NATIONAL BUREAU OF STANDARDS REPORT

5336

CAPACITY OF A FEDDERS WINDOW-TYPE AIR CONDITIONER

MODEL 611-DG-53

by

C. W. Phillips

W. F. Goddard, Jr.

Report to

Quality Control Division

Public Building Service

General Services Administration

U. S. DEPARTMENT OF COMMERCE
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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1000-30-4830 June 19, 1957 5336

CAPACITY OF A FEDDERS WINDOW-TYPE AIR CONDITIONER

MODEL 611-DG-53

by

C. W. Phillips

W. F. Goddard, Jr.

Air Conditioning, Heating, and Refrigeration Section

Building Technology Division

(

Report to

Quality Control Division

Public Building Service

General Services Administration

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to reproduce additional copies for its own use.<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
.
CAPACITY OF A FEDDERS WINDOW- TYPE AIR CONDITIONER

MODEL 611-DG-53

by

C. W. Phillips and W. F. Goddard, Jr.

Abstract

A Fedders window- type room air conditioning unit,

Model No. 611-DG-53 , Serial No. 245-034 was tested

to determine if the net total cooling effect or

capacity, under standard specified conditions,

exceeded a purchase contract requirement of 7500

Btu per hour. The unit had an observed capacity

of 7850 Btu per hour, about five percent greater

than required. Other performance characteristics

relating to capacity, such as the ratio of the

sensible cooling effect to net total cooling effect,

cooling effect to power input ratio, and power

factor were determined, but no determination of

compliance with other requirements of the Federal

Specification 00-A-372, referenced in the procurement contract, or requirements in the procurement

contract itself, was made.

The capacity test reported required the construction

and calibration of a special insulated calorimeter

in which the air conditioner could be tested. This

was constructed using the ASRE Standard No. 16-56,

"Methods of Rating and Testing Air Conditioners" as

a general guide, but it did not conform to all details

of the standard.

INTRODUCTION

In accordance with Request No. 57-62 from the General

Services Administration dated February 13 , 1957, a test was

made to determine whether the neb room cooling effect of a Fedders room air conditioner, Model No. 611-DG-53, manufactured by the Fedders-Quigan Corporation, Maspeth, Long Island,

N. Y. , exceeded a bid requirement of 7500 Btu per hour minimum

under specified conditions. This report presents the results

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obtained when the sample air conditioner, Serial No. 21+5-031+,

was tested under standard rating conditions of 95F dry bulb,

75F wet bulb for the condenser (or outdoor) side and 80F dry

bulb, 67F wet bulb for the evaporator (or indoor) side. The

test procedure and apparatus was patterned after, but was not

in exact conformance with the American Society of Refrigerating

Engineers Standard No. l 6 -% entitled "Methods of Rating and

Testing Air Conditioners". Theucontract on which this conditioner was purchased required that the units furnished conform

to Federal Specification OO-A-372, entitled "Self-Contained,

Electric Motor Driven, Air-Conditioning Units" and Amendment

No . 1.

DESCRIPTION OF THE TEST SPECIMEN

The air conditioning unit was identified as follows;

Fedders-Quigan Corporation, Model 611-DG-53? Serial No.

2 !+5-03 1+. It was assigned NBS No. 129-57* This particular model

was known as "Fedders Weather Bureau Deluxe". Figures 1 and 2

show the assembled unit from front and rear, respectively.

In Figure 1, the discharge air opening is the circular one on

the left and the return air opening is on the right. The

circular discharge grille could be rotated to direct air in

any desired direction. Figure 3 shows the machine section

withdrawn from the cabinet housing. The unit was designed

for operation on alternating current 208 volts, single phase,

60 cycle. It was designed for installation in a window or

similar1 wall .opening, with the condenser section on the outside of such opening and the evaporator section on the inside

in the space to be cooled. The electrical controls for operation of the air conditioning unit were mounted as push-buttons

under the room air intake or return opening. They were

labeled "Exhaust, Cooling, Ventilate, and Off".

The unit was equipped with a single motor driving both

evaporator and condenser fans, rated at 1/20 horsepower. The

evaporator fan was of the centrifugal type, whereas the condenser fan was of the propeller type.

The air conditioner was equipped with a hermetic motorcompressor with the symbol "1 HP" painted on the case,

indicating that it was a nominal one-housepower unit.

According to a name plate on the unit, the unit was charged

with CHCIF2 , the compressor was one horsepower, and the

current requirement for cooling at 208 volts was 8.8 amperes,

with 85 percent power factor. A heavy-duty cord with polarized

plug was attached to the unit for connection to a suitable

electrical receptacle.
>

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TEST APPARATUS AND PROCEDURE

ASRE Standard No. 16-56, published by the American

Society of Refrigerating Engineers, entitled "Methods of

Rating and Testing Air Conditioners", was used as a guide in

setting up the apparatus and procedure used in determining

the capacity of the air conditioning unit. The net total

room cooling effect of an air conditioner, as defined by the

ASRE Standard, is the total useful capacity of the unit for

removing heat from the space to be cooled, expressed in Btu

per hour. Federal Specification OO-A-372, entitled "Air

Conditioning Units (Room and Space Coolers) Electric, MotorDriven, Self-Contained", referenced in the purchase specification, required a sensible to net total capacity; ratio of

from 70 to 80 percent. The apparatus was set up to provide

this information.

An insulated calorimeter was constructed in a tempera

ature-controlled test room, and the air conditioner was mounted

in one wall of the calorimeter. Figures 4 and 5 show the

calorimeter with the access door removed and in place,

respectively.!! In Figure 4 , which is a view through the calorimeter access door, the evaporator side of the air conditioner

can be seen as placed for test.

Also in Figure 4 , on the right, the duct which contains

the heaters and a fan can be seen. The fan at the lower left

was used to obtain satisfactory temperature distribution in

the calorimeter. Figure 5 shows the access door of the

calorimeter in place and shows some of the apparatus for sensing

and controlling humidity and temperature of the test room in

which the calorimeter was installed at the right side of the

photograph. The exterior and interior surfaces of the calori=

meter were covered with aluminum foil. All joints were taped

or otherwise sealed to minimize transfer of water vapor.

Figure 6 shows the evaporator side of the air conditioner as

installed for test. The humidity sensing element for the

discharge air can be seen on the left, and part of the grid

arrangement of five thermocouples can be seen on the face of

the return grille. The tube at the right contains the thermocouples and humidity sensing elements used to determine the

air conditionsodf the calorimeter. Air was drawn through this

tube by a small blower not shown in the Figure. Therperforated

plastic ball at the center right of Figure 6 is attached to

one leg of a micromanometer used to determine the pressure

difference between the calorimeter and the test room, and a
' : fi'I ii D*i ajsr?^ e*rorn lo desd arfBTs-' e_i" giilTHt- D9v*rs2do
-4-

similar ball, attached to the other leg of the manometer, was

positioned in the test room. Figure 6 also shows the control

panel arrangement of the air conditioner.

The calorimeter was calibrated for heat transfer, first

with a glass window in the opening for the air conditioner and

then with the air conditioner in place. This calibration was

used as a basis for computing the part of the sensible heat

load of the air conditioner that was contributed by heat

leakage through the calorimeter walls, floor and ceiling.

Electric heaters were mounted in a vertical metal duct with a fan at the top to provide the remainder of the sensible heat

load of the unit. A humidifier consisting of an electric

heating element immersed in water was also placed inside the

calorimeter to provide the necessary humidity. Make up water

for the humidifier was supplied from a vessel mounted on a scale outside of the test room.

The calorimeter was constructed to be reasonably airtight and provisions were made to assure equalization of

pressure between the inside and outside by removing air from

or introducing air into the calorimeter. This was done by

means of a small blower whose air delivery was regulated so

the pressure difference between the calorimeter and the test

room was zero plus or minus 0.002 inch water guage. Calibrated

watt hour meters were used to measure electric energy consumption.. Temperatures were measured by means of calibrated

thermocouples and an electronic constant-balance type of

potentiometer. Calibrated lithium chloride-coated sensing

elements and an electric hygrometer were used to measure

humidity of the calorimeter and test room. These humidity

measurements were checked with a 24-inch motorized psychrometer

.

The calorimeter was calibrated by heating the interior

to approximately 95F while holding the test room at about

75F and measuring the electric power required to hold this

temperature difference. Tests of calorimeter heat leakage

were made with the air conditioner in position and with a window in place of the air conditioner to compare the heat

leakage of the air conditioner and the window. The capacity

test of the air conditioner was continued for more than

four hours at steady state conditions.

TEST RESULTS

The desired test conditions and the actual conditions

observed during the steady-state test of more than four hours

are given in Table 1. The air conditioner was tested with
. . .

t' 3
TABLE 1

Capacity Test of Fedders Window Air Conditioner

Model 611-DG-53, Serial No. 245-034

Desired Test Conditions:

Air Conditions on Condenser Side

Dry Bulb Temp. , °F 95

Wet Bulb Temp., °F 75

Relative Humidity, % 40

Air Conditions on Evaporator Side

Dry Bulb Temp., °F 80

Wet Bulb Temp., °F 67

Relative Humidity, % 251

Voltage at Compressor Terminals 208

Observed Test Conditions:

Air Conditions on Condenser Side

Dry Bulb Temp., °F 95*3

Wet Bulb Temp., °F 75.

2

Relative Humidity, % 39 *7

Dry Bulb Temperature at Condenser Air Outlet, °F 121.9

Air Conditions on Evaporator Side

Dry Bulb Temp., °F 80.1

Wet Bulb Temp., °F 67.2

Relative Humidity, % 51*3

Dry Bulb Temperature at Evaporator Air Inlet 7 3*9

Air Conditions at Evaporator Outlet

Dry Bulb Temp., °F 56.2

Wet Bulb Temp., °F 54.0

Dew Point, °F 53*0

Air Conditioner Power Consumption, watts 1482

Air Conditioner Current, amperes 8.1

Voltage at Compressor Terminals 209

Power Factor, % 87.6

Sensible Cooling Ca-pacity, Btu per hour 5620
» ‘ •
TABLE 1 (continued)

Observed Test Conditions:

Latent Cooling Capacity, Btu per hour 2230

Total Net Cooling Capacity, Btu per hour 7 850

Sensible Heat Ratio, % 71.6

Cooling Capacity - power ratio, Btu per watt hour 5*3

Length of Steady-State Test, hours 4.57

-5-

the ventilating damper (s) closed but not sealed and some air

had to be added to the calorimeter during the test to maintain

the pressure in the calorimeter within 0.002 inch W.G. of

the test room pressure. The amount of air added was not

measured, and, therefore, no measure was made of the reduction

of total net cooling capacity due to this ventilating air

load

.

The total net cooling capacity of the air conditioner

was 7850 Btu per hour; the sensible cooling capacity was

5620 Btu per hour; the latent cooling capacity was 2230

Btu per hour. The sensible heat ratio was 71.6 percent and

the cooling capacity-power ratio was 5". 3 Btu per watt hour.

The average power consumption of the unit during the test

was 1482 watts at 209 volts. The current drawn was 8.1

amperes, and the power factor was 87.6 percent.

The temperature and humidity conditions during the test

averaged 80.1F dry bulb, 67 . 2F wet bulb, 5l*3 percent relative

humidity inside the calorimeter and 95»3F dry bulb, 75. 2F

wet bulb, 39.7 percent relative humidity in the surrounding

test room.

The temperature of the air entering the evaporator,

measured at the grille face, averaged 73»9F, and the temperature of the air leaving the condenser averaged 121. 9F.

The heat transfer rates of the calorimeter walls, floor

and ceiling, determined by calibration first with the air

conditioner in position and then with a window in place of

the air conditioner were, respectively, 17*5 Btu per hour

(°F) and 17.8 Btu per hour (°F).

No tests were made to determine any performance

characteristics other than those described and relating to

cooling capacity.

CONCLUSIONS AND DISCUSSION

The Fedders air conditioner tested had a total net

cooling capacity in excess of 7500 Btu per hour, the minimum

capacity requirement of the contract under which a number of

air conditioners similar to the test specimen were procured.

The observed capacity of 7850 Btu per hour exceeds this

requirement by about 4.5 percent. Federal Specification

OO-A-372, referenced in the contract, contains many requirements for these Type I air conditioners, but conformance with
* '

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requirements other than those relating to capacity was not

determined as a part of these tests. The measured sensible

cooling capacity ratio of 71.6 percent was within the range

of 70 to 80 percent permitted by the specification and the

computed power factor of 87.6 percent was satisfactory.

The measured cooling capacity to power input ratio of 5*3

Btu per watt hour, however, fell short of the Federal

Specification requirement for Type I units of 5*5 Btu

per watt hour minimum.

Two factors may have been instrumental in holding

the measured capacity, to 7^50 Btu per hour. First, some

ventilation occurred when the ventilating dampers were

closed requiring the introduction of test room air into the

calorimeter to hold balanced pressures inside and outside of

the calorimeter. Since this air flow was not measured, no

figure can be given for the size of the penalty imposed. If,

for example, 15 cubic feet per minute of unwanted ventilation

occurred, at the test conditions, this would reduce the total

net cooling capacity by approximately *+50 .Btu per hour.

Secondly, apparent diort ^circuiting of some of the cold disp

charge air back into the return grille, causing the average

inlet evaporator air at the face of the grille to be about

7^F whereas the calorimeter air temperature, measured a short

distance from the front of the grille was about 80F. If it

is assumed that this difference of 6 degrees was directly

reflected in a corresponding change in the compressor

suction pressure, eliminating the short-circuiting of the cold

air could have raised the cooling capacity a maximum of about

ten percent. The use of a calorimeter somewhat smaller than

the apparatus recommended in ASRE Standard 16-56 may have

contributed to the short-circuiting but this is considered

unlikely.

The small difference observed in the heat transfer rate

of the calorimeter with the air conditioner in position as

compared to that with a window in place of the air conditioner

was interesting. The difference, 0.3 Btu per hour (°F), was

probably smaller than the deviations that would have been

observed in repetitive tests, but showed that, if the

difference was real, the air conditioner did not cause greater

heat leakage than the glass it replaced.

The total net cooling effect was determined by the

following equation:

Qtr ~ 3 Al(Er

+ Qxc + (^wl “ ^w2

)

wr
•

•

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whearei

Qtr' = total net cooling effect, Btu per hour

£Er

= total power to calorimeter, watts

Ql_ c = heat leakage of calorimeter, Btu per hour

hw-] = enthalpy of water supplied to the calorimeter to maintain

humidity Btu per lb.

h^2

= enthalpy of condensed water leaving the calorimeter,

assumed to be at 54-F, Btu per lb

W

p = water evaporated in humidifier, lb per hour

The sensible cooling effect was computed using the

following equation:

Qsc ~ Qtr “ ^060 W

p

where

:

Q sc

= sensible cooling effect, Btu per hour

Qt r = tptajj. net cpp^lng effect. Btu per hour

1060 = latent heat of evaporation of water (from ASRE 16-56)

W

p = water evaporated in humidifier, lb per hour

Although many manufacturers advertise that "nominal

3/4- horsepower" air conditioners have a capacity of 7500 Btu

per hour or more at the standard conditions of this procurement, the unit submitted for these tests contained a compressor

marked "one horsepower" by the manufacturer.
.


Figure









U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A, V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

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