NBSIR 80-2110

Recommended Testing and

Calculation Procedures for

Estimating the Seasonal

Performance of Residential

Condensing Furnaces and Boilers

George E. Kelly

Mark E. Kuklewicz

Building Equipment Division

Center for Building Technology

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

April 1981

Sponsored by

Department of Energy

j^QQ Washington, DC 20585

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80-2110

1981

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NBSIR 81-2110

RECOMMENDED TESTING AND

CALCULATION PROCEDURES FOR

ESTIMATING THE SEASONAL

PERFORMANCE OF RESIDENTIAL

" CONDENSING FURNACES AND BOILERS

George E. Kelly

Mark E. Kuklewicz

Building Equipment Division

Center for Building Technology

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

April 1981

Sponsored by

U.S. Department of Energy

Washington, DC 20585

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

Procedures are developed for testing and rating the performance of residential

central furnaces and boilers of the condensing type. A condensing furnace or boiler is a unit designed to condense part of the water vapor generated by

the burning of hydrogen in the fuel and equipped with a means of draining

this condensate. The test procedure is similar to one developed by the

National Bureau of Standards for the Department of Energy covering non- condensing central heating equipment, except that it requires slightly

tighter control of the laboratory temperature, a return water temperature of

120*F (48.9®C) with a 20 degree Fahrenheit (11.1 degree Celsius) water temperature rise for hot water boilers, and offers an optional test procedure

for condensing units having no off-period losses. The rating procedure provides a method for estimating the steady-state, part-load and annual fuel

utilization efficiencies of condensing furnaces and boilers. It accounts

for the fact that the latent heat loss for a condensing unit is smaller than

for a conventional furnace or boiler, since some of the water vapor generated

from burning hydrogen in the fuel is condensed and thereby gives up part of

its latent heat to the heat exchanger and jacket.

Key Words: Annual fuel utilization efficiency; annual operating costs;

central heating equipment; condensing boilers; condensing

furnaces; part-load performance; rating procedure; seasonal

efficiency.

iii
ACKN0WLEDO4ENTS

The authors are Indebted to the Department of Energy for funding this study.

They also wish to acknowledge the valuable contribution of Mrs. Mary Reppert

of the Center for Building Technology, National Bureau of Standards, for

editing this report and for her many valuable suggestions for improving its

readability.

Note: Based largely upon the recommendations in this report, the Department

of Energy (DOE) published a "Final Rulemaking Regarding Amendments to Test

Procedures for Furnaces" in the Federal Register; Volume 45, No. 157, August

12, 1980, page 53714 through 53728. This DOE rulemaking covers test procedures

for condensing furnaces and boilers and is the official legally binding version

of the test procedure which manufacturers of the covered products are required

to follow.

iv
TABLE OF CONTENTS

Page

ABSTRACT iii

ACKNOWLEDGMENTS iv

1. INTRODUCTION 1

1.1 Description of Recommended Test Procedures 1 1.2 Description of Recommended Calculation Procedure for Determining

the Fuel Utilization Efficiency and the Annual Operating Cost .. 2

2. TEST INSTALLATION AND INSTRUMENTATION 3

2.1 Installation of Test Plenum, Duct Work, and Piping 3

2.2 Flue Requirements 4

2.3 Fuel Supply 4

2.4 Burner Adjustments 3

2.5 Circulating Air and Water Flow Requirements 5

2.6 Location of Temperature Measuring Instrumentation 6

2.7 Combustion Measurement Instrumentation 7 2.8 Energy Flow Instrumentation 7 2.9 Room Ambient Temperature 7 2.10 Equipment Used to Measure More Flow Rate Through the Furnace or Boiler 7

3. TESTING AND MEASUREMENT 7

3.1 Steady State Testing 7 3.2 Cool Down Test 8

3.3 Heat Up Test 9

3.4 Jacket Loss Measurement 10

3.5 Measurement for Determining the Effectiveness of Automatic Flue

Dampers 10

3.6 Optional Procedure for Determining Dp and Dp for Pulse Combustion

Units or Power Burners 10

3.7 Optional Procedures for Condensing Furnaces and Boilers Which Have

No Off-Period Flue Losses 11

4. CALCULATION OF DERIVED RESULTS FROM TEST MEASUREMENTS 12

4.1 Recommended Procedure for Calculating the Annual Fuel Utilization

Efficiency for Condensing Furnaces and Boilers 12

4.2 Recommended Procedures for Calculating the Annual Cost of Operation of a Condensing Furnace or Boiler Located in Different

Climate Regions of the Country and in Buildings with Different

Design Heating Requirements 16

V
TABLE OF CONTENTS (con't)

Page

4.3 Additional Calculations for Condensing Furnaces or Boilers

Utilizing Automatic Flue Dampers 16

4.4 Additional Calculation Procedures for Furnaces or Boilers with

Power Burners 16

REFERENCES 16

APPENDIX A: Calculation Procedures for Non-Condensing Furnaces and

Boilers 19

APPENDIX B: Computerized Calculation Procedure for Condensing and NonCondensing Furnaces and Boilers 60

APPENDIX C: Using Condensate Measurement for Calculation of Annual

Fuel Utilization Efficiency of Condensing Furnaces

and Boilers 89

Vi
1. INTRODUCTION

The test and calculation procedures recommended herein apply to residential

central furnaces and boilers of the condensing type. A condensing furnace or boiler is a unit which is designed to condense part of the water vapor generated by the burning of hydrogen in the fuel and is equipped with a means of

draining this condensate. For the purposes of this test procedure, a furnace

or boiler shall be considered to be of the condensing type if the latent heat

loss coefficient defined in step 68 of the calculation procedure, in

section 4.1 is less than 1 when the unit is evaluated in a hypothetical test

cycle having a percent on-time of 22.5% and, if the unit is a boiler, the

return water temperature is 120°F (48.9®C).

1.1 DESCRIPTION OF RECOMMENDED TEST PROCEDURES

The testing procedure for condensing furnaces and boilers is almost identical

to the procedure that has been developed for non-condensing units [1,2]. It

consists of a steady-state performance test and cool-down and heat-up tests

to determine the flue gas tenperature vs. time profiles during the off-and

on-periods. It differs from the conventional furnace and boiler test procedure

in that it requires control of laboratory ten5)erature between 65 °F and 85 °F, a return water temperature of 120“F (48.9°C) with a 20 degree Fahrenheit

(11.1 degree Celsius) water temperature rise for hot water boilers, and

offers an optional test procedure (section 3.7) for condensing units whose

design is such that there is absolutely no chance of air flow through

the combustion chamber during the off-period. This optional procedure allows

a manufacturer to test and rate his unit using only the steady-state test,

thereby neglecting the slight gain in performance that his unit is likely

to experience during the on-period when operating in a cyclic manner. This

effect is not expected to be very large and allowing the manufacturer to

eliminate the cool-down and heat-up test greatly simplifies the test and

calculation procedures.

The requirements that the boiler be tested with a return water temperature of

120°F (48.9°C) and a water temperature rise of 20 degrees Fahrenheit (11.1

degrees Celsius) should result in an average distribution system water

temperature, of approximately 130®F (54.4‘*C). This value was selected

using the assumption that the average boiler water temperature used to meet

the building load at an outdoor design temperature of 5°F (-15°C) might

typically be 190°F (87.8“C) and that the heat transfer from baseboard

convectors to the room air was proportional to (T^y - where T^ is the

room air temperature [3]. Assuming a typical residential zero-load temperature of 65°F (18.3“C) and continuous water circulation, it can then be shown

that an average boiler water tenqjerature of approximately 130®F (54.4°C)

would be required to meet the house's heating load at an outdoor temperature

of 42°F (5.56°C), which is the average heating season tenperature used to

rate non-condensing furnaces and boilers in NBSIR 78-1543 [1]. While cyclic

operation of the pump will tend to raise the ten5>erature of the water

required during the on-period to meet the building load, its exact effect

depends on factors outside the control of the boiler manufacture (i. e. the mass of and water content in distribution system, the type of distribution

1
system, the size of the house, etc. ) and has been Ignored In the present

version of this test procedure. The average boiler water temperature rise

of 20 degrees Fahrenheit (11.1 degrees Celsius) was selected because it is

believed to be typical of tenqjerature rises found in the field and results

in uniform heat^g ^3^ a house without the designer of the distribution system

having to be concerned about excessive temperature drops throughout the system.

1.2 DESCRIPTION OF RECOMMENDED CALCULATION PROCEDURE FOR DETERMINING THE

FUEL UTILIZATION EFFICIENCY AND THE ANNUAL OPERATING COST

Condensing furnaces and boilers are extremely complex heating devices. Their

efficiency, as measured by the input/output method, is dependent on the return

water (or air) temperature, the temperature and moisture content of the incoming

combustion air, and even the barometric pressure. These effects would tend

to make it extremely difficult to devise a test and rating procedure which

yielded consistent and repeatable results if it were not for the fact that

a preliminary test of a pulse combustion, condensing boiler at the National

Bureau of Standards tended to show that the flue gas temperature was primarily

a function of the return water temperature. Large changes in the tenqperature

and absolute humidity of the incoming combustion air (and also, by implication,

the barometric pressure) had an almost negligible effect on the measured

flue gas temperature. These findings indicated than an acceptable procedure

for rating a condensing boiler/furnace would be to determine its flue gas

temperature at a typical return water/air temperature and then to calculate

its flue losses assuming dry combustion air having an average (heating

season) temperature of 42**F (5.56®C). This assumes that most of these

condensing units will be of the direct-vent type which uses outdoor air for

combustion, and that this combustion air would typically have a very low

water vapor content (be nearly dry). To keep the calculation procedure as close as possible to that given for non-condensing units in section 4. 1 of

NBSIR 78-1543 and to avoid confusion, it was decided that all condensing

furnaces and boilers (including direct exhaust units using indoor combustion

air) should be rated as direct-vent devices. This is expected to result in an insignificant error for condensing units using indoor combustion air for

the following reasons: the combustion air must be heated up regardless of

whether it comes from inside or outside the residence; direct vent and direct

exhaust units do not use dilution air for draft control (S/F=l); and con- densing furnaces and boilers have very low flue gas temperatures (and thus

very low losses).

As a result of the observations and assumptions described above, the calculation procedure for determining the steady-state (ngg) part-load (^^)

efficiencies of condensing furnaces and boilers is only slightly changed

from the procedure specified in section 4.1 of NBSIR 78-1543 for non- condensing units [1]. The major difference is that, for condensing boilers,

the steady-state efficiency is the value measured in the steady-state test

corrected to a return water temperature of 180®F (82.2“C), and, for condensing furnaces and boilers, a procedure is provided (in steps 68 and 69) to

account for the fact that the latent heat loss, Lj^ is reduced, since some

of the water vapor (generated from the burning of fiydrogen in the fuel) is

condensed and gives up part of its latent heat to the heat exchanger and

2
jacket. In addition, a procedure is given to calculate using only

steady-state operating losses, if the optional test procedure in section 3.7

is employed for a pulse combustion unit whose design is such that there is

absolutely no chance of air flow through the unit during the off-period.

As in the case of non-condensing units, the part-load efficiency, n^> is

found for a single cycle having a percent on-time of 22.5% and then corrected

for the effect of the pilot light during the non-heating season, if

applicable, to arrive at the annual fuel utilization efficiency, EFFY.. The

procedure for calculating the annual cost of operation of condensing furnaces

and boilers is unchanged from that specified in section 4.2 of NBSIR 78-1543

[ 1 ].

2. TEST INSTALLATION AND INSTRUMENTATION

The test requirements for gas and oil-fired condensing furnaces and boilers

are, in general, identical to those described in NBSIR 78-1543 for forced air

furnaces and hot water boilers, except that:

a) tighter room temperature control is required during the condensing

furnace test, and

b) different supply and return water temperatures are employed in testing

condensing boilers, and a means must be provided to maintain these water

temperatures within strict limits.

2.1

INSTALLATION OF TEST PLENUM. DUCT WORK, AND PIPING

2.1.1 Condensing Furnaces

For gas-fueled condensing furnaces, the plenum and test duct requirements are

the same as those specified for gas-fueled, forced-air furnaces in sections

2.1.9 and 2.1.10 of ANSI Standard Z21. 47-1973. For oil-fueled condensing

furnaces, the plenum and test duct requirements are identical to those specified

in section 6.2 of ANSI Standard Z91. 1-1972.

2.1.2 Condensing Boilers

Piping requirements are identical to those described in section 2.9 of ANSI

Standard Z21. 13-1974 for gas-fueled condensing boilers and those described in

sections 7.0 and 8.1.1 through 8.1.3 of the Hydronic Institute’s Testing and

Rating for Cast Iron and Steel Heating Boilers, January 1977 edition, for

oil-fueled condensing boilers, except that a means shall be provided to

supply 120°F (48.9“C) return water, at a constant rate, to the test boiler

during both the steady-state and heat-up tests described below. This will

typically, although not necessarily, require the use of a large water tank, an auxiliary boiler, and two pumps.

3
2.2

FLUE REQURIEMENTS

The exhaust/air intake system supplied by the manufacturer shall be in place

during all tests. Units intended for installation with a variety of ventpipe lengths shall be tested with the minimum vent length recommended by the

manufacturer. A furnace or boiler employing a direct-vent system shall not

be connected to a chimney or induced draft source, but shall depend for venting of the combustion products solely on the provision for venting incorporated in the furnace and the exhaust/air intake system supplied with it. The

first 18 inches of vent pipe downstream of the furnace outlet shall be covered

with a layer of insulation having an R value not less than 7 (°F-h-f t^/Btu)

and an outer layer of aluminum foil. Care should be taken to not block the

air intake with insulation, where appropriate.

2.3

FUEL SUPPLY

2.3.1 Natural Gas

For a furnace or boiler utilizing natural gas, maintain the gas supply to

the unit under test at a normal inlet test pressure immediately ahead of all

controls at 7 to 10 Inches water column. The regulator outlet pressure at

normal test pressure shall be that recommended by the manufacturer. Use

natural gas having a specific gravity of approximately 0.65 and a higher

heating value within + 5% of 1025 Btu per standard ruble foot. Determine

the actual higher heating value in Btu's per standard cubic foot for the

natural gas to be used in the test with an error no greater than one percent.

2.3.2 Propane Gas

For a furnace or boiler utilizing propane gas, maintain the gas supply to the

unit under test at a normal inlet pressure immediately ahead of all controls

of 11 to 13 Inches water column and a specific gravity of 1.53. The regulator

outlet pressure, on units so equipped, shall be approximately that recom- mended by the manufacturer. Use propane HD-5 having a specific gravity of

approximately 1.53 and a higher heating value within + 5% of 2500 Btu's per

standard cubic foot. Determine the actual higher heating value in Btu's per

standard cubic foot for the propane to be. used in the test with an error no greater than one percent.

2.3.3 Other Test Gas

The specific gravity of other test gases shall approximate the values given

in Table IX of ANSI Standard A21. 47-1973. The test pressures immediately

ahead of all controls shall be maintained between the "normal" and "increased"

values of test pressures given in Table X in the above ANSI Standard. The

measured higher heating values shall be within + 5% of the values specified

in Table IX, in ANSI Standard Z21. 47-1973. The actual higher heating value

of the gas used in the test shall be determined with an error no greater than

one percent.

4
2.3.4

Fuel Oil

For a furnace or boiler utilizing fuel oil, the fuel oil used shall be No. 1 or No. 2 fuel oil and shall conform to the specifications outlined in Tables

2 and 3 of ANSI Standard Z91. 1-1972. The higher heating value of the test

2.3.5 fuel oil shall be measured with an error no greater than one percent.

Electrical Supply

For an electric furnace or boiler, or for an auxiliary electric component of

the gas-and oil-fueled furnace or boiler, maintain the electrical supply to

the test unit within one percent of the nameplate voltage for the entire

portion of the test cycle. If a voltage range is used for nameplate voltage,

maintain the electrical supply within one percent of the center of the

nameplate voltage range.

2.4 BURNER ADJUSTMENTS

The burners on gas- or oil-fueled, condensing furnaces and boilers shall be

adjusted to give, during the steady-state performance test described below,

the CO 2 reading recommended by the manufacturer (if applicable) and an hourly

Btu input rate which is within + 2% of the manufacturer’s specified nominal

hourly Btu input rating (nameplate rating). During the steady-state performance test, the concentration of carbon monoxide present in dry flue gas

shall not exceed 0.04 percent by volume. For oil-fired condensing units, the

smoke in the flue gases shall not exceed No. 1 smoke during the steady-state

performance test as measured by the procedure in ANSI Standard Zl 1.182 - 1965

(R 1971) (ASTM D2 156-65 (1970)). If the carbon monoxide or smoke exceeds

these specified limits during the steady-state test, the burner shall be

readjusted to give a lower CO

2 reading and all tests shall be started over. Once the burner is properly adjusted, no additional adjustments shall be made

to it during the required series of performance tests.

If a vent-limiting means is provided on a gas pressure regulator, it shall be

in place during all tests.

2.5 CIRCULATING AIR AND WATER FLOW REQUIREMENTS

2.5.1 Condensing Furnaces

For gas-fueled, condensing furnaces, the external static pressure and air

throughout shall be adjusted as specified in sections 2.1.11, 2.1.12 and

2.1.13 of ANSI Standard Z21. 47-1973, except that the temperature rise during

the steady-state test described below shall be the maximum temperature rise

specified by the manufacturer.

For oil-fueled, condensing furnaces, the external static pressure and air

throughput shall be adjusted as specified in Table 5 and section 6.2 of

ANSI Standard Z9 1.1-1 972, except that the temperature rise during the steadystate test described below shall be the maximum temperature rise specified

by the manufacturer.

5
During the steady-state and heat-up tests described below, the return air

temperature to the gas-or oil-fueled, condensing furnace shall remain within

+ 5 degrees Fahrenheit (+2.8 degrees Celsius) of the value of the room

temperatures, measured during the steady-state performance test.

2.5.2 Condensing Boilers

The water flow rate through the condensing boiler shall be adjusted to produce a water temperature rise, during the steady-state test described below,

which is between 19.5 and 20.5 degrees Fahrenheit (10.8 and 11. A degrees

Celsius). During the steady-state test and the heat-up test, the condensing

boiler shall be supplied with return water having a temperature of 120®F

(A8.9*C). The maximum permissible variation of the return water temperature

from the required value, during the steady-state and heat-up tests, shall not

exceed plus or minus 2 degrees Fahrenheit (1.1 degrees Celsius), except

during the first 30 seconds after start up it shall not exceed plus or minus

10 degrees Fahrenheit (5.56 degrees Celsius) and between 30 and 60 seconds

after start up it shall not exceed plus or minus 5 degrees Fahrenheit (2.78

degrees Celsius).

2.6 LOCATION OF TEMPERATURE MJilASURING INSTRUMENTATION

A grid of thermocouples shall be installed in a test plane parallel to and

located within 12 Inches (30.5 cm) of the furnace or boiler outlet. The grid

shall consist of either 9 or 17 thermocouples (manufacturer's option) if the

nominal inside diameter of the flue pipe is greater than 2 inches (5.1 cm)

and 5 thermocouples if the nominal inside diameter of the flue pipe is less

than or equal to 2 inches (5.1 cm). The thermocouples making up the grid

shall be wired in pax allel and the length of all thermocouple leads shall be

equal before paralleling. Locate one thermocouple in the center of the vent

pipe and eight (sixteen) [four] thermocouples along imaginary lines intersecting at right (45 degree) [right] angles in this test plane at points 1/3

and 2/3 (1/3 and 2/3) [half] the distance between the center of the flue

pipe and the pipe wall.

Bead-type thermocouples shall be used having wire size not greater than No.

24 American Wire Gauge (AWG). If there is a possibility that the thermocouples could receive direct radiation from the fire, radiation shields shall

be installed on the fire-side of the thermocouples only and the shields

positioned so that they do not touch the thermocouple junctions.

The location of thermocouples used for measuring conditioned warm air are described in ANSI Z21. 47-1973, sections 2.1.9 and 2.9.1. The temperature of

the inlet air shall be established by means of a single No. 24 AWG bead-type

thermocouple, suitably shielded from direct radiation and location in the

center of the plane of each inlet air opening.

The inlet and outlet water temperatures on both gas-fueled and oil-fueled hot

water boilers shall be measured using sheathed thermocouples inserted through

pipe plugs that are located within 12 Inches (30.5 cm) of the inlet and

outlet of the boiler. A minimum of 6 Inches (15.3 cm) of thermocouple lead.

6
Immediately upstream of the thermocouple Junction, shall be Immersed in the

water between the pipe plug and the boiler inlet/outlet. The remainder of

the thermocouple lead shall be run along the surface of the pipe (and under

any Insulation) for a distance of not less than 3 feet (183 cm). The three

feet of pipe immediately before the boiler inlet and the three feet immediately after the boiler outlet shall be covered with insulation having an

R value of not less than 7

( ®F-h-f t^/Btu) and an outer layer of aluminum

foil.

2.7

COMBUSTION MEASUREMENT INSTRUMENTATION

The flue gases for condensing furnaces and boilers shall be analyzed to

determine the concentration by volume of carbon dioxide (CO 2 ) present in the

dry flue gas, with instrumentation which will result in a determination of

the CO2 concentration with an error no larger than + 0. 1 percentage points.

2.8

ENERGY FLOW INSTRUMENTATION

Install one or more instruments which measure the quantity of electrical

energy and gas or fuel oil supplied to the furnace or boiler during the

steady-state and heat-up tests with an error no larger than one percent.

2.9

ROOM AMBIENT TEMPERATURE

During the time period required to perform all the testing and measurement

procedures specified in section 3, the laboratory room temperature shall remain

within + 5 degrees Fahrenheit (+ 2.8 degrees Celsius) of the value Tj^ measured

during the steady-state performance test. At no time during these tests

shall the room temperature exceed 85*F (37.8®C) or fall below 65®F (18.3®C).

Use the procedure outlined in section 2.1.14 of ANSI Standard 21.47-1973 to

measure room temperature.

2.10

EQUIPMENT USED TO MEASURE MASS FLOW RATE OF AIR THROUGH THE FURNACE OR

BOILER DURING THE OFF-PERIOD

The tracer gas chosen for this task should have a density which is less than

or approximately equal to the density or air. It shall be of different

chemical species or significantly larger concentration from the flue gas to

be measured and shall be unreactive with the environment to be encountered.

Instrumentation used to measure the concentration of tracer gas may be

either the batch or continuous type which will result in a reading having

an error no larger than + 2% of the value of the concentration measured.

3. TESTING AND MEASUREMENT

3. 1 STEADY-STATE TESTING

The furnace or boiler shall be set up as specified in sections 2.1, 2.2, 2.3

and 2.6. Begin the test by operating the burner and circulating air blower

or water pump, with the adjustments specified in 2.4 and 2.5, until

7
steady-state conditions are obtained, as indicated by a temperature variation

in three successive readings taken 15 minutes apart of not more than 1 degree

Fahrenheit (0,56 degrees Celsius) in the flue gas temperature and the supply

(outlet) water temperature, for hot water boilers.

Measure the room temperature (Tj^) as described in section 2.9, and measure

the steady-state flue gas temperature (Tp gg) using the thermocouple grid

described in section 2,6. A sample of the flue gas shall be secured in the

plane of temperature measurement or within 3 1/2 feet (107 cm) of this plane

on the downstream side and analyzed to determine the concentration by volume

of CO 2 ^^C02 ,F' present in the dry flue gas. If the location of sampling

the CO 2 differs from the temperature measurement plane, care should be taken

to assure that there are no air leaks in the flue pipe between these two

locations.

The steady-state heat input rate (Q^j^)> including pilot light gas input if

appropriate, shall be determined by multiplying the measured higher heating

value of the test fuel by the measured steady-state input rate. If gas is

the fuel used, correct the input rate to standard conditions of 60°F (15.6°C)

and 30 inches of mercury (762 mm of measuring) using measured values of gas

temperature and pressure at the meter and the measured barometric pressure.

Measure the steady-state electric power to the burner (PE), if appropriate.

For furnaces, measure the steady-state electrical power to the conditioned

air blower (BE). For hot water boilers, use a steady-state water pump power

of BE = 0.13 kW.

Record all measured values.

3.2 COOL-DOWN TEST

3.2.1 Gas-and Oil-Fueled Condensing Furnaces

After steady-state testing is completed and all required measurements made,

the burner shall be turned off and the flue gas temperature measured, (T^ off^

by means of the thermocouple grid described in 2.6, at 1.5 minutes (t 2

) and

9.0 minutes (t^) after the burner shuts off. Units employing flue dampers

or a stack damper in conjunction with a barometric damper shall have their

flue or stack dampers closed during the cool-down test. During this off-period,

there shall be a time delay, t"*", between burner shut-down and blower shut-down

of either 1.5 minutes or until the supply air temperature drops to a value

of 40 degrees Fahrenheit (22.2 degrees Celsius) above the inlet air temperature,

whichever results in the longer blower on-time. An exception to this is that

if the furnace employs a single motor drive a power burner and an indoor

air circulating blower, the blower and the burner shall be shut off together.

If the blower delay time exceeds 1.5 minutes, the time between burner shut-off

and blower shut-off shall be measured using a stop watch and the quantity

t'*' shall be set equal to this measured delay time or 13.30 minutes, whichever

is smaller. For units equipped with a continuously burning pilot light,

the main burner(s) shall remain off until equilibrium conditions are attained.

8
as indicated by variations in the flue gas ten5>erature of not more than

0.5 degrees Fahrenheit (0.28 degrees Celsius) in three sucessive readings

taken 15 minutes apart, and then a third flue gas temperature measurement

shall be made to determine the off-period minimum flue gas temperature

q££(®)). For units not equipped with a continuously operating pilot

ligAt, Tp off^“) shall be set equal to the measured room temperature Tj^

and the unit shall remain off for a minimum time period of 20 minutes.

During the cool-down test, the energy input rate to the pilot light (Qp), if

the unit is so equipped, shall be measured to within an accuracy of + 3%.

Record all measured values.

3.2.2 Gas- and Oil-Fueled Condensing Boilers

After steady-state testing is completed, the main burner(s) shall be turned

off and the flue gas temperature, Tp measured at 3.75 (t3

) and 22.5

(t^) minutes after the burner(s) shuts off, using the thermocouple grid

described in section 2.6. During this off-period, no water shall be allowed

to circulate through the boiler. A third flue gas temperature shall be

made 45 minutes after the burner (s) shuts off to determine the off-period

minimum flue gas temperature (T^ off^“^^* during this cool-down test, the

energy input rate to the pilot light (Qp), if the unit is so equipped, shall

be measured with an error no larger than + 3%. For units equipped with flue

dampers, the damper shall be closed during the cool-down test. Record all

measured values.

3.3 HEAT-UP TEST

3.3.1 Gas- and Oil-Fueled Condensing Furnaces

After the cool-down test is completed, the furnace shall be turned on and the

flue gas temperature measured. fT/- "i nslne the thermneonple grid described

comes on. During this on-period, there shall be a time delay, t~, between

the burner start-up and blower start-up of 1.5 minutes. Two exceptions to

this are: if the furnace employs a single motor to drive a power burner and

an indoor air circulating blower, both shall be started together; and if a 1.5 minute blower delay time results in the operation of the high limit

control to shut the burner off, the fan control shall be permitted to

automatically start the blower provided that, if it is adjustable, it is set

to turn the blower on at the highest flue gas temperature. If the fan control

is permitted to start the blower, the time delay, t”, between burner and

blower start-up shall be measured using a stop watch. Record the measured

values.

3.3.2 Gas- and Oil-Fueled Condensing Boilers

Fifty minutes after the main burner(s) is turned off for the cool-down test,

the condensing boiler shall be turned on and the flue gas temperature measured,

(Tf,on) using the thermocouple grid described in section 2.6 at 1.0 minute (t^)

in section 2.6 main burner(s)

9
and 5.5 minutes (t 2

) after the main burner comes on. The pump circulating

the water through the boiler shall be started simultaneously with the main

burner(s), the water flow rate shall be the same as that maintained during

the steady state test described in 3.1, and the return water temperature

shall be within the limits specified in section 2.5,2. 3.4

JACKET LOSS MEASUREMENT

A jacket loss test is specified only for units intended to be installed out

of doors. Measure the jacket loss (Lj) in accordance with the following ANSI

standards, and record the total loss and ambient room temperature during the

test:

(a) Gas-fueled forced-air condensing furnaces - ANSI Z21. 47-1973, section

2.9.1 and Appendix F.

(b) Gas- or oil-fueled hot water condensing boilers - ANSI Z21, 47-1973,

section 2.9.1 and Appendix F.

(c) Oil-fueled forced-air condensing furnaces - Z91. 1-1972, Appendix B.

3.5

MEASUREMENT FOR DETERMINING EFFECTIVENESS OF AUTOMATIC STACK DAMPER

The effectiveness of an automatic stack damper (D^) , on furnaces so equipped,

shall be determined by measuring the cross-sectional area of the stack (Ag),

the net area of the damper plate (A^) (the area of the damper plate minus the area of any holes in the plate), and the angle which the damper plate makes

when closed with a plane perpendicular to the axis of the stack. The equation in section 4,3 is then employed to calculate D^.

3.6

OPTIONAL PROCEDURE FOR DETERMINING Dp AND Dp

On furnaces or boilers where design is such that there is absolutely no chance

of air flow through the combustion chamber and heat exchanger when the unit is

off. Dp and Dp may be set equal to 0.0.

For other units using pulse combustion or power burners, the values of Dp and

Dp may be obtained as described below. On. systems not employing automatic

stack dampers or power-burner systems with a stack damper and a draft diverter

or draft hood. Dp shall be measured during the cool-down test described in

section 3.2. On systems for which the flue or stack damper is to be closed

during the cool-down test described in section 3.2, Dp shall be measured

during a separate cool-down test. This separate cool-down test shall be

conducted after the heat-up test described in section 3.3 is completed.

It shall be conducted by letting the unit run after the heat-up test until

steady-state conditions are reached, as Indicated by temperature variation in

three successive readings taken 15 minutes apart of not more than plus or minus

1“F (0,56°C) in the flue gas temperature and the outlet water temperature, for

hot water boilers, and then shutting the unit off with the stack or flue

damper controls by-passed or adjusted so that the stack or flue damper remains

open during the resulting cool-down period. If a draft was maintained on

10
oil-fueled units in the flue pipe during the steady-state performance test

described in section 3.1, the same draft (within -0.001 and +0.005 inches of

water gauge of the average steady-state draft) shall be maintained during

this cool-down period.

The flue gas mass flow rate (m^ Qpp) during the cool-down test described

above shall be measured at a specific off-period flue gas temperature and then

corrected to obtain its value at the steady-state flue gas temperature

gg), using the procedure described in 4.4.

Within one minute after the unit is shut off to start the cool-down test for

determining Dp, begin feeding a tracer gas into the combustion chamber at a constant flow rate of V-p, and at a point which will allow for the best possible mixing with the air flowing through the chamber. On units equipped with

an oil-fired power burner, the best location for injecting this tracer gas

appears to be through a hole drilled in the blast tube. The value of Vp

shall be periodically measured with an instantaneously reading flow meter

which will result in a reading having an error no larger than + 3% of the

quantity measured and shall be less than 1% ot the air flow rate through the

furnace. If a combustible tracer gas is used, there should be a delay period

between the time the unit is shut off and the time the tracer gas is first

injected, to prevent ignition of the tracer gas. Great care should be exer- cised when employing tracer gases which are combustible or dangerous, to

prevent human injury.

Between 5 and 6 minutes after the^unit is shut off to start the cool-down

test, the flue gas temperature, Tp qfF* shall be measured using the nine

thermocouples described above. At ’the same instant the flue gas temperature

is measured, the percent volumetric concentration of tracer gas, Cp, in the

flue gas shall also be measured in the same plane where Tp Qpp is determined.

The concentration of tracer gas shall be obtained using an* instrument which

will result in a reading having an error no larger thatn + 2% of the value of

Cp measured and may be either a batch or continuous reading type instrument.

If the sampling arrangement on a continuously reading instrument results

in a delay time between drawing of a sample and its analysis, this delay

should be taken into account so that the temperature measurement and the

measurement of tracer gas concentration coincide. In addition, the temperature

(Tp) of the tracer gas entering the flow meter and the barometric pressure

(Pg) shall also be determined.

The rate of the flue gas mass flow through the furnace and the factors Dp,

Dp, and Dg are calculated by the equations in section 4.4.

3.7 OPTIONAL PROCEDURES FOR CONDENSING FURNACES AND BOILERS WHICH HAVE NO

OFF-PERIOD FLUE LOSSES

At the discretion of the manufacturer, the cool-down and heat-up tests

specified in 3.2 and 3.3 may be omitted on condensing units whose design is

such that there is absolutely no chance of air flow through the combustion

chamber and heat exchanger when the burner(s) is off. This type of unit has no off-period heat losses up the flue and the above option (in conjunction

11
with the calculation procedure in section 4.1) allows the manufacturer to

give up the slight gain in efficiency that his unit would typically experience during the on-period (due to a lower average, on-period, flue gas

tenperature ) and use the efficiency achieved during the steady state test

described in 3.1 in place of the part-load efficiency

4. CALCULATION OF DERIVED RESULTS FROM TEST MEASUREMENTS

4.1 RECOMMENDED PROCEDURE FOR CALCULATING THE ANNUAL FUEL UTILIZATION

EFFICIENCY FOR CONDENSING FURNACES AND BOILERS

The recommended procedure for calculating the annual fuel utilization

efficiency, EFFY^, consists of two types of tasks, namely;

* Collecting measured quantities from the tests and the assignment of

characterisitc constants associated with the system under evaluation.

® Calculation of losses (l.e. , latent heat loss, Lj^ on-cycle sensible

heat loss, Lg and off-cycle sensible heat loss, L _-) and the

annual fuel utilization efficiency, EFFY^.

The calculation procedure involves carrying out each of the following numbered

steps and entering the result, in the column having the same number, on the

worksheet given in Figure 10 of NBSIR 78-1543 [1]. In order to facilitate a comparison with the calculation procedure for non-condensing furnaces and

boilers, these steps are presented, whenever possible, as modifications to

the corresponding steps in section 4 of NBSIR 78-1543 [1]. The list of

nomenclature, section 4, the figures, and the tables from NBSIR 78-1543 [1] are reproduced in Appendix A for the benefit of those readers who do not have

a copy of [1].

Numbered Steps and Columns in Figure 10 of NBSIR 78-1543 (Refer to Appendix

A):

1. Select the appropriate system number SYS// from Table 2 of NBSIR 78-

1543. This table shall apply to both direct vent and direct exhaust,

condensing units.

2-7. Same as steps 2 through 7 in 4. 1 of NBSIR 78-1543.

8-9. Enter 0.0.

10,11. Same as steps 10 and 11 in 4.1 of NBSIR 78-1543.

12-16. Same as steps 12 through 16 in 4.1 of NBSIR 78-1543 except enter 0.0

if optional procedure described in section 3.7 is enq)loyed.

17-18. Same as steps 17 and 18 in 4.1 of NBSIR 78-1543.

12
, 19. Enter S/F = 1.0.

! 20. Enter the off-period flue gas factor, Dp, selected from Table 2 of

! NBSIR 78-1543 for SYS// (column 1) under consideration or obtained in

I accordance with section 3.6.

j 21. Enter Dg = Dp (col. 20) in column 21.

li

I 22-28. Same as steps 22 through 28 in 4.1 of NBSIR 78-1543.

ij 29. Using the value of R.J. p (column 28) and ATp gg = . t^F,SS (column 11) -

'll Tj^(column 17)] read from Figure 2 of NBSIR* 78-1543 the average sens-

! ible heat loss during the steady-state test, Lg

gg and enter in

;|! column 29.

’ *

1

I; 30. Calculate and enter the steady-state efficiency (excluding jacket

j losses and corresponding to a return water temperature of 180°F

. (82.2®C) for boilers) using:

I ' '

j i^SS ” “

^S, SS furnaces

j '^SS “ ^S,SS,A^^°^*

! _ (100)(.24)(180 - 120) (1 + (Rt, ^(col. 28))(A/F(col. 25))) boilers

I HHV^(col. 24)

*

|i

where and are found in steps 68 and 69 respectively, and, if

the optional procedure described in section 3.7 was employed, proceed

I directly to step 64 skipping all intermediate steps. If optional

! procedure in section 3.7 is not employed, continue with step 31.

31-38. Same as steps 31 through 38 in 4.1 of NBSIR 78-1543.

Tp <,<j(col. 11) - 42

39. Enter Cq = ^ in column 39

Tf,ss(co1. 11) - 70

40-48. Same as steps 40 through 48 in 4.1 of NBSIR 78-1543.

49. Calculate and enter: Qp 0 ^t on ^ ®F 0 using the

definition of C^. in step 49 of 4.1, ^IbSiR 78-1543.

50-63. Same as steps 50 through 63 in 4.1 of NBSIR 78-1543.

64. If optional procedure described in 3.7 was employed, calculate and

enter:

13
100 “ Lj^ ^(col* 26) ” Lq “ Cj-(col«

tQjjCcol. 45) + PF (col. 23) t^ffCcol.

27)Lj(col. 18) — X C_(col. 39)

46) ®

X Lg gg ^(col. 29)

where is found using the procedure described in step 68, Lq is

found in step 69

and Cs = ^F,SS(<=°1- ~

. ^ Tp^ggCcOl. 11) -70

If optional procedure described in 3.7 was NOT employed, calculate

and enter:

100 - Cl Ll ^(col. 26) - L^. - Cj(col.

tonCcol. 45) + PF (col. 23) tQf£(col.

27)

46)

X Lj(col. 18)

60)

^S,off

where Cl is found using the procedure described in step 68 and Lq is

found in step 69.

65-67. Same as steps 65 through 67 in 4.1 of NBSIR 78-1543.

68. Calculate and enter the latent heat loss coefficient. Cl, using the

following four-step procedure:

(a) Calculate what the partial pressure, p^, of water vapor would be

in the flue gases if there were no condensation and the atmospheric

pressure was equal to 14.7 psla:

_ “v %G

p^ = X X

mFG M,

(14.7)

HHV^(col. 24) X 26)

where is the weight of water vapor

'' (100) X (1053.3)

generated per unit weight of fuel burnt.

®FG ~ 1 A/F(col. 25) x p(col. 28) is the weight of flue gases

generated per unit weight of fuel burnt.

= 18 is the approximate molecular weight of water

14
29.0 No. 1 and No. 2 fuel oil

28.0 natural gas

27.5 manufactured gas

28.5 butane and propane

are the approximate apparent

molecular weights of flue

gases for different fuels.

1053.3 is the assumed latent heat/lb of water.

(b) Calculate the average flue gas temperature, Tp during the

on-period using;

^F,on "

’^F,SS

/a(co1. 49) \ e .(col. 11) + ^

;2S. (col. 47)

^on /

'on \ (col 47) on

if the optional procedure described in 3.7 was NOT employed.

Use Tp = Tp gg (col. 11), if optional procedure described in 3.7 was employed. *

(c) F rom Table 1 find the saturated vapor pressure, p^®, at temperature

Tp and the saturated vapor pressure Pv® at Tp

(d) If p^ < Pv^» ^ unit does not meet the definition

given in the Introduction for a condensing furnace or boiler and the

furnace or boiler should be re-tested using the procedures specified

in NBSIR 78-1543. If Pv < Pv®', C£ = 1.

If p^ > p^®, calculate the latent heat loss coefficient, using;

I If Pv ^ Pv®, calculate the latent heat. loss coefficient, C^, using;

15
69 Calculate the loss and Lq, in percent, due to hot condensate going

down the drain and correct for the fact that this condensate did not

go up the flue as heated vapor (as was assumed in determining

Lc

Ll ^(col. 26)(1 - C^Ccol. 68d))

* 105373

X

(1.0 (Tp^gg(col. 11) - 70) - 0.45 (Tj.^gg(col. 11) - 42))

^L,A

1053.3

(1.0(Tf^ss^^o1*^^> - 70) - 0.45 (Tp^gg (col. H)-42))

4.2 RECOMMENDED PROCEDURES FOR CALCULATING THE ANNUAL COST OF OPERATION OF A

CONDENSING FURNACE OR BOILER LOCATED IN DIFFERENT CLIMATIC REGIONS OF

THE COUNTRY AND IN BUILDINGS WITH DIFFERENT DESIGN HEATING REQUIREMENTS

These procedures are the same as those in section 4.2 of NBSIR 78-1543.

4.3

ADDITIONAL CALCULATIONS FOR CONDENSING FURNACES OR BOILERS UTILIZING

AUTOMATIC FLUE DAMPERS

These calculations are identical to those given in section 4.3 of NBSIR

78-1543.

4.4

ADDITIONAL CALCULATION PROCEDURES FOR FURNACES OR BOILERS EQUIPPED WITH

POWER BURNERS

These procedures are the same as the procedures given in section 4.4 of

NBSIR 78-1543.

REFERENCES

1. Kelly, G. E., CHI, J., and Kuklewicz, M. E. , "Recommended Testing and

Calculation Procedures for Determining the Seasonal Performance of

Residential Central Furnaces and Boilers," NBSIR 78-1543, October 1978.

2. Department of Energy, "Test Procedure for Furnaces and Vented House

Heating Equipment, " Federal Register, Vol. 43, No. 91, Wednesday, May 10,

1978, pages 20108 through 20205.

3. American Society of Heating, Refrigerating and Air-Conditioning Engineers,

ASHRAE Handbook and Product Directory - 1979 Equipment Volume, New York,

New York, 1979, page 284.

16
Table 1. Saturated Vapor Pressure of Water at Different Temperatures

Temp. (“F) Pressure (psla) Temp. (®F) Pressure (pi

700.0 3094.3 140.0 2.8892

600.0 1543.2 139.0 2.8157

500.0 680.86 138.0 2.7438

400.0 247.26 137.0 2.6735

300.0 67.005 136.0 2.6047

200.0 11.526

135.0 2.5375

180.0 7.5110 134.0 2.4717

179.0 7.3460 133.0 2.4074

178.0 7.1840 132.0 2.3445

177.0 7.0250 131.0 2.2830

176.0 6.8690

130.0 2.2230

175.0 6.7159 129.0 2.1642

174.0 6.5656 128.0 2.1068

173.0 6.4182 127.0 2.0507

172.0 6.2736 126.0 1.9959

171.0 6.1318

125.0 1.9424

170.0 5.9926 124.0 1.8901

169.0 5.8562 123.0 1.8390

168.0 5.7223 122.0 1.7891

167.0 5.5911 121.0 1.7403

166.0 5.4623

120.0 1.6927

165.0 5.3361 119.0 1.6463

164.0 5.2124 118.0 1.6009

163.0 5.0911 117.0 1.5566

162.0 4.9722 116.0 1.5133

161.0 4.8556

115.0 1.4711

160.0 4.7414 114.0 1.4299

159.0 4.6294 113.0 1.3898

158.0 4.5197 112.0 1.3505

157.0 4.4122 111.0 1.3123

156.0 4.3068

110.0 1.2750

155.0 4.2036 109.0 1.2385

154.0 4.1025 108.0 1.2030

153.0 4.0035 107.0 1.1684

152.0 3.9065 106.0 1.1347

151.0 3.8114

105.0 1.10174

150.0 3.7184 104.0 1.06965

149.0 3.6273 103.0 1.03838

148.0 3.5381 102.0 1.00789

147.0 3.4508 101.0 0.97818

146.0 3.3653

100.0 0.94924

145.0 3.2816 99.0 0.92103

144.0 3.1997 98.0 0.89356

143.0 3.1195 97.0 0.86679

142.0 3.0411 96.0 0.84072

141.0 2.9642

17
Table 1. Saturated Vapor Pressure of Water at Different Temperatures (con*t)

Temp. (“F) Pressure (psla)

95.0 0.81534

94.0 0.79062

93.0 0.76655

92.0 0.74313

91.0 0.72032

90.0 0.69813

89.0 0.67653

88.0 0.65551

87.0 0.63507

86.0 0.61518

85.0 0.59583

84.0 0.57702

83.0 0.55872

82.0 0.54093

81.0 0.52364

80.0 0.50683

79.0 0.49049

78.0 0.47461

77.0 0.45919

76.0 0.44420

75.0 0.42964

74.0 0.41550

73.0 0.40177

72.0 0.38844

71.0 0.37549

70.0 0.36292

69.0 0.35073

68.0 0.33889

67.0 0.32740

66.0 0.31626

65.0 0.30545

64.0 0.29497

63.0 0.28480

62.0 0.27494

61.0 0.26538

18
APPENDIX A. CALCULATION PROCEDURE FOR NON-CONDENSING

FURNACES AND BOILERS

In order to assist readers who do not have a copy of NBSIR 78-1543 [1], the

following Items from [1] are reproduced In this appendix: the list of

nomenclature, section 4 (which gives the calculation procedure for non- condensing furnaces and boilers), Tables 1 through 5, and Figures 1 through

10 .

19
NOMENCLATURE

net area of stack or flue damper plate

cross sectional area of stack where flue or stack damper is located,

in square inches

A/F mass ratio of stoichiometric air to fuel

BE electrical power to circulating air blower or water pump, in kW

^IID correction factors for units using intermittent devices or cycling

pilots

Cj jacket loss factor

Cg, Cg on-period and off-period correction factors for outdoor units, units

Intended for installation in unheated spaces or units equipped with

direct vent systems

Cip concentration by volume of tracer gas present in flue gas

^t.OFF cool-down temperature profile correction factor for the effect of

cycling

^t,ON heat-up temperature profile correction factor for the effect of

cycling

DD degree days

stack or flue damper effectiveness factor

°F off-cycle draft factor for flue gas flow

Dp power burner effectiveness factor

off-cycle draft factor for stack gas flow

EFFY^ Annual Fuel Utilization Efficiency

^IN measured electrical power input for electric furnaces and boilers,

in watts

F3, F4,

F5. F6,

F7, F8

functions defined by Figures 3 through 8

HHV measured higher heating value of test gas, in Btu/lb

HHVa average higher heating value of typical fuel, in Btu/lb

20
HLH heating-load hours, in hours

HR number of non-heating season hours that pilot light is assumed

wasted

*^I,OFF multiplication factor for infiltration loss during off-period

^I,ON multiplication factor for infiltration loss during on-period

^S,OFF multiplication factor for sensible heat loss during off-period

^S,ON multiplication factor for sensible heat loss during on-period

^I,OFF off-cycle infiltration loss, in %

^I,ON on-cycle infiltration loss, in %

jacket loss, in %

H.a latent heat loss, in %

^S,OFF off-cycle sensible heat loss, in %

^S,ON on-cycle sensible heat loss, in %

^S,SS,A sensible heat loss at steady-state operation, in %

A •“f,off off-cycle flue gas flow rate, in Ib/min

•®F,SS flue gas flow rate at steady-state operation, in Ib/min

barometric pressure, in inches of Hg

PE electrical power to power burner, in kW

PF ratio of Qp to Qp^^lN

^IN fuel energy input rate at steady-state operation (including any

pilot light input), in Btu/hr

Qp fuel energy input rate to pilot light in Btu/h

%,F ratio of combustion air to stoichiometric air

%,S ratio of combustion air and draft relief air to stoichiometric air

S/F ratio of stack gas mass flow rate to flue gas mass flow rate at

steady-state operation and an average outdoor temperature equal to

42*F (5.6®C)

t time, in minutes

21
’^OFF off-time per cycle, in minutes

^ON on-time per cycle, in minutes

ti» t2,

^3>

different times at which flue and/or stack gas temeprature are measured, in minutes

t+ delay time between burner shut off and blower shut off, in minutes

t" delay time between burner, start up and blower start up, in minutes

"^FUEL type of fuel defined in step 2 of section 4,2

*^F,OFF off-period flue gas temperature while the system is in cyclic

operation, in ®F

*^F,OFF off-period flue gas temperature when tracer gas concentration is

measured, in °F

’^F,OFF,X off-cycle flue gas temperature after shut down of the system from

steady-state operation, in ®F

’^F,ON on-cycle flue gas temperature while the system is in cyclic

operation, in °F

"^F,ON,X on-cycle flue gas temperature after start-up of the system from

"equilibrium” condition, in *F

T^F,SS flue gas temperature at steady-state, in “F

Tp minimum flue gas temperature, in °F

average outdoor air temperature assumed equal to 42®F (S.b^C)

Tra laboratory room temperature, in ®F

'^S,OFF off-cycle stack gas temperature while the system is in cyclic

operation, in ®F

'^S,OFF,X off-cycle stack gas temperature after shut down of the system

from steady-state operation, in ®F

*^8, ON on-cycle stack gas temperature while the system is in cyclic

operation, in ®F

'^S,ON,X on-cycle stack gas temperature after start-up of the system from

"equilibrium" condition, in ®F

’^8,88 calculated stack gas temperature at steady-state, under typical

field conditions, in ®F

22
measured steady-state stack gas temperature, in ®F '^S,SS,X

Tg OFF^**^ minimum stack gas temperature, in °F

Tt temperature of tracer gas entering flow meter

^C02,F concentration by volume of CO2 present in dry flue gas, in %

^C02,S concentration by volume of CO2 present in dry stack gas, in %

Vt flow rate of tracer gas in cu ft/min

y ratio of blower on time to burner on time

a oversizing factor

Y angle stack or flue damper plate makes when closed with plane

perpendicular to axis of stack or flue

^'^F,SS temperature difference defined as Tp gg - Tj^

^'^S,SS temperature difference defined as Tg gg - Tj^

’^SS steady-state efficiency

^u part-load utilization efficiency

®F temperature difference defined as (Tpgg - Tp qjj)

CD o temperature difference defined by step 49 in section 4.2

®F,0,X temperature difference defined by step 33 in section 4.2

Pf density of flue gas, in Ib/cu ft

heat-up time constant defined in step 32 of section 4.2, in minutes

^OFF cool-down time constant defined in step 34 of section 4.2, in minutes

<!> infiltration parameter assumed equal to 0.7

'^F temperature difference defined as (Tp Qpp

- Tp qfF^*”^^

'^F,0 temperature difference defined by step 50 in section 4.2

'*V,0,X temperature difference defined by step 35 in section 4.2

4^,00 temperature difference defined by step 51 in section 4.2

'^,«,x temperature difference defined by (Tp OFF^**^ ~

23
'I'S,0

s,o,x

'I' CO S, •

s, ,x

temperature

temperature

temperature

temperature

difference

difference

difference

difference

defined by

defined by

defined by

defined by

step 52 in

step 38 in

step 52 in

step 37 in

section 4.2

section 4.2

section 4.2

section 4.2

24
4. CALCULATION OF DERIVED RESULTS FROM TEST MEASUREMENT (FOR NON-CONDENSING

FURNACES AND BOILERS)

The test procedures for furnaces and boilers were outlined in sections 2 and 3

above.* A calculation procedure is described below, in subsection 4.1, for

determining the annual fuel utilization efficiency, EFFY^, for gas- and oilfired central heating equipment. The fuel utilization efficiency for electric

furnaces and boilers is assumed to be 100% for indoor units, and is given by

EFFY^ = (100 - 3.3Lj) and EFFY^ = (100 - 4.7Lj) for electric furnaces and

boilers, respectively. Intended for Installation out of doors or in unheated

spaces (such as an attic or a crawl space). In subsection 4.2, recommended

procedures for calculating the annual cost of operation in different climate

regions of the country and an average operating cost for the continental

United States are described. Sections 4.3 and 4.4 provide additional calculations relating to gas- or oil-fueled furnaces and boilers equipped with

stack dangers and/or power burners.

4.1 RECOMMENDED PROCEDURE FOR CALCULATING THE ANNUAL FUEL UTILIZATION

EFFICIENCY FOR FOSSIL-FUEL HEATING SYSTEMS

The recommended procedure for calculating the annual fuel utilization efficiency, EFFY^, consists of these types of tasks, namely:

® Collection of measured quantities from the tests and characteristic

constants (see tables 2 and 3) associated with the system under

evaluation.

* Calculation of losses (l.e., latent heat loss, Lj^ on-cycle sensible

heat loss, Lg qj^, off-cycle sensible heat loss, Lg qff» on-cycle

infiltration loss, Lj off-cycle infiltration loss, Lj qfF^

annual fuel utilization efficiency, EFFY^. These tasks are performed

by carrying out each of the following numbered steps and entering the

result in the column having the same number on the worksheet (Figure

10 ).

Numbered Steps and Columns in Figure 10 are as follows:

1. Enter in column 1 the system number SYS# (see tables 1 and 2) for type of

system under evaluation.

2. Enter type of fuel used, TFUEL. Use "1” for No. 1 oil, "2" for No. 2

oil, "3" for natural gas, "4" for manufactured gas, ”5" for propane,

and ”6" for butane.

3. Enter measured higher heating value of fuel used, HHV, in Btu/lb.

4. Enter fuel input rate (including fuel supply to pilot flame) at full-

* i.e.

sections 2 and 3 of NBSIR78-1543 [Ij.

25
load steady-state operation, Qjj^, in Btu/h.

5. Enter fuel input rate to pilot flame, Qp, in Btu/h.

6 . Enter power burner electric energy input rate at full-load steady-state

operation, PE, in kW.

7. Enter circulating-air blower (or circulating-water pump) electric energy

input rate at full-load steady-state operation, BE, in kW.

8 . For furnaces or boilers with draft diverters; Enter the CO2 concentration S volume) in dry stack gas at full-load steady-state

operation measured in accordance with section 2. For units employing

draft hoods, barometric damper or direct vent systems: Enter 0.0 in

column 8 .

9. For furnaces or boilers with draft diverters; Enter the stack gas temperature at full-load steady-state operation, Tg gg measured in

accordance with section 2 .

* *

For units employing draft hood, barometric dampers or direct vent systems

Enter 0.0 in column 9.

10. Enter the CO 2 concentration ^C02 ,F (% by volume) in dry flue gas at

full-load steady-state operation measured in accordance with section 2 .

11. Enter the flue gas temperature at full-load steady-state operation,

Tp^gg measured in accordance with section 2 .

12. , 13. Enter the flue gas tenqjeratures in ®F at the start-up of the system

burner from equilibrium, Tp

"^F 0N^*^2^ columns 12 and 13,

respectively. * *

For furnace: tj^ = 0.5 minute, t 2 = 2.5 minutes.

For boiler; t^ = 1 minute, t2 = 5.5 minutes.

14. , 15. Enter the flue gas temperature in “F after the shut-down of the

system burner from steady-state operation, Tp 0FF^*-3^ *-F OFF ^^4^

in columns 14 and 15, respectively. * ’

For furnace; t^ = 1.5 minutes, t^ = 9 minutes.

For boiler; 13 = 3.75 minutes, t^ •* 22.5 minutes.

16. Enter the minimum flue gas temperature in “F as measured in accordance

with section 3.2 while the burner is off, Tp qfF^“^* furnaces not

employing a continuously operating pilot ligAt, Tp qfF^"^ equals the

room temperture. *

17. Enter the laboratory room temperature, Tj^, in ®F.

26
18, For indoor unit: Enter 0,0 in column 18,

For outdoor unit or units intended for installation in unheated spaces

(such as an attic or a crawl space): Enter jacket loss Lj, measured in

accordance with section 2 ,

19, Enter the average ratio of stack-gas mass flow rate to flue-gas mass flow rate at full-load steady-state operation, S/F, S/F is selected

from tables 1 and 2 for the SYS// (column 1) under consideration.

20, Enter the off-cycle flue gas draft factor, Dp, selected from tables 1 and 2 for the SYS// (column 1) under consideration or measured in

accordance with section 3,6,

21, For SYS// (column 1) equal to 9 through 12: Enter 0,0 in column 20,

For SYS// (column 1) equal to 1 through 8 : Enter off-cycle stack gas

draft factor, Dg, Dg may either be selected from table 1 for the SYS//

(column 1 ) under consideration or determined in accordance with section

3,6.

- t'\

22, Enter value of y equal to 1 + \ 3 gy y for furnaces, and y equal to

1,00 for boilers or furnaces employing a single motor to drive a power

burner and an indoor-air circulating blower.

23,

Calculate and enter the ratio of pilot flame fuel input rate to the

system full-load fuel (including pilot flame fuel) input rate:

Qp (col, 5)

(col, 4)

24,

For the type of fuel used, obtain the average higher heating value,

HHV^, in Btu/lb from table 3 and enter in column 24, Calculate

HHV (col, 3)

HHV^ (col, 24)

and proceed to step 25 only if 0,95 < HHV (col, 3)

HHV^ (col, 24) < 1,05.

25,, 26, Read average values of stoichiometric air-to-fuel ratio, A/F, and

latent heat loss ^

from table 3 for TFUEL (column 2) under consideration, and enter th4se values in columns 25 and 26, respectively.

27, Enter Cj equal to 3,3 for furnaces and 4,7 for boilers,

28, Using TFUEL (column 2) and ^cq2 p

10), read from figure 1 the

ratio of combustion air to stoichiometric air, RTM „ and enter this

value.

29,

For furnaces or boilers with draft diverters: Using TFUEL (column 2)

and Xqq

g

(column 8 ), read from figure 1 the ratio of the sum of

27
combustion and relief air to stoichiometric air, Rq; g* Then using this

Rq.

g

value and *

SS ** SS X

(column 9) - Tj,. (column 17)] read from figure 2 for

the*TFUEL (c6lu&n 2) under consideration the average sensible heat loss

at full“load steady-state operation Lg

gg ^

and enter this value In

column 29. * *

For units equipped with draft hoods, barometric dampers or dlrect-vent

systems: Using value of Rq, p (column 28) and Z\Tp gg

= [Tp

gg

(column

11) - T„, (column 17)] read*from figure 2 the average senslWeLe heat loss

at steady-state operation, Lg

gg ^

and enter this value In column 29.

30 . Calculate and enter the steady-state efficiency (excluding jacket loss).

^ss “ H.,A “ ^,SS,A

31. Calculate and enter In column 31.

Ts,ss = (s/F) (Col. 19) ^

^'^F,SS "*^RA ^RA

32. Calculate and enter on-cycle time constant

(^2 - ti)

'ON

Jtn

T? rr(co1» 11) ** T-p /txT(ti ) (col. 12)

Lp'gglcol. 11) - Tp')^M(t 9 )(col. 13) F,0N'‘'^2-

where (t 2 ” tj^) = 2 for furnace, and (t 2 ” tj^) = 4.5 for boiler.

33.

Calculate and enter effective flue gas temperature difference at startup under test conditions:

•1

TM ~ Tp Qjj(tj^ ) (col. 12)] X e

where tj * 0.5 for furnace and tj = 1 for boiler.

34. Calculate and enter off-cycle time constant:

(^4 ~ ^ 3

^

Tqjj(co1. 32)

‘OFF

Jin F,nFF ^^3^ . ~ ^gjOFF^ v^nw^^A^Ccol. 15) “ ^f|oFF^

”)(col. 16)

_ ^F,0FF'^^4 *)(col. 16)

where (t^ - t^) =7.5 for furnace and (t^ - t^) = 18.75 for boiler.

35. Calculate and enter effective flue gas temperature difference at shut

down under test conditions:

%,0,X ^"^F,0FF^^ 3^ ®

Where t^ = 1.5 for furnace and tg = 3.75 for boiler.

28
36. Calculate and enter minimum flue gas temperature difference above the

room temperature:

“ ^F,OFF^*^ (col. 16) - Tj^(col. 17)

37. For SYS// (col. 1) equal to 1 through 4 and systems 5 through 8 for

which (S/F)(col. 19) x Dg(col. 21) > Dp (col. 20), calculate and enter

in column 37

Dp(col. 20) X \|ip ^^(col. 36) " (S/F)(col. 19) x'Dg(col. 21)

For SYS// (col. 1) equal to 5 through 8 for which (S/F)(col. 19) x

Dg(col. 21) ^

Dp (col. 20), calculate and enter in column 37;

’>'S,»,X “

’J’F,»,X <col. 36).

For SYS// (col. 1) equal to 9 through 12: Leave column 37 blank.

38. For SYS// (col. 1) equal to 1 through 4 and systems 5 through 8 for which

(S/F) (col. 19) X Dg (col. 21) > Dp (col. 20), calculate and enter in

column 38:

Dp(col. 20) X i|;p Q

j^(col. 35) ” (S/F)(col. 19) X Dg(col. 21)

For SYS// (col. 1) equal to 5 through 8 for which (S/F) (col. 19) x

Dg(col. 21) ^Dp (col. 20), calculate and enter in column 38:

’•'8,0, X

“

’*'F,0,X^^°^*

For SYS// (col. 1) equal to 9 through 12): Leave column 38 blank.

39. For SYS// (col. 1) equal to 1 through 8: Leave column 39 blank.

For SYS// (col. 1) equal to 9 through 12; Calculate and enter a correction factor for the use of outdoor air instead of indoor air for

combustion:

28 X q„„(col. 30)

^ [Tp^gs(col. 11) - Tj^(col. 17)] (100)

40. Calculate and enter multiplication factor for sensible heat loss during

the on-period. Kg qjj:

24 X [1 + R.J. p(col. 28) X (A/F)(col. 25)]

" HHV^(col. 24)

29
41.

Calculate and enter multiplication factor for sensible heat loss during

the off~periodj Kg OFF*

For SYS// (col. 1) equal to 1 through 4:

*^S,OFF ^ (Tf.sS^''®^* 530)1*19

0.56

(Tf^ss(^°i* 11) " Tra^^°i* 1^))

X Dp(col. 20) X Kg Qjj(col. 40)

For SYS// (col. 1) equal to 5 through 8:

^S,0FF “

X

For SYS//

(To qq(co1. 31) - Tra(co1. 17) + 530)1*19 ^

X Ds(col.

0.56

(Ts^SS^^°l* ^1) “ 1^Ra(^°1* 1^) 2®)

(S/F)(co1. 19) X Kg Qjj(col. 40)

(col. 1) equal to 9 through 12:

21 )

KS,0FF

(T„ „(col. 11) - T«.(col. 17) + 530)1-19 - ^ 1 1 X Df(co1. 20)

0.56

(Tf^SS^^^®!* 11) 1rA^^°1* 1^) 2®)

X Kg

^ Qjj (col. 40)

42. For SYS// (col. 1) equal to 1 through 8: Calculate and enter multiplication factor for infiltration loss during the on-period:

^I,0N ~ (®*^) ^ (S/F)(co1. 19) X Kg^Qjj(col. 40)

For SYS// (col. 1) equal to 9 through 12: Leave column 42 blank.

43. For SYS// (col.l) equal to 1 through 8: Calculate and enter in column 43

the multiplication factor for infiltration loss during the off-period:

K - (^S.SsCcol- 31) - T^Ccol. 17) ^ 530)1-19

^

I, OFF (Tg^gg(col. 31) - T ( c o1

17) +

28)^*^^

X Dg(col. 21)

For SYS// (col. 1) equal to 9 through 12: Leave column 43 blank.

44.

Enter the value of the average outdoor temperature, Tq^ equal to 42®F.

30
45. For furnace: Enter column 45 the average on-time per cycle, tQjj, equal

to 3.87 minutes.

For boiler: Enter column 45 the average on-time per cycle, tQjj, equal

to 9.68 minutes.

46. For furnace: Enter column 46 the average off-time per cycle, tQFF*

equal to 13.30 minutes.

For boiler: Enter column 46 the average off-time per cycle, tQpp, equal

to 33.26 minutes.

47., 48. Calculate tQjj(col. 45 )/ton(co1. 32) and tQpp(col. 46)/xQpp(col. 34)

and enter columns 47 and 48, respectively.

49., 50., 51., 52., 53. Correct the heat-up and cool-down temperature profiles for the effect of cycling:

For SYS# (col. 1) equal to 1 through 8, calculate and enter:

®F,0 (col. 49) = ^t,0N^F,0,x(^°^*

'1'f, 0

(col. 50) = C^^Qppij;p^Q^x(col» 35)

ipp«, (col. 51) =

'I'f,<»,x(^°^*

'l^S,© (col. 52) » C^,^Qpp ips,0,x(^®^*

’I'S," (col. 53) =» ’Ps,«,x(col« 37)

For SYS# (col. 1) equal to 9 through 12, leave columns 52 and 53 blank,

calculate and enter:

0p q(co1. 49) “ Qjj X Cg(col. 39) x 0f^o,x(co1» 33)

I '^F,o(col» 50) = ^t,0FF * ^S ^ ’^F,0,x(col» 35)

Vf,» (col. 51) * Cg X ’Pf,«,x(co1» 36)

where Cg* = 1.22

31
1 -

't,ON

^T? n y(co1» 35) X e (Tp^gg(COl. 11) — Tp^Qpp(“) (col. 16))

- ( )(col. 48)

OFF

[®F 0 ^ ’^F 0 ^ ®

>i-Vcol. 47) +(>EON / V OFF

(Tp^gg(col. 11) ~ Tp^Qpp(®“)(col. 16))

- ( -T^ )(col. 47)

ON

Ct,OFF =

Qp Q v(col» 33) X e

^"^F, ~ Tp^qFfC**) (*^ol* 16))

/e

-(( «> n£E.

OFF

\-

)

Cl ID

1 for units with continuously operating pilot lights

0.90 for units with Intermittent Ignition devices or cycling pilots

54. For SYS# (col. 1) equal to 1 through 4: Read from figure 3 and enter

column 54; F3[ 4^p^q(co1. 50), (tQpp/'TQpp)(col. 48)]:

For SYS# (col. 1) equal to 5 through 12: Leave column 54 blank.

55. For SYS# (col. 1) equal to 1 through 4: Read from figure 4 and enter

column 55: F4 [ '|^p^q(co 1. 50), (tQpp/TQpp)(col. 48)].

For SYS# (col. 1) equal to 5 through 12 ;• Leave column 55 blank.

56. For SYS# (col. 1) equal to 1 through 4: Leave column 56 blank.

For SYS# (col. 1) equal to 5 through 8; Read from figure 5 and enter

column 56: F5[ ipg^Q(col. 52), (tQpp/TQpp)(col. 48)].

For SYS# (col. 1) equal to 9 through 12: Read from figure 5 and enter

column 56; F5[ iJ^p^q(co 1. 50), (tQpp/TQpp)(col. 48)].

57. For SYS# (col. 1) equal to 1 through 4: Leave column 57 blank.

For SYS# (col. 1) equal to 5 through 8; Read from figure 6 and enter

column 57: F6[ 'j^g^Q(col. 52), (tQpp/'TQpp)(col. 48)].

32
For SYS// (col. 1) equal to 9 through 12; Read from figure 6 and enter

in column 57; q(co1. 50), (^Qpp/*^QPp) (col. 48)].

58. For SYS// (col. 1) equal to 1 through 8 ; Read from figure 7 and enter

column 58; F7[’l'g q(co1. 52), (tQpp/TQpp)(col. 48)].

For SYS// (col. 1) equal to 9 through 12; Leave column 58 blank.

59. For SYS// (col. 1) equal to 1 through 8 ; Read from figure 8 and enter

column 59; F8 [’l»g q(co1. 52), (tQpp/tQpp)(col. 48)].

For SYS// (col. 1) equal to 9 through 12; Leave column 59 blank.

60.

For SYS// (col. 1) equal to 1 through 8 ; Calculate and enter on-cycle

sensible heat loss;

‘•S.ON - I-S.SS.aC^oI- 29) - Ks.0n(«1- ^0) x 49) x

47 )

-4^(col. 47)

^ON

X (1 - e ).

For SYS// (col. 1) equal to 9 through 12; Calculate and enter on-cycle

sensible heat loss;

^,0N = Cg(col. 39) X Lg gg^^(col. 29) - Kg on<co1. 40) x 0p qCcoI. 49)

- (col. 47)

^ON * (W’on)(<=°2- 92) * ®

61.

For SYS// (col. 1) equal to 1 through 4, calculate and enter the offperiod sensible heat loss;

tnw(col. 46) « , _ ^S,0FF “ ^S,0FF^^°^* * tQjj(col. 45) * (col. 54) + ipp,„(col. 51)

X F4 (col. 55)].

For SYS// (col. 1) equal to 5 through 8 , calulate and enter the offperiod sensible heat loss;

J-S.OFF - Ks,0Ff(c°1- 91) X (“>1- *

9s.” (‘^“l- ^3)

X F6 (col. 57) ]

33
For SYS# (col. 1) equal to 9 through 12, calculate and enter the

off-perlod sensible heat loss:

^,OFF ^S,OFF^^°^* 41)

tQjj (col. 45)

[F5 (col. 56) + iDf^„(co1. 51)

X F6 (col . 57) ]

62. For SYS# (col. 1) equal to 1 through 8: Calculate and enter on-cycle

infiltration heat loss:

^I,ON “

For SYS# (col. 1) equal to 9 through 12: Enter on-cycle infiltration

heat loss, Lj qn

”

63. For SYS# (col. 1) equal to 1 through 8: Calculate and enter off-cycle

infiltration loss:

^I,OFF ~ ^l,OFF^^°^* 1 tQjg (col. 45)

X [F7 (col. 58) + \|>s,oo(®ol* 53) x F8 (col. 59)]

For SYS# (col. 1) equal to 9 through 12: Enter off-cycle infiltration

heat loss, OFF

~

64.

Calculate and enter part-load fuel utilization efficiency, for Indoor

unit

Hu = 100 - Lj, .(col. 26) - -

tQ^(col. 45)

lon(co 1. 45) + PF(col. 23)tQpp(col. 46)

* [^S,0N^®®^* ^S,0FF^®®^* ^ ^I,0FF^®®^* 1

For outdoor unit or units Intended for installation in unheated spaces

(such as an attic or crawl space)

Hu = 100 - Ll^^(co1. 26) - Cj(col. 27) x Lj(col. 18)

t/-\M(col. 45)

X [Lq onC^oI

tQjj(col. 45) + PF(col. 23)tQpp(col. 46)

60)

^

^S,0FF^®®^*

65.

Enter the value of the average annual heating degree days for the U.S.,

DD, equal to 5200.

34
66. Enter the average total number of non-heating season hours per year that

the energy to the pilot light is assumed wasted, HR, equal to 4600.

67. Calculate and enter annual fuel utilization efficiency:

EFFY^ =

hss^col. 30) X n^^Ccol. 64) x DD (col. 65)

HssCcol. 30) X DD (col. 65) + (2.5) x n^(col. 64) x PF(col. 23) (1. 7 ) (HR(col. 66)

4.2 RECOMMENDED PROCEDURE FOR CALCULATING THE ANNUAL COST OF OPERATION OF A

FURNACE OR BOILER LOCATED IN DIFFERENT CLIMATIC REGIONS OF THE COUNTRY

AND IN BUILDINGS WITH DIFFERENT DESIGN HEATING REQUIREMENTS

The annual cost of operating a gas- or oil-fired furnace or boiler located in

various geographic locations of the United States and in buildings with different design heating requirements shall be determined using the following

three-step procedure:

Step 1 . Determine the number of burner operating hours using the

equation:

Burner Operating Hours = A (HLH) (C) (design heating requirement) - B (HLH)

where the number of heating load hours, HLH, may be obtained from Figure 9

for the region of interest, the "design heating requirement" is the heating

requirement to be met by the furnace or boiler in kBtu per hour at the 97 1/2

percent outdoor design temperature, and C = 0.77 is an "experience factor"

which tends to Improve the agreement between the average calculated burner

operating hours and the average burner operating hours found in the field.

It is strongly recommended that this "experience factor" be eliminated as soon as an improved method is available to more accurately estimate residential heating requirements. Typical values for the design heating requirement

are given in Table 4 for different furnace or boiler output capacities Qqux* where Qqux ^

’^SS ^ QiN ^ Qjjq (col. 4) rounded off to the

nearest 1000 Btu/h for units intended for installation in a heated space and

_ /QTia(col. 4)\

QqUT 1

) ^’^SS (col* “ 3.3 Lj (col. 18)) rounded off to the

nearest 1000 Btu/h for units intended for installation out of doors or in an unheated space. The constants A and B are unique to the unit under tests and

may be calculated using information contained in the work sheet and the

following expressions:

35
100,000

341,300 (PE + y BE) + (Q^j - Qp)nu

(2)(A)(Qp)(Tiu)

100,000

where y

=

1 + (-

~ ^

) for furnace

V 3.87 /

1.00 for boilers or furnaces employing a single motor to

drive a power burner and an indoor-air circulating blower.

Step 2 . Determine the annual fuel consumption (in Btu) and the annual

electricity consumption (in kWh) using:

Annual Fuel Consumption = (Qjjg ~ Qp) (Burner Operating Hours) + 8760 Qp

Annual Electricity Consumption = (PE + yBE) (Burner Operating Hours)

Step 3 . The annual cost of operation is then:

1 Annual Cost of Operation = (Annual Fuel Consumption) (-j^) ($ per unit of fuel)

+ (Annual Electricity Consumption) ($ per kWh),

where K is the Btu content per unit of fuel that the fuel cost is given in

terms of (e.g. K = 100,000 Btu/therm if cost is given in dollars per therm;

K = 140,000 Btu/gallon if cost is expressed as dollars per gallon of No. 2

fuel oil). The annual cost of operation should be rounded off to the nearest

five dollars.

The annual cost of operating an electric furnace or boiler in various geographic

locations of the United States and in buildings with different design heating

requirements shall be determined using the equation:

Annual Cost of Operation = 100 (HLH) (C) (design heating requirement)

EFFY^

X —\— ($ per kWh)

3.413

'^100 for units Intended for installation in a heated space

(100 - 3.3 Lj) for electric furnaces intended for

Installation out of doors or in unheated

spaces (such as an attic or a crawl space)

(100 - 4.7 Lj) for electric boilers intended for installation out of doors or in unheated space

(such as an attic or a crawl space)

and C 5 0.77 is the "experience factor" mentioned above.

where EFFY^ = ngs

“

36
The number of heating load hours, HLH, for different geographical regions is

given in Figure 10, and the "design heating requirement" is the building heating requirement in kBtu per hour at the 97 1/2 percent outdoor design temperature. Typical value for the design heating requirement are given in Table 4 for electric furnaces and boilers having different output capacities 0qut»

where Qqux ~ (Ejjg) (3.413) rounded off to the nearest 1000 Btu/h for

(Etjj)(3.413)

units intended for installation in a heated space and Qqux " j^Q

X (100 - 3.3 Lj) for units intended for installation out of doors or in an unheated space. The annual cost of operation should be rounded off to the

nearest five dollars.

In order to facilitate performance comparison by the user of furnaces,

boilers and heat pumps, it is recommended that the annual cost of operation

be calculated for all of the appropriate typical design heating requirements

shown in Table 4 and for a variety of heating load hours, HLH. For example,

a furnace with an output capacity of 80 kBtu/h could have its annual cost of

operation calculated at design heating requirements of 40, 45, 50 and 60

kBtu/h, and heating load hours of 750, 1250, 1750, 2250 and 2750 hours. This

approach has the advantage of being able to handle different sizing relationships between the furnace or boiler and a residence's design heating requirement in different geographical locations and could be incorporated, along with

the effect of different fuel costs, in a table having the following form:

DESIGN HEATING

REQUIREMENT

REGION (kBtu/h)

EFFY

A

COST OF FUEL ($ /THERM)

.20 .25 .30 .35 .40

40

I 45

(750 HLH) 50

60

40

II 45

(1250 HLH) 50

60

40

III 45

(1750 HLH) 50

60

40

IV 45

(2250 HLH) 50

60

40

V 45

(2750 HLH) 50

60

37
If a single operating cost figure Is required for a furnace or boiler that

represents the national average, It Is recommended that the preceding appropriate equations be used with HLH set equal to 2080 hours and the design

heating requirement set equal to the average design heating requirement given

In Table 4 for the appropriate value of furnace or boiler output capacity

Qout*

4.3 ADDITIONAL CALCULATIONS FOR FURNACES OR BOILERS UTILIZING AN AUTOMATIC

STACK (OR FLUE) DAMPER

Calculate the automatic stack (or flue) damper effectiveness, D^, defined as:

where Aj^' * Ajj cos (y)

Ag » cross sectional area of the stack determined In accordance with

section 3.3 of this appendix. In square Inches

Ajj « net area of the damper plate determined In accordance with section

3.5 of this appendix. In square Inches

Y = the angle the damper makes when closed with a plane perpendicular

to the axis of the stack determined In accordance with section 3.5.

4.4 ADDITIONAL CALCULATION PROCEDURES FOR FURNACES OR BOILERS EQUIPPED WITH

POWER BURNERS

4.4.1 Optional Procedure for Determination of Dp for Furnaces or Boilers

Employing a Power Burner

Calculate the ratio (D ) of the rate of flue-gas mass flow through the furnace or boiler during the orf-perlod, mp OFF^^F SS^» rate of flue-gas mass flow during the on-perlod, mp SS^^F*SS'» defined as:

D,o

38
for gas-fueled units or

Vt =

^

Hf.SS ~ ^RA 1^*^^ r '^F,OFF 1

L%,OFF ”"^RA J L^F,SS * J

1.19

.OFF ”"^RA

oil-fueled units for which no draft is maintained

during the steady-state tests or cool down test.

1, for oil-fueled units tested with an imposed draft as described

in section 3.6.

flow rate of tracer gas through the furnace measured in accordance

with section 3.6, in cubic feet per minute.

concentration by volume of tracer gas present in the flue gas sampl

measured in accordance with section 3.6, in percent.

the density the flue gas would have at the measured barometric pres

sure, Pg, and the measured temperature, T.j, in lb. per cu. ft. It

may be approximated by the equation:

Pp “ 1.325 B

+ 460

T.p = temperature of tracer gas entering the flow meter measured in

accordance with section 3.6, in degrees Fahrenheit.

Pg = barometric pressure measured in accordance with section 3.6, in

Inches of mercury.

4.4.2 Optional Procedure for Determination of Off-Cycle Draft Factor for

Flue-Gas Flow for Furnaces or Boilers Employing a Power Burner

Calculate the off-cycle draft factor for flue gas flow. Dp, defined as:

for systems numbered 2, 4, 6, 8 or 10: Dp = Dp

for system number 12: Dp = (Dp)(Dq)

4.4.3 Optional procedure for Determination of Off-Cycle Draft Factor for

Stack-Gas Flow for Furnaces or Boilers Employing a Power Burner

Calculate the off-cycle draft factor for stack-gas flow, Dg, defined as:

for system number 2:

for system number 4

for system number 6

for system number 8

Dg = 1.0

Dg = (0.79 + D )/1.4

Dc

39
(D„)(Dp), If D„ X

^

(Do)(Dp) +

(o.85 - (D^)(Dp))(p^ -

(1 - °o ^(S/F)

(S/F)

40
Table

1.

Factors

Describing

Air

Flow

Rate

for

Gas

and

Oil-Fired

Furnaces

or

Boilers

Utilizing

Indoor

Air

for

Combustion

and

Draft

Control

>>Oo

cd

C "O

•H c a ^ o .

cti CO d PQz

Ta

a; 4-) CO (d

Cd fO T3

_

(U

O

<uu

cd „

'S

C3

O CO

(dU P9o

CJ T> 3 C

cd

CO CO CO TJ (U o

Vs •H 4J

A Cd -o

T3 3 4J o |3 4-) CJ

C cd CO cd 4J Vs CO a 4J o (3

>4H •H o

fa o 4J CJ

Cd CO 3 iH Vs V—/ Cd 3 <u

<u

a '3 1 Vs •H 3 3 CO 3 o PQ Q Vs 1—

<U

B

Cd 4J r^ 3 3 •H

C&4

O fa «4S

O fH •Ha

Q CO 4-t o 43

Cd

u

O z Vs 1 cd o (U <3 <u f-1 43 cd CO • n-^ 4J (U

CO

V|oQ

Sto m

00 +o

Ph Q

(VVs

<u

4J cd Td cd Vs

0) Vs <U a. o > O 43 (U I—I co CO

<U rH

<U *>43 TJ <U

Vs TJ

<u :a (U

Vs 4J c

(U Cd *H

!» Vs cd

0> 4J

CO 4J .o

Vs ^ O O rH

4J cd u CJ sj

Cd -H cd

>4-1 r4 -o

43

(U 3 T) > CU rH o <u

(U *H

Cd x:

4-) (U X (3

C

H *H Cd

41
Table 2. Factors Describing Air Flow Rates for Gas or Oil-Fired Furnaces/Boilers

Intended for Installation Out Doors or in Unheated Spaces (such as an

attic or crawl space) or Intended for Indoor Installation but Equipped

With a Direct Vent System

Type of

Burner

Units Without a Stack

or Flue Damper

Units With a Flue Damper Type of Draft S/F

System // Dp System # Dp None 1

Atmosphere 9 1.00 11 Do barometric

damper

1.4

Power 10 0.40 12 0.40 X Do draft

diverter

2.4

The above factors were developed by the National Bureau of Standards and are based

upon information in the public literature, laboratory and computer simulation

studies conducted at NBS, and laboratory and field data obtained by several research

firms under contract to NBS and DoE.

Table 3. Values of Higher Heating Value (HHV^), Stoichiometric Air/Fuel Ratio (A/F),

and Latent Heat Loss (Lj^ for Typical Fuels

Fuels HHV^(Btu/lb) A/F(~) Dl,a^^^

No. 1 Oil 19,800 14.56 6.55

No. 2 Oil 19,500 14.49 6.50

Natural Gas 20,120 14.45 9.55

Manufactured Gas 18,500 11.81 10.14

Propane 21,500 15.58 7.99

Butane 20,890 15.36 7.79

42
Table 4. Average and Typical Design Heating Requirements for

Furnaces and Boilers with Different Output Capacities

Furnace or Boiler Output Average Design Typical Design

Capacity, QoUT Heating Requirements Heating Requirements

(Btu/h) (kBtu/h) (kBtu/h)

26,000

35,000 —

34.000

42.000

20

25

15, 20

20, 25, 30

43,000 - 51,000 30 25, 30, 35

52,000 - 59,000 35 30, 35, 40, 45

60,000 - 76,000 40 35, 40, 45, 50

77,000 - 93,000 50 40, 45, 50, 60

94,000 - 110,000 60 50, 60, 70, 80

111,000 - 127,000 70 60, 70, 80, 90

128,000 - 144,000 80 70, 80, 90, 100

145,000 - 161,000 90 80, 90, 100, 110, 120

162,000 - 178,000 100 90, 100, 110, 120, 130

179,000 - 195,000 110 100, 110, 120, 130, 140

196,000 - 237,000 130 120, 130, 140, 150, 160

238,000 - 271,000 150 120, 140, 160, 180, 200

272,000 - 305,000 170 140, 160, 180, 200, 220

43
•o

(dV

C/3 iJO

CO

01 a

0)

•H

(0

fl

0) CO«

4J

CO 4J CO

•5*

«0V9 CO o cr •H wCO O ae o

PU *Ho

00 »H V 4-1 4J U

2!§ a U CO CO u

fr* CO m

.o

CO H

NO NO NO r*^ 1 1 pH pH pH pH 1o 1o 1o o 1o 1o p^ pH ^H ^H o K K M X X X O ON • o •o o 5

r«* CA r>. Pm <*• CM ON CA CM O ON CM 00 CA

NO CM CO lA ON pH

cn

O NO ^H 00 o NA CM CA

r-C1 pH CA pH lA1 r**1

fN| CM CM CM CM CM rM1 1 pH ^H pH pH 1o 1O 1o 1o 1o o pH pH ^H ^H pH H K K X X K

/-N ON 00 •O o CM pH W On pH ON

Pm o cn On CM rv NO

CJ On ON -O NO o ON 4A ON CA CM

NO o O pH NO CM <n CA 00 <r O On

f-H pH CM CA1 CM pH1

ON ON oo 00 001 001 *o *o *o *o 1o 1o pH pH ^H pH K K K X X X

/-s cn NO r*«. 00 CM CA ro. Sm/ o ON CA NA CA

Pm fO 00 OO oo

O CA

CJ vO 00 lA CA lAO o ON 00 CA pH CM

ON o 00 00 CA 00

GO CA lA pH o

00 00 ^H pH

NO NO1 NO NO 1 r**. 1 o 1o *o o 1O 1o pH pH pH pH pH K K X X X X

CM ON nO CM lA -o »A

•o GOO CA o O Pm -o NO CO •«o NO o U CM »A Hf r*- O A* nO 'O CA A- lA r> CO NO On fO CA rs.! NO1 pH

pH pH pH pH 1o *o 1o *o 1o o ^H ^H pH ^H pH K K X X X X \ CA 00 CM ON rSm/ <n nO Hf CA «o

Pm 00 pH •o NO CM U NO pH ON 00 CA pH NO -o ON NO pH

•o CA ON lA ^H o

•O lA NO lA iA

CM CM CM CM CM CM

CM nO o O CA

CM CA ON pH nO ON

PQ •O o o CM CM

^H pH pH pH fH

00 •O NO o o ON NO ON •o pH 00

r«M NO pH sO «o o NO NO ON ON 00 00 < o o o o o o o o o < lA o lA -o ON ON m lA lA pH ON rs. NO NO ON d f*». fs- pH

NO ON lA ^H 00 NO

Pm lA Ht 00 lA CA < «o •O pH lA 4A

pH ^H pH pH pH o o o o o o < o o CM o o ON

00 lA lA lA GO

nB ON ON o 00 pH o pH CM pH CM CM

*o

00 4>

<9

U

pH

O 9

•H •H 4J o o pH O 00 «

OB CO COa 0) 5 CM u 4H <3 <0 a

Am 9 9 Ok <0 • • 4J a o 4H o O CO CO u 9

as 2 2 X c^ (0

NO

pH1opHX

lA rs. Sm/ rs* < CA O r^0CA

•O

NO

CM

pH1opH

P-N

X

pH < CM o CA

CA

»A

CM

•O'

rs*1

ooopH

/—\ X

CAw pH < r*s lA

000NO

rs. CM

lA1OpHX

<p\ CM NO

Nw/ CM < pH o 0NO

CMO

CA1

pH•o

pHK

/p\ pH pH CM

pH < CM u

Air

2.5A6

44
45

Fig.

1.

Ratio

of

Total

Combustion

to

Stoichiometric

Air

Versus
Fig. 2A. Steady-State Sensible Heat Loss Versus Ratio of Total Combustion

to Stoichiometric Air (For No. 1 Oil)

46

Ijl

SS'Jiv

MO

SS'SJV
Fig, 2B . Steady-State Sensible Heat Loss Versus Ratio of Total Combustion

to Stoichiometric Air (For 2 Oil)

47

(Jl

SS'JlV

DO

SS'Siv
700 600 500 400 350

</>

</>

</9

**T,s OR Rt,f (-1

Fig. 2C. Steady-State Sensible Heat Loss Versus Ratio of Total Combustion

to Stoichiometric Air (For Natural Gas)

48

(j|

SS'JiV

no

SS'SJV
800 700 600 500

•*T,S l*T,F

Fig. 2D. Steady-State Sensible Heat Loss Versus Ratio of Total Combustion

to Stoichiometric Air (For Manufactured Gas)

49

ATs,SS

OR

ATf,ss

(F|
400 350

</> u>

**T,s OR Rt,f (')

Fig. 2E. Steady-State Sensible Heat Loss Versus Ratio of Total Combustion

to Stoichiometric Air (For Propane)

50

iJl

SS'Jiv

HO

SS'SjV
Rt,S 0*? ®T.F I- Fig. 2P, Steady-State Sensible Heat Loss Versus Ratio of Total Combustion

to Stoichiometric Air (For. Bu tane)

51

(j)

SS'Jiv

HO

SS‘Siv
>p

CO

do

•H

(^£•08) 2d

52

Values

of

the

F3

Function
00

•H

53

Values

of

the

F4

Function
in

00

“tH

54

Values

of

the

F5

Function
55

Values

of

the

F6

Function
(£9*0-^) li

56

^^8*

Values

of

the

F7

Function
8y.

57

Fig.

8.

Values

of

the

F8

Function
oooc

58

Fig. 9,

Map

of

Heating

Load

Hours
FIGOBE 10

\nwt SHEET FOR FORMACE/BOILER STSTEH

Maaaurad Quantltlas and'Syitam Ch«r&ctBrlscle Constanta

1 2 3 4 5 6 7 8 STS#

(-) TFUEL(-) HB7Btu/lb. «J9hr. Btu/hr. FE

IcW BEkW

^02.

•

j

] 9 10 11 12 ' 13 14 15 16 ^s.ss.x

Oy

^C02,F ’^F.SS ®F ®F

’^F,0H^'^2> ^ ®F

^F,0FF^*=3)

®F

^F,0FF^'^4^

®F .

T f*) f.off'- ' op

/

17 . 18 19 20 21. 22 ^RA

®F Z

S/F

(-) °F

(-) ”5. 7

(-)

i Oarlvad Systsm Faranatars

23 24 25 26 27 28 29 30 PF

(“) HHV^

Btu/lb.

A/F

(-) ^L.A

Z

Cj

(-> W 4,SS,A

Z

'’ss Z

** 31 32 33 34 35 36 37 38 s.ssF ^OH *F.0,X

®F‘

“^OFF alnutas

'*'7.0,X ®F

’"f.-.x ®F

'^S •* X \*o.x

® F

40 - 41 42 43

(-) S.OH

(Z)/F

^•°”0 37 CZ)/R

*4,0H

(Z)/F (Z)/r0-37

;

‘ Calculation of Systaa Lossaa and Annual Fual Utilization Efflciancy

*44 45 46 47 48 49 50 51 OA

F

®0M

mlnutaa

Sff

ffllnutas

^oh/'^om

(-)

' 'off/'^off

(-) ®7.0

®F

'^F. 0 «F _'*'f.--F

52 53 54 55 56 57 58- 59 . "^S.O®F •f

F3 R 0.37

F4 ^-0.63

F5 yO.37F6

j^-0.63

F7 ^-0.63F8 ^-1.63

60 61 62 63 64 65 66 67 ^S,0N

Z ^S.OFF

Z ^,0N

Z h:,oFF

z \

Z

DO

•F-daya

HR

hours

effy^

z

59
APPENDIX B

Computerized Calculation Procedure for Condensing

and Non-Condensing Furnaces and Boilers

The computerized calculation procedure consists of a main program and

three subroutines. The fortran program is listed in Figure B-1, and may

require modifications when used on some computer systems. The subroutines

FUNT 4 and SENL0S5 perform the functions described in Appendix B of NBSIR 78-1543

[1]. The newer CLFTR2 subroutine calculates the latent heat loss coefficient,

C , and condensate loss correction factor, L , used in steps 68 and 69

or the calculation procedure for condensing furnaces and boilers.

Three sample sets of data given in Figure B-2 are supplied to exercise

the program calculation paths for condensing units. The previous eleven

sample sets in reference [1] can also be used to check this program, which

is why the three sets are assigned numbers 12 through 14. These three sets

of input data are supplied to check the condensing type unit calculation

paths, but do not represent specific tests of condensing units. Consequently,

these output performances should not be referenced as typical or representative

values for condensing heating units.

The program and subroutine flow charts. Figures B-3 through B-6, are provided to assist future users in understanding or revising the program.

Numbers in the left column of the flow chart Indicate corresponding program

statements in Figure B-1.

Input to the program must follow the order presented in Figure B-7 entitled

Input Data Code Sheet for NBSFBS7. All input values which are listed as

zero or blank in the written procedure should have a value of ”0.0” placed

in their input field.

This program uses tjie implicit scheme for processor recognition of integer

and real number input variables. The only integer inputs are IFB, INST, NSYS,

and IFUEL. All other input variables are real positive numbers. Although the use of real number Inputs greater than zero without the decimal is allowed

on many processors, each user will need to check the specific requirements

for his or her processor.

The freefield inputs used by NBS on our Fortran V compiler may not be

acceptable for use on other systems. It is not possible to anticipate all

future alternate input or output format needs, so no attempt has been made

to prepare alternate formats. Thus format changes may be necessary for program

implementation on other systems. Use of a 72-character-wide output format will

require modification to the output formats of the initial 67 quantities which

are written for a carriage 132 characters wide.

The fuel cost rates printed out in the regional annual operating cost table

are not likely to agree with current Federal Trade Commission fact sheet requirements for specific fuels. Adjustment of CBFBS7 program statements 270 and

313 through 315 is necessary for the desired fuel price ranges.

60
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61
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62
116

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117

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CONTINUE

119

C

120

C

COLUMNS

44

THROUGH

53

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63
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CLFTR2

SUBROUTINE CLFTRC CL.QLC, IFUEL, AFR, RT, HHVA, QL, lOPTN.ZETFO

, TFSS , TTON)

C

c **5»:CALCULATI0N OF CL AND OLC***

C ***APRIL 1980***FOR USE WITH QLC*:*::#: DIMENSION FGMW(6)

DATA (FGMW(J), J= 1 ,6)/29. ,29. ,28. ,27.5,28.5,28.5/

FGM = l.+AFR^RT

VM = HHVA*QL/( 100.:C1053.3)

PV = VM*FGMW( IFUEL)*14.7/(FGM:*!l8.)

IF( lOPTN.NE. 1) GO TO 100

AVTFON = TFSS

GO TO 101

100 AVTFON = TFSS - ZETFO^I 1

. -EXP( -TTON) ) /TTON

101 PVS = . 49 12:l«EXP( 15. 4638-7284. /(AVTFON+392.))

IF(PV.GT.PVS) GO TO 110

CL = 1. WRITE(6,990)

GO TO 120

110 CL = PVS«( 14.7-PV)/(PVH:( 14.7-PVS))

120 QLC = QL^( l.-CL)*( l.*(TFSS-70.)-.45*(TFSS-42.))/1053.3

990 FORMAT! ///15X’Hc*WARNING5i«#CL=l**’/5X’:#:5t:UNIT SHOULD BE TESTED AND

, RATED AS A NONCONOENSING HEATING SYSTEM** ’/5X’**ALL CALCULATED

,RESTJLTS WHICH FOLLOW ARE INVALID**’)

RETURN

END

FUNT4

SUBROUT I NE FUNT4 ( N , S I , TTOFF , REFTOA, REFTRM, F I , FJ

T1 = REFTRM-REFTOA

Cl=l.

T2=REFTRM+460.

IF(N.E0.4) T1=0.

IF(N.EQ.B) C1=0.0

X=0.

FI =0.

FJ =0.

DX = TTOFF /500.

FFl 1=(SI+T1)**0.56*SI**C1/(SI+T2)**1. 19

FF21=(SI+T1+1©0. )**0.56*(S 1+100. )**C1/(S I+T2+ 100.)**!. 19

DO 150 1=1,250

X=X+DX

XX=SI *EXP(-X)

FF 12= ( XX+Tl ) **0. 56*XX**C l/( XX+T2) **1.19

FF22=(XX+T1+100. )**0.56*(XX+100. ) **Cl/( XX+T2+ 100. ) **1 . 19

X=X+DX

XX=SI *EXP(-X)

FF 13= ( XX+Tl ) **0 . 56*( XX) **C l/( XX+T2) **1.19

FF23=( XX+Tl +100. ) **0.56*(XX+100. ) **Cl/( XX+T2+ 100. ) **1 . 19

FI =FI +(FF1 1+4.*FF12+FF13)

FJ =FJ +(FF21+4.*FF22+FF23)

FF11=FF13

150 FF21=FF23

IF( ( ABS(FJ-FI )) .LE. 0.0000001) GOTO 110

FJ =(FJ -FI )/( 100.*TTOFF ) FJ =DX *FJ /3.

GOTO 1 12

110 FJ =0.

112 FI =FI *DX /(3.*TT0FF ) RETURN

END

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©

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d Cl CM CM TO TO CM TO TO ^ HB

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©

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«> CA CJ tn

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B©B TO 03

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70
CALCULATED

VALUES-

(»M

— o NH ^ 1-1 > O CA D-. o

fa + fa +

fa lA CA® yj o CO

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IN CO lO lO v£> X o t-N o © « CO o fa fa © © © + t—

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a!

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GO Cl HHQ fa lO faN • ©©

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u

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73
FIG. B-3. MAIN NBSFBS7 PROGRAM FLOW CHART

1

5

25

30

36

51

53

^

START ^

3

PROGRAM STORAGE

ASSIGNMENTS AND INITIALING

OF FIXED VALUES

READ NRUN

DO 600

INPUT AND PRINT

BACK OF TITLE

WITHOUT ALTERATION

FROM STATEMENT 278

IFB = 1,2,3

IFB = 4,5

CONDENSING

ICOND = I") ICQND

CONDENSING OUTPUT^

- ol

NONCONDENSING OUTPU T I

c 992 xy

INDOOR OR OUTDOOTI

READ AND OUTPUT

INPUT LINES 5 AND 6

lOPTN = 0 I i CONDENSING

IFB=1,2,3,4,5

IOPTN=l 1 <J : '

1 READ INPUT LINE 7 | CALL SENLOS SUBROUTINE /

UNITS WITHOUT HEAT-UP/

COOL-DOWN TESTS

OPTION

TFONl = TFON2 =0

AND IFB = 4 OR 5

OUTPUT OF VALUES

17 TO 22 AND

FORMAT 878 MESSAGE

SET OF PF =QP/QNP

AND CJ VALUES

62 lOPTN

<>

I0PTN?^1

GO TO NEXT STATEMENT

GO TO 994 ONLY WHEN

USING OPTIONAL PROCEDURE

FOR CONDENSING FURNACES

AND BOILERS (IFB=4 OR 5)

74
66

78

V V 84

88

90

1

TSSS

IF BOILER

IF FURNACE OR

SPACE HEATER

IF SPACE HEATER

IF FURNACE

OR BOILER

NSYS-9,10.11.12

- SET C VALUES . SET C VALUES

FOR FURNACE FOR BOILERS

NSYS - 5, 6, 7, 8 AND

PASSES DS TEST

NSYS-1,2,3,4

TO STATEMENT 99

TAON TAON-0.

ZETFOX ZETFOX-0.

94 97

OSF sisix - SIFIX SISIX-0.

SIS IX SISOX « SIFOX SlSOX-0.

SISOX

-A

75
99

100

103

112

118

TO MAIN PROGRAM

STATEMENT 122

76
122

128

135

137

149

<.95 WRITE HHV

TEST FUEL

IS TOO LOW

> 1.05 WRITE HHV

TEST FUEL

IS TOO HIGH

J

FUEL HEAT VALUE TESTS

BY RATIO HHV/HHVA

IF UNIT IS VAPORIZING OIL BURNER SPACE HEATER

IF UNIT IS FURNACE

OR BOILER

TTON TTON-10.**20

SET TO FIXED VALUE

CALCULATION OF ON-CYCLE

TIME CONSTANT RATIO FOR

LATER USE IN ON-PERIOD

SENSIBLE HEAT LOSS

DETERMINATION

IF IGNITION DEVICE EQUIPPED RESET OF FFOFF

VALUE BY *. 90.

J

NSYS-9,10,11,12 WHICH USE OUTDOOR AIR FOR COMBUSTION

JISYS • 1 TO 8

ZETFO w/CS‘

IFB=1,2,3

IFB= 4,5

RESET ZETFO

w/o CS :

ZETFO

SIPO SIFO Mll.ll

SIFI SlFl W/1.22

SISO SISO-0 . SISI SISI-C .

VCORRECTION OF HEAT UP

' AND COOL DOWN TEMP.

PROFILES FOR THE EFFECT

OF CYCLING.

J

STATEMENT 156

77
154

189

191

NSYS-9 TO 12. OUTDOOR & DIRECT VENT SYSTEMS

NSYS-5 TO 8, UNITS WITH STACK DAMPERS

I

CALL FUNT 4 (FOR F3& F4)

T

NSYS-1 TO 4 178

^ K>•4 F3, F4 - 0

N • 6

F3, F4, F7, F8 - 0 N - 6

CALL FUNT 4 (FOR F5& F6)

1

CALL FUNT 4 (FOR F5& F6)

F5, F6 • 0 N - 8 T

N-8

CALL FUNT 4 (FOR F7& F8)

T

T

CALL FUNT 4 (FOR F7& F8)

QSON,

QION,

QSOFF

QIOFF

QSON, QSOFF

QION, QIOFF

QSON, QSOFF

QION-QIOFF-0

1 1

CMvOH

U

X

M

H

<

H

COX

0

01

Em

TRANSFER FOR CALCULATION OF CON-

DENSING UNITS USING OPTIONAL PROCEDURE WHERE

NO OFF-CYCLE AIR FLOW PRESENT. TRANSFER BASED

UPON I0PTN = 1

IOPTN=l

CALL

CLFTR

gOPTN=l)

THIS PATH FOR CONDEN- , ^ SING UNITS WITHOUT 200 ^995)

heat-up/cooldoWn test.

F iFB=f -furnace

EFFYSS RESET=f (CL*QLC

T

IF BOILER

EFFYSS RESET

THIS PATH FOR ALL

UNITS USING HEATUP/COOLDOWN TESTS

CONT. ON NEXT PAGE

CONT. ON NEXT PAGE

78
194

195

199

213

FROM EFFYS EVALUATIONS FOR CON- FROM 995 ON

DENSING FURNACES AND BOILERS PRECEDING PAGE

CONTINUED ON NEXT PAGE

79
' ' , i- '. ;

•:.-.»,SFROM 120 ON

PREVIOUS PAGE

218

OUTPUT OF STEPS

23 TO 30

31 TO 38

39 TO 43

44 TO 51

52 TO 59

EEn-A

DETERMINATION

/ OUTPl

/ 60 T(

JT OF /

3 67 /

C 997

FROM TRANSFER STATEMENT NUMBER

199 ON PRECEDING SHEET WHEN OPTIONM.

PROCEDURE USED FOR CONDENSING UNITS.

225

DETERMINATION OF

A USING QNP

B= 0.0

PILOT UNITS RESET OF B

IID

WHEN QP<0.1 B»A*QP*EFFYU* (0 . 00002)

0

OUTPUT OF

A & B 7

QOUT CALCULATION

TO STATEMENT 230

80
CALCUmiON

AND

PRINT

OUT

OF

^^EGiONAL

ANNUAL

OPERATING

COST

TABLE

FROM STATEMENT 229

231

247

T

254

IF IQOUT TEST SERIES

14 IF TESTS USED TO

SET A consta.-;t which

DETERMINES THE VALUES

OF DHR READ FROM THE

DATA TABLE.

AVERAGE ANNUAL

CONSUMPTION AND COST

OUTPUT AVERAGE

ANNUAL EFFYA & COST

I

7

DESIGN LOADS FROM

TABLE 4 SET TO

GENERATE REGIONAL

ANNUAL COST TABLE

L

OUT PUT

TABLE HEADING 7

263

271

OUTPUT OF COST

AT EACH DESIGN

LOAD WITHIN

EACH REGION

DO 1200 IHLH

IHLH-1,5

DO 1201 NL'MBER DESIGN LOADS

D01202 COSTS

COSTS CALCULATED

n

“I

j

TO STATEMENT 278

81
278

279

281

329

82
FIG. B-4. SUBROUTINE CLFTR FLOW CHART

10

SUBROUTINE CLFTR ENTRY

INITIALIZATION AND STORAGE

OF SIX FLUE GAS MOLECULAR WEIGHTS'

USED IN PV CALCULATION

|FGM=1 + AFR * RT~1

VM, WEIGHT WATER VAPOR

3

THIS IS THE BEGINNING

OF STEP 68 IN THE CONDENSING BOILER CALCULATION PROCEDURE.

PV, PARTIAL PRESSURE OF WATER VAPO^

14

lOPTN

AVTFON=TFSS - ^ETFO ^ -TTOn)

TTON V ^ 12 AVTON=»TFSS

(l OlW

PVS=0.4912e 7284

VTFON+39

PV<PVS so UNIT IS NOT OPERATING

IN CONDENSING MODE.

20

PV>PVS

UNIT IS OPERATING IN

THE CONDENSING MODE

STEP 68d

IN CALCULATION

PROCEDURE

ICL-I-O

WARNING-NONCONDENSING

PRINTOUT

21

25

QLC WHICH IS STEP 69, L^ EVALUATION

IN THE CALCULATION PROCEDURE

RETURN OF CL

AND QLC VALUES

TO MAIN PROGRAM

83
FIG. B-5. SUBROUTINE FUNT 4 FLOW CHART

84
FIG. B-6 SUBROUTINE SENLOS FLOW CHART

1

3

25

32

39

THIS BRANCH MEANS

PROGRAM USES XC02

AND TSS FLUE VALUES

IN FOLLOWING RT EVALUATION.

TO CONTINUATION OF

STATEMENT 39

85
CONTINUATION FROM

STATEMENT 39

CALCULATION OF FIFTH ORDER

EQUATIONS USING COEFFICIENTS

INPUT IN STATEMENTS 11 to 24.

86
FOR

DATA

OF

TEST

NO

FIG. B-7. INPUT DATA CODE SHEET FOR NBSFS7

Line 1: NRUN

Enter number of sets of test data to be analyzed as a left justified integer. Set this value equal to the number of sets of data

lines 2 through 8 to be analyzed by the NBSFBS program.

Line 2: TITLE

<

May be one to 80 characters.

Line 3 ; SUBTITLE

May be one to 80 characters.

Line 4 ; IFB, INST

Use IFB = 1 if the unit is a furnace, 2 if the unit is a boiler,

3 if the unit is a vented heater, 4 if the unit is a condensing

furnace, or 5 if the unit is a condensing boiler.

For central furnaces installed indoors, vented wall furnaces, and

vented room heaters, use INST = 1. For floor furnaces and central

furnaces installed outdoors or in unheated spaces, use INST = 2.

When using IFB equal to 4 or 5, INST should always be set equal to 2

Line 5; SYS#, IFUEL, HHV, Qjjj, Qp , PE, BE, Xgo^,S

* SYS# must be an integer as found in tables 1 and 2 for each

system being analyzed. Condensing systems should always be

input as 9 through 12.

* IFUEL must be an integer as given as IFUEL in Step 2 of section

4.1.

* HHV is the measured higher heating value of the test fuel, in

B tu/ lb .

* ^IN Qp measured steady-state and pilot input rates,

respectfully, in Btu/hr.

* PE and BE are power burner and blower (or pump) input powers,

respectfully, in kW

* is the concentration by volume of CO

2

in dry stack gas,

in %

^S,SS,X» ^C02^* ^F,SS» '^F,0n(^1^» ‘^F,0N^^2^» , OFF ^ »

^F,0FF^^4^» ^F,0FF^*'5^

Input values of line six to be given in positive real numbers

using units of degree F for temperatures, and percent (%) for X^^Q^p.

87
Input values for condensing units tested using optional procedure given In section 3.7 requiring no heat-up/cooldown test

must have the values of through T^. equal to

zero (0.) and IFB must be 4 or 5.

Vaporizing type oil burners must have Input values of Tj. gg equal to and Tp^Qj,(t

2 >. Line 7 ; Qj, S/F, Dp, Dg , Y, QNP

* ^RA Input as a degree F temperature.

* Qj Is a percent (%)

* S/F, Dj>, and Dg are positive real numbers using values found

In Table 2.

NOTE ; For vented heaters with draft diverters or draft hoods

enter value of S/F from Table 2; program automatically calculates S/F = (1.3) (R.J, g/Rj y) » compares It with the entered

value, and uses the larger of the two.

* Y - Is a positive real number. See step 22 of calculation

procedure for value to be entered.

* QNP Is the nameplate Input rate In Btu/h.

Line 8 ; FLCOST, ELCOST, K

* FLCOST is given in dollars per unit of fuel.

* ELCOST Is given as dollars per kWh.

* K is Btu content per unit of fuel.

M ^ .

I Test data number two and successive tests are to be Input as repeats of lines

H o 2 V

^ through 8.

through 8.

through 8.

Note ; This program is written to use free field format input as given by

FORMAT No. 801. All input variables must be separated by cocoas or spaces as required by tt^ computer processor system used.
APPENDIX C

Using Condensate Measurement for Calculation

of Annual Puel Utilization Efficiency of Condensing

Furnaces and Boilers

Cl. Background

An alternative test and calculation procedure to that presented in the main

body of this report is discussed within this Appendix. This condensate

collection procedure is considered to be a viable evaluation method for

distinguishing the relative efficiency of one unit to another only if

great care is taken to be consistent in the design and operation of the

test setup in which each unit is evaluated. Therefore, it is a procedure

that might best be conducted on a single test rig with the same experienced

personnel

Condensate collection can be used in conjunction with the test procedures

for non-condensing heating systems to estimate the efficiencies of condensing furnaces and boilers^. The steady-state, cool-down, and heat-up

tests are required. Condensate is collected during a cyclic operation test.

The quantity of collected condensate is used to determine the latent heat

gain due to flue gas water vapor condensation as it is recovered within the

confines of the furnace or boiler and not the flue or stack. The percent

heat gain is then added to the non-condensing Annual Fuel Utilization

Efficiency (AFUE) to estimate the condensing Annual Fuel Utilization

Efficiency. Details of test procedures for condensate collection and

evaluation are given in the following sub-sections.

Federal Register, Volume 45, No. 252, Wednesday, December 31, 1980,

pp. 86526.

89
C2. Condensate Collection Instrumentation

The test unit shall be Installed according to the requirements given in

section 2. Control devices shall be Installed to allow cyclic operation

of the unit and return water or air flows as described in sections 3.2

and 3.3 of this recommended procedure. The test unit shall be leveled

prior to test. Operation times and beginning and end of condensate collection

shall be determined by a clock or timer with a minimum resolution to one

second. Control of on and off operation actions shall be within +6 seconds of

the scheduled time. Condensate drain lines shall be attached to the unit

as recommended by the manufacturer.

The flue pipe installation must not allow condensate formed in the flue

pipe to flow back into the unit. An initial downward slope from the unit’s

exit, an< offset with a drip leg, annuldr collection rings, or drain

holes must be Included in the flue pipe installation without disturbing

normal flue gas flow (as given in section 2.2), and temperature measurement instrumentation (as given in section 2.6). Flue gases shall not flow

out of the drain with the condensate.

Collection-containers must be glass or polished stainless steel, so removal

of Interior deposits can be easily made. The collection-container shall

have a vent opening to the atmosphere.

The scale for measuring the containers and condensate sample mass shall be

calibrated with an error no larger than +0.5 percent over the range of

interest.

90
C3. Cyclic Test Method for Condensate Collection

The condensing furnace or boiler Is to have steady-state, cool-down, and

heat-up tests conducted by the procedures for non-condensing units given

In NBSIR 78-1543 section 3, using the flue gas, air or water flow, and room

ambient conditions given In section 2 of the condensing furnace and boiler

test procedure. The condensate collection containers shall be dried prior

to each use and be at room ambient temperature prior to a sample collection.

Tare weight of the collection-container must be measured and recorded

» '

i prior to each sample collection.

Operating times for on and off cycles at 22.5% on time schedule shall

be 9 minutes 41 seconds on and 33 minutes 16 seconds off for boilers and

3 minutes 52 seconds on and 13 minutes 20 seconds off for furnaces.

The unit should be operated In a cyclic manner until flue gas temperatures

at the end of each on-cycle are within 5*F (2.8*C) of each other

for two consecutive cycles. Then begin the three test cycles. Return

water temperature for boilers or return air temperature for furnaces shall

be equal to those required for steady-state test periods, and shall remain

within the limits given in sections 2.5.1 and 2.5.2 of this procedure.

Operation of the furnace blower or boiler pump shall conform to time delay

requirements given in sections 3.2 and 3.3 for cool-down and heat-up tests.

Begin condensate collection at one minute before start up of the first

test on-period. Three cycles later, the container shall be removed at

the end of the cool down cycle one minute prior to the beginning of what

would be the fourth cycle period. Condensate mass shall be measured

immediately at the end of collection period to prevent evaporation loss

from the sample.

91
Fuel input shall be recorded during the entire test period starting at

the beginning of the on-time of the first cycle to the beginning of the

on-time of the second cycle, etc., for each of the three test cycles.

Fuel Higher Heating Value (HHV) , temperature and pressures necessary for

determining fuel energy input, Q^, will be observed and recorded. The

fuel quantity and HHV shall be measured with errors no greater than one

percent.

C4. Recommended Procedure for Calculating Annual Fuel Utilization Efficiency

Using Collected Condensate Techniques

Using the conditions for a condensing furnace or boiler, and the procedure

for the steady-state, cool-down, heat-up of the non-condensing furnace or

boiler; calculations shall be performed to determine the Annual Fuel

Utilization Efficiency (AFUE) (Col. 67). The calculation steps for the

non-condensing procedure are presented in section 4 of NBSIR 78-1543 [1]

using a direct vent system number.

To determine the AFUE for the condensing units, use the following steps:

(1) Determine the mass of condensate for three cycles, m^, by

subtracting the tare container weight from the total container and

condensate weight at end of three cycles of operation.

(2) Calculate the fuel energy input during the three cycles, Q^, in

Btu/ (3 cycles).

(3) Calculate the heat gain due to condensation, L^, in percent by

the following equation:

m^ (lbm/(3 cycle)) x 1053.3 (Btu/lbm) x 100

(Btu/ (3 cycle)

(4) Calculate the loss due to hot condensate going down the drain

correcting for the fact that this condensate did not go up the

flue as heated vapor.

92
I-c ' 10553 * ("-o <^F,SS - “-^=

(^F.ss

“> -

(5) Calculate the condensing AFUE by adding the percent heat gain due to

condensation, L^, to the previously calculated non-condensing

AFUE (col. 67), and by subtracting the loss L^.

Condensing AFUE = non-condensing AFUE (col. 67) + Lg ”

93
NBS-114A (REV. 9-7B)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 80-2110

4. TITLE AND SUBTITLE

RECOMMENDED TESTING AND CALCULATION PROCEDURES FOR

ESTIMATING THE SEASONAL PERFORMANCE OF RESIDENTIAL

CONDENSING FURNACES AND BOILERS

5. Publication Date April 1981

7. AUTHOR(S)

George E. Kelly and Mark E. Kuklewicz

8. Performing Organ. Report No. NBSIR 80-2110

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

iO. PiDjeetA«sk/Wbik Unit No. 742 2506

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS rsfreer. city, srate, ZIP)

Department of Energy

20 Massachusetts Ave., NW

Washington, DC 20585

13. Type of Report & Period Covered Final

15. SUPPLEMENTARY NOTES

I

I Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or leaa factual summary of moat significant information. If document includes a significant bibliography or

literature survey, mention it here,)

Procedures are developed for testing and rating the performance of residential

central furnaces and boilers of the condensing type. A condensing furnace or boiler is a unit designed to condense part of the water vapor generated by

the burning of hydrogen in the fuel and equipped with a means of draining

this condensate. The test procedure is similar to one developed by the

National Bureau of Standards for the Department of Energy covering noncondensing central heating equipment, except that it requires slightly tighter

control of the laboratory temperature, a return water temperature of 120°F

(48.9°C) with a 20 degree Fahrenheit (11,1 degree Celsius) water temperature

rise for hot water boilers, and offers an optional test procedure for con- densing units having no off-period losses. The rating procedure provides

a method for estimating the steady-state, part-load and annual fuel utilization efficiencies of condensing furnaces and boilers. It accounts for the

fact that the latent heat loss for a condensing unit is smaller than for a conventional furnace or boiler, since some of the water vapor generated from

burning hydrogen in the fuel is condensed and thereby gives up part of its

latent heat to the heat exchanger and jacket.

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)

Annual fuel utilization efficiency; annual operating costs; central heating

equipment; condensing boilers; condensing furnaces; part—load performance;

rating procedure; seasonal efficiency.

18. AVAILABILITY Unlimited

I I For Official Distribution. Do Not Release to NTIS

(31 Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

f I Order From National Technical Information Service (NTIS), Springfield, VA. 22161

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(THIS REPORT)

UNCLASSIFIED

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21. NO. OF

PRINTED PAGES

93

22. Price$9.50

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