum Service Temperature : The maximum temperature to which a component will be exposed

in actual service, either with or without the flow of heat transfer fluid.

Minimum Service Temperature : The minimum temperature to which a component will be exposed

in actual service, either with or without the flow of heat transfer fluid.

MPS 4900.1 : FHA "Minimum Property Standards For One and Two Family Dwellings."

MPS 4910.1 : FHA "Minimum Property Standards For Multifamily Housing."

"No-Flow" Condition : That condition obtained when the heat transfer fluid is not flowing

through the collector array due to shut-down or malfunction and the collector is exposed

to the amount of solar radiation that it would receive under normal operating conditions.

Non-Potable Water : Water containing impurities in amounts sufficient to cause disease or harmful physiological effects and not conforming in its bacteriological and chemical quality

to the requirements of the Public Health Service Drinking Water Standards or the regulations

of the public health authority having jurisdiction.

Outgassing : The emission of gases by materials and components usually during exposure to elevated temperature or reduced pressure.

Passive Solar System : An assembly of natural and architectural components including collectors, thermal storage device (s) and tranfer fluid which converts solar energy into

thermal energy in a controlled manner and in which no fans or pumps are used to accomplish

the transfer of thermal energy. The prime elements in a passive solar system are usually

some form of thermal capacitance and solar energy control.

Pitting : The process by which localized material loss is caused in materials or components

by erosion or chemical decomposition.

Physical Compatibility : The ability of materials and components in contact with each other

to resist degradation by physical actions such as differential thermal expansion.

Plasticizer migration : The process by which plasticizers used in plastics migrate within

the specimen and either concentrate in a narrow boundary area or migrate to another material

in connection with the specimen.

Potable Water : Water free from impurities present in amounts sufficient to cause disease

or harmful physiological effects and conforming in its bacteriological and chemical quality

to the requirements of the Public Health Service Drinking Water Standards or the regulations

of the public health authority having jurisdiction.

Pphm : Parts per hundred million.

Premature (Failure, etc.) : Failure that occurs before the design lifetime.

Safety Glass : Glazing materials predominately inorganic in character which meet the appropriate requirements of the ANSI Standard and includes laminated glass, tempered glass and

wired glass.

Safety Glazing Materials : Glazing materials so constructed, treated or combined with other

materials as to minimize the likelihood of cutting and piercing injuries resulting from

human contact with these glazing materials.

Significant (Deterioration. Loss, etc.) : Deterioration that either results in a decrease

in performance greater than the design limits or in the creation of a hazard.

Solar Absorptance : The ratio of the amount of solar radiation absorbed by a surface to the

amount of radiation incident on it (for terrestrial applications usually calculated for

Air Mass 2 characteristics).
Solar Building : A building which utilizes solar energy by means of an active or passive

solar system.

Solar Degradation : The process by which exposure to sunlight deteriorates the properties

of materials and components.

Solar Energy : The photon energy originating from the sun's radiation in the wavelength

region from 0.3 to 2.7 micrometers.

Solar Heating System : The complete assembly of subsystems and components necessary to convert solar energy into thermal energy for heating purposes in combination with aux- iliary energy when required.

Solar Time : The hours of the day as reckoned by the apparent position of the sun. Solar noon is that instant on any day at which time the sun reaches its maximum altitude for

that day. Solar time is very rarely the same as local standard time in any locality.

Storage Subsystem : The assembly used for storing thermal energy so that it can be used

when required.

Subsystem : A major, separable, functional assembly of a system such as complete collector,

or storage, assembly, etc.

System : The complete assembly necessary to supply heat and/or domestic hot water to the

dwelling.

Thermal Energy : Heat possessed by a material resulting from the motion of molecules

which can do work.

TLV, Threshold Limit Values : Threshold limit values refer to airborne concentrations of

substances and represent conditions under which it is believed that nearly all workers

may be repeatedly exposed day after day without adverse effect. Threshold limit values

refer to time-weighted concentrations for a 7 or 8-hour workday and 40-hour workweek.

Toxic Fluids : Gases or liquids which are poisonous, irritating and/or suffocating, as classified in the Hazardous Substances Act, Code of Federal Regulations, Title 16, Part 1500.

Transmittance : The ratio of the radiant flux transmitted through and emerging from a body to the total flux incident on it.

UV: Ultra-violet radiation, that part of the terrestrial solar spectrum between 0.3 and

0.4 micrometers.

Water Hammer : The term used to identify the hammering noises and severe shocks that may

occur in pressurized water supply systems when flow is halted abruptly by the rapid

closure of a valve or faucet (NBS)

.

Water Hammer Arrester : A manufactured device, other than an air chamber, containing a permanently sealed cushion of gas or air designed to provide protection against excessive

shock pressure without maintenance.

97 1/2% Winter Design Temperature : The outdoor air temperature will be lower than the

stated values for not more than 65 hours per year (2 1/2% of the 2,160 hours in December,

January and February)

.

D-4
APPENDIX E

REFERENCED STANDARDS

AASHTO H20-44 Standard Specification for Highway Bridges

ANSI A13.1 (1956) Scheme for the Identification of Piping Systems

ANSI A58.1 (1972) Building Code Requirements for Minimum Design Loads

in Buildings and Other Structures

ANSI A112.1.1 (1971) Performance Requirements, Methods of Test for

(ASSE 1001-1970) Pipe-Applied Atmospheric-Type Anti-Siphon Vacuum Breakers

ANSI A112.1.2 Air Gaps in Plumbing Systems (Reaffirmation and redesignation of

A40. 4-1942)

ANSI B9.1 (1971) Safety Code for Mechanical Refrigeration

ANSI B15.1 (1972) Safety Standard for Mechanical Power Transmission Apparatus

ANSI B16.18 (1972) Cast Bronze Solder Joint Pressure Fittings

ANSI B31.1, Section I (1973) Power Piping

ANSI B96.1 (1973) Specification for Welded Aluminum-Alloy Field-Erected

Storage Tanks

ANSI B124.1 (1971) Safety Standard for Air Filter Units (UL 900-April 1971)

ANSI B137.1 (1971) Steel Underground Tanks for Flammable and Combustible

Liquids (UL 58-July 1971)

ANSI B191.1 (1976) Standard for Heat Pumps (UL 559)

ANSI S2.8 (1972) Guide for Describing the Characteristics of Resilient Mountings

ANSI Z95.1 (1974) Oil Burning Equipment (NFPA 31-1972)

ANSI Z97.1 (1975) Performance Specifications and Methods of Test for

Safety Glazing Material Used in Buildings

ARI Standard 240 (1975) Standard for Unitary Heat Pump Equipment

ARI Standard 260 (1967) Standard for Application, Installation, and

Servicing of Unitary Systems

ARI Standard 410 Forced Circulation Air-Cooling and Air-Heating Coils

ARI Standard 760 (1975) Standard for Solenoid Valves for Use with

Volatile Refrigerants and Water

ASHRAE 37-69 Method of Testing for Unitary Air Conditioning and Heat

Pump Equipment

ASHRAE 55-74 (1974) Thermal Environmental Conditions for Human Occupancy

ASHRAE 90-75 (1975) Energy Conservation in New Building Design

ASHRAE 93-77 (1977) Methods of Testing Solar Collectors Based on Thermal Performance

ASHRAE 94-77 (1977) Method of Testing Thermal Storage Devices Based on Thermal

Performance

E-l
ASHRAE Handbook of Fundamentals

ASME SA-53, Section VIII Boiler and Pressure Vessel Code

ASSE 1011 Performance Requirements for Hose Connection Vacuum Breakers

ASSE 1012 Performance Requirements for Backflow Preventers with Intermediate

Atomospheric Vent

ASSE 1013 Performance Requirements for Reduced Pressure Principle Back

Pressure Backflow Preventers

ASSE 1015 Performance Requirements for Double Check Valve Type Back Pressure

Backflow Preventers

ASSE 1020 Performance Requirements for Vacuum Breakers, Anti-Siphon, Pressure

Type

ASTM A53-75 Specification for Welded and Seamless Steel Pipe

ASTM C739-73, Section 10.4 (1973) Flame Resistance Permanency

ASTM D471-75 Test for Rubber Property - Effect of Liquids

ASTM D660-44 (1970) Evaluating Degree of Resistance to Checking of

Exterior Paints

ASTM D661-44 (1975) Evaluating Degree of Resistance to Cracking of Exterior

Paints

ASTM D714-56 (1974) Evaluating Degree of Blistering of Paints

ASTM D750-68 (1974) Recommended Practice for Operating Light-and-Weather

Exposure Apparatus (Carbon-Arc Type) for Artificial Weather Testing of

Rubber Compounds

ASTM D772-47 (1975) Evaluating Degree of Flaking (Scaling) of Exterior Paint

ASTM D822-60 (1973) Recommended Practice for Operating Light-and-Water-Exposure

Apparatus (Carbon-Arc Type) for Testing Paint, Varnish, Lacquer, and

Related Products

ASTM D1081-60 (1974) Test for Evaluating Pressure Sealing Properties of

Rubber and Rubber-Like Materials

ASTM D1149-64 (1970) Test for Accelerated Ozone Cracking of Vulcanized Rubber

ASTM D1308-57 (1973) Test for Effect of Household Chemical on Clear and

Pigmented Organic Finishes

ASTM D1384-70 Corrosion Test for Engine Antifreeze in Glassware

ASTM D2247-68 (1973) Testing Coated Metal Specimens at 100 Percent Relative

Humidity

ASTM D2570-73 Simulated Service Corrosion Testing of Engine Antifreeze

ASTM D2776-72 Tests for Corrosivity of Water in the Absence of Heat Transfer

(Electrical Methods)

ASTM E72-74a Conducting Strength Tests of Panels for Building Construction

ASTM E84-70 (1970) Surface Burning Characteristics of Building Materials

E-2
ASTM E108-75 (1975) Methods of Fire Tests of Roof Coverings (NFPA 256-1970)

ASTM E154-68 Testing Materials for Use as Vapor Barriers Under Concrete

Slabs and as Ground Cover in Crawl Spaces

ASTM E424-71 Test for Solar Energy Transmittance and Reflectance (Terrestrial)

of Sheet Materials

ASTM F146-72 Test for Fluid Resistance of Gasket Materials

ASTM Gl-72 Recommended Practice for Preparing, Cleaning, and Evaluating

Corrosion Test Specimens

ASTM G16-71 Recommended Practice for Applying Statistics to Analysis of

Corrosion Data

ASTM G46-76 Recommended Practice for Examination and Evaluation of

Pitting Corrosion

AWWA C203-73 Standard for Coal-Tar Protective Coatings and Linings for

Steel Water Pipelines

AWWA C506-69 Backflow Prevention Devices-Reduced Pressure Principle and

Double Check Valve Types

AWWA D100 (1967) Steel Tanks - Standpipes, Reservoirs and Elevated Tanks

for Water Storage

AWWA D102 Painting and Repainting Steel Tanks, Standpipes, Reservoirs, and

Elevated Tanks for Water Storage

BMC, Section M302 (1975) Specific Requirements for the Materials, Design,

and Fabrication of Ductwork

CPSC 16 CFR, Part 1201 (1976) Architectural Glazing (Code of Federal

Regulation)

Federal Hazardous Substances Act, Code of Federal Regulations, Title 16, Part 1500

FCCCHR, Chapter 10 Manual of Cross-Connection Control (Foundation for Cross

Connection Control Research)

FS-DD-G-451C (1972) Glass, Plate, Sheet, Figured (Float, Flat, for Glazing,

Corrugated, Mirrors and Other Uses)

FS-TT-C-00598C(1) Caulking Compound, Oil and Resin Base Type (For Building

Construction) (18 March 1971)

FS-TT-S-001543A Sealing Compound: Silicone Rubber Base (For Caulking,

Sealing, and Glazing in Buildings and Other Structures) (9 June 1971)

FS-TT-S-001657 Sealing Compound: Single Component, Butyl Rubber Based,

Solvent Release Type (for Buildings and Other Types of Construction)

(8 October 1970)

FS-TT-S-00227E(3) Sealing Compound Elastomeric Type, Multi-compound (For

Caulking, Sealing and Glazing in Buildings and Other Structures)

(9 October 1970)

FS-TT-S-00230C (2) Sealing Compound: Elastomeric Type, Single Component

(For Caulking, Sealing and Glazing in Buildings and Other Structures)

(9 October 1970)

E-3
FS-TT-P-95A(3) Paint, Rubber: For Swimming Pools and Other Concrete and

Masonry Surfaces, 27 May 1966

FS-WW-U-516B Unions, Brass or Bronze, Threaded Pipe Connections and SolderJoint Tube Connections

FS-WW-U-531D Unions, Pipe, Steel or Malleable Iron; Threaded Connection,

150 lbs. and 250 lbs.

FS-WW-V-35B (1973) Valve, Ball

IAPMO PS 31-74 Specification for Backflow Prevention Devices

IAPMO PSI Prefabricated Concrete Septic Tanks (1966)

NACE TM-01-69 (1972) Laboratory Corrosion Testing of Metals for the Process

Industries

NACE TM-02-70 Method of Conducting Controlled Velocity Laboratory Corrosion

Tests

NACE TM-01-71 Autoclave Corrosion Testing of Metals in High Temperature Water

NACE TM-02-74 Dynamic Corrosion Testing of Metals in High Temperature

National Primary Drinking Water Regulation - Federal Register, 24 December 1975

NFPA 30 (1973) Flammable and Combustible Liquids Code

NFPA 31 (1974) Standard for the Installation of Oil Burning Equipment

NFPA 54 (1974) National Fuel Gas Code

NFPA 70 (1976) Section 240.24, National Electrical Code

NFPA 89M (1971) Clearances for Heat Producing Appliances

NFPA 90A (1976) Standard for the Installation of Air Conditioning and Ventilating

Systems

NFPA 90B (1973) Standard for the Installation of Warm Air Heating and Air

Conditioning Systems

NFPA 211 (1972) Standard for Chimneys, Fireplaces, and Vents

NFPA 321 (1973) Basic Classification of Flammable and Combustible Liquids

NFO 8 National Forest Products Association, The Wood Tank

NRCA - A Manual of Roofing Practice 1970 (71)

NSPC, Section 2.13 Ratproofing

MIL-T-52777 21 February 1974 Military Specifications for Tanks:

Storage, Underground, Glass Fiber Reinforced Plastic

MSS SP-73 Silver Brazing Joints for Cast and Wrought Solder Joint Fittings

SAE J447e(1964) Prevention of Corrosion of Metals

E-4
SAE J20e(1974) Coolant System Hoses

Threshold Limit Values for Chemical Substances and Physical Agents in the Work- room Environment with Intended Changes, 1975 - American Conference of Governmental Industrial Hygienists

UL 58 (1973) Standard for Steel Underground Tanks for Flammable and Combustible

Liquids (ANSI B137. 1-1971)

UL 174 (1972) Standard for Household Electric Storage-Tank Water Heaters (ANSI

C33. 87-1972)

UL 181-74, Section 10 Factory-Made Air Duct Materials and Air Duct Connectors

UL 296 (1974) Standard for Oil Burners

UL 573 (1972) Standard for Electric Space-Heating Equipment (ANSI C33. 12-1972)

UL 726 (1973) Standard for Oil-Fired Boiler Assemblies

UL 727 (1973) Standard for Oil-Fired Central Furnaces (ANSI Z96. 1-1973)

UL 730 (1974) Standard for Oil-Fired Wall Furnaces

UL 732 (1974) Standard for Oil-Fired Water Heaters

UL 900 (1971) Safety Standard for Air Filter Units (ANSI B124. 1-1971)

UL 1042 (1973) Standard for Electric Baseboard Heating Equipment (ANSI C33.95-

1973)

Water Quality Criteria 1972, National Academy of Science and National Academy

of Engineering

E-5
:

. -•••
APPENDIX F

ABBREVIATIONS

(Code Groups, Associations, and Gov't Agencies)

AASHTO

AGA

AMCA

ANSI

ARI ASHRAE

ASME

ASSE

ASTM

AWWA

BMC

BOCA

CISPI

CPSC

CS

FCCCHR

FSHUD

HVI

IAPMO IBR

ICBO

IEC

ISES

ISO

MCA

MSS

NACE

NAS/NRC

NBS

NEMA

NESCA

NFO

NFPA

NRCA

NSF

NSPC

PL

SAE

SBI

SMACNA

SPMA

TEMA

UBC

UPC

UMC

UL

American Association of State Highway and Transportation Officials

American Gas Association

Air Moving and Conditioning Association, Inc. American National Standards Institute

Air-Conditioning and Refrigeration Institute

American Society of Heating, Refrigerating, and Air Conditioning

Engineers

American Society of Mechanical Engineers

American Society of Sanitary Engineering

American Society for Testing and Materials

American Water Works Association, Inc. Basic Mechanical Code (Division of BOCA)

Building Officials and Code Administrators International, Inc. Cast Iron Soil Pipe Institute

Consumer Product Safety Commission

Commercial Standard

Foundation for Cross-Connection Control and Hydraulic Research

Federal Specifications

Department of Housing and Urban Development

Home Ventilating Institute

International Association of Plumbing and Mechanical Officials

Institute of Boiler and Radiator Manufacturers (Now Hydronic Inst.)

International Conference of Building Officials

International Electrotechnical Commission

International Solar Energy Society

International Standards Organization

Mechanical Contractor's Association

Manufacturer's Standardization Society of the Valve and

Fitting Industry

National Association of Corrosion Engineers

National Academy of Science/National Research Council

National Bureau of Standards

National Electrical Manufacturer's Association

National Environmental Systems Contractors Association

National Forest Products Association

National Fire Protection Association

National Roofing Contractor's Association

National Sanitation Foundation Testing Laboratory, Inc. National Standard Plumbing Code

Public Law

Society for Automotive Engineers

Steel Boiler Institute (Now Hydronic Institute)

Sheet Metal and Air Conditioning Contractors National

Association, Inc. Sump Pump Manufacturer's Association

Tubular Exchanger Manufacturer's Association, Inc. Uniform Building Code

Uniform Plumbing Code

Uniform Mechanical Code

Underwriter's Laboratories, Inc.

F-l
NBS-1 14A {REV. 7-73)

U .S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 77-12722. Gov't Accession

No.

3. Recipient’s Accession No.

4. T1TI !•: AND SUBTITLE

Intermediate Standards for Solar Domestic Hot Water Systems/

HUD Initiative

5. Publication Date July 1977

6. Performing Organization ( ode 465.00

). AU I llfc)

Solar Energy Program Team, Center for Building Technology

8 . Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4656500

11. Contract/Grant No. IAA-H-38-76

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Division of Energy, Building Technology & Standards

Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D.C. 20410

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRAC I (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) This report presents standards for the use of solar domestic hot water systems in

residential applications. The standards have been developed for application in numerous housing programs of the Department of Housing and Urban Development and are a companion document to be used in conjunction with the HUD "Minimum Property

Standards for One and Two Family Dwellings," 4900, and "Minimum Property Standards

for Multifamily Housing," 4910. To the greatest extent possible, these standards

are based on current state-of-the-art practice and on nationally recognized standards

including the MPS and the HUD "Interim Performance Criteria for Solar Heating and

Combined Heating/Cooling Systems and Dwellings."

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Solar buildings; solar collectors; solar domestic hot water systems; standards;

thermal storage

18. AVAILABILITY [^Unlimited

For Official Distribution. Do Not Release to NTIS

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIEIED

21. NO. OF PAGES

151

f j Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402. SD Cat. No. C13

20. SECURITY CLASS

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22. Price

Order h rom National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED $6.75

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