NATIONAL BUREAU OF STANDARDS REPORT

8000

THE HEATING PERFORMANCE OF AIR-TO-AIR HEAT PUMPS

IN MILITARY HOUSING

by

C. W. Phillips and p. R. Achenbach

Mechanical Systems Section

Building Research Division

Report to

Office of the Chief of Engineers

Bureau of Yards and Docks

Department of the Air Force

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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Documents, Government Printing Office, Washington 25, D.C.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003-20-10431 May 22, 1963 8000

THE HEATING PERFORMANCE OF AIR-TO-AIR HEAT PUMPS

IN MIUTAH! HOUSING

by

C. W. Phillips and p. R. Achenbach

Mechanical Systems Section

Building Research Division

Report to

Office of the Chief of Engineers

Bureau of Yards and Docks

Department of the Air Force

IMPORTANT NOTICE NATIONAL BUREAU f for use within the Govern and review. For this rea: whole or in part, is not Bureau of Standards, Wi

the Report has been spec

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

progress accounting documents intended

ed it is subjected to additional evaluation

erature listing of this Report, either in om the Office of the Director, National

ver, by the Government agency for which

Uonal copies for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

THE HEATING PERFORMANCE OF AIR-TO-AIR HEAT PUMPS

IN MILITARY

- HOUSING

by

C. W. Phillips and P. R. Achenbach

1. Introduction

The National Bureau of Standards conducted a field study of yearround air conditioning systems in a number of Air Force housing projects

under the sponsorship of the U.S. Air Force, the Office of the Chief of

Engineers, and the Bureau of Yards and Docks. In one part of this investigation the heating characteristics of the air-to-air heat pumps

installed at Seymour Johnson and Columbus Air Force Bases were studied.

Five dwelling units were selected for study at each air base. Instrumentation was installed in each dwelling unit to determine the amouat of

electric energy used by the heat pump and each of the other major appliances, the amount of heat delivered to the dwelling by the heat pump and

by the other appliances, the heat loss of the dwelling at design outdoor

temperature, the coefficient of performance of the heat pump as installed,

the indoor and outdoor temperatures, the lowest outdoor temperature at

which the heat pump could maintain the desired indoor temperature, the

requirements for supplementary resistance heating, energy-usage factors

relating energy requirements, severity of the weather, and dwelling size,

and corollary information on air leakage of the distribution system.

Observations were taken successively at the two air bases for a period

of about one month each during the colder winter months.

2. Description of Sample Dwellings

Five dwelling units were selected from the total of 1500 at Seymour

Johnson Air Force Base and an equal number were chosen from the total of

480 at Columbus Air Force Base for this study. The sample dwellings at

both bases are identified in Table 1 with respect to street address,

type of dwelling unit, number of bedrooms, inside floor area, gross exterior wall area, window and door area, ceiling area, perimeter of exterior walls, and volume of heated space.

- 1-

IDENTIFICATION

OF

SAMPLE

IMELLINGS

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-la-
All of the dwelling units at Seymour Johnson Air Force Base were of

single story construction built on concrete slabs on grade. Seven different floor plans were used, designated by type as A to G. The five dwellings selected for study were of types A to E which comprised all but 12

in the entire development. Dwelling unit types A to D were of duplex

construction, having rectangular floor plans for each unit. The two units

had a common end wall in some cases, and in other cases were joined only

at a comer. House type E was T-shaped and of detached construction. In

the sample used for this study, dwelling unit A had a common end wall with

another unit, dwelling unit B was c orner-connected with another unit, and

dwelling units C and D were the two units of a duplex structure with a common end wall. Figure 1 is a front view of units C and D in the sample,

and Figure 2 is a front view of the detached type E house. Figures 3-7 > inclusive, are floor plans of houses type A to E, respectively, showing

the room arrangement, the doors and windows, and the location of the heat

pump and air distribution system.

The exterior walls of the sample dwelling units at Seymour Johnson

Air Force Base were principally of brick veneer construction, although

selected parts, which varied from unit to unit, were finished on the exterior with grooved plywood. The stud spaces in the frame walls were

filled with 3-inch batts of glass fiber insulation, covered on the inside

with l/2-inch gypsum wallboard and on the outside with 5/l6-±nch exterior

plywood sheathing and waterproof building paper. The brick veneer was

separated from the sheathing by a 1-inch air space, whereas the exterior

grooved plywood finish was supported on 3/^-inch furring strips. The

reinforced concrete floors were 4 inches thick laid over a waterproof membrane and a 4-inch layer of crushed stone. The floor was insulated at

the edge with 1-inch thick rigid insulation in an L shape reaching 2 feet

inward from the edge and vertically upward at the edge to the floor surface level. The floor slab rested on the foundation. The floor covering

was ceramic tile in the bathroom and vinyl tile in the remainder of the

dwelling, in types A to D, inclusive. The floors of the entrance hallway

and living room were of slate and carpet over wood, respectively, in the

sample type E house, but otherwise the floor covering was like that in

the other dwellings. Except for the living room and dining room in the

type E house, ceilings were made of 2- by 6-inch joists with l/2 inch of

plaster finish on l/2-inch gypsum on the under side, and 6 inches of

glass fiber insulation between joists. In the type E house, the ceiling

finish was applied to the under side of the 2- by 8-inch roof rafters

over the living room and dining room. Insulation, 6 inches thick, was

placed between the roof rafters for these two rooms. Roofs were built to

a slope of 2 l/2 inches per foot. The roof rafters were covered with

5/ 8-inch plywood sheathing, 4-ply built-up roofing, and gravel. Attic

spaces were ventilated by slatted louvers in each gable, and by continuous screened openings in the under side of the overhanging eaves.

Single-glazed aluminum- frame windows with horizontally sliding sash were

used throughout all dwelling types. Exterior doors were of wood, 1 3/4

inch thick, with solid core.

- 2-
All of the dwellings at Columbus Air Force Base were of single- storyconstruction built on reinforced concrete slabs on grade. Four different

floor plans were used, with several variations in exterior finish for each

floor plan. The dwelling units for airmen were of duplex construction with

a common end wall, whereas some of the dwellings for officers were detached

and others were of duplex construction. The three variations of the twobedroom dwellings for aiimen were designated as types A2D1, A2D2, and A2D3>

whereas the corresponding designations for the three-bedroom dwellings for

airmen were A3D1, A3D2, and A3D3. The corresponding duplex dwellings for

officers were identified as 02D1, 02D2, and 02D3 for 2-bedroom units and

03D1, 03D2 , and 03D3 for 3-bedroom units. The officers* detached houses

had three or four bedrooms. The variations in the 3-bedroom houses were

designated as types 03S1, 03S2, and 03S3 if the kitchen and carport were

on the left end, and types 03S1R, 03S2R, and 03S3R if the kitchen and carport were on the right end of the structure. The variations in the 4-

bedroom detached officers' houses were designated as types 04S1, 04S2,

04S1R, and 04S2R. Table 1 indicates that two type A3D1 dwellings and one each of types A2D1, 03S1R, and 03S3 were used for the sample. Figures 8

and 9 are front views of the types A3D1 and 03S3 dwellings, respectively.

Figures 10-12, inclusive, are floor plans of dwelling types A2D1, A3D1,

and 03S3, respectively, showing the room arrangement, the doors and windows, and the location of the heat pump and air distribution system.

The exterior walls of all the sample dwellings at Columbus Air Force

Base, except type 03S3? were of frame construction with different portions

finished on the exterior with brick veneer, shake siding, vertical siding,

or exterior grade grooved plywood. The locations of the portions using

these different finish materials were the same for all dwellings of the

same floor plan with a given letter and number designation. In house type

03S3, cavity brick walls 8 inches thick were used for a part of the exterior

walls. The stud spaces in the frame walls contained glass fiber batts 2

inches thick with a vapor barrier on the inside. The interior wall finish

consisted of 3/8-inch rock lath and 3/4 inch of plaster. The studs were

covered on the outside with 3/4-inch plywood sheathing and grade D building

paper. The exterior brick were separated from the sheathing by a 1 l/4-inch

air space, whereas the grooved plywood, the vertical siding, and

the lapped shake siding were applied directly on the sheathing. The reinforced concrete floors were 4 inches thick laid over a 6-mi], plastic

membrane and a 4-inch layer of washed gravel fill. The slabs were thickened at the edges to provide integral concrete footings. Where shake siding,

vertical siding, or grooved plywood was used as an exterior wall covering,

vertical edge insulation 1 inch thick was applied to the concrete floor to

a depth of 8 inches below grade. The floor covering was ceramic tile in the

bathrooms, grease-proof asphalt tile in the kitchens, and parquet wood tile

in the other rooms of all dwellings. Trussed rafters, spaced at 2-foot

interval s r were used in the ceiling and roof construction. A 2-inch thickness of glass fiber insulation was placed between the ceiling joists with a vapor barrier on the under side. The ceiling finish consisted of 3/8-inch

rock lath and 3/^ inch of plaster. The roofs were built to a slope of 3 in.

- 3

-
per foot. The roof sheathing was 3/4-inch plywood which was covered with

15-lb roofing felt and asphalt shingles. Attic spaces were provided with

slatted louvers in each gable, but these were sealed during the winter.

Screened openings were provided on the under side of the overhanging eaves

,

and these wens not sealed. Single-glazed aluminum-frame windows, with one horizontally-sliding sash and one fixed sash, were used in all dwellings.

Exierior doors were of wood, 1 3/4 inches thick, and were solid cone except for the door leading to the terrace. Only the kitchen door contained

a glass panel.

3. Description of Mechanical Equipment

3.1 Seymour Johnson Air Force Base

A single air-to-air heat pump of the split type was installed in each

dwelling unit at Seymour Johnson Air Force Base. The indoor and outdoor

units in each of the sample houses are identified in Table 2, which also

tabulates the compressor horsepower and the nominal capacity of the supplementary resistance heaters for each installation. The location of the

indoor and outdoor units and the supply and return ducts in the sample

houses is shown in the floor plans in Figures 3-7 > inclusive.

The indoor units in dwellings A to D at Seymour Johnson Air Force Base

were installed in the attics over the hallways at approximately the center

of the dwelling and adjacent to the access door for the attic. Figure 13

shows such an installation as viewed at an upward angle through the open

access door to the attic. The supply air from the indoor unit was carried

to the several rooms through ducts, part of which were supported on the

ceiling joists over the insulation, and part of which were furred down from

the ceiling. The air was discharged into the rooms through high sidewall

grilles in each case. Ducts in the attic were insulated with glass fiber

with paper vapor barrier, sealed at the joints. The return air entered a louvered gillie near the floor level and flowed upward to the attic through

a passage provided in a part of a space originally planned as a closet.

The glass fiber air filter was attached to the back of the louvered grille.

The blower was on the downstream side of the indoor coil, and the supplementary resistance heaters were located in the discharge side of the blower.

The indoor unit for the E type house at Seymour Johnson Air Force Base

was installed in a closet adjacent to the front hall and living room. Figure 14 shows this installation. The supplementary resistance heaters were

located in the separate housing mounted on top of the unit casing. The

supply air plenum extended through the closet ceiling into the attic where

short ducts connected the plenum to high sidewall grilles on interior

partitions in the living room and dining room. The supply air to the

kitchen, 3 bedrooms, and 2 baths flowed through short attic ducts and then

through elbows to ducts furred down from the ceiling and to high sidewall

grilles on an interior partition in each room. The attic ducts and plenum

were covered with glass fiber insulation and a vapor barrier. The return

-4-
TABLE 2

IDENTIFICATION OF HEAT PUMP COMPONENTS IN

DWELLING UNITS AT SEYMOUR JOHNSON AFB

Outdoor Unit Indoor Unit

Type of Comp. Supp.

Dwelling Street Mathes Co. Motor Model Resistance

Unit Address Model No. Size No. Heater Cap.

h£ kW

A 402 March lane 27-HAR-IE-HP 2.5 38LEB-HP 7.2

B 413 Carswell Lane 38-HAR-IE-HP 3.6 38REB-HP 3.6

C 217 Chanute Road 27-HAR-IE-HP 2.5 27REB-HP 7.2

D 215 Chanute Road 27-HAR-ID-HP 2.5 27REB-HP 7.2

E 301 Carswell lane 38-HAR-IE-HP 3.6 38VEB-IE-HP

H-20* 7.2

*The resistance heaters were in a separate housing in this unit.

-5-
air entered the utility closet through louvers in the closet door and

through a low-wall grille in the living room. The glass fiber air filters

were located in the return air openings of the indoor unit.

In all indoor units at Seymour Johnson Air Force Base, the condensate

was collected in a pan forming the bottom of the unit; it was conveyed by

a pipe to the floor slab level and thence to the outside through a fiber

pipe embedded in the floor slab with a slight slope in the direction of

flow. In dwelling types A to D, inclusive, the room thermostats were

located in the branch hall to the bathroom, whereas it was located on an

inside partition at the entrance end of the hallway serving the bedrooms

in the type E house. All thermostats were located at a height of 5 feet

above the floor.

The outdoor unit for all dwellings at Seymour Johnson Air Force Base

was located on a concrete base a few feet from the back side of the house,

as illustrated in Figure 15* The outdoor air inlet faced the house and the

discharge was on the opposite side of the steel cabinet. The refrigerant

lines connecting the indoor and outdoor units ran underground through

asphalt impregnated fiber duct, whereas the electric service was enclosed

in metal conduit.

Each dwelling unit was equipped with a water heater, clothes dryer,

automatic washer, dishwasher, cooking range, and refrigerator, all

electrically-operated. The water heater had a storage capacity of 66 gallons in the type E dwelling and 52 gallons in the other four sample houses..

An upper heating element of 3 W nominal heating capacity and a lower heating element of 2 kW heating capacity was used in each water heater. An

interlock prevented the two elements from being energized simultaneously.

Each clothes diyer was equipped with a l/3-hp motor and a heater of either

4.6 or 5*6 kW capacity, depending on the type of dwelling unit. Each dishwasher was equipped with a l/ 6-hp motor and a heating element of 0.56 kW

capacity.

3.2 Columbus Air Force Base

A single unitary air-to-air heat pump was installed in each dwelling

unit. The same model. General Electric Company WT-44C1, equipped with a 5-hp compressor motor, was used in eveiy dwelling. Each unit was provided

with supplementary resistance heaters with a capacity of 10 kW. The heat

pump was installed in a utility closet which was adjacent to the front door

in dwelling types A3D1, 03S3> and 03SIR and which was at the rear of the

dwelling in type A2D1. The location of the heat pump unit and the arrangement of the supply and return air ducts in the sample dwellings are shown

on the floor plans in Figures 10-12, inclusive. Figure 16 is a view of the

complete heat pump as seen through the door of the utility closet. Figure

17 is a view from the same position with the front of the metal casing of

the heat pump removed to show the arrangement of the major components of

the system.

-6-
The warm air supply ducts in dwelling types A2D1 and A3D1 crossed the

utility closet beneath the ceiling and then passed through the closet wall

to the space above the furred ceiling which was provided over the entire

hall and entrance area. The furred ceiling was not closed on the upper

side, but the supply ducts and furred ceiling were covered by the ceiling

insulation. The warm air was introduced into each room through a high

sidewall register and into the entrance hall through a ceiling diffuser.

The warm air supply system to the bedrooms in the officers* duplex dwellings was similarly arranged. The attic ducts in the officers* detached

dwellings delivered warm air to the living room, dining room, and kitchen

through short wall stacks and high sidewall registers. Only the duct to

the kitchen contained a volume damper. The return air entered a louvered

grille off the hallway opposite the utility closet in all dwelling units.

It traversed a closet through a duct near the floor in dwelling types A2D1

and A3D1 to enter the utility closet, whereas in dwelling types 03S3 and

03S1R the utility closet adjoined the hall so the return duct only penetrated the common wall between these two spaces. The glass fiber air

filter was attached to the return air opening of the heat pump unit in each

installation and there was little space between the air filter and the face

of the indoor coil. The indoor blower was on the downstream side of the

indoor coil, and the supplementary resistance heaters were located on the

discharge side of this blower.

Each dwelling unit was equipped with a water heater, clothes dryer,

automatic washer, dishwasher, cooking range, electric resistance heater in

the bathroom, and a refrigerator, all electrically-operated. The water

heater had a storage capacity of 50 gallons and was equipped with upper and

lower heating elements, each with a capacity of 4.5 HW. An interlock prevented the two elements from being energized simultaneously. The total

connected load of other major appliances was as follows: clothes dryer,

5 kW; dishwasher, 1.5 kW; bathroom heater, 1.5 kW; and cooking range,

12.7 kW.

4.0 Test Apparatus

Eight watthour meters were installed in each sample dwelling at Seymour Johnson AFB and nine in each sample dwelling at Columbus AFB to integrate the energy used by each of the major appliances and the total energy

used by the dwelling. In the former site the meters were installed on the

rear of the dwellings and in the latter site, in the storage rooms at the

end of the dwellings, as illustrated in Figures 18 and 19, respectively.

The meters were wired to measure the energy used by the following loads:

(a) Total house load

(b) Total heat pump load

(c) Heat pump compressor and blower motors

(d) Supplementary resistance heaters in the heat pump

(e) Cooking range

(f) Hot water heater

(g) Clothes diyer

(h) Lighting and miscellaneous loads

(i) Bathroom heater (Columbus AFB only)

-7

-
At Seymour Johnson AFB, the smallest graduation on the last dial of

seven of the watthour meters represented 100 watthours, whereas a corresponding interval on the eighth meter, which measured the energy use of the

supplementary resistance heaters, represented 10 watthours. At Columbus

AFB, the smallest graduation on the meters for the total house load and

the total heat pump load represented 10 kWh, the smallest graduation on

the meter for the supplementary resistance heaters represented 0.01 kWh,

and a corresponding interval on the other six meters represented 1 kWh.

Running time meters were installed on the compressor motor circuit in each

sample dwelling at both sites to indicate the cumulative operating time of

the heat pump compressor. A recording voltmeter was installed on the incoming electric lines for each dwelling at Seymour Johnson AFB, and on one

dwelling in Columbus AFB. Pressure gages were installed on the suction and

discharge lines of the compressor for each dwelling unit at Seymour Johnson

AFB, but these instruments were not used at Columbus AFB because the heat

pump systems were of the sealed type.

A 16-point recording potentiometer was installed in the storage room

of each sample dwelling unit at both sites for continuous recording of

temperature at selected places, in the air distribution system, refrigerant

circuit, living space, attic, and outdoors, using copper-constantan thermocouples of 30-gage wire. A pyrheliometer was used to measure incident solar

radiation at each site. A typical location of the outdoor air thermocouple

and the pyrheliometer is shown in Figure 20. A micromanometer was used to

measure impact pressures and static pressures at selected places in the air

distribution system.

5*0 Test Procedure

Observations of all of the watthour meters at each dwelling unit were

taken and recorded at 2-hour intervals on a staggered time basis for the

duration of the study, approximately one month at each site. The running

time meters and pressure gages were read on the same time schedule as the

watthour meters. In a typical installation the potentiometer recorded air

temperatures at the return grille of the air distribution system, at the

inlet to the indoor and outdoor coils, at the inlet to the indoor blower,

in the discharge plenum of the indoor unit, at the center of one or more

rooms 6 feet above the floor, at two stations in the attic midway between

ceiling insulation and roof ridge and 1/3 the distance from each end of the

attic space, and at one outdoor station near the roof level at the end of

the carport, as well as the surface temperature of the case of the room

thermostat. The temperatures of the refrigerant vapor line were also recorded at the compressor suction, and near its connections to both the

indoor and outdoor coils. Multiple thermocouple junctions in parallel

were used at all stations in the indoor air distribution circuit and at

the inlet to the outdoor coil to obtain a better average of the air temperatures. In some instances the air temperatures upstream and downstream

of the indoor coil were recorded more frequently than the other temperatures in order to obtain a more detailed record of the change in air temperature during cyclic operation of the heat pumps.

-8-
Calibration tests were made at the beginning of the investigation in

each dwelling unit to Treasure the rate of air circulation through the indoor coil and air distribution system. These tests consisted of measuring

the temperature rise produced in the circulated air when one or more elements of the supplementary resistance heaters were energized and the energy

input was measured. The housing and supply plenum of the heat pump were

well insulated so the heat loss through this short section was neglected

in computing the air circulation rate. Clean air filters were used in the

system during the calibration tests and the supply registers and grilles

were in the same position as for normal operation. In the type E dwelling at

Seymour Johnson AFB a check test of air circulation rate was made by connecting a straight duct, about 10 feet long and 14 inches in diameter, to

the return air grille and using a Pitot tube to measure air velocity in the

straight duct, while simultaneously measuring air temperature rise produced

by a measured electric energy dissipation in the supplementary resistance

heaters. This comparison was made in a system known to have little extraneous air leakage into the duct system or indoor unit casing.

During the course of the tests at each air base, it became obvious

that an appreciable amount of air was being drawn into the return air duct

system from the attic. At Seymour Johnson AFB the leakage occurred principally where the return duct was fitted into the ceiling of the closet

that was converted into a return-air passage as a modification of the

original plans. At Columbus AFB the leakage occurred between the attic

and the utility closet where the main supply duct passed through the utility closet wall into the space above a section of furred ceiling. The opening in the wall was larger than the duct, leaving a passage for air leakage

as indicated by the darkest area at the right side of Figure 21. Therefore, near the end of the investigation at each site some measurements were

made from which the order of magnitude of the air leakage could be determined. For this purpose, the return air grille and all of the supply

grilles except one were covered to prevent any air flow through them. A

6-inch diameter duct was fitted to the one supply grille with an airtight

connection. With the indoor fan running, all of the air that leaked into

the return system from the attic was discharged through the 6-inch duct,

assuming that no air leakage occurred in the discharge duct system. By

measuring the air flow rate in the 6-inch duct, a minimum value of air

leakage could be determined. Static pressures were measured downstream

of the return air grille and in the supply plenum under the special conditions just described and also under normal operating conditions, so corrections to the measured air leakage could be made to account for difference in the pressure conditions at the points of leakage. The relation

between the temperatures at the return air grille, at the inlet to the

indoor coil, and in the attic during normal operating conditions were also

used to compute the probable amount of air leakage from the attic.

Hourly data on dry-bulb and wet-bulb temperatures, and wind velocity

and direction, and the total precipitation for consecutive 6-hour intervals were obtained from the weather station at each air base for the period

covered by the tests.

-9-
6.0 Heat Pomp System Performance

6.1 Steady State Heating Capacity

The heating capacity of the compression system in the heat pump in

each sample dwelling was determined for a range of outdoor temperature

by observing the temperature rise produced in the circulated air as it

passed through the indoor coil. The test period selected for these

determinations was usually between midnight and 6:00 a.m. when outdoor

temperatures were reasonably steady and when the indoor temperatures

were typically undisturbed by the activities of the occupants. The computation of steady-state heating capacity was based on the recorded temperature rise of the circulated air between inlet and outlet of the

indoor unit near the end of a running period and when the supplementary

resistance heaters were not energized, and the rate of air circulation

which was determined in separate tests using the supplementary resistance heaters alone as a heat source.

The principal data required for computing heating capacity and coefficient of performance of the heat pump and performance factor of the

system are summarized for a range of outdoor temperature in Tables 3-7 > inclusive, for the five sample dwellings at Seymour Johnson AFB, and in

Tables 8-11, inclusive, for four sample dwellings at Columbus AFB. The

heating capacity for the heat pump in the type A2D1 dwelling at 122 Vernon Avenue at Columbus AFB was not determined because the running periods

of the heat pump were too short to produce a representative temperature

rise in the air. A typical set of operating data is tabulated for outdoor temperature increments of about 5°F rather than all of the values

obtained at each outdoor temperature level. The heating capacity of

each of the nine units is plotted against outdoor temperature in Figure

22. The dry-bulb temperatures shown in Tables 3-H> inclusive, and

plotted in Figure 22 are those recorded at the weather stations at the

two air bases for the corresponding time of observation. The outdoor

temperatures observed adjacent to the sample dwellings did not differ

from the airport temperatures more than 1 degree in most cases, although

the differences were occasionally greater than this because of local wind

currents or solar radiation.

The lower group of six curves in Figure 22 applies to the heat pumps

at Seymour Johnson AFB, whereas the upper group of three curves with a discontinuity at midlength represents the performance of four identical

heat pumps used at Columbus AFB. It will be noted that the steady- state

heating capacity of each of the heat pumps at Seymour Johnson AFB increased with rising outdoor temperature. The increase was approximately

linear with outdoor temperature and ranged from 25 percent to 50 percent

for the temperature range from 20°F to 50°F. The outdoor units of the

heat pumps in dwelling types A, C, and D had similar compressor displacements and the indoor units in dwelling types C and D were identical.

The heating capacities of these three systems did not differ greatly as

shown in Figure 22. Dwelling types B and E had identical outdoor units

-10-
and similarly rated indoor units installed in them, but their measured

capacities were different. Two capacity curves are shown in Figure 22

for dwelling E. The lower curve represents the capacities observed during the early part of the test period and the upper curve represents the

capacities observed later after repair and maintenance operations were

performed. After determining that the system did not appear to be

developing its full capacity, the capillary tube on the indoor unit was

replaced and the system was recharged with refrigerant. The improved

performance is indicated by the comparison of the two capacity curves

in Figure 22.

The heat pumps installed in the dwellings at Columbus AFB were

three-cylinder compressors equipped with a hydraulic device to lift the

suction valve on one cylinder on a rising outdoor temperature between

30 and 40°F to reduce the capacity of the system. The data in the upper

part of Figure 22 indicate that the heating capacity of the heat pump

units in the sample dwellings ranged from about 40,000 to 45,000 Btu/hr

at an outdoor temperature of 15°F. Based on the few data taken at outdoor temperatures between 15°F and 30°F, the heating capacity of the

sample units appeared to increase at a rate of about ^>,000 Btu/hr for

a 10-degree rise in outdoor temperature in this outdoor temperature

range, for which the compressors were

functioning as 3-cylinder compressors. The data in Figure 22 also indicate that the compressors in the four sample houses operated as 2-cylinder

compressors at outdoor temperatures above 32°F. The discontinuities in

the capacity curves for the heat pumps in the type 03S1R house and the

two A3D1 type dwellings indicate that these units experienced a decrease

in capacity of 5500 to 7500 Btu/hr when changing from 3“cylirider to

2-cylinder operation. The rate of increase in compressor capacity with

increase in outdoor temperature was about the same for 2- and 3-cylinder

operation.

The observed values of steady state heating capacity for the heat

pumps at Columbus AFB are somewhat scattered for any given dwelling.

Some values obtained at Seymour Johnson AFB also deviate from the curves

drawn through most of the plotted points. Such deviations could be

caused by variations in air flow rate through the indoor coil resulting

from dust accumulation on the air filter, by the effects of wind on the

heat transfer in the outdoor coil, by variations in the indoor temperature level, and by other abnormalities in operating conditions.

6.2 Air Flow Rate

The air flow rate through the indoor coil of each heat pump was

measured using the supplementary resistance heaters as a calibration

mechanism. The air flow rate was computed from the density and specific

heat of the air, the temperature rise produced by the resistance heaters,

and the electrical energy dissipated in the resistance heaters. Table

12 shows a typical set of results from the dwelling at 215 Chanute Road

at Seymour Johnson AFB. Separate tests were made with one to four re- sistance elements energized, and with only the circulating fan adding

energy to the air stream. The table shows that the computed air circulation rate ranged from 93^ CFM with four heating elements energized to

-11-
1003 cfm with one element energized, corresponding to an average of 956

cfm. The air flow rate computed from the fan energy only should be discounted because the observed temperature rise of about 0.7°F was too

small for precise measurement under these conditions. A sixth determination of the air flow rate was made with the pressure drop across

the air filter arbitrarily increased from 0.11 to 0.2 in. W.G. to simulate a reasonable dust load on the filter. A comparison of the test

results at the two levels of pressure drop across the filter indicated

that an increase in pressure drop of 0.09 in. W.G. reduced the air flow

rate about 10 percent. The measured air flow rates through the indoor

units of the ten sample houses are summarized in Table 13

.

The precision of this method for determining air flow rate would be

affected by the heat loss from the insulated casing of the heat pump upstream of the discharge temperature-measuring station, as well as the

extent to which radiation from the heating elements affected the thermocouple indications. The thermocouples at both the inlet and outlet stations were out of sight of the heating elements, thus minimizing the

radiation effect. The computed air flow rate did not always decrease

with increasing heat input in every unit, as is indicated in Table 12.

In one dwelling, simultaneous determinations of the air circulation

rate were made using the supplementary resistance heaters for one calculation and pitot tube measurements of velocity in a straight section of

duct connected to the return air grille as a second method. The two

results differed by only 1.6$ in this case. However, this method was

not employed in other dwellings to determine the air circulation rate

because the leakage of air into the return duct from the attic would

have prevented a direct comparison. The average of the values of air

circulation rate determined for the several tests with different numbers

of the supplementary resistance heaters energized was used in calculating the steady state heating capacities of the heat pumps as summarized

in Tables 3-11, inclusive.

6.3 Operating Time of Heat pumps

The running time meters attached to the compressor circuits in the

sample dwellings integrated the hours of operation of the compressors.

The meters were graduated to tenths of an hour and estimates of one- hundredth hour were possible. The running time meters totalled all of

the operating time of the compressors including the defrosting time,

which comprised a very small part of the total operating time except

during rainy weather when the outdoor temperature was a little above

32°F. The heat pumps at each base were equipped with automatic defrosting controls. At Columbus Air Force Base the defrost cycle was

initiated by a pressure switch actuated by an increasing air pressure

- 12-
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2.26
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- 21-
MEASUREMENT

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5

percent

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temperature.
difference between the upstream and downstream sides of the outdoor coil;

and at Seymour Johnson Air Force Base, by a temperature switch activated

by an increasing temperature difference between the outdoor coil and the

air entering the coil. In the ten sample houses no operating difficulty

was observed with the defrost controls during this study, and the loss

of heating time caused by the defrost cycle was minimal. No determination was made of the effect of defrost operation on performance characteristics.

Figures 23 to 27, inclusive, show the relation of operating time

to outdoor temperature for the five sample houses at Seymour Johnson AFB,

and Figures 28 to 30, inclusive, show similar data for the type 03S3 and

03S1R houses and one of the type A3D1 dwelling units at Columbus AFB.

Corresponding data for the other two dwelling units at Columbus AFB were

not reported because their occupants consistently lowered the thermostat setting at night, so the indoor temperature level was changing

during an appreciable part of the night hours. Each plotted point in

these figures represents heat pump operating time during a continuous

period of about 8 hours between 2200 hours and 0800 hours when a minimum amount of miscellaneous heat release occurred in the dwellings.

Figures 23 to 30 show that the relation between running time and

outdoor temperature can be represented reasonably by a straight line at

both housing projects. A discontinuity or change in slope of the operating time characteristic curve would have been expected for the heat

pumps at Columbus AFB at the outdoor temperature corresponding to the

shift from 3-cylinder to 2-cylinder operation. Such a discontinuity

is not evident in Figs. 28 to 30, however, perhaps because of the scattering of the plotted points or the scarcity of data at low outdoor

temperatures.

In Figs. 24, 26, 27, 29, and 30 data are plotted for night operation with and without setback of the thermostat. When the setback of

the thermostat was no more than 2 - 5°F, the operating time did not

differ markedly from that without setback, as indicated in Figs. 26

and 27 • A larger setback of the thermostat caused significantly less

operating time for the heat pump at a given outdoor temperature, as

shown in Figs. 29 and 30.

Although there were few data obtained at outdoor temperatures

above 55°F, extrapolation of the straight lines indicate that the highest outdoor temperature requiring heat pump operation ranged from 58.5°F

to 63°F in different dwellings, even though these data were taken principally during the normal hours of sleep when other sources of heat

generation would be minimal.

By extending the straight lines in Figs. 23 to 30 until they

reached the horizontal line representing 100 percent operating time,

the balance point for the heat pump in each house was determined.

-23-
The balance point for a heat pump is defined as the lowest outdoor temperature at which the compressor system can maintain the desired indoor

temperature level with constant operation. In the five sample houses

at Seymour Johnson AFB the balance point ranged from about 31°F in the

type B house down to about 28.5°F in the type D house, whereas it ranged

from 15 °F down to about -3°F for the three houses at the Columbus AFB.

In the latter case, the balance points were all obtained by extrapolating the observed data. An examination of Figs. 23 to 27 indicates that

the balance point varied from day to day. This was to be expected,

since the heat loss of a house at a given outdoor temperature varies

with wind velocity and direction. Furthermore, no effort was nude to

limit or control the use of miscellaneous heat -producing equipment inside the houses, except to choose a period of the day for this analysis

when such use would normally be small.

It will be noted in Figs. 23, 25, and 27 that some use of the supplementary resistance heaters occurred at times when the compression

system was operating between 90 and 100 percent of the time. This was

probably caused either by a sudden advance of two degrees or more in

the thermostat setting, or by a sudden cooling of the thermostat from

an open door or similar occurrence. The thermostats in the dwellings

at both bases were of the two-step heating type designed to energize

the compression system on the first step and energize the supplementary

resistance heaters (subject to the outdoor thermostat) on the second

step. whenever the room temperature fell 2 degrees below the first step

setting. The heat pumps at both bases were equipped with outdoor thermostats to prevent use of supplementary resistance heaters when the outdoor temperature rose above the set point of the thermostat. At Seymour

Johnson AFB one outdoor thermostat controlled all heaters, whereas at

Columbus AFB two outdoor theimostats, set several degrees

apart, were provided, each controlling half the installed heater elements.

6.4 Coefficient of Performance

The ratio of the heat delivery rate of the compression system of a heat pump to the power input to the system, expressed in the same units,

is called the coefficient of performance. The coefficients of performance of the heat pumps in five sample houses at Seymour Johnson AFB and

in four sample houses at Columbus AFB are reported in Tables 3 to 11,

inclusive, and plotted in Figures 31 to 39, inclusive, for the range of

outdoor temperature that occurred during the test periods. These coefficients were based on the measured power input to the compressor

motor and two fan motors, and the heat delivery rate calculated from

the measured air circulation rate and the temperature rise produced in

the warmed air during steady operation or near the end of an operating

cycle

-24-
An inspection of Figs. 31 to 3^ indicates that the coefficient of

performance was nearly constant in house types A, B, and D, and increased only slightly in house type C at Seymour Johnson AFB for the

outdoor temperature range from 20°F to 50°F. At an outdoor temperature

of 20°F, the coefficients of performance ranged from about 1.4 in house

type A to about 1.8 in house type D, with an average of I.67 for the

four systems. When tested in the laboratory, the coefficient of performance of the model heat pump used in house type C was I.52 and the

heating capacity was 14,300 Btu/hr at the same outdoor temperature but

with the temperature at the inlet to the indoor coil controlled at 70 °F.

Two curves for the coefficient of performance of the heat pump in

house type E are plotted in Fig. 35 > with the lower and upper curves

representing the performance before and after repair and maintenance

was performed on the unit, respectively. As described earlier in this

report, a new capillary tube was installed in this unit and the system

was recharged with refrigerant. As shown in Table 9 and Fig. 35 > these

repairs and maintenance operations increased the heating capacity about

50 percent and the coefficient of performance about 65 percent at an

outdoor temperature of 35°F without an increase in power input. A

laboratory test of the same model heat pump as that installed in the

type E house indicated a coefficient of performance of 1.91 and a heating capacity of 24,000 Btu/hr at an outdoor temperature of 20°F and an

indoor temperature of 70°F. There is no certainty, however, that all

components in the two units of the same model number were identical.

Tables 8 to 10 and Figs. 36 to 38 indicate that the coefficients

of performance of the unitary type heat pumps in three of the sample

houses at Columbus AFB was about 2.0 at an outdoor temperature of 14°F

and increased to 2.4, more or less, at an outdoor temperature of 45°F.

Comparable values of the coefficient of performance were not obtained

in the type A2D1 house because of the short periods of compressor operation required to maintain the house temperature. The effect on coefficient of performance of shifting from 3-cylinder to 2-cylinder

operation in the outdoor temperature range between 30°F and 40°F is

not clearly evident except in Fig. 37* In this instance, a coefficient

of performance of 2.65 was observed for 3-cylinder operation at an and

outdoor temperature of 32«5°F, whereas coefficients of performance of 2.3/

2.2 were observed for 2-cylinder operation in the outdoor temperature

range from 32°F to 38°F.

The progressive shortening of the periods of compressor operation

required to maintain the desired indoor temperature at higher outdoor

temperatures may account for the relatively small change observed in

the coefficient of performance with increasing outdoor temperature.

That is, the coefficient of performance calculated from the heat delivery rate near the end of a short running period is probably lower

than the steady state value, but on the other hand, it is higher than

the average value realized for the whole of the short running period.

These relationships can be illustrated by Figs. 40 and 41, which show

the progressive change in the temperature rise of the air produced by

the heat pumps after starting, as measured in the supply plenum and at

the inlet to the indoor coil.

-25 -
Figure 40 shows the pattern of temperature rise of the warmed air

in the type D dwelling at Seymour Johnson AFB during two running periods each about 15 minutes in length in the lower curve, and during two

running periods of 25 and 40 minutes* length in the upper curve. The

longer running periods indicate that the temperature rise had reached

a steady value, for practical purposes, in about 14 minutes after the

blower started. The lower curves do not permit a definite evaluation

because of the short running time, even though a steady temperature

rise was probably being approached at the end of the running periods.

At Seymour Johnson AFB, heat pump operation was initiated by the room

thermostat on a decrease in room temperature; and the indoor blower was

started by a pressure-activated control which sensed the condensing

pressure in the indoor coil. It will be noted that a temperature decrease of 2 to 3 degrees occurred immediately after the blower started

before the longer pattern of temperature rise occurred. The temperature rise decreased sharply at the end of the running period of the

heat pump because the blower continued to run for a minute, more or

less, after the compressor stopped.

Figure 41 shows the pattern of temperature rise of the warmed air

in the type A3D1 dwelling at Columbus AFB during four running periods

each about 10 to 13 minutes in length in the upper curve and during

three running periods each 28 to 32 minutes in length in the lower

curve. Both curves indicate that the temperature rise reached a steady

value, for practical purposes, in 8 or 9 minutes after the blower

started. In the dwellings at Columbus AFB the blower was started and

stopped simultaneously with the compressor under the control of the

room thermostat. Fig. 41 shows that the temperature in the supply

plenum increased a few degrees after the blower and heat pump stopped

because of the heat stored in the indoor coil, blower, and the sheet

metal housing.

In Figure 42 the temperature rise of the warmed air is plotted as

a percent of the steady state temperature rise in relation to the

elapsed time after the start of blower operation in the type D and A3D1

dwellings. This figure indicates that the larger heat pump at Columbus

AFB reached 90 percent of the steady state value of temperature rise in

about 3 minutes, whereas the corresponding percentage was not attained

by the smaller heat pump at Seymour Johnson until approximately 6 minutes after blower operation was initiated. If it is assumed that the

electrical power input to the heat pumps was a constant from the instant of starting in these two installations, the transient coefficients of performance of the two units would be proportional to the percent of steady state temperature rise, since the heat delivered by the

unit is directly proportional to the temperature rise of the warmed air.

The average coefficient of performance of a heat pump during cyclic

operation could be approximated by averaging the ordinates of curves

like those in Figure 42 for the duration of the running period. Figs.

-26-
40 to 42, inclusive, indicate that coefficients of performance based on

the temperature rise at the end of running periods of 15 minutes or

more in the dwellings at Columbus AFB would not deviate from the steady

state value by more than a percent or two.

Very little of the heat stored in the indoor unit and supply duct

system of an attic installation like those in dwelling types A to D,

inclusive, at Seymour Johnson .AFB would be delivered by natural convection through the unit during the time the indoor blower was stopped.

Since the supply grilles were at a level lower than the attic -mounted

unit and the vertical portion of the return system was at room temperature, there would be virtually no motive force for natural circulation

of air through the attic unit.

In the dwellings at Columbus AFB and the type E dwelling at Seymour

Johnson AFB, the indoor coil was in a vertical housing a few feet above

the floor level. In this type of installation enough chimney effect

would be created in the vertical portion of the supply system to produce a low rate of natural circulation causing some of the heat stored

in the system to be delivered at the supply grilles during the time the

indoor blower was stopped.

Tha data taken during the field study did not provide a means for

evaluating the amount of natural circulation of air through the systems

when the indoor blower was stopped.

6.5 System Performance Factor

It will be noted in Tables 3 to 6, inclusive, and 8 to 11, inclusive, that the air temperature at the inlet to the cooling coil was

lower than at the return air grille by amounts ranging from 3 to 7 degrees at the lowest outdoor temperature reported. This decrease in air

temperature from the return grille to the coil inlet was caused principally by air leakage into the return system from the attic through

openings described earlier in this report. The measurement of this air

leakage is discussed in Section 6.6 of this report.

The unnecessary leakage of cold air from the attic into the return

system represented a loss of useful heating capacity and a decrease in

performance effectiveness of the system, since the return air had to be

warmed from a lower temperature level because of the leakage. The total

adverse effect of this air leakage would be related both to the percent

running time of the blower and to the attic temperature. Since the

attic temperature typically decreased and the percent running time increased as the outdoor temperature decreased, the cumulative penalty of

the air leakage was compounded as the weather became colder.

- 27-
A system performance factor was computed for each heat pump and

air distribution system in which attic air leakage was observed, for

comparison with the coefficient of performance of the heat pump itself.

The system performance factor is defined as the ratio of the heat dissipation rate in the living space, computed from the difference between

air temperatures at the supply plenum and the return air grille, to the

heat equivalent of the power input to the compressor and fan motors.

The system performance factors for four systems at Seymour Johnson AFB

and four systems at Columbus AFB are shown in Tables 3 to 6 and Tables

8 to 11, respectively. These system performance factors are also

plotted in Figs. Jl to 3^ and Figs. 2>6 to 39 for graphical comparison

with the coefficients of performance. The system performance factors

were about 0.25 lower than the coefficients of performance at both

housing projects for an outdoor temperature of about 45°F, whereas this

disparity was 0.40 to 0.50 at the lowest outdoor temperatures experienced during the study at the two sites. The loss in useful heating

capacity of the unit caused by the leakage of attic air into the return

system was about 1000 Btu/hr at Seymour Johnson AFB and about 1500 Btu/hr

at Columbus AFB for each degree F difference between the air temperature

at the return grille and the inlet to the cooling coil. These losses

could be avoided by a duct construction that prevented air leakage into

the system from cold spaces.

Table 7 shows that there was less than 1 degree difference between

the air temperature at the return grille and the inlet to the cooling

coil in the type E house at Seymour Johnson AFB, in which the heat pump

unit was located in a closet adjacent to the hall. Although the^e were

some openings in the ceiling construction of this closet communicating

with the attic, there was a negligible pressure difference across the

louvered door and the grille through which the return air entered the

utility closet, so little air leakage occurred from the attic.

6.6 Air Leakage in the Return Air System

The points at which air leakage occurred into the return system

from the attics of the sample houses at both air bases have been described, and the effects of the air leakage on heating capacity and performance of the heat pump systems have been evaluated. The amount of

air leakage was determined by two methods; namely, (a) by computation

using the observed temperatures in the attic, at the return grille, and

at the inlet to the cooling coil in conjunction with the total measured

air flow rate, and (b) from air flow measurements made at one supply

grille with the return grille and all the other supply grilles covered

and sealed, together with static pressure measurements in the system.

The air flow measurements were adjusted for the difference in the static

pressures in the return system during normal operation and during operation with all but one supply grille covered and sealed.

-28-
The average leakage rates of attic air computed from the temperatures of the attic air, return air, and the mixture are summarized in

Table 13 for the sample houses at each air base, whereas the leakage

rates based on measured air flow values adjusted for static pressure

changes in the return systems are shown in Table 14. The data in Table

13 indicate that the air leakage rates ranged from 45 cfm in the type E

house to 180 in the type B house at Seymour Johnson AFB, corresponding

to 3 percent and 19 percent of the total air delivery rates of the

blowers, respectively. The air leakage rates at Columbus AFB ranged

from 220 to 350 cfm or 15 to 25 percent of the total air delivery rates

of the blowers. The leakage rates computed from the measured air delivery at one supply grille while all other grilles were sealed, as

summarized in Table 14, are of the same order of magnitude as those

obtained by computation from air temperatures. In Table 14 it is shown

that a dirty filter or a dirty return grille increased the negative

pressure in the return system about threefold and the air leakage from

the attic by 70 to 80 percent for one dwelling at Seymour Johnson AFB

and for two dwellings at Columbus AFB.

Tables 13 and 14 indicate that the leakage rates of attic air

ranged from 0.5 to 1.2 air changes per hour in four of the five dwellings at Seymour Johnson AFB and from 1.3 to 2-5 air changes per hour in

the five dwellings at Columbus AFB when the filters and return grilles

were clean. While the high air intake rate from the attic would tend

to pressurize the living space a small amount, it would not prevent

normal infiltration into the living space under even moderately windy

conditions. Thus, it is probable that the total volume of air leakage

into the dwellings exceeded the rates indicated in Tables 13 and 14 by

significant amounts.

7.0 Average Power Usage

Since the separate watthour meters connected to each of the major

appliances in the sample houses were read every two hours during the

test period, the amount of energy used by each appliance could be determined for selected periods of the day. For the purpose of analysis and

comparison, the day was divided into three 8-hour periods: from midnight to 0800 hours, from 0800 to 1600 hours, and from 1600 to 2400

hours, approximtely. The actual periods are staggered somewhat because the houses were visited consecutively by the observers during the

test.

-29 -
TABLE 13

COMPUTED ATTIC AIR LEAKAGE RATE INTO RETURN SYSTEM

BASED ON OBSERVED AIR TEMPERATURE

Measured Air Leakage from Attic

Total Air Percent of

Dwelling Circula- House Total Cir- Air

Type Street Address tion Rate Volume Rate culation Change

cfm ft3 cfm

Seymour Johnson AFB

A 402 March Lane 926 795^ 143 15 1.1

B 413 Cra swell Lane 970 8995 180 19 1.2

C 217 Chanute Road 873 8138 123 14 0.9

D 215 Chanute Road 956 9316 83 9 0.5

E 301 Carswell Lane 1467 11190 45 3 0.2

Columbus AFB

A2D1 122 Vernon Ave. 1289 7^33 277 23 2.2

A3D1 117 Caledonia Loop 1524 8234 227 15 1.7

A3D1 119 Caledonia Loop 1350 8234 336 25 2.5

03SIR 116 Florida Ave. 1439 10397 222 15 1.3

0333 118 Florida Ave. 1384 10397 351 25 2.0

-30 -
ATTIC

AIR

LEAKAGE

RATE

INTO

RETURN

SYSTEM

BASED

ON

MEASURED

VALUES,

ADJUSTED

FOR

PRESSURE

DI o

•H

-P

-P<6OP0

bD X

ctJ P

•H

co0 P bo CM CM CM CV CM VAOO 00

•H G 1 • • • <* ctf 1—1

rH rH O rH CM rH r—1

,GO1 O p G

•H O

P> 0 •H G -p 00 00 rH -G" NO 00 0 rH rt H rH CM H 1 1 CM r—1 1—1 0 or! rH P -P G 0 O 0

Oh Eh 0

-P&

-G- 00 (—I O- i—I *H vflNH OOO bO i—I i—I CM i—| i—I >HrH

hfl <D 53

Or—I I r—I -3" I CM

VA -G" VA CM VA rH H -U- 3" ^ rH CO CA CM CM 3- CM .3- CM

CO 3 0 ,Sj

CD O P3 CQ OGH 0i—I \ X)

ON {N- 00 bio O O O O CM -H • • • • • rH O O O O O bfl 0s a O N 00 00 vAOMOiN O O O CM O CM O O O O O O O O

CO

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tj<3; -p0B

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rH G E NO O CANO C^- On -G- O ON -G" • G g « S 0 CM O- O- va 1 s

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rH 0 4H CO On ON 00 On CM va CA 1 -G- 1 CA &

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CtJ Ctl CO 1—I 1—I rH O O O P-. P< (P - 3 -S -3 . . t 'd t

rH rH OOO

CM C^- ON ON NO MD 00

CM 1—I rH rH 1—I 1—I rH 0G (U

1—j r—I rH r—J 1—! 1—I CA Q Q a Q CO CO CO

cm ca ca ca ca ca ca

<] <jJ <J <1 o o o o%

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52c *d O bO fP

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-31-
7.1 Average Power Usage of Appliances

The average power used by each appliance during the three consecutive 8-hour periods and the daily average power for the five dwellings

at each air base are shown in the bar graphs in Figures 43 and 44 for

the duration of the test period. In the sample houses at Seymour

Johnson AFB the total power and the incremental values for the water

heater, dryer, and range were a maximum during the middle of the day,

whereas the power used by the heat pump and strip heaters was a maximum

during the 8-hour period from 0030 to 0830 hours and the miscellaneous

power reached a maximum during the evening hours. In the sample houses

at Columbus AFB the total power, and the incremental values for the

heat pump, water heater, and diyer were a maximum during the middle of

the day, whereas the power used by the miscellaneous devices was a maximum during the evening hours. The 24-hour average power usage was

3.96 KW for the five sample dwellings at Seymour Johnson AFB and 4.40

KW for the five sample dwellings at Columbus AFB.

The average daily energy usage by each component load and the sum

for all component loads are shown in Table 15 for each of the five

sample dwellings and as an average for all five dwellings at each of

the two air bases. The percent of the total energy usage represented

by each component is also shown for the five-dwelling average at each

site. It will be noted that 52 to 55 percent of the total energy usage

was used by the heat pump compressor, the supplementary resistance heaters, and the bathroom heater (bathroom heaters were installed only at

Columbus AFB) which comprised the equipment installed specifically for

house heating. The energy used for water heating ranged from 25 to 3°

percent of the total, and the remainder of the energy (17 to 20 percent) was used for the ranges, clothes dryers, and miscellaneous devices.

Inspection of Table 15 indicates that the ratio of the largest to

the smallest usage of energy in the individual dwellings at Seymour

Johnson AFB was about 2 to 1 for all components of the load except for

the clothes dryer, for which the ratio exceeded 3 to 1, and the supplementary resistance heaters with a ratio of 18 to 1. The energy

used for the heat pump in the C type dwelling was the lowest by a considerable margin. The families in the B and C type dwellings were

not at home for about a week during the test. In these two cases the

dwellings continued to be heated, but the low values of energy usage

recorded for cooking, water heating, clothes drying, and miscellaneous

devices during these absences were not included in obtaining the

average daily energy usage values in Table 15 . Deletion of these

values raised the average daily use for the whole house about 10 and

5 percent for the B and C dwellings, respectively. Absences of the

other families during the test period were negligible. The average

daily energy usage for the five sample dwellings was 95 KWH.

-32-
TABLE 15

AVERAGE DAILY ENERGY USAGE BY ELECTRICAL APPLIANCES

IN THE SAMPLE HOUSES, KWH

Seymour Johnson AFB

Appliance Dwelling Type Percent

A B C D E Avg of Total

Heat Pump Compressor 42.52 56.13 33.^2 42.48 60.59 47.03 49.4

Supp. Resistance Heaters 2.96 2.86 0.75 5.34 13.54 5.09 5-3

Water Heater 29.27 21.18 14.75 32.13 21.40 23.75 25.0

Range 1.59 4.76 1.76 3.75 3.91 3.15 3.3

Clothes Diyer 2.17 6.28 3.59 6.47 1.86 4.07 4.3

Miscellaneous Devices 8.35 13.36 8.30 16.11 14.23 12.07 12.7

Total 82.86 104.57 62.57 106.28 115.53 95-16 100.0

Columbus AFB

A2D1

Dwelling Type

A3D1 A3D1 03S1R 03S3

Percent

Avg of Total

Heat Pump Compressor 34.34 49.40 29.11 64.13 59.38 47.27 44.8

Supp. Resistance Heaters 1.78 2.32 3.06 1.08 3.30 2.31 2.2

Bathroom Heater 4.28 0.72 16.78 5. 20 1.46 5.69 5.4

Water Heater 27.21 36.99 41.59 24.28 30.ll 32.04 30.3

Range 2.16 2.26 6.12 1.79 1.82 2.83 2.7

Clothes Dryer 2.77 5.04 5.83 2.92 3.27 3.97 3.8

Miscellaneous Devices 7.74 9.24 18.42 11.96 9.87 11.45 10.8

Total 80.28 105.97 120.91 III.36 109.21 IO5.56 100.0

-33-
Table 15 shows that the ratio of the largest to the smallest usage

of energy in the individual dwellings at Columbus AFB was about 2 to 1

for the heat pump, the water heater, the clothes dryer, and the miscellaneous devices, and was about 3 to 1 for the supplementary resistance

heaters and the cooking range. The energy usage for the bathroom heater

was the most widely divergent of all appliances due to the high value

observed in one of the type A3D1 dwellings. The occupant of the 03S3

dwelling was absent for about 3 weeks during the test period, so the

use of energy for all appliances except the heat pump and supplementary

resistance heaters was almost zero during this period. The daily averages shown in Table 15 for this dwelling cover the entire test period

for the heat pump and supplementary resistance heaters, but cover only

the 12 days when the house was occupied in the case of the other appliances. The average daily energy usage for the five sample dwellings

was about 106 KWH.

It will be observed in Table 15 that the proportion of the total

energy used in the various appliances was significantly different in

one of the A3D1 type dwellings than for the other four dwellings. It

appears that a significant part of the house heating was accomplished

by the bathroom heater, range, and miscellaneous devices in this house.

The energy use by these three appliances exceeded that used by the heat

pump and supplementary resistance heaters by about 30 percent in this

particular dwelling. This dwelling also had the highest average daily

energy usage for all purposes among the five sample dwellings.

-34-
7.2 House Heating by Range, Water Heater, and Miscellaneous Devices

The energy used by an electric range, an electric water heater, and

the miscellaneous electric devices in a house makes some contribution

toward heating the house in any season of the year. This auxiliary heat

ing reduces the load on the heating system in cold weather and may overheat the house in mild weather. In evaluating the contribution of these

appliances to house heating during this field study, it was assumed that

all of the energy input to the cooking range and to the miscellaneous

devices such as electric lights, radio and television sets, refrigeration, electric iron, etc. assisted in warming the dwelling with very

little time lag.

The jacket loss of the water heater would warm the house, if the

heater were located in the living space, and a variable fraction of the

heat in the warm water used for bathing, dishwashing, and laundry would

be transferred to the air in the house as sensible or latent heat. At

Seymour Johnson AFB the water heater was located inside the living space

in four dwellings and outside the living space in the fifth, whereas at

Columbus AFB it was located in the utility closet for the heat pump in

two dwellings and in outside storage closets in the remaining three

dwellings. Observations of the energy usage of the water heaters in a number of the sample dwellings during the night when no water was being

drawn indicated that the jacket losses averaged about 150 watts. Apart

from the jacket loss, it was assumed that 10 percent of the heat added

to the water was effective in warming the dwelling.

It was assumed that the electric dryer contributed nothing toward

heating the house. Although the clothes dryer had some jacket heat loss

it was equipped with a small blower which used room air to carry the

water vapor and some sensible heat outside through a connected vent during the clothes-drying process. Such a blower would increase the infiltration of outdoor air when in operation which, in cold weather, would

probably more than offset the jacket heat loss.

On the basis of the foregoing observations and assumptions, the

contribution of the electric range, water heater, and miscellaneous devices to house heating was determined by equation (1) when the water

heater was located inside the heated space, and by equation (2) when it

was in a closet outside the heated space:

kw-hr^ = kw-hr^ + kw-hr^ + 0.1(kw-hr^ -0.15) + 0.15 (1)

kw-hr^ = kw-hr^ + kw-hr^ + 0 . 1( kw-hr-.r -0. 15) (2)

- 35-
where kw - hr^, kw - hr^, and kw - hr^ are the metered electric energy use

of the electric range, the miscellaneous devices, and the water heater,

respectively, in kilowatt hours for the period of time under consideration;

kw - hr^ is the computed contribution of these three appliances to house

heating in kilowatt hours; and the constant 0.15 represents an average hourly

observed jacket loss of the water heater in kilowatt hours.

Using equations (1) and (2) and the heat equivalent of electric

energy, it was found that the range, water heater, and miscellaneous devices produced a heating effect ranging from 1500 Btu/hr during the eighthour period beginning at midnight to about 3700 Btu/hr during the evening

hours in the sample houses at Seymour Johnson AFB, whereas the corresponding range of values was from 1400 Btu/hr to 3^00 Btu/hr at Columbus

AFB. The daily average heating effect of these appliances was 2720 Btu/hr

and 2510 Btu/hr, respectively, at the two sites. The data on the heat

contribution of these appliances for the three eight -hour periods and the

daily average are summarized in Table 16. It will be noted that the miscellaneous devices accounted for one-half to two-thirds of the total

heating effect of this group of appliances.

7.3 Total Power and Total Power for Heating

The total power used for all purposes and the total power that contributed toward heating are shown in Figs. 45 to 47 as an average for

the five sample houses at Seymour Johnson AFB, and in Figs. 48 to 50 as

an average for the five sample houses at Columbus AFB. The power consumptions are plotted separately for the three eight-hour periods of the

day in relation to outdoor temperature. The plotted values are scattered in all of these figures with the scatter being somewhat more pronounced for the values of the total power used for all appliances than

for the power used for heating. This indicates that the power used for

water heating and dryer functions was quite variable and was not appreciably dependent on outdoor temperature. The best-fitted curves for

total power for all appliances and total power for heating were approximately parallel in each figure, with a slight upward curvature at lower

outdoor temperatures.

The difference in power usages for heating and for all purposes

was about 1 kw at both sites for the daytime and evening periods represented by Figures 46, 47, 49 and 50* As would be expected, this difference was considerably smaller, 1/5 to 1/3 kw, during the eight-hour

period after midnight when there was little usage of the water heater

or dryer. It will be noted that the power used for heating was on the

order of 1 kw at outdoor temperatures in the range from 65 °F to 70°F

for the daytime and evening hours and somewhat lower during the hours

after midnight. This suggests that the power used by appliances other

than the heat pump would probably begin to overheat the dwellings at an

outdoor temperature of 70 °F, more or less.

-36-
TABLE 16

AVERAGE HOUSE HEATING ACCOMPLISHED

BY RANGE, WATER HEATER, AND MISCELLANEOUS DEVICES IN SAMPLE DWELLINGS,

btu/hr

Appliance Period of Day, Hours

Seymour Johnson AFB

Range

Miscellaneous

Water Heater

Devices

0030-0830

i4o

840

530

0830-1630

540

1620

810

1630-0030

525

2450

710

All Day

4oo

1640

680

Total 1510 2970 3685 2720

Columbus AFB

Range

Miscellaneous

Water Heater

Devices

2300-0700

120

910

370

0700-1500

“ 620

1420

670

1500-2300

3^0

2260

630

All Day

420

1530

560

Total 1400 2710 3400 2510

-37-
7.4 Correlation of Energy Input to the Heat Pump

with Heating Degree-Days

The energy used by the heat pump in each sample dwelling, including

the supplementary resistance heaters, was correlated with house size and

severity of the weather by computing an energy-usage factor having the

units kw-hr/degree-day (1000 ft2 ). For this purpose, the daily degreedays were computed from the average of the hourly outdoor temperatures

recorded at the weather station at each base and an indoor reference

temperature of 65 °F; and the inside floor areas of the dwellings were

used. The daily values of the energy usage factor are plotted in Figs.

51 to 60 for the ten sample dwellings with degree-days per day as the

independent variable. The average values for the entire test period at

each site are summarized in Table 17

Figs. 51 to 55 show a considerable variation in the value of the

energy-usage factor in each of the sample dwellings at Seymour Johnson

AFB for any selected value of degree-days. The energy-usage factor was

significantly higher in mild weather, when the degree-days per day were

in the range from 5 to 10, for three of the five sample dwellings.

This could be the result of opening windows for ventilation or greater

movement between indoors and outdoors in mild weather. However, no

effort was made to observe these practices during the tests. At lower

outdoor temperatures the average of the energy-usage factors remained

relatively constant for the entire range of degree-days experienced

during the test period. The energy-usage factors in the D and E type

dwellings are shown to be much more variable than in the other three

sample dwellings. As noted previously, replacement of the capillary

tube and recharging with refrigerant was performed on the unit in the

type E dwelling during the course of the tests, and the outdoor check

valve in parallel with the capillary tube in the type D dwelling was

erratic in its operation during a part of the time. These abnormal

operating conditions probably accounted for the greater variability in

energy usage in these two dwellings. Nearly all of the high values of

the energy-usage factor observed in the E type dwelling occurred prior

to repair of the heat pump.

Figs. 56 to 60 show that the energy-usage factor was also quite

variable in the sample houses at Columbus AFB, but there was less indication of a sharp increase of this factor in mild weather than at the

other site. Except for the type A3D1 dwelling at 119 Caledonia Loop,

the average value of the energy-usage factor was approximately constant

throughout the range of outdoor conditions experienced during the test.

The energy-usage factor was significantly lower in this type A3D1

dwelling than for the four others at this site. Reference to the

average daily energy usage by all appliances summarized in Table 15 and

the discussion thereof, indicates that much greater use of the bathroom

heater, range, and miscellaneous devices occurred in this dwelling.

This undoubtedly reduced the need for heat pump operation and correspondingly reduced the energy-usage factor computed on the basis of

energy consumption by the heat pump only.

-38-
TABLE 17

AVERAGE ENERGY USAGE FACTORS

FOR THE HEAT PUMPS IN TEN SAMPLE DWELLINGS

Dwelling

Identification

Average Energy Usage Factor,

KWH/deg-day( 1000 ft 2

) Seymour Johnson AFB

A 2.42

B 2.74

C 1.67

D 2.32

E 2.97

Avg. Outdoor Temp. , °F 46

Columbus AFB

A2D1 1.65

A3D1 1.90

A3D1 1.10

03S1R 1.93

03S3 1.88

Avg. Outdoor Temp., °F 39

-39 -
Table 17 shows that the energy-us age factors in four of the five

dwellings at Seymour Johnson AFB were higher than those for the -dwellings

at Columbus AFB. The following design factors, applicable to Seymour

Johnson AFB, probably contributed to the higher energy-usage factor and

lower coefficient of performance observed at this base.

(a) More use of the supplementary resistance heaters was

required because the heat pumps were selected for a higher balance point temperature.

(b) There was some loss of heating capacity in the refrigerant lines connecting the indoor and outdoor units of

the split systems.

(c) Very little of the heat absorbed by the attic ducts

and attic -momted heat pjmp units was brought into the

living space by natural convection when the indoor

blower stopped.

(d) The use of the bathroom heaters in the dwellings at

Columbus AFB would contribute to a lower energy-usage

factor for the heat pumps at this site.

8.0 Heating Requirements

The heating requirements of the sample dwellings were determined by

calculation using conventional methods and by direct measurement using

two different procedures. In one procedure, each sample dwelling was

heated by the electric resistance heaters in the heat pump units during

one or more cold days, without assistance from the compression system,

to determine the heat requirement of the dwelling per unit indoor- outdoor

temperature difference. The observed heat loss could then be extrapolated

and corrected to the design outdoor conditions. In the second procedure

the heat delivered to each dwelling by the heat pumps, operating normally,

was determined from the measured air circulation rate and the integrated

temperature rise of the warmed air during each running period; the heat

delivered by other appliances was determined by either equation (1) or (2), discussed in Section 7*2 of this report; and the sensible heat input

by the occupants was estimated on the basis of size of family and probable

metabolic rate.

- 40-
8.1 Calculated Heating Load of Dwellings

The heating load of each of the sample dwellings was calculated

using the procedures described in the Guide of the American Society of

Heating, Refrigerating, and Air-Conditioning Engineers. The areas of

each of the exterior components of the dwellings and the heat transmission coefficients of each element of the structures were calculated

mainly from the dimensions and description of materials shown in the

as-built or architect's drawings. Some details of construction were

obtained from the installation engineer's office at the site. The computed heat transmission coefficients for each type of exterior wall

construction, for the windows, doors, ceilings, and floors, and the

unit heat loss per linear foot of exposed floor edge are summarized in

Table 18 for each site. The heat transmission factors were corrected

for framing members in the construction.

The heat loss of each component of the ten sample dwellings was

calculated using the areas summarized in Table 1 and the heat transmission factors summarized in Table 18. The design outdoor temperatures

used for these calculations were the temperatures specified for the

housing project designs; namely, 10°F at Columbus AFB and 20°F at

Seymour Johnson AFB. The total computed transmission heat loss is

shown as a subtotal for each dwelling in Table 19. Because of the excessive infiltration of air from the attic in most of the sample houses,

the infiltration heating loads corresponding to 1, 1 l/2, and 2 air

changes per hour of outdoor air are shown separately in Table 19.

Table 19 shows that the computed heat transmission loss of the four

dwellings at Seymour Johnson AFB, each a part of a duplex structure,

ranged from 21,600 to 24,800 Btu/hr, whereas that of the detached type E

house was 37,700 Btu/hr at design outdoor temperature. The corresponding values for the total heating load with infiltration of outdoor air

assumed to be one air change per hour are 28,800 to 32,900 Btu/hr for

the duplex-type dwellings and 47,800 Btu/hr for the type E house. The

air leakage rates from the attic, summarized in Tables 13 and 14, indicate that the total infiltration of outdoor air was probably one air

change/hr or greater in four of the sample dwellings at Seymour Johnson

AFB. However, air brought in from the attic was typically 13 to 20

degrees warmer than the outdoor air at design outdoor temperature, so the penalty of this attic air leakage would not be as great as indicated

by the tabulated values for infiltration load in Table 19 . The type E nouse

did not have significant leakage from the attic.

Table 19 shows that the computed heat transmission loss of the

duplex-type dwellings at Columbus AFB ranged from 23,800 to 26,400 Btu/hr,

whereas, that for the detached officers' dwellings was about 36*400 Btu/hr

at design outdoor temperatures. The corresponding values for the total

heating load with infiltration of outdoor air assumed to be one air

-41-
TABLE 18

COMPUTED HEAT TRANSMISSION FACTORS

FOR COMPONENTS OF SAMPLE HOUSES

Building Component Heat Transmission Factor

Btu/hr(ft2 )(°F)

Seymour Johnson AFB

Exterior Walls

Brick Veneer Finish 0.073

Grooved Plywood Finish 0.071

Cavity Brick O. 38O

Ceiling (Ventilated Attic) 0.047

Windows, Single 1.24

Doors, Solid Core 0.40

Floor Edge, Insulated 35a/

Columbus AFB

Exterior Walls

Brick Veneer Finish 0.088

Exterior Plywood Finish 0.092

Shake Siding Finish 0.093

Vertical V- joint Siding 0.093

Ceiling and Roof Combined ( Unventilated Attic) 0.090

Windows, Single 1.24

Doors, Solid Core 0.40

Floor Edge, Insulated 35^

Floor Edge, Uninsulated 50±/

—^Units of floor factor: Btu/hr (linear foot of cold floor edge)
TABLE 19

CALCULATED DESIGN HEAT LOSS RATES

OF SAMPLE EWELLINGS

Building Component Heat Loss Rate, Btu/hr

Dwelling Type , Seymour Johnson AFB

A B C D E

Exterior Walls 2530 3250 2570 2870 8710

Windows 11900 13030 11900 13080 18040

Doors 300 800 800 800 1160

Ceiling 2330 2640 2390 2730 3070

Floor 4060 5010 4130 4550 6760

Total Transmission Load 21620 24780 21790 24030 37740

Infiltration Load, 1 air change/ hr 7160 8100 7320 8380 10070

i£ " »i »» 10740 12140 10990 12580 15110

2

" it 11 14320 16190 14650 16770 20140

Dwelling Type, Columbus AF3

A2Dl —1351— 03S1R 03S3

Exterior Walls 3420 3670 5890 6000

Windows 9150 10860 14430 14430

Doors 1340 1340 1340 1340

Ceiling and Roof 5010 5550 7010 7010

Floor 4830 4930 7820 7430

Total Transmission Load 23750 26350 36490 36210

Infiltration Load, 1 air change/hr 8030 8890 11230 11230

ii •• ii 11 12040 13340 16840 16840

2 " 11 n 16060 17790 22460 22460

-43-
change per hour are 31*800 to 35*200 Btu/hr for the duplex-type dwellings and about 47,600 Btu/hr for the detached houses, types 03S1R and

03S3. The air leakage rates from the attic, summarized in Tables 13

and 14, indicate that the total infiltration rate of outdoor air

probably exceeded two air changes per hour in several of the sample

dwellings at Columbus AFB. In the coldest weather experienced during

the test period, with snow on the roof, the attic air temperature was

25 to 30 degrees warmer than the outdoor air. However, in milder

weather, with outdoor temperature near freezing but without snow on

the roof; the attic air temperature was only 5 "to 10 degrees warmer than

the outdoor air, even though the gable louvers were sealed. Thus the

increment of heating load caused by air leakage from the attic might be

either larger or smaller than the values shown in Table 19 for one air

change per hour of outdoor air, depending on the attic temperature.

8.2 Heat Loss Calibration by Resistance Heating

Each of the ten sample dwellings was heated solely by electric

resistance heating for one or more cold days to evaluate the heat loss

per degree indoor- outdoor temperature difference. The supplementary

resistance heaters in the heat pump were used for this purpose and the

indoor blower was operated continuously in some cases, and intermittently in phase with the heaters in other cases. The data taken during

the night between the hours of 2200 and 0800 were used for analysis to

avoid the effects of solar radiation, the more variable daytime outdoor

temperature, and the highly variable appliance usage by the occupants.

The heat contribution of the water heater, range, miscellaneous

appliances, and occupants was added to the metered energy use by the

supplementary resistance heaters to determine the total heat supplied

to the dwelling. The indoor-outdoor temperature difference was based

on the temperature observed at the weather station of the air base and

the indoor temperature measured at the thermostat. This latter temperature differed from the return air teirperature in some cases, but

was considered to be more representative of the temperature which

determined the overall heat loss of the structure.

The data observed during the calibration tests with electric resistance heating are summarized in Tables 20 and 21 for the sample

dwellings at Seymour Johnson AEB and Columbus AFB, respectively. In

most instances the sample dwellings were heated by resistance heating

for two or more days, with variations in outdoor temperature and wind

velocity on different days. All valid tests conducted in each dwelling

are summarized in Tables 20 and 21.

-44-
HEAT

LOSS

CALIBRATION

WITH

RESISTANCE

HEATING

SEYMOUR

JOHNSON

AFB,

DECEMBER

1959-

JANUARY

I960 oo

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LOSS

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COLUMBUS

AFB,

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Design

Conditions,

Btu/hr

31,300

32,480

34,350

34,390

36,840

36,590

43,370

43,550

53,170

47,140

50,900
In each of these tables the observed indoor and outdoor conditions

during the tests were first summarized, followed by a summation of the

observed heat input rates into the dwellings from all sources. An

observed heat transmission factor with the units Btu/hr(°F) was computed from the total heat input rate and the observed indoor- outdoor

temperature. These heat transmission factors were then used to compute the heat requirements of the dwellings at the design indooroutdoor temperature difference of 50°F at Seymour Johnson AFB and 60°F

at Columbus AFB by an extrapolation or interpolation procedure.

It will be noted that the average wind velocity during the calibration tests ranged from calm to 5*5 mPh at the two bases. Thus, a heat requirement at design indoor- outdoor temperature difference based

on heat transmission factors observed at these low wind velocities would

probably not be representative of the design heat loss with a 15 mph wind.

Two corrections were made to these computed heat requirements: one to

account for the additional heat transmission through the windows caused

by a 15 mph wind and the other to account for the increased intake of

attic air caused by the higher percentage of blower operation at design

conditions. The corrections for window heat transmission were made in

accordance with the values of the coefficients for single glass at various wind velocities tabulated in the ASHRAE Guide. The corrections for

air leakage from the attic were based on the increase in operating time

of the indoor blower and the change in the temperature difference between the attic and the living space at design outdoor conditions. No

corrections were made to the heat transmission of walls, floor, and ceiling since an increase in wind velocity to 15 mph would cause only about

one percent increase in the heat transmission factors of these elements

of the structures. The corrected heat loss rate at design conditions

cited at the bottom of Tables 20 and 21 incorporate the two corrections

described above and represent the best estimate of the design heat loss

that can reasonably be derived from the calibration tests with the re- sistance heaters.

Tables 20 and 21 show that data were taken in eight of the ten

sample dwellings under calm outdoor conditions and also with a wind

velocity of about 5 mph. In six of these dwellings the heat transmission factor in Btu/hr per degree indoor-outdoor temperature difference

was higher for the test with a 5 mph wind than for the test with calm

weather, by amounts ranging from 6 to 15 percent. When the corrections

were made in these six dwellings for the increased heat transmission

through the windows and the increased attic air leakage at design outdoor conditions as described above, the corrected heat loss values for

the two conditions of wind differed by amounts ranging from 0.1 to 3*7

percent. In the other two houses in which duplicate tests were made,

the type E house at Seymour Johnson AFB and the type 03S3 house at

Columbus AFB, the disparity between the corrected heat loss rates for

duplicate tests was 11 and 4 percent, respectively. In the type E

-^7

-
house the thermostat was responsive only to the return air temperature

from the bedroom section of the house. In this house the air temperature

at the thermostat was several degrees colder than the air at the return

grille, whereas the reverse relationship existed in the other dwellings

at Seymour Johnson AFB. It is not known whether the different relation

between thermostat temperature and return air temperature in the E type

house had any bearing on the greater inconsistency of test results described above.

A comparison of the corrected heat loss rates at design conditions

in Table 20 with the computed heat loss rates in Table 19 for the dwellings at Seymour Johnson AFB shows that the values derived from the calibration tests exceeded the computed total heat transmission loads in each

case. However, they were less than the sum of the computed total heat

transmission load and the infiltration load corresponding to one air change

per hour of outdoor air, by amounts ranging from 2000 Btu/hr in the type

A dwelling to 8350 Btu/hr in the type E house. This latter disparity

suggests that the total heating load caused by infiltration of air by

all avenues of entry was less than the equivalent of one air change per

hour of air at outdoor temperature.

A comparison of the corrected heat loss rates at design conditions

in Table 21 with the computed heat loss rates in Table 19 for the dwellings at Columbus AFB shows that the values derived from the calibration

tests also exceeded the computed total heat transmission loads in each

case. However, they were less than the sum of the computed total heat

transmission load and the infiltration load corresponding to one air

change per hour of outdoor air in the type 03S1R dwelling and one of the

type A3D1 dwellings, and greater than this sum in the other three dwellings. These comparisons suggest that the total heating load caused by

infiltration of air by all avenues of entry was somewhat less in some

dwellings and somewhat more in others than the equivalent of one air

change per hour of air at outdoor temperature.

These comparisons of measured and computed loads indicate that the

intake of attic air may have supplanted normal infiltration to a considerable extent. The intake of attic air, even though excessive in amount

may not have augmented the heating load as much as might have been expected because it was preheated appreciably by the heat transfer through

the ceiling.

-48-
8.3 Heat Supplied to Dwellings during Normal Operation

The heat supplied to each of the sample dwellings during normal

operation of the heating system was determined for a range of outdoor

temperature. These determinations were based on the heat delivered by

the heat pump, and the calculated contribution toward heating by other

appliances and by the sensible heat output of the occupants. The hours

between midnight and 0800 hours were used for this analysis to avoid

the variable effects of solar heating and the greater use of other

appliances by the occupants during the day. Operating data which appeared to be distorted by setback of the thermostat at the time of re- tiring were discarded. The heat supplied by the heat pump during the

periods of analysis was calculated from the air delivery rate of the

blower, the total blower operating time, and the integrated temperature

rise of the warmed air between the return grille in the house and the

supply plenum for each operating period of the blower. This method of

calculation excluded any heat that might have been supplied to the

dwelling by natural convection when the blower was stopped and also

excluded the heat used to warm the air brought into the system from the

attic. As noted earlier in this report, natural convection probably

supplied virtually no heat to the dwellings in which the heat pump and

duct system was installed in the attic.

The quantities of heat supplied by the heat pump alone and from

all sources are shown in Figs. 61 to 65 for the sample dwellings at

Seymour Johnson AFB, and in Figs. 66 to 70 for the sample dwellings at

Columbus AFB for a range of indoor- outdoor temperature difference. The

corresponding values of heat input during the calibration tests with

resistance heaters are superimposed on these graphs for comparison.

In each case the plotted values of heat supplied to the dwelling does

not include that required to warm the leakage air from the attic.

In most cases a straight line was the best representation of the

relation between the heat supplied to the dwellings and the indooroutdoor temperature difference within the range of values available.

Exceptions will be noted in Figs. 64 , 69 and 70 in which the slopes of

the curves decreased somewhat for mild weather. Although it was not

verified by actual observation, the most probable explanation for this

condition is that the occupants opened windows more frequently at night

in mild weather. Occupants were requested to leave windows closed during the tests, and did so generally, but not in all cases.

In nearly every graph there are a few days for which the calculated heat supply rate deviates appreciably from the straight line

relationship. In some cases high values can be attributed to a higherthan-average wind velocity, but there was not full correlation between

these factors. In some dwellings, such as those at 122 Vernon Avenue

and 119 Caledonia Loop at Columbus AFB, only a few useful data were

-49 -
obtained because the occupants regularly set their thermostats back

several degrees before retiring. Under these conditions the heat loss

from the building did not approach a steady state for a number of hours

after setback of the thermostat, and in many cases, significantly less

heat was required during the period of hours selected for this analysis.

Additional heat was required to restore the interior temperature when

the thermostat was reset to normal temperatures. This heating requirement has not been analyzed.

In most cases the heat requirements determined during the calibration tests with resistance heating agreed well with the values determined for normal operation of the heating system at the same indooroutdoor temperature difference as illustrated in Figs. 63-68, inclusive.

In Figs. 69 and 70 the heat requirement determined by electric resistance heating was appreciably lower than the observed values during

normal heating at the design temperature difference of oO°F. However,

as noted previously, there was a heavy layer of snow on the roofs and

higher-than- anticipated attic temperatures in the dwellings at Columbus

AFB during the period of calibration with the resistance heaters at low

outdoor temperature. This may account for the lower heat requirement

observed in these two cases during the calibration tests.

Table 22 provides a comparison of the heat requirements of the

sample dwellings by various methods of evaluation. The first three

columns of the table list the computed heat loss of the dwellings with

a 15 -mph wind, but without infiltration; the observed heat requirements

by electric resistance calibration and -under normal operation of the

heating system but not including the effect of attic air leakage in

either case. The values in the second and third columns are directly

comparable except for variations in wind velocity and unknown variations in living habits such as the opening of windows for ventilation.

The calculated values in the first column arc not directly comparable

with the values in the second and third columns in that the calculated

values of heat loss are computed from coefficients based on a 15 -mph

wind, and include no allowance for infiltration whereas the values in

the second and third columns take into account existing wind velocities

and whatever normal infiltration occurred in the dwellings below the

ceiling level at the time the observations were taken. As shown in

Tables 20 and 21, the window heat transmission for a 15-mph wind velocity exceeded that for the wind velocity which prevailed during the calibration tests by amounts ranging from 1460 to 64-70 Btu/hr in different

tests and in different dwellings. It will be noted in Table 22 that

the calculated values of heat loss in the first column exceeded the

observed values in the second and third columns by amounts in about the

same range of magnitude.

-50-
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The fourth and fifth columns in Table 22 provide a comparison of

the calculated heat loss for a 15 -mph wind and an infiltration of one air change per hour at outdoor temperature with the observed value obtained by electric resistance calibration after correcting the latter

for a 15 -mph wind and the increased attic air leakage at design conditions. The values in these latter two columns are directly comparable

if the attic air leakage is considered to be a part of the overall infiltration. It will be noted that the calculated heat losses at design

conditions in the fourth column exceeded the observed values (corrected)

in the fifth column for the dwellings at Seymour Johnson AFB, by amounts

ranging from 2000 to 8350 Btu/hr. At Columbus AFB the computed values

ranged from 4250 Btu/hr higher to 2720 Btu/hr lower than the corrected

values derived from electric resistance calibration. It is evident from

the data in Tables 20 to 22 that the observed heat requirements of the

sample dwellings under the most severe outdoor and indoor conditions

that existed during the month-long test periods were considerably below

the calculated heat loss of the structures at design outdoor conditions

of temperature and wind. The significance of a 15-mph wind on the heat

transmission rate of windows and on air leakage is evident from these

c omparis ons

-52-
8.4 Daily Average Energy Usage Rate

The hourly energy usage rate, averaged on a daily basis, was determined for each day of the test period for each of the sample dwellings.

These average energy usage rates for the heat pump by itself and for all

components contributing toward heating the dwellings are plotted for a range of outdoor temperature in Figs. 71 to 80, inclusive. The energy

usage rates are plotted in units of Btu/hr to facilitate comparison with

similar graphs in Figs. 60 to 70 showing the heat supplied to the dwellings. Except for the difference in the time period used for averaging

the data in these two groups of graphs, the ratio of the heat supplied

to a given dwelling to the energy usage rate expressed in the same units

represents what might be termed a performance factor for the house. Such

a performance factor includes all appliances that contributed to heating

as a part of the heating system, even though the primary purpose for a part of the energy use was for some other function such as cooking, lighting, etc.

It will be noted that the energy usage curves in Figs. 71 to 80 all

became steeper as the outdoor temperature decreased. This trend was to

be expected since the coefficient of performance of the compression system decreased with outdoor temperature, and in the case of the dwellings

at Seymour Johnson A.FB a correspondingly higher percentage of supplementary resistance heating was required.

Except for the type D house at Seymour Johnson AFB in which poor

performance of the heat pump was experienced for part of the test period,

the energy usage curves indicate that the energy usage rate of the heat

pump would become zero for outdoor temperatures in the range from 60°F

to 70°F. Other appliances accounted for an energy usage rate for heating

in the range from 1000 to 3000 Btu/hr, except for the type A3D1 dwelling

at 119 Caledonia Loop, which averaged about 550° Btu/hr. Reference to

Table 15 indicates that this latter dwelling was the one with unusually

high energy consumption for the bathroom heater, the miscellaneous devices, the cooking range, and the water heater and a correspondingly

low energy usage for the heat pump.

It should be noted that Figs. 71 to 80 automatically take into

account the effect of solar heating during the day; unusual infiltration

rates caused by exhaust fans, open windows, and attic leakage; overheating caused by the miscellaneous appliances in mild weather; night setback

of the thermostat; and any other practices of a given family or factors

of a given dwelling that affected the magnitude of the heat requirements

.

That is, the data represent the heat requirements of the structure on an

"as-used” basis for the duration of the test.

-53-
8.5 Comparison of Average Electric Energy Use in Sample Dwellings

with That in Larger Groups

The average energy use for all purposes in the five sample dwellings

was compared for a 31-day period with the metered energy use in other

groups of dwellings at the same sites. At Seymour Johnson AFB such a comparison was possible with groups of 8, 11, 58, 225, and 1500 dwellings,

the latter figure comprising the entire housing project. At Columbus AFB

the comparison could be made between the five sample dwellings and the

entire housing project, comprising 480 dwellings. At the former site the

metering periods for the several groups of dwellings were identical,

whereas at the latter site the metering periods for the sample dwellings

and the entire project were staggered by one day.

The average energy use data are summarized in Table 23. The average

energy use in the five sample dwellings at Seymour Johnson AFB was 95*3$

of the average for the entire housing project, wheieas the average energy

use for the group of 8 dwellings was as low as 83*f and that of the group

of 225 dwellings as high as 102$ of the average for the entire project.

At Columbus AFB the average energy use for the five sample dwellings was

99.1$ of the average for the entire housing project comprising 480 dwellings.

TABLE 23

COMPARISON OF AVERAGE ENERGY USE IN SAMPLE DWELLINGS WITH

THAT IN LARGER GROUPS OF DWELLINGS

No. of Period of Average Energy Use for 31-Day Period,

Dwellings Analysis for Entire Dwelling, Kwh

Seymour Johnson AFB

5 ( Sample 12/ 22/59

D*re llings) to 1/22/60 2867

8 it 2500

11 11 2771

58 11 2917

225

15 00 (Entire

11 3072

Project) n

Columbus AFB

3009

5 ( Sample 2/23/60

Dwellings

to 3/23/60 2889

480 (Entire 2/22/60

Project) to 3/22/60 2916

-54-
9.0 Other Observations

The heat pumps at Columbus AFB produced a higher noise level in

the dwellings than those at Seymour Johnson AFB in two ways. The air

noise at the discharge grilles was higher, and the mechanical sounds

caused by starting and stopping of the compressor and outdoor fan were

transmitted into the house structure more noticeably from the indoor

location of the units at Columbus AFB than from the outdoor location

of this component at Seymour Johns an AFB.

Outdoor thermostats to limit use of supplementary resistance heating for outdoor temperatures above approximately 30°F were installed

and in working order in the heat pumps in the five sample dwellings at

Columbus AFB. There were two such thermostats, each controlling half

of the supplementary heaters and set to operate a few degrees apart.

The heat pumps in five sample dwellings at Seymour Johnson were each

equipped with a single such thermostat, either shunted or set to permit operation of the supplementary heaters at outdoor temperatures

considerably above the balance point for these houses. At both sites

the supplementary resistance heaters were not energized unless also

called for by the indoor thermostat or the defrost control.

The indoor thermostats in the five sample dwellings at Colunbus

AFB were located either in the living room or in the hall area adjacent to the main air return to the utility closet containing the heat

pump. The indoor thermostats in four of the sample dwellings at Seymour Johnson AFB were installed in the hall area adjacent to the main

air return and filter. In the type E house, the thermostat was not

responsive to the living-dining room air temperature, but was influenced primarily by air temperatures in the front entrance hall and by

air returning from the bedrooms.

In four of the sample dwellings at Columbus AFB, the entire heat

pump was readily accessible for service. In the type A2D1 dwelling,

the closet containing the heat pjmp could be entered only by removing

an access panel in the clothes closet in the master bedroom, and unit

replacement required removal of a section of the living roan wall.

The outdoor units of the heat pjmps at Seymour Johnson AFB were readily accessible for servicing. In four of the sample dwellings servicing of the indoor units was handicapped by the limited access area

in the attic. In the type E dwelling, the indoor unit was in a first

floor utility closet and readily accessible.

The main return air louver from the hall to the utility closet

in the five sample dwellings at Columbus AFB was designed to eliminate

line -of- sight openings and the fin spacing was close enough so dust

could accumulate on the louver. Enough dust had collected on the re- turn louver in one dwe lling prior to the test to increase the pressure

-55-
drop across ths louver from 0.08 to 0.20 in. W.G. under normal operation

of the heat pump, thus increasing the amount of leakage air drawn from

the attic. As described earlier in the report, air filters in four of

the sample dwellings at Seymour Johnson AFB produced similar effects on attic air leakage as the filters became loaded with dust.

Control of indoor fan operation during heating was different in

the two types of heat pumps. At Columbus AFB the indoor fan, under

automatic operation, started and stopped simultaneously with the compressor under control of the indoor thermostat, and continued to run

during defrost cycles. At least a part of the supplementary heaters

were energized during defrost cycles in these units. At Seymour Johnson AFB, the indoor fan, under automatic control, started and stopped

in response to a pressure switch connected into the vapor refrigerant

line of the indoor coil, and did not run during defrost cycles unless

the indoor thermostat called for supplementary heating.

No repairs other than minor adjustments were required for the heat

pumps in the five sample dwellings at Columbus AFB during the test period covered by this report. Some repairs were required at Seymour

Johnson AFB. In addition to minor adjustments and addition of refrigerant to some or all of the heat pump systems in the five sample houses

at Seymour Johnson AFB, the following maintenance and repair functions

were required:

1. The upstream faces of the indoor coils were cleaned in two

systems

2. The outdoor restrictor tube and check valve and the outdoor

fan wheel and fan bearings were replaced in one system.

3. The outdoor restrictor tube and check valve were replaced

in a second system.

The compressors in the heat pumps in the five sample dwellings at

Columbus AFB were of 3-cylinder construction, the third cylinder used

to increase heating capacity for outdoor temperatures lower than 30° to

40°F and unloaded at other conditions. Two-cylinder compressors were

used in the test units at Seymour Johnson AFB. Overloading due to high

discharge pressure during mild weather heating was prevented at Columbus AFB by unloading the third cylinder at high outdoor air temperatures, and at Seymour Johnson AFB by stopping the outdoor fan in re- sponse to a pressure switch sensing the refrigerant pressure in the

indoor coil. Each system functioned satisfactorily during the two test

periods.

Defrost cycles were initiated for the heat pumps at Columbus AFB

by a pressure switch sensing the pressure drop in the air flow through

the outdoor coil, and at Seymour Johnson AFB by a temperature switch

sensing the temperature differential between the refrigerant in the

outdoor coil and the air flowing through the outdoor coil. One defrost

switch required adjustment at Seymour Johnson AFB. Otherwise, the two

systems performed satisfactorily in the five sample dwellings at each

site for the respective test periods.

-56-
10.0 Discussion and Conclusions

This study of the heating performance of the air-to-air heat pumps

in 5 sample dwellings at Seymour Johnson AFB and an equal number at

Columbus AFB provides useful information on the performance characteristics of the heat pump itself, on the heat distribution system, on the

heat requirements of the dwellings at design conditions, on energy usage

for all electric appliances, and on the effect of the living habits of

the occupants on the heat requirements of the dwellings. Whereas there

was malfunctioning of the heat pumps in a few sample dwellings during

the test period which required maintenance and repair, it was not the

purpose of this investigation to make any systematic record or study of

the maintenance requirements in the sample dwellings or the housing

project in general.

Some of the principal conclusions indicated by this study may be

sunxnarized as follows:

1. The steady state heating capacity of the air-to-air heat pumps increased approximately linearly with increasing outdoor temperature.

The observed steady state heating capacities of the compression

systems in the heat pumps at outdoor temperatures near design conditions, as reported in Tables 3 to 11, indicated that the compression systems would provide from 51 to 82 percent of the heat re- quirement of the sample dwellings at Seymour Johnson AFB and from

99 to 116 percent of the heat requirements of the sample dwellings

at Columbus AFB at design outdoor temperatures and wind velocities

based on the calibration tests with resistance heaters as summarized in Table 22. In each case the supplementary resistance heaters provided considerably more than the required amount of additional heating capacity. Changing from 3-cylinder to 2-cylinder

operation at an outdoor temperature between 30°F and 40°F reduced

the heating capacity of the heat pumps at Columbus AFB by 5503 to

7500 Btu/hr, approximately 10 to 15 percent.

2. The highest outdoor temperatures requiring heat pump operaticn

ranged from 58.5°F to 65°F in the various sample dwellings based on conditions prevailing during the night. For the wind conditions

that occurred during the test periods , the balance point temperature ranged from about 28°F to 31°F in the five sample houses at

Seymour Johnson AFB and from -3°F to 15 °F for the three sample

houses at Columbus AFB in which satisfactory data could be obtained.

Obviously, the balance point would vary some with wind velocity,

use of miscellaneous appliances in the house, and living habits.

3. The coefficients of performance of the heat pumps at S3ymour Johnson AFB ranged from about 1.4 to 1.8 in dwellings A, B, C and D,

and was about 2.4 in the type E house, after repair of the unit,

for an outdoor temperature of 20 °F. The coefficients of performance

of the heat pumps in three of the sample dwellings at Columbus AFB

were about 2.0 at an outdoor temperature of 14°F and increased to 2.4,

-57-
more or less, at an outdoor temperature of 45 °F. These coefficients

were based on approximately steady state operating conditions, and

do not include the warmup period for the supply air at the beginning

of each operating cycle.

4. The air circulation rates through the indoor coil of the heat pump

units ranged from 873 cfta. to 970 cfm in dwelling types A, B, C, and

D .and it was 1467 cfm in house type E at Seymour Johnson AFB. The

air circulation rates in the 03S1R, 03S3» and two A3D1 dwellings at

Columbus AFB ranged from 1350 cfm to 1524 cfm. These values were

based on the temperature rise produced in the air by a measured

amount of energy dissipation in the supplementary resistance heaters

and in the indoor fan motor. A significant amount of attic air was

drawn into the return duct system of the A to D type dwellings at

Seymour Johnson AFB because the return duct and its frame were not

well-fitted into the ceiling of the closet that was used as a return

air passage; and in all of the dwellings at Columbus AFB because the

opening in the utility closet wall through which the main supply duct

entered the attic space was considerably larger than the duct. The

attic air leakage ranged from 9 to 19 percent of the total air circulation rate in the four dwellings at Seymour Johnson AFB and from 15

to 25 percent in the five dwellings at Columbas AFB.

5. A system performance factor was computed which did not credit the

heat pump system with the heat required to warm the leakage air from

the attic up to the return air temperature from the house. At both

air bases this factor was about 0.25 lower than the coefficient of

performance for an outdoor temperature of 45 °F and from 0.40 to 0.50

lower than the coefficient of performance at outdoor temperatures

near the design value.

6. It was observed that 52 to 55 percent of the average energy used for

all parposes in the sample dwellings at the two sites was used by

the heat pump compressor and fans, the supplementary resistance heaters, and the bathroom heaters at Columbus AFB. The energy used for

water heating ranged from 25 to 30 percent of the total, and the re- mainder of the energy, 17 to 20 percent, was used by the ranges,

clothes dryers, and the miscellaneous devices. The ratio of the

largest to the smallest usage of energy in the individual dwellings

was typically about 2 to 1 for the heat pump and water heater, whereas

this ratio was typically larger for the supplementary resistance

heater, and was sometimes larger for the clothes dryer and cooking

range

7. The portion of the electric energy usage by the cooking range, water

heater, and miscellaneous devices in each dwelling, that could reasonably be expected to contribute toward house heating,

averaged about 2600 Btu/hr for the day and ranged from about

1400 Btu/hr during the eight-hour period after midnight to about

3700 Btu/hr during the eight-hour period before midnight.

-58-
8. The average power usage in the five sample dwellings at each base for

all purposes varied with the time of day and with outdoor temperature.

This average ranged from about 1 KW during the hours after midnight

when the outdoor temperature was 65°F to about 7 KW during the daytime hours when the outdoor temperature was approximately 30°F, which

was the lowest daytime temperature observed during the tests.

9. Energy-usage factors expressed in KW-hr/degree-day( 1000 ft 2

) were

used to correlate energy usage, degree-days based on a 65°F reference

temperature and inside floor area for the ten sample dwellings.

These factors ranged from 2.32 to 2.97 for four of the sample houses

at Seymour Johnson AFB and from I.65 to 1.93 for four of the sample

houses at Columbus AFB, whereas the factor was below this range in the

fifth dwelling at each site. The values of the energy-usage factors

were relatively stable for the range of outdoor temperature experienced during the tests, except that the factor became appreciably

higher for very mild weather in several of the dwellings at Seymour

Johnson AFB. Some of the design factors at Seymour Johnson AFB which

probably contributed to higher energy-usage factors at this site are:

(a) the balance point temperature was higher, (b) loss of heating

capacity in the refrigerant lines connecting indoor and outdoor units,

(c) little or no recovery of heat from the attic-mounted system when

the blower was stopped, and (d) use of bathroom heaters at Columbus

AFB.

10.

The observed heat requirements of the sample dwellings during normal

operation of the heat pump system agreed with those determined by

calibration with resistance heaters at the same outdoor temperatures

in most cases. Since the design wind velocity of 15 mph did not oc- cur in combination with design outdoor temperature during the test

period at either site, no direct comparison of observed heat loss and

calculated heat loss at this condition was possible. However, when

the observed values were corrected for increased heat transmission

through the windows and increased attic air leakage corresponding to

a 15 -mph wind, comparisons between these corrected values and the

calculated values were possible. It was found that the calculated

heat loss at design outdoor conditions and with an infiltration rate

of one air change per hour at outdoor temperature exceeded the calibration heat loss, after correction, by amounts ranging from 7 to 21

percent in the five sample dwellings at Seymour Johnson AFB. This

comparison indicates that the combination of normal infiltration and

air leakage from the attic may not have created a heating load as large as one air change per hour at outdoor temperature at this site.

At Columbus AFB the calculated heat loss at design outdoor conditions

and with an infiltration rate of one air change per hour at outdoor

temperature bracketed the calibration heat loss, after correction.

The calculated values ranged from 6 percent below to 10 percent above

the corrected values based on the calibration tests, indicating that,

on the average , the heating load of the overall leakage of air by

normal infiltration and attic leakage may have approximated that

caused by one air change per hour of air at outdoor temperature. The

significance of the 15 -mph wind in augmenting the heating load of

these dwellings was made evident by these comparisons.

-59-
11. The sample dwellings selected for study at each site were fairly

representative of the entire project with respect to average energy

use even though the proportion of dwellings of the several types

differed in the two groups. The average energy use in the five

sample dwellings at Seymour Johnson AFB was 95*3$ of the average

for the 1500 dwellings comprising the project, whereas the average

energy use of the five sample dwellings at Columbus AFB was 99 • 1%

of the average for the 480 dwellings in the project, during the 31-

day periods available for comparison.

Ackn owledgment

The cooperation and assistance received from the occupants of the

ten sample houses, from civilian and military personnel at the two bases

who participated in the tests , and from staff members of the National

Bureau of Standards who assisted in the conduct of the study and analysis

of the data is gratefully acknowledged.

-60-
Fig.

1.

Front

view,

type

C

(left)

and D

dwellings,

Seymour

Johnson

AFB

Fig.

2.

Front

view,

type

E

house,

Seymour

Johnson

AFB

outdoor UNIT \ 1

I-a:o

Q.s

Fig.

3.

plan

View

of

Type A

House,

Seymour

Johnson

Air

Force

Base

no

<toj- o—02 I 7

Fig.

4.

Plan

View

of

Type B

House,

Seymour

Johnson

Air

Force

Base

DroO

Fig.

5.

Plan

View

of

Type C

House,

Seymour

Johnson

Air

Force

Base

Fig.

6.

Plan

View

of

Type

D

House,

Seymour

Johnson

Air

Force

Base

Fig.

7.

Plan

View

of

Type

E

House,

Seymour

Johnson

Air

Force

Base

Fig.

8.

Front

view

of

two

type

A3D1

dwellings,

Columbus

AFB



OUTRIDE

Fig.

10.

Plan

View

of

Type

A2D1

House,

Columbus

Air

Force

Base

44'2

uiwl-

<t ui £3

UHJ

“1 IlI II rii» *

CDV

PvJ I I I I I I I I I I

Fig;.

11.

Plan

View

of

Type

A3D1

House,

Columbus

Air

Force

Base

00

go

j

j^ig.

12.

Plan

View

of

Type

03S3

House,

Columbus

Air

Force

Base

Attic

installation

ol

indoor

unit

viewed

through

trap

door,

Seymour

Johnson

AFB

Fig. 14. Indoor unit in type E house viewed through closet door.,

Seymour Johnson AFB

Fig.

15.

Typical

location

of

outdoor

unit*

Seymour

Johnson

AFB

Typical installation of unitary heat pump in utility

ninspf.. Columbus AFB

Fig. 17. View of typical unitary heat pump with front

panel removed, Columbus AF3
.
Fig.

18

.

Typical

installation

of

watthour

meters,

Seymour

Johnson

AFB

Fig.

19.

Typical

installation

of

watthour

meters,

Columbus

AFB

•

20.

Typical

installation,

of

pyrheliorneter*

and

outdoor

1

air

the

rmo

couple

utility

closet,

Columbus

Ll. o

a

E

Cj COo

.5

• rlE fl> a» &

4-> 3

rn -*-> >3 rt m t .

co

>3 03

rd0) +JCO

CMCM

tc si

in

dH/ma 1 AllOVdVO 9NI1V3H 31V1S AQV31S

OUTDOOR

TEMPERATURE

,

o

N

*

O

<

m >

cr

j?

o

CD

O 0

in

O

o

ro

O

CVJ

O

o

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00

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CD

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CVJ

3

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<C &

c- Q)

Cl, <b S

_c 0/

*-> F-<

•in oo

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* co

CM

•H

CXh

!N30d3d * 31AII1 9NI±Vid3dO dWDd 1V3H

OUTDOOR

TEMPERATURE
.

.
±N30d3d ' 31NI1 9NI±Vd3dO dWIfld 1V3H

3

f—

oQ

3t p

>i j-i e— n> 0) E

Cj E~

C/3

•H

xJ

ctf 0) a

o

•H

OUTDOOR

TEMPERATURE

o

S'

ctF*ix c

04

hD

•H

CxOUTDOOR

TEMPERATURE
.
o

N

Ll

o

<La

fii a

E

O

o

'3

C

•H

-1-3 h

O

o

-H

C*.

OUTDOOR

TEMPERATURE
'

-
'll to3

o

o

0> f- CL 3

>5 -P

E-< crj P. jz a

-t-3 E

0) •H

Pi CL O

E O

• H

u-> cOP.B. O

C'-

Cvl

tu) •H

OUTDOOR

TEMPERATURE
-

- - :

i

-

' '•
±N30d3d ‘ 31AJIX 9NUVd3dO dlMfld 1V3H

OUTDOOR

TEMPERATURE

o

o

o

o

CD

O

ID

Ll. o

O

o

ro

O

CVJ

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00

o

CD

O o

OJ

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a

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±N30d3d * 3WI± 9NI±VU3dO dl/MHd 1V3H

OUTDOOR

TEMPERATURE
-

.

fe:

• •

.
±N30d3d ‘ 31AJI JL 9l\|l±Vd3dO dlAIDd 1V3H

OUTDOOR

TEMPERATURE

A

\ i

r

HEAT PUMP ONLY

A ENTIRE SYSTEM (INCL. DUCTS)

"

A A

A A & A £

A

A

*

fc

A

AA

a

A

>“

Li

***. t

* —

402 MARCH LANE

SEYMOUR JOHNSON, AFB

DEC., 59, JAN., 60

1 1 1

1 1 D 30 50 70

OUTDOOR TEMPERATURE °F

31. Heat Pump Coefficient of performance and System Performance Factor for the Type A

levelling, Seymour Johnson AFB, for a Range of Outdoor Temperature
- . . ; ; - I
SYSTEM

PERFORMANCE

FACTOR,

HEAT

PUMP

COEFFICIENT

OF

PERFORMANCE

3

0

A HEAT PUMP ONLY

A ENTIRE SYSTEM (INCL. DUCTS)

A

A

^A & Aa A

ma

A

AAA

a\

AA

AA

$

A

a A

^A

A

413 CARSWELL LANE

SEYMOUR JOHNSON, AFB

DEC., 59, JAN.,60

10 30 50

OUTDOOR TEMPERATURE °F

70

Fig. 32. Heat pump Coefficient of Performance and System performance Factor for the Type B Dwelling, Seymour Johnson AFB, for a Range of Outdoor Temperature
'

t
UJ

o

o cc *“ o

CJ Ll

< CT

Ll LU

cl

LUO o

§!z

cr lu

°oLl y

CT Ll

LU Ll

CL LU

O

:>°

LU

cn 5

> 3

01 CL

f-

<

LU

Ll o —

A HEAT PUMP ONLY

A ENTIRE SYSTEM (INCL. DUCTS)

/A

A

A

A A

AA

A

s

A A

A

A

217 CHANUTE ROAD

SEYMOUR JOHNSON , AFB

DEC.,59, JAN. ,60

0

10 30 50

OUTDOOR TEMPERATURE °F

70

Fig. 33 * Heat pump Coefficient of Performance and System Performance Factor for the Type C

Dwelling, Seymour Johnson AFB, for a Range of Outdoor Temperature
.

'

.
3

LlI

o

-<

CCS o£1-0

Gu-

<oc

2: LjJ

CL

C£ LlI

eg

K Ul

LULl

Ql lu

O SO

LU

cn S

> =>

CO CL

\—

<

LU

OL

10

A HEAT PUMP ONLY

ENTIRE SYSTEM(INCL. DUCTS)

A

A

215 CHANUTE ROAD

SEYMOUR JOHNSON , AFB

DEC.,59, JAN., 60

30 50

OUTDOOR TEMPERATURE °F

70

Fig. 3^. Heat pump Coefficient of Performance and System Performance Factor for the Type D

Duelling, Seymour Johnson AFB, for a Range of Outdoor Temperature

LUO

<

OC

O

ti- erLU

Q_

Ll

o

UJ

o

Ll

Ll

LU

O

O

Q_

Z>

CL

h-

<

LU

X

A A

A

A

A

O

O

O

O

O

O

O- BEFORE MAINTENANCE

A- AFTER MAINTENANCE

1

1 I I L_ 20 30 40 50 60

AMBIENT TEMPERATURE , °F

35 * Heat Pump Coefficient of Performance for the Type E House,

Seymour Johnson AFB, for a Range of Outdoor Temperature

3

LUO

rS<

£ 2 o

h"O

O

Ll

< cr

Ll LjJ

LUO LlO

guj

Ll

oc

LU

CL

O

Ll

Ll

LU

O

o

LU _ cn

^

cn Ql

A

A

A

A

A

A A

A

A

A

A

AA A

A

A

117 CALEDONIA LOOP

COLUMBUS , AFB

I — FEB. ,60

A HEAT PUMP ONLY

A ENTIRE SYSTEM (INCL. DUCTS)

I-

<

LU

0L

10

OUTDOOR TEMPERATURE °F

70

Fig. 36. Haat Pump Coefficient of Performance and System Performance Factor

for the Type A3D1 Dwelling at 117 Caledonia Loop, Columbus AFB,

for a Range of Outdoor Temperature
II
3

UJ

o

goo u_

2“-

LUO

Ll

O

< I—

2 2

(Z LU Oo

Li.

q:

LU

CL

Ljl

Ll

LUOO

LU CL

O)

>

CO

3

CL

h—

<

LUX

ft

A

.A

A

A

A A

A

A

A

A

119 CALEDONIA LOOP

COLUMBUS , AFB

FEB., 60

A HEAT PUMP ONLY

A ENTIRE SYSTEM (INCL. DUCTS)

0l

10

1

30 50

OUTDOOR TEMPERATURE °F

70

Fig. 37. Heat Pump Coefficient of performance and System Performance Factor

for the Type A3D1 Dwelling at 119 Caledonia Loop, Columbus AF3,

for a Range of Outdoor Temperature

SYSTEM

PERFORMANCE

FACTOR

,

HEAT

PUMP

COEFFICIENT

OF

PERFORMANCE

3

2

1 1

A #

4

i r

A

A 4

*

*

A „A

"

4

^ #

4*

^

A —

116 FLORIDA AVE. — COLUMBUS , AFB —

FEB., 60

A HEAT PUMP ONLY

A ENTIRE SYSTEM

1 1 1

(INCL. DUCTS)

1 L

10 30 50 70

OUTDOOR TEMPERATURE °F

Fig. 33. Heat Pump Coefficient of Performance and System Performance Factor

for the Type 03S1R House, Columbus AFB, for a Range of Outdoor

Temperature

3

LUO

- <x

cr

o

ho

<

Ucr

o

Ucr

LU

Q.

LU Ll_

o o

2 z

cn LU

£o

Qd

UJ

Q.

u_

Li.

UJ

o

o

UJ

ICO

^5

>- Z>

CO O.

h-

<

UJ

X

A

2 —

A

A

A A

118 FLORIDA AVE.

COLUMBUS , AFB

FEB.,60

A HEAT PUMP ONLY

A ENTIRE SYSTEM (INCL. DUCTS)

0

10 30 50

OUTDOOR TEMPERATURE °F

39. Heat rtimp Coefficient of Performance and System Performance Factor

for the Type 03S3 House, Columbus AF3, for a Range of Outdoor

Temperature

70

o

do

l 131NI HOD aOOC)NI-WnN31d

AlddflS ‘ 30N3d3d3IQ 3dD±Vd3dW3±

Fig.

40.

pattern

of

Temperature

Rise

cf

Warned

Air

Produced

by

the

Heat

Pump

in

the

Type

C

Dwelling

During

Long

(Upper

Curve)

and

Short

(Lower

Curve)

Running

Periods

o

do

l 13~INI “1100 U00aNI-IAinN3“ld

AlddflS ‘ 30N3d3Jdld 3dniVd3dl/\l3±

TIME,

MINUTES

Fig.

41.

Patt-om

of

Temperature

Rise

of

Warned

Air

Produced

by

the

Heat

Pump

in

a

Type

A3D1

Dwelling

During

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Fig.

42.

Ratio

of

Temperature

Rise

of

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Air

to

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State

Temperature

Rise

Plotted

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Time

after

Start

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Heating

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0030-0830

0830-1630

1630-0030

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DAY

TIME

INTERVAL

,

HOURS
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POWER USAGE (AVG. OF FIVE HOUSES)

10 20 30 40 50 60 70

OUTDOOR TEMPERATURE ,°F

Fig. 45. Average Power Used for Heating and for All Purposes During the Hours

0030 to 0830 in the Five Sample Houses at Seymour Johnson AFB,

for a Range of Outdoor Temperature

7

6

5

4

3

2

I

0

H

POWER USAGE (AVG. OF FIVE HOUSES)

DEC. 1959 - JAN. I960

) 20 30 40 50 60 70

OUTDOOR TEMPERATURE , °F

* Average Power Used for Heating and for All Purposes During the Hours 0830 to 1630

in the Five Sample Houses at Seymour Johnson AFB for a Range of Outdoor Temperature

POWER USAGE (AVG. OF FIVE HOUSES)

OUTDOOR TEMPERATURE , °F

Fig. 47. Average Power Used for Heating and for All Purposes During the

Hours I63O to 0030 in the Five Sample Houses at Seymour Johnson

AF3 for a Range of Outdoor Temperature

POWER USAGE (AVG- OF FIVE HOUSES)

OUTDOOR TEMPERATURE ,°F

Fig. 43. Average Power Used for Heating and for All Purposes During the Hours 2300 to 0700

in the Five Sample Houses at Columbus APB for a Range of Outdoor Temperature

POWER USAGE (AVG. OF FIVE HOUSES)

Fig. ^49. Average power Used for Heating ana xor a-i~l purposss During the Hours

0700 to 1500 in the Five Sample Houses at Colunbus AF3,

for a Range of Outdoor Temperature

10 20 30 40 50 60 70

OUTDOOR TEMPERATURE , °F

Fig. 50. Average Power Used for Heating and for A ses During the Hours

1500 to 2300 in the Five Sample Houses at 0dumbus AF5, for a Range of Outdoor Temperature

ENERGYUSAGE

FACTOR

,

KWH/

DEG

-DAY

(IOOO

FT

CVJ TOTAL HEAT PUMP ENERGY INPUT

0

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o

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o

o o

402 MARCH LANE

SEYMOUR JOHNSON , AFB

DEC., 59 , JAN., 60

o

10 20 30

DEGREE DAYS/DAY (65 F BASE)

Fig. 51. The Energy-Usage Factor of the Heat Pump Unit in the Type A Dwelling,

Seymour Johnson AFB, for a Range of Degree Days per Day
-

.
ENERGYUSAGE

FACTOR

.KWH/DEG-DAY

(IOOO

FT

5

CM

4 I—

3 -

TOTAL HEAT PUMP ENERGY INPUT

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0

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ooO

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o

o

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(9

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— 413 CARSWELL LANE

SEYMOUR JOHNSON, AFB

DEC., 59, JAN. ,60

o

o o

o

10 20 30

DEGREE DAYS/DAY (65 F BASE)

o

o

Fig. 52. The Energy-Usage Factor of the Heat Pump Unit in the Typz B Dwelling,

S5ymour Johnson AFB, for a Range of Degree Days per Day

ENERGYUSAGE

FACTOR,

KWH/DEG-DAY

(IOOO

FT

5

CM

TOTAL HEAT PUMP ENERGY INPUT

2

o

o

o o

k\IG.V

c

o°

1 o

o

o o £* °o

o

°o

217 CHANUTE ROAD

SEYMOUR JOHNSON , AFB

DEC. ,59 , JAN. ,60

o

10 20

o

0)0 °

° o

30

DEGREE DAYS/DAY (65 F BASE)

Fig. 53 - The Energy-Usage Factor of the Heat Pump Unit in the Type G Dwelling,

Seymour Johnson 4.F3, for a Range of Degree Days per Day

ENERGYUSAGE

FACTOR,

KWH/DEG-DAY

(IOOO

FT

5

CM o n

TOTAL HEAT PUMP ENERGY INPUT

o

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215 CHANUTE ROAD

SEYMOUR JOHNSON, AFB

DEC., 59 , JAN., 60

1 1 J

10 20 30

DEGREE DAYS/DAY (65 F BASE)

Fig. 5^. The Energy-Usage Factor of the Heat Pump Unit in the Type D Dwelling,

Seymour Johnson AFB, for a Range of Degree Days per Day

ENERGYUSAGE

FACTOR

,

KWH

/DEG

-DAY

(IOOO

FT

5

CM

0

TOTAL HEAT PUMP ENERGY INPUT

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— 301 CARSWELL LANE —

SEYMOUR JOHNSON, AFB

DEC., 59 , JAN., 60

1 1 1

o

10 20 30

DEGREE DAYS/DAY (65 F BASE)

Fig. 55 • The Energy- Usage Factor of Lhe Heat pjmp Unit in the Type E House,

Seymour Johnson AFB , for a Range of Degree Days per Day

3

TOTAL HEAT PUMP ENERGY INPUT

CVJ cr

o o

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122 VERNON AVE.

COLUMBUS, AFB

FEG., MAR., 60

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o

o

o

CD

O o

10 20 30

DEGREE- DAYS /DAY (65 F BASE)

Fig. 56 . The Energy-Usage Factor of the Heat Pump Unit in the Type A2D1

Dwelling , Columbus AFB, for a Range of Degree -Days per Day

3

TOTAL HEAT PUMP ENERGY INPUT

tr

o

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COLUMBUS, AFB

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o

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10 20 30

DEGREE-DAYS/DAY (65F BASE)

Fig. 57* The Energy-Usage Factor of the Heat Pump Unit in the Type A3D1

Dwelling at 117 Caledonia Loop, Columbus AFB,

for a Range of Degree-Days per Day

3

TOTAL HEAT PUMP ENERGY INPUT

cr

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10 20 30

DEGREE-DAYS/DAY (65F BASE)

Fig. 58. The Ensrgy-Usage Factor of the Heat Pump Unit in the Type A3D1 Dwelling

at 119 Caledonia Loop, Columbus AFB, for a Range of Degree-Days per Day

3

or

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116 FLORIDA AVE.

COLUMBUS , AFB

FEB., MAR. ,60

o

a

- o

10 20 30

DEGREE-DAYS/DAY (65F BASE)

Fig. 59. The Energy-Usage Factor of the Heat pump in the Type 03SIR House,

Columbus AF3, for a Range of Degree-Days per E&y

I
-

•

.
3

TOTAL HEAT PUMP ENERGY INPUT

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DEGREE-DAYS/DAY (65F BASE)

Fig, 60. The Energy-Usage Factor of the Heat Pump Unit in the Type 03S3 House,

Columbus AFB, for a Pange of Degree -Days per Day

INDOOR -OUTDOOR TEMPERATURE DIFFERENCE

Fig. 61. Heat Supplied to tne Type A Dwelling, Seymour Johnson AFB,

during Normal Heating for a Range of Outdoor Temperature

HEAT

SUPPLIED

TO

DWELLING

,

BTU/hr

INDOOR - OUTDOOR TEMPERATURE DIFFERENCE

Fir. '2. Heat Supplier to the Type B Dwelling, Seymour Johnson AFB,

during Normal Heating for a R. age of Outdoor Temperature

HEAT

SUPPLIED

TO

DWELLING

,

BTU/hr

INDOOR- OUTDOOR TEMPERATURE DIFFERENCE

Fig. ^3* Heat Supplied to the Type G Dwelling, Seymour Johnson AFn

, During Normal Heating for a Range of Outdoor Temperature
k l - - E ~

-

•

r

'
INDOOR -OUTDOOR TEMPERATURE DIFFERENCE

Fig. 64. Heat Supplied to tne Type D Dwelling, Seymour Johnson AFB,

during Normal Heating for a Range of Outdoor Temperature

Fig. 65. Heat Supplied to tne Type E House, Seymour Johnson AFB,

during Normal Heating for a Range of OutdoorJI^mperatu^

I

INDOOR - OUTDOOR TEMPERATURE DIFFERENCE

Fig. Heat Supplied to the Type A2D1 Duelling, Columbus AFB,

during Normal Heating for a Range of Outdoor Temperature
.
INDOOR -OUTDOOR TEMPERATURE DIFFERENCE

Fig. 67 . Heat Supplied to the Type A3D1 Excelling at 117 Caledonia Loop,

Columbus AFB, during Normal Heating for a Range of Outdoor

Temperature

INDOOR- OUTDOOR TEMPERATURE DIFFERENCE

Fig. ^3. Heat Supplied to trie Type A3Di Dwelling at 119 Caledonia Loop,

Columbus AF3, during Normal Heating for a Range of Outdoor

Temperature

INDOOR- OUTDOOR TEMPERATURE DIFFERENCE

Fig. 69. Heat Supplied to tne Type 03S1H House, Coiurrbus AFB,

during Normal Heating for a Range of Outdoor Temperature

INDOOR- OUTDOOR TEMPERATURE DIFFERENCE

Fig. 70. Heat Supplied to tne Type 03S3 House, Columbus AFP,

during Normal Heating for a Range of Outdoor Temperature

TOTAL

HEAT

PUMP

ENERGY

TOTAL

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FOR

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NATIONAL BHRFIAU OK STAND AllDS

\. V. Aslin, l)i rrctm

I NK NATIONAL BUREAU OF STANDARDS

The s. ope of aetivitiesof the National Bureau of Standards at its major laboratories in Washington, D.C., and

Moulder, (hdnrado, is suggested in the following listing of the divisions and sections engaged in technical work.

In gem ral, each section carries cut specialized research, development, and engineering in the field indicated by

its title. \ brief description of the activities, and of the resultant publications, appears on the inside ofthe

front cover. WASHINGTON, ILL.

Electricity. Resistance and Reactance. Electrochemistry. Electrical Instruments. Magnetic Measurements

Dicier tiics. High Voltage.

Metrology. Photometry and Colorimetry. Refractometrv. Photographic Research. Length. Engineering Metrology.

Mass and Scale. Volumetry and Densimetry. Heat Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Pure Substances. Spectrochemistry. Solution Chemistry. Standard Refer- ence Mat erials. Applied Analytical Research. Crystal Chemistry.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Control s. Polymers. Macromolecules: Synthesis and Structure. Polymer Chemistry. Polymer Physics. Polymer Characterization. Polymer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research.

Metallurgy. Engineering Metallurgy. Microscopy and Diffraction. Metal Reactions. Metal Physics. Electrolysis

and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Glass. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials. Codes and Safety Standards. Heat Transfer. Inorganic Building Materials. Metallic Building Materials.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics. Operations Research. Data fYocessing Systems. Components and Techniques. Computer Technology. Measurements Automation.

Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Far l ltraviolet Physics. Solid State Physics. Electron

Ph\sics. Atomic Physics. Plasma Spectroscopy.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instru- ments. Basic Instrumentation.

Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Ele- mentary Processes. Mass Spectrometry. Photochemistry and Radiation Chemistry.

Office of Weights and Measures. BOULDER, COLO.

Cryogenic Engineering Laboratory. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Cryogenic Technical .Services. CENTRAL RADIO PROPAGATION LABORATORY

Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Research. Prediction .Services, Sun-Earth Relationships. Field Engineering. Radio Warning Services. Vertical Soundings Research.

Radio Propagation Engineering. Data Reduction Instrumentation. Radio Noise. Tropospheric Measurements.

Tropospheric Analysis. Propagation-Terrain Effects. Radio-Meteorology. Lower Atmosphere Physics.

Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency Research. Fre- quency I tilization. Modulation Research. Antenna Research. Radiodetermination.

Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. High Latitude Ionosphere

Physics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Physics. Radio Broadcast Service. Radio and Microwave Materials. Atomic Frequency and Time-Interval

Standards. Radio Plasma. Millimeter-Wav? Research.

Circuit Standards. High Frequency Fllectrical Standards. High Frequency Calibration Services. High Frequency

Impedance Standards. Microwave Calibration Services. Microwave Circuit Standards. Low Frequency Calibration

Services.