NATIONAL BUREAU OF STANDARDS REPORT

223^

PERFORMANCE OF A YORK 3/4 HP WINDOW

AIR CONDITIONING UNIT, MODEL 24-1

by

Henry Karger

Paul R. Achenbach

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Charles Sawyer, Secretary

NATIONAL BUREAU OF STANDARDS

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

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003=40-4700 F-lv-uary 2 , 1953 223^

PERFORMANCE OF A YORK 3/4 HP WINDOW

AIR CONDITIONING UNIT, MODEL 24-1

by

Henry Karger

Paul R. Achenbacb

Heating and Air Conditioning Section

Building Technology Division

f* Q-r*

Headquarters

United States Marine Corps

Department of the Navy

Washington, D, C.

The publication, reprinti

unless permission isobta

25, D, C, Such permissi

tally prepared If that a|

Approved for public release by the

Director of the National Institute of

las been speclfi- Standards and Technology (NIST) on October 9, 2015.

Performance of a York 3/4 HP Window

Air Conditioning Unit, Model 24-1

by

Henry Karger

Paul R. Achenbach

Abstract

Performance tests were made of a 3/4 HP window air

conditioning unit, Model 24-1, manufactured by York

Corporation to determine compliance with Federal

Specification OO-A-372, dated July 26, 1951, and

Amendment 1 dated May 20, 1952. Performance was

evaluated with respect to the paragraphs of the

specification entitled capacity-rating test, overload test, condensation test, low refrigerant temperature test, minimum air quantity, and outside air

quantity. The capacity tests, made in accordance

with the requirements of Standard l6-R of the American

Society of Refrigerating Engineers, showed that the

capacity was ^^.6 percent of the required value as

received and 94.5 percent of the required value after

sealing some air leaks and adding a running capacitor

to the compressor mPtor. The running capacitor was

required to permit satisfactory operation at 90 percent of rated voltage. All other specification requirements on performance were met.

I. INTRODUCTION

In accordance with a request from Headquarters, United States

Marine Corps, dated September 4, 1952, tests of a 3/4 HP electric,

self-contained, window-type air conditioning unit were made to determine compliance of this unit with the performance requirements

of Federal Specification OO-A-372, dated July 26, 1951, modified

in Amendment 1, dated May 20, 1952, as outlined in Contract

NOm-63744 , issued by the United States Marine Corps on June 30,

1952 . The air conditioning unit was manufactured by ^York Corporation,

York, Pennsylvania. The tests were made in accordance with the

requirements of paragraph 4.3 of Federal Specification OO-A-372.

II. DESCRIPTION OF TEST SPECIMEN

Two air conditioning units were submitted for tests by the

manufacturer. The first sample submitted was returned to the manufacturer because of three obvious deviations from the requirements

of the specifications:

- 2 -

1. The condenser fan of the unit was bent out of shape.

2. The refrigerating system of the unit contained service

valves. Such valves are not permitted on a hermetic refrigerating system, which was required by the contract.

3. The unit contained a capacity modulating device. The

manufacturer stated that this device would not be furnished

on units for delivery under the contract.

The second sample submitted for tests was identified as

follows

:

(NB3 Test Specimen 90-52)

York Corporation, York, Fa.

F'odel 2Zi-l

Serial A142729

3/4 Horsepower

All tests were made with this specimen. The unit was built

for operation on alternatin!? current, 115 volts, single phase,

60 cycle. It was designed for Installation :n a window, X'/ith

the condenser section of the unit on the outside of the window

and the evaporator section on the inside of the xvindow in the

space to be corle'';. ’"he unit xvas enclosed in a sheet steel hous^-

ing,. and a decorative housing made of s.teel and plastic surrounded this on the room side of the unit.

The electrical controls for operation of the air conditioning unit were located on the top of the evaporator section, under

a small flap mounted flush in the decorative cover. A threenosition control switch v;as used v;hich could be placed in the

’’Fan-’, ’’Off”, or ’’Cool” positions. If placed in the ’’Fan” posi-’

tion, only the single motor driving both condenser and evaporator

fan would operate. If placed in the ’’Cool” position, the compressor as xvell as the fan motor would operate. The flap under

which the electrical control switch was located, can be seen in

Fig, 1,

A fresh-air damper was located at the bottom edge of the

front of the evaporator section, as *can be seen in Fig. 2 just

below the filters. The damper was hinged at the bottom and

could be opened by pulling outward and downward on the handle

shown in Fi.o-^ 2. The discharge grill was made of plastic and

wa.3 rotatable on horizontal pivots in the top of the front

section of the decorative cover.

The condenser fan was of the propeller type and a water

slinger was located in front of this fan to throw the condensate

from the evaporator coil against the condenser for evaporation

on the outside of the conditioned space. A car^llary tube was

used as the refrigerant flow control.
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A view of the unit from the room side is shown in Fig. 1.

Fig. 2 is the same view of the unit, with the top of the condenser section and the decorative cover 'of the evaporator section rem.oved. A view of the condenser and part of the machine

compartment is shown in Fig. 3. Fig. 4 is a top view of the

unit, showing the location of the compressor, the fan motor,

the fans, and the insulated partition separating the evaporator section from the condensing unit compartment.

The physical dim.ensions of the unit were as follows:

Length, inch

Width, inch

Height, inch

Weight, including sill adapter plate.

33 3/^

26 1/4

14 3/S

lbs. 179

The unit was equipped with a York motor-compressor. Model 646D,

Series B, rated at 3/4-horsepower, 10 amperes, and 115 volts.

The fan motor -was a Delco Model A-5153 motor rated at 1/9-

horsepower, 2. S amperes, and 115 volts.

III. TEST PROCEDURE

Circular No. I6-R, published by the American Society of

Refrigerating’ Engineers , entitled ^Methods of Rating and Testing Air Conditioners", was used as a general guide in selecting

the procedure to be used in determining the capacity of the air

conditioning unit. The ASRE circular states that the capacity

rating of self-contained air conditioning units shall be the

net total room cooling effect in British Thermal Units per hour.

The following apparatus was used to determine this net room

cooling capacity:

A protable, 150 cu, ft, warehouse normally used for the

refrigerated storage of various materials was used as a calorimeter, The air conditioning unit was mounted in an opening

in one wall of the warehouse in such a manner that the evaporator side of the unit was on the inside of this warehouse, and

the condenser side was on the outside of the warehouse. The

warehouse, with the unit in place, was calibrated to determine

the heat transmission per degree temperature difference between

the inside and outside, which constitutes part of the sensible

heat load. Electric heaters were placed on the inside of this

warehouse-calorimeter to provide the remainder of the sensible

heat load for the air conditioning unit. A humidifier consisting of an electric heating element immersed in water was also

placed inside the calorimeter to provide the necessary humidity.

The calorimeter was made as airtight as was considered necessary,

and provisions were made to measure the amount of air which was

introduced into or exhausted from the warehouse-calorimeter by

the air conditioning unit during operation. This was done by

- 4

-

removing air from or introducing air into the calorimeter

through a pipe by means of a blower. The air quantities were

measured by calibrated gas meters or a pitot tube placed inside of the pipe. The amount of air flowing through the pipe

was rep:ulated by a throttling valve so that the pressure difference between the inside and the outside of the calorimeter

was zero ± 0.002 in. W.G. Calibrated watthour meters were

used to measure all electric energy consumption. Temperatures

were measured by means of calibrated thermocouples using an

electronic, constant-balance type potentiometer. Humidity

measurements were made utilizing calibrated lithium-chloridecoated elements in conjunction with a micro-am.meter . Humidity

measurements observed with this electric hygrometer were checked regularly with a 24” m.echanical psychrometer

.

The results obtained with this testing m.ethod will be essentially the same as the results obtained by follov/ing the

t'esting method outlined in ASRE Circular 16-R even though a

less elaborate calorimeter was used. The most important difference is that the amount of heat rejected by the condenser

of the air conditioning unit was not measured to compare with

and check the total net cooling effect measured in the calorijseter because such additional apparatus has not been available

at this Bureau, ASRE Circular 16-R requires that this heat

balance should be obtained to check the accuracy of the capacity

determination made on the room side of the air conditioning unit.

However, a constant check of all instruments used during the

test made here, such as comparing watthour meter readings with

voltage and current readings taken simultaneously on the electric

heaters used to provide the sensible and latent heat loads, checking of the electric hygrometer elements before and after each

test with a precision mechanical psychrometer, and frequent

checking of the potentiometer against an ice-bath reference,

are believed to make the accuracy of the results obtained as

good or better than the accur^acy of the results obtained using

the test method outlined in ASRE Circular 16-R.

In the test apparatus used by this Bureau, the condition

of the air (i.e. dry bulb temperature and relative hum.idity)

on the room side of the air conditioning unit were determined

at the entrance to the evaporator itself because of the limited

space in the calorimeter. Circular l6-R requires that the dry

and wet bulb temperature (or relative humidity) of the room air

be mieasured at a little distance away from the evaporator inlet,

so that any short-circuiting of the conditioned air from the

discharge to the inlet of the unit, which may be inherent in

the construction of some air conditioners, would not result in

a higher capacity rating than was justified. However, since

there was practically no possibilityof short-circuiting between

the outlet and inlet of the evaporator in the York unit under

test, this difference in location of the measuring instruments

is believed to have had no effort on the measured capacity of

the unit.

Measurements of the quantities of air circulated were

made by means of a pitot tube located inside a smooth, round

duct o This duct was connected to the outlet of the evaporator or condenser fan by means of a plenum chamber and an exhaust blower was attached to the other end of the duct. The

air flow through the duct was regulated by a throttling device so that the static pressure at the evaporator or condenser

fan outlet was zero ± 0,002 in ¥,G. with respect to the pressure

in the test room to determine the free-air delivery of the fans,

IV, TEST RESULTS

Tests were made of the air conditioning unit to determine compliance with the requirements of the following paragraphs of Federal Specification OO-A-372:

(A) Capacity Test (paragraph 4.3<«1)

Performance Factor (paragraph 3»5«1.1)

Sensible Heat Ratio (paragraph 3.5.1)

(B) Overload Test (paragraph 4. 3. 2,1)

(C) Copdensation Test (paragraph 4. 3. 2, 2)

(D) iLow-Refrigerant-Temperature Test (paragraph 4. 3. 2. 4)

(E) Minimum Air Quantities (paragraph 3.9.1)

(F) Outside Air Quantity (paragraph 3. 9. 1.1)

The results of the above tests are discussed in the following

paragraphs

.

( A ) Capacity Test

The results of the capacity tests are summarized in Table 1.

Test number 1 was made with the unit as received from the manufacturer, After this test, a representative of the manufacturer

sealed up some air leaks in the partition on the unit to cut down

the undesired air exchange between condenser and evaporator compartments, Test number 2 was made after the sealing was done.

At a later date, it became necessary to install a 17.5 mfd running

capacitor in the electrical circuit of the unit in order to enable

it to meet the requiremaents of the Overload Test of para.q;raph

4.3 o 2,1, This running capacitor was furnished by the manufacturer and was installed by Bureau personnel under direction of a

representative of the manufacturer. The capacity test was then

repeated and the results of this final run are tabulated under

test number 3. As can be seen fromi Table 1, the unit did not

meet the requirem.ents of the contract for Total Net Cooling

Capacity, the capacity being 437 BTU/hr less than the required

gOOO BTU/hr in test number 3. The air conditioner did meet the

requirements of Sensible Heat Ratio and Performance Factor, as

is shown in Table 1 for test number 3.

^ TABLE 1

Capacity Tests of York Model 24TM1 Windov/ Air

Conditioner, NBS Specimen 90-52

Test Nuinber

Ambient Air Conditions

Dry Bulb Temp., °F

Wet Bulb Temp,, °F

Relative Humidity, ^

Dry Bulb Temp, at Condenser

Outlet, °F

Air Conditions at Evaporator Inlet

Dry Bulb Temp op

op Wet Bulb Temp

Relative Humidity, %

Dry Bulb Temp.,

Wet Bulb Temp.

,

op

op

Compressor Power, watts

Fan Motor Power, watts

Total Power, watts

Total Net Cooling Capacity,

BTU/hr

Latent Heat Load, BTU/hr

Sensible Heat Load, BTU/hr

Sensible Heat Ratio, %

Performance Factor,

BTU/hr per watt

Specification

and Contract Observed Performance

Requirement

1 2 3

95.0 95.4 95.2 95.6

75.0 73.^ 74.0 74.8

1+0 ,

0

36,5 37.7 38.5

11B.6 117.

S

118.2

Inlet

^0,0 79.5 79.9 79.7

67.0 66.6 67.0 66. S

51.0 50.6 51.0 51.2

Outlet

62.9 63.3 63.5 — 60.0 60,4 60.5

1062 1077 1011

172 170 169 — 1234 1247 1150

^000 70^4 7566 7563

1250 15^0 1716

5^34 59^6 5547

70-^0 ^2 79 77

5.5 5.7 6,1 6,4

{ minimum)

Terminal Voltage 115 115 115 115

- 1 -

(B) Overload Test

The specification requires that tests be made of the air

conditioning unit at 90' percent, 100 percent, and 110 percent

of rated voltage by operating the unit continuously for four

hours at the following conditions:

Temperature of ambient air

1^5°F dry bulb, ^0°F wet bulb

Temperature of air entering evaporator

95°F dry bulb, 75°F wet bulb

After the 4-hour test periods, the current shall be turned off

for 10 seconds and then reapplied, and the unit shall resume

normal operation within 5 minutes. In addition, during the

tests the unit shall operate without interruption caused by

tripping of the motor-overload devices. The average corfditions

maintained during the three tests are summarized in Table 2.

TABLE 2

Overload Tests of York Model 24-1 Window Air

Conditioner, NBS Specimen 90-52

Test Number 1 2 3

Ambient Air Conditions

Dry Bulb Temp,, °F 115.7 115.5 115.6

Wet Bulb Temp., °F SOoO SO.l ^0,0

Air Conditions at Evaporator

Dry Bulb Temp., °F

Inlet

94.5 95.0 94.9

Wet Bulb Temp., ®F 74 9 4 74.6 74.6

Terminal Voltage 103.5 115.^ 126,2

Percent of rated Voltage 90,0 100.7 109.7

Power Consumption, watts 1453 1390 1405

Current, amperes 17.0 15.3 15.4

As submitted, the unit would not operate satisfactorily at 90

percent of rated voltage. A running capacitor was then installed on the unit, after which no further operational troubles

were encountered. No tripping of the overload mechanism occurred during the tests, and .‘the unit started satisfactorily

after each of the 10-second interruptions of electric current,

( C ) Condensation Test

As required by the specification, the unit was operated

for six hours under the following conditions:
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Temperature of ambient air

^0°F dry bulb, 70°F wet bulb

Temperature of air entering evaporator

^0°F dry bulb, ?5°F wet bulb

All condensate collected on the evaporator coil was diffused

by the unit in a satisfactory manner, and the condensate receiver did not overflow at any time during the test. The average conditions maintained during the test were summarized in

Table 3.

TABLE 3

Condensation Test of York Model 24-1 Window

J\.ir Conditioner, NBS Specimen 90-52

Ambient Air Conditions

Dry ^ulb Temp., °F 79*9

Wet ^Ib Temp., °F 75.3

Air Conditions at Evaporator Inlet

Dry Bulb Temp.', °F BO,

6

Wet Bulb Temp., °F 76.1

( D) Lof/i^-Refrigerant-Temperature Test

Federal Specification OO-A-372 requires that a unit

equipped v/ith a capillary tube to control refrigerant flow

should be operated under conditions of ambient air and air

entering the evaporator of 75°F dry bulb, 63 °F wet bulb to

determine whether or not any evidence of ice formation is

shown on the evaporator coil of the unit. In addition, a

superheat of at least 5°F must be evident in the lowside refrigerant circuit. The unit was operated in accordance with

this requirement under the above conditions. No evidence of

ice formation was observed, and the superheat observed was

36.9°F. The average conditions maintained during the test

are shown in Table 4.

TABLE 4

Low-Refrigerant-Temperature test of York Model 24-1

Window Air Conditioner, NBS Specimen 90-52

Ambient Air Conditions

Dry Bulb Temp. , °F 75 «

4

Wat Bulb" Temp., ®F 62.

B

Air Conditions at Evaporator Inlet

Dry Bulb Temp., °F 76.5

West Bulb Temp., °F 64.2

Superheat , °F 36.9

- 9

( E) Minimum Air Quantities

The air quantities circulated by the evaporator and condenser fans were determined on this unit. Paragraph 3.9.1 of

the specification requires a minimum air circulating capacity

for each fan of 30 ’cfm per 1000 BTU/hr required cooling capacity,

or, for this unit, a minimum of 240 cfm. As can be seen from

Table 5, below, the air conditioning unit met these requirements

adequately.

TABLE 5

Air Circulating Capacities of York Model 24-1

Window Unit, NBS Specimen 90-52

Specification Air Temp, of Air

Requirement Capacity OF

cfm cfm DB WB

Evaporator Fan 240 (minimum) 320 79 62

Condenser Fan 240 (minimum) 450 51 62

Ventilating Air 40 (minimum) 110 99 76

(F) Outside Air Quantity

The amount of outside ventilating air introduced by the

unit into the conditioned space through the fresh air clamper

was measured and found to be in compliance with the requirem.ents of paragraph 3. 9. 1.1 of the specification. The results

are summarized in Table 5, above. In addition, the amount of

unwahted ventilating air which leaked through the air conditioner operating v^ith the damper closed but not sealed was measured

during the capacity tests. This am.ounted to 10.5 cfm. during

the first capacity test. After the unit was sealed, however,

as described in the section on capacity tests, there was no

measurable leakage of air through the unit.

V. 3U1VFARY AND CONCLUSIONS

As received, the York air conditioning unit tested had a

capacity of percent of the specified value and would not

operate satisfactorily at 90 percent of rated voltage as required bv Federal Specification OO-A-372. After the installation of a runninsr capacitor and sealing of some air leaks in

the partition between the evaporator and condenser sections,

the unit operated satisfactorily at 90 percent of rated voltage and the total npt cooling capacity was observed to be 94.5

percent of the required capacity. It is believed that the errors

in the measurements made during the capacity test did not exceed 2 percent.

The air conditioner specimen met all other requirements of

section 4.3 entitled Acceptance Test and Inspection of the Federal Specification on Air Conditioning Units OO-A-372 and Amendment 1.

FIG

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THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

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

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These include the development and maintenance of the national standards of

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Bureau of Standards (25 cents). Both are available from the 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.
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