NATIONAL BUREAU OF STANDARDS REPORT

i|213

PERFORMANCE OF A GAS-FIRED WALL HEATER WITH AND

WITHOUT AN AUXILIARY AIR DISTRIBUTION SYSTEM

by

0* N. McDorman

P. R. Achenbach

Report to

Federal Housing Administration

Washington, D, C,

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

IOO3-3O-U83O July 13, 1955 4213

PERFORMANCE OF A GAS-FIRED WALL HEATER WITH AND

WITHOUT AN AUXILIARY AIR DISTRIBUTION SYSTEM

by

0. N» McDorman

Po R. Achenbach

To

Federal Housing Administration

Washington, D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication, 1

unlesspermission

25, D.C. Such p

cally prepared if

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 201 5.

ir In part, is prohibited

Standards, Washington

•eport has been speclfireport for its own use.

PERFORMANCE OF A GAS-FIRED WALL HEATER WITH AND

WITHOUT AN AUXILIARY AIR DISTRIBUTION SYSTEM

Oo N. McDorman and Po Ro Achenbach

Abstract

An investigation was made of the performance

of a gas-fired wall heater in a house without

a basement employing the booster blowers in

the heater alone and in combination with an

auxiliary distribution system for circulating

the air througji the house. The auxiliary

system consisted of a 7 l/2-inch propeller fan

mounted in the ceiling near the heater forcing

air througja an attic plenum and three connecting ducts to ceiling grilles in three remote

rooms. It was found that the distribution of

warmed air to the five rooms of the Test Bungalow was reasonably good without the auxiliary

system and that the auxiliary system did not

decrease the difference between the warmest

and coldest room. The auxiliary system decreased the vertical temperature differences

in the living zone and between floor and ceiling, but these differences were still higher

than desired at an outdoor temperature of 0°F

even with the auxiliary system in operation.

The observed heat loss was about 15% lower

than the value computed by recognized methods

for this house. This heater, as Installed and

operated, produced considerable noise,

1, INTRODUCTION

In accordance with a request of the Federal Housing

Administration dated August 16, 1954 ^ study was made of

the performance of a specimen gas-fired wall heater in

the Test Bungalow for two methods of air distribution.

In one case air was circulated through the heater and the

house without the use of ducts by means of the twin centrifugal booster blowers inside the heater casing. In

the second case this same air circulation was supplemented by a propeller fan and three attic ducts to

= 2

provide direct movement of warm air from the hall adjacent to the heater to the two bedrooms and bath.

The horizontal and vertical temperature distribution

and the heat loss of the house were observed for each

method of air distribution at outdoor temperatures of 32°F

and 0°F, The noise level produced by the equipment was

also observed in the various rooms of the Test Bungalow.

2o DESCRIPTION OF TEST SPECIMEN AND DISTRIBUTION SYSTEM

The Royal Jet Heater, model FF 72, Serial No. 65I43 employed twin raised port burners ignited by a pilot located

near one of the burners. Twin dimpled heat exchangers were

enclosed in the furnace casing, designed for vertical mounting. The specimen was rated at 72^000 Btu/hr input and

54,000 Btu/nr output. The overall dimensions were 19 I/I4-

inch deep, 19-inch wide and 88 l/[|-inch high. The heater

was equipped with a centrifugal type fan with twin scrolls

mounted at the two ends of the motor shaft. The motor was

rated at 1550 rpm and 107 watts. The blowers were arranged

for free discharge of air vertically upward through the

heater.

As tested the heater was equipped with three supply

grilles and three return grilles facing toward the living

room, kitchen, and hall. The center line of the supply

grilles were 78 inches above the floor whereas the center

line of the return grilles were 12 inches above the floor

for kitchen and living room and 17 inches for the hall

grille. The openings in the warm air plenum inside the

heater casing were smaller than the grilles in some cases.

The dimensions of the plenum openings and perforated areas

of the supply and return grilles are summarized below.

Room

Openings in

Plenum, Inches

Supply

Grilles, in.

Return

Grilles, in.

Kitchen 6x7 1/2

Living Room 14x7 5/8

Hall 6x6 3/8

15x9 5/6

15x9 5/8

14 5/8x14 1/4

14x8 3/4

15 1/2x10

22 3/4x14 1/8

Two views of the heater installation in the Test Bungalow are shown in Fig. 1 and 2. Fig. 1 shows the heater as

seen from the kitchen, and Fig, 2 shows it as seen from the

hall.

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- 3

“

Since the heater capacity was in excess of the heat

loss of the house it was operated under thermostatic control

during the tests* The thermostat used was a wall thermostat

manufactured by General Controls Company employing a thermoelectric circuit for actuation of the control*

The auxiliary distribution system consisted of a 7 l/2

inch diameter propeller type fan rated at ^8 watts mounted

in the center hallway ceiling exhausting into a 10'’'xl0"xl6‘*

plenum above the ceiling. Extending from this plenum in

the attic were three six inch diameter Insulated ducts

connected to supply registers in the ceilings of the bath,

north bedroom and south bedroom.

The lengths of these ducts were, nine feet for the bath,

eight feet for the north bedroom and 12 feet for the south

bedroom. The location of the auxiliary fan with respect to

the heater is shown in Fig, 2. The location of the heater

and the attic ducts are indicated on the plan of the Test

Bungalow shown in Fig, 3»

3* TEST EQUIPMENT MD PROCEDURE

The Test Bungalow remained in the same condition with

respect to insulation and construction features, as for other

heating systems recently tested* Significant factors were

as follows? plastered ceiling, fluorescent illumination,

weatherstripped windows and doors, uninsulated outside walls,

basement ceiling consisted of 1-lnch rigid insulation board

nailed directly to the under side of the floor joists. The

ceiling was Insulated from the attic space with two layers

of commercial "double thick" rock wool. The effective

thickness was determined to be 5<>l4 inches. The Test Bungalow was operated as a basementless house for these tests

even though it had a full basement. The basement temperature was controlled for similar tests to provide comparative data.

The temperature distribution was ascertained by means

of 200 thermocouples enclosed in three inch cork spheres

located at five stations and five levels in each of the

four large room and three stations and five levels in the

bath and at other suitable stations on the floor, embedded

in the celling surface, on the sidewalls, and in basement,

attic and out-of-doors. Additional thermocouples, of the

parallel multiple- junction type were placed at the heater

Inlets and outlets. The temperature of the gas supply was

measured by means of a thermocouple inserted in the gas

stream*
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The absolute values of the heat transmitted to the

attic were determined with the aid of twenty heat flow

meters placed over the first layer of rock wool insulation

in the attic*

After steady state conditions had been maintained in

outside and inside temperatures for approximately eight

hours, test periods of about 12 hours conimenced, during

which observations of the inside temperatures for approximately 150 stations were recorded at four hour intervals*

Hourly recordings were made of the following temperatures

s

outside air, J>0-^inch level at five room centers, five

positions in basement, five locations on furnace, gas

supply temperature, and the closet. The accuracy of the

measuring circuit was checked hourly using melting ice

as a standard* Gas consumption, electrical energy used

for lighting the house, electrical energy consumed by

fan motors, and gas pressure were recorded hourly*

4* TEST RESULTS AND CONCLUSIONS

The temperature distributions observed in the Test

Bungalow during four tests under steady state conditions

are sumraarized in Tables 1-4 inclusive. Table 5 summarizes the performance of the heater, the heat loss of the

house, and some of the more significant temperatures in

the structure. Two tests were made at outdoor temperatures

of 32 °F and 0°P, respectively, without the auxiliary distribution system. Tests were then made under these same

conditions with the auxiliary distribution system in use.

Table 6 summarizes the results of the noise measurements

made in the house*

Temperature Distribution

The average of the temperatures observed at five

levels in each of the five rooms of the house are summarl zed in Tables 1 and 4 when the auxiliary distribution

system was not in use and in Tables 2 and 3 when it was in

use* The station at the center of the living room 2>Q

Inches above the floor was used as the control point although the thermostat was located on an inside wall of the

living room at the same height above the floor. It will

be noted in these four tables that the variation in average temperature between rooms at the 30 inch level was

approximately one degree and it was independent of whether

the auxiliary system was used or not. The variation in
t
“ 5

"

average temperature between rooms was considerably greater

at all other levels of observation than at the 30 -inch

level increasing to 6,9°P at the 60-inch level with the

auxiliary system in operation and 5o2°F at the same level

without the auxiliary system for an outdoor temperature of

0°F in each case. The horizontal temperature distribution

was not significantly Improved in this house by the operation of the auxiliary distribution systemo

The vertical temperature differences in the living

zone, from two to sixty inches above the floor, and from

floor to ceiling, two to ninty-four Inches above the floor,

are summarized below:

Vertical Temperature Differences

Height Above

Floor, Inches

With Auxiliary

System

Without Auxiliary

System

Outdoor temperature J>2^F

2-60 9.5 10,4

2-94 l^oO 17<.3

Outdoor temperature 0°F

2-60 16,7 19.1

2-9U 26.0 30.5

This summary shows that the auxiliary distribution system

lowered the vertical temperature differences from one to

2ol\ degrees in the living zone and from 2,3 to ijo5 degrees

from floor to celling for the range of outdoor temperatures

used. Tables 1-4 show that the reduction in vertical temperature differences from floor to celling was accomplished

primarily by lowering the temperature at the 914 -inch level.

Tables 1-4 show that the maximum horizontal temperature

variation within rooms was not greatly affected by the auxiliary distribution system. The average of the intraroom

variations was about 2„2®P at an outdoor temperature of

32*^F and 3»5°F at an outdoor temperature of 0°F/

The attic temperature was Increased only slightly

by the use of the auxiliary ducts indicating that the

attic ducts and plenum did not transfer much heat to the

attic

.

b

Heat Loss

If the average total heat requirement for these tests

as shown in Table 5 is plotted ae:ainst the indoor - outdoor

temperature difference based on average temperature at the

30“inch level a tangent of I41

8

Btu/hr ( '^P) would be obtained.

This value is very nearly equal to that obtained in the

Test Bungalow with other heaters of this type.

The observed heat loss of the house was substantially

the same irrespective of whether the auxiliary distribution

system was used or not. The computed heat loss of the Test

Bungalow using the methods recommended in the 1954 '‘Guide"

of the American society of Heating and Air Conditioning

Engineers averaged about 15 percent higher than the observed values.

The heat loss from the living space to the attic was

measured with 20 heat flow meters distributed over the entire ceiling area so that each represented approximately

an equal area. The observed heat loss through the ceiling,

insulated with 5»4 inches of rock wool, averaged about five

percent of the total heat loss of the house. The heat loss

through the ceiling v-rlth the auxiliary distribution system

in use was about half of one percent less than without it.

This is attributed partly to the lower temperature beneath

the ceiling and partly to the higher temperature in the

attic when the auxiliary system was In use.

The temiperature rise of the air between return and

supply grilles indicates that the blowers in the heater

circulated about pGO cfm of air when operating. A comparison of the air temperature at the ret^ui^n grilles in

Table 5 the temperatures at the two inch level in the

several rooms of the house indicates that the return air

was dravjn into the heater at a level considerably above

the floor or it was warmed several degrees before reaching

the heater if taken from floor level.

Noise

The noise level observed in three rooms of the house

at levels 2 I4 and 60 Inches above the floor are reported in

Table 6 . The noise level ranged from 55 to 59 decibels

on the LjO db weighted netv/ork, from 59 to b5 decibels on

the 70 db weighted network, and from 6l to 69 decibels on

the flat network. These values are all higher than those

cited in the 195^ ASHAE Guide for representative residences.

The system could have been made quieter by using sheet metal

screws in some of the vibrating members or by the use of the

speed control in the fan circuit which was not installed by

the manufacturer for these tests.

5. DISCUSSION AND CONCLUSIONS

The data observed in the Test Bungalow while operating

the Model FF-72 Royal heater with and without the au:xiliary

distribution system Indicate the following conclusions:

1. The difference in average temperature between

rooms was quite low at the 30 ~ii^ch level and exceeded 5 °F

only slightly in the living zone When the heater used its

own blowers and the outdoor temperature was 0°F. The

auxiliary distribution system did not significantly improve the horizontal temperature pattern.

The auxiliary distribution would probably be of

greater value in houses whose floor plan did not permit

the heater to be located as near the center of the house

as for the test installation,

2. The vertical temperature differences in the

living zone at an outdoor temperature of 0 ®P were a little

greater than the 15 °F that experience has indicated is

about the maximum that can be tolerated with comfort. The

auxiliary air distribution system decreased the vertical

temperature difference in the living zone 2,i|°F on the

average at this same outdoor temperature,

3. The insulation on the attic plenum and ducts

appeared to effectively limit the heat transfer from these

components to the attic.

I|« Radiation from the celling surface to floor

did not play a significant role for this system. Average

ceiling surface temperatures ranged from 77 °F to 8)4 '^ for

this series of tests.

5o The test results do not indicate that the

heat requirements, of a house using this model heater

would be greater than the computed heat loss.

6 . The heater was considered to be undesirably

noisy when the fans were operating at full speed.

TABLE 1

Temperature Distribution with Royal Heater, Model FF-72.

Outdoor Temperature 31»3^F

Height

Above

Floor

Average Room Temperature

Average

of

5 Rooms

Maximum

Hori zontal

Temperature

Difference

Between

Kitchen Rooms

Living

Room

Bath

Room

North

Bedroom

South

Bedroom

inches °P '^F Op Op °F

2 66.1 66, 8 67.1 63.8 65.7 63.9 30

30 70.1 70.3 70.7 69.0 70. ii 70,3 0.9

60 77.0 76. 8 77.6 7l|.0 75.9 76.3 3.6

78 82.2 80 ,

4

82 .

6

76.2 78,1 79.9 6,4

9U 86.3 83.7 86.1 79.2 80.7 83,2 7.1

Maximum Horizontal 'Temperature Variation Within Rooms

30 2.8 2,2 3.- # ii.|' 2.ii 2,6 2.3

Vertical Temperatur'e Difference, Room Average

2-60 10.9 10.0 10.5 10,2 10.2 10,

4

2-91* 20.2 16.9 19.0 15 • i'r 15.0 17.3

Average Basement Temperature i|6.9°F

Average Attic Temperature 1*3. S“F

Average Celling Surface Temperature 78.3 F

Average Floor Surface Temperature 65*5 F

TABLE 2

Temperature Distribu t ion with Royal Heater, Model FF--72

Outdoor TemperatiJire 31«7’^F

Auxiliary Distribution System

Height

Abo ve

Floor

Average Room T(smperature Average

of

5 Rooms

Maximum

Hori zontal

Temperature

Difference

Between

Kitchen Rooms

Living

Room

Bath

Room

North

Bedroom

South

Bedroom

Inches '"F

• °F °F °F °F

2 66.0 66.9 67.0 66,1 65 . 6 66 ,

3

1.4

30 70 . )4 70.7 70.8 71.3 70,6 70.8 0.9

60 76.6 76. 6 77.5 73«2 75 . 14 75.9 14.3

78 80.9 80.3 79.

8

714.3 76,9 78.14 6.6

94 84.9 83 . s 82.2 77.0 79.1 81.3 7.9

Maximum Horizontal Temper atur e Variations Within Rooms

30 3.0 2.2 1.2 2,4 2.2 2,2

2-60

2-94

Vertical Temperature Difference, Room Average

10,6 9.7 10.5 7.1 9,8 9.5

18.9 16.6 15.2 10.9 13,5 15,0

Average Basement Temperature 47«5^F

Average Attic Temperature 44*1°F

Average Celling Surface Temperature 76.7°F

Average Floor Surface Temperature 65«6°F
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TABLE 3

Temperature Distribut ion with Royal Heater, Model FF-72

Outdoor Temperature 0,0 '^F ~ Au:xiliary Distribution System

Maximum

Horizontal

Temperature

Height Average Room Temperature Average Difference

Above Living Bath North South Of Betvjeen

Ploor Kitchen Room Room Bearoom Bedroom 5 Rooms Rooms

Inches -p -p -p -p

2 61.2 63.2 62.9 60.4 61,4 61.8 2.8

30 69.5 70.2 70.2 70.9 69.

6

70.1 1,4

60 77.7 80.0 81,9 75.0 78.2 78.6 6.9

78 87.0 86.9 84.7 77.2 80.9 83.3 9.8

94 92.3 91.8 68.4 81,6 Qh.Q 87.8 10.7

Maximum Horizontal Temperature Variations With Rooms

30 4»5 3.5 2.2 2.1 4.1 3.3

Vertical Temperature Difference, Room Average

2-60 16,5 16,8 19.0 II4.6 16.8 16.7

2-94 31.1 28.6 25.5 21.2 23.4 26.0

Average Basement Temperature 37.9^P

Average Attic Temperature 26,l‘"P

Average Ceiling Surface Temperature 80,5°P

Average Ploor Surface Temperature 6l.7°P
v-li
TABLE I4 Temperature Distribution with Royal He ater, Model FF -72

Outdoor Temperature -»Qo 3

^

Height Average Room Temperature Average

Maximum

Horizontal

Temperature

Difference

Above

Floor Kitchen

Living Bath North

Room Room Bedroom

South

Bedroom 5

of

Rooms

Between

Rooms

Inches °F 0 0 °F °F °F

2 61.8 63.9 64.7 59 c 4 61,9 62.3 5.3

30 70.4 70.6 71.3 89.9 70.3 70,5 .1,4

60 82,8 82.3 83.5 78.3 80,

§

81.5 5 o 2

78 91.3 88.9 91.3 82.3 84.

s

87.7 9 c 0

94 96,9 94.1 96.7 87.3 89,0 92.8 9.6

Maximum Horizontal Temperature Variations with Rooms

30 4*5 3.7 2.0 4.0 4.0 3.6

2-60

2-94

Vertical Temperature Difference. Room Average

21.0 18.4 18.8 18.9 18.6 19ol

35.1 30.2 32.0 27 o 9.. 27.1 30.5

Average Basement Temperature

Average A^ttic Temperature

Average Ceiling Surface Temperature

Average Floor Surface Temperature

37 . 7 “F

24 . 5 °F

83,9®F

62 . 5 °F
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TABLE 5

SUMMARY OF RESULTS

PERFORMANCE OF ROYAL JET HEATER

MODEL FF -72

Test No. 1 2 3 4

Auxiliary

Distribution Blower

Method of Air Circulation Blower and Blower Only

Outside Temperature Op 31*3 31.7 0.0 -0.3

Observed Gas Consumption cu. ft/hr 20.^0 20.59 60.148 39,47

Correction Factor 0.97 0,97 0,98 0.98

Corrected Gas Consumption cu. ft/hr 19.79 19.97 39.67 38,68

Heating Value Btu/cu. ft IO4I4 1042; 1039 1040

Heat Input to Furnace Btu/hr 20,660 20,810 [41,220 40,230

CO2 in Flue Gases Percent 6,75 6.75 6.75 6,75

Stack Temperature Op 737 737 737 737

Indirect Efficiency Percent 68 68 68 68

Heat Output of Furnace Btu/hr 14,050 114,150 28,030 27,360

Electrical Heat Input Btu/hr 2,000 2,070 2,190 2,020

Observed Heat Loss of House Btu/hr 16,050 16,220 30,220 29,380

Ceiling Heat Loss Btu/hr 670 800 1,340 1,440

Computed Heat Loss of House Btu/hr 18,590 18,640 33,410 33,750

Power Consumption of Blower V/atts 60 84 121 79

Average Temp., 30 inch Level °F 70,3 70,8 70.1 70,5

Basement Air Temperature 46.9 47.5 37.9 37.7

Attic Air Temperature °F 43.5 44 • 1 26,1 24.5

Celling Surface Temperature

Average Cold Wall Temp. 30

78.3 76.7 80.5 83,9

to 60 in. above floor °F 66.3 66,1 62,8 65.7

Floor Surface Temperature °F 65.5 65.6 61.7 62.5

Air Temp, at Return Grilles °F 70.7 71.1 66,9 68.2

Air Temp, at Supply Grilles °F 203.3 201.1 195.4 197.5
%A
TABLE 6

Summary of Sound Level Measurements in Test Bunp;alow

with Royal Jet Heater, Model FF-72

Height of

Microphone Sound Level^ Decibel s Above Floor Weip;htin^ Fan on

Room Inches Net Work Background Max. Speed

Kitchen 60 flat 48 69

70 34 65

40 24- 59

Kitchen flat 48 67

70 34 64

40 24- 59

Living Room 60 flat 46 65

70 31 63

40 24- 59

Living Room 2l\ flat 46 63

70 31 62

40 24- 59

South Bedroom 60 flat 44 62

70 3I4 59

40 24 - 55

South Bedroom 24 flat 44 61

70 34 59

40 24 - 56

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of tbe Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions,

which provides data for determining the best frequencies to use for radio communications throughout

the world. There are also five series of nonperiodical publications: Tbe Applied Mathematics

Series, Circulars, Handbooks, Building Materials and Structures Reports, and Miscellaneous

Publications.

Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

tbe National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office. Inquiries regarding the Bureau’s reports and

publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.