NATIONAL BUREAU OF STANDARDS REPORT

2241

MODEL lOP 045 FRIGIDAIRE ELECTRIC DRINKING

WATER COOLER

Henry Karger

C. W. Phillips

P. 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 mbs REPORT

1003-40-4700 February 3 , 1953 2241

MODEL lOP 045 FRIGIDAIRE ELECTRIC DRINKING

v;ater cooler

manufactured by

Frigidaire Division

General Motors Corporation

by

Henry Karger

C. W. Phillips

P. R. Achenbach

Heating and Air Conditioning Section

Building Technology Division

to

Philadelphia Quartermaster Depot

U. S. Army

Philadelphia, Pa.

The publication, reprinfli

unless permission is obtal 25,D. C, Such permlsslc

cally prepared If that a;

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

Model lOP 045 Frigidaire Electric Drinking

Water Cooler

by

Henry Karger

C. W. Phillips

P. R. Achenbach

Abstract

A specimen of Model lOP 045 electric drinking water

cooler manufactured by the Frigidaire Division of

General Motors Corporation was tested to determine

compliance with Federal Specification 00-C-566b and

Amendment 2, as modified in the Quartermaster Invitation to Bid No. QM 11-009-52-1263. Performance

tests only were made as requested. The specimen, as

submitted, met all requirements of the performance

tests except those for the drinking-water thermostat

and one of the requirements for the water regulator

and valve. The latter deficiency was corrected by

adjustment. The installation of a second drinking-,

water thermostat by a representative of the manufacturer did not permit the cooler to meet the requirements of the thermostat test.

I. INTRODUCTION

In accordance with a request from the Quartermaster Inspection Division, Chicago Quartermaster Depot, in a letter

dated July 17, 1952, tests of one specimen of Model lOP 045

electric drinking water cooler manufactured by Frigidaire

Division of General Motors Corporation, Dayton, Ohio, were

made to determine compliance with Federal Specification

00-C-566b, with Amendm.ent 2 dated January 21, 1952, and as

m.odified by the exceptions in the Quartermaster Invitation

for Bid No‘. QM 11-009-52-1263.

The performance of the specimen was determined by direct

tests as described in the Federal Specification and the pertinent modifications. Special tests described herein were made

to determine the performance of certain components. Inspections

to determine compliance of the specimen with regard to materials and construction were not requested by the Quarterniaster

Inspection Division. The tests made did not require any dismantling of the specimen cooler.
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II. DESCRIPTION OF TEST SPECB'^EN

The water cooler specimen submitted for test was identified as follows:

NBS Test Specimen 96-52, Specification T^.'-pe I, Size 10

Frigidaire Model lOP 045

Serial Number 5440S29

The cooler specimen was housed in a formed, one-piece steel

enclosure which constituted the back and the sides of the

cooler. This housing enclosed the condensing unit compartment and evaporator section and provided structural support

for the unit. The front panel could be removed, after loosening two screws at the bottom of the panel, by pulling the panel

away from the cooler at the bottom and dovm from, the recess

formed by the top of the cooler. With the exception of the

bubbler solenoid valve, all other controls and electric connections were accessible from the front side after the front

panel was removed. It was necessary to rem.ove the basin top

of the cooler to expose the bubbler solenoid valve for replacement or servicing.

A front view of the cooler is shown in Fig, 1, Fig. 2

shows a rear view of the cooler, and the machine compartment

is shovm in Fig, 3. The dimensions and weight of the cooler

were as follows:

Height, in. 41-1/4

Width and depth, in, l6

Weight, including wood shipping base, lbs. 140

III. TEST PROCEDURE

Tests of the specimen were made to determine compliance

with the performance requirements of the following paragraphs

of the specification, some of v/hich were modified in the

Invitation to Bid:

(1) D-1, E-1, F-3& Capacity Test

(2) D-la, F-3d Peak Draw Test

(3) D-lb, F-3b Maximum Operating Test

( 4

)

D-6a Jet of Water

(5) D-6d Water Regulator and Valve Test

(6) D-lOd Refrigeration Control Test

(7) D-lOd(l), F-7 Freezing Test

{^) D-llb Motor Overload Protection Test

(9) D-13a Operation at Varying Water Pre

(10) D-13b Drain Capacity

(11) D-lla, F-3c Overload Test

All performance tests listed above were conducted in a

temperature-controlled room under the general conditions set

forth in paragraph F-3'^ of the Federal Specification, except

where the paragraph applicable for a specific test called for

a different set of conditions. Temperatures were measured by

means of calibrated therm.ocouples using an electronic, constantbalance type of potentiometer. Accuracy of this instrument was

checked at intervals during the tests by means of ice-bath

references. Inlet and outlet drinking water temperatures were

measured by thermocouples in thin-walled stainless steel wells

four inches long, mounted so that the thermiocouple junctions

were approximately in the plane of the exterior surface of the

cooler cabinet. Water-flow rates were determined in a m.anner

that did not interfere with the flow of cooled water through

the precooler. Supply water temperatures and pressures were

controlled by close-differential mechanical devices.

Additional information on the test procedure for particular tests is included with the report of the test results to

further clarify how the results were obtained in cases where

the specification did not provide adequate details.

IV. TEST RESULTS

The following paragraphs show the results obtained on the

cooler specimen during the perform.ance tests listed under the

section on Test Procedures.

(1) Capacity Test (Paragraphs D-1, E-1, F-32^)

Table 1, which follows, summarizes the results obtained

during the capacity test and compares the observed performance

with the specification requirements. The entry entitled ’’Drinking Water Flow Rate, Corrected for 30°F Temperature Difference,

gph” gives the calculated water flow rate for a 30°F difference

between supply and drinking water temperatures when the actual

difference during the test was not exactly 30°F. Table 1 shows

that the observed capacity of the specimen exceeded the required

capacity for Type I, Size 10 coolers.

TABLE 1. CAPACITY TEST OF SPECIMEN NBS 96-52

Performiance Characteristics

Required Observed

Performance Performance

Ambient Temperature, ®F 90

Electric Power Input, watts

Terminal Voltage 1L5

Total Current, amps

Drinking Water, Inlet Temp., ®F SO

Drinking Water, Outlet Temp., °F 50

Drinking Water, Temp. Diff . , °F 30

Spill through precooler, % 60

Drinking Water Flow Rate, observed, gph

Drinking Water Flov/ Rate, corrected

for 30 °F temp, difference, gph

S9.2

264

115

3.6

50.0

50.1

29.9

59.7

11.7

9.0 (M:n.) 11.7

- 4 -

(2) Peak- Draw Test (Paragraphs D-la, F-3ci)

The specification required that 37-1/2 percent of the

required hourly capacity shall be drawn off in 15 minutes.

The water temperature at the beginning of the 15-minute period

must not be lower than 45°F or higher than 50 °F and shall not

rise more than 10°F at any time during the 15-minute period.

The water must be drawn off, beginning immediately after the

compressor-motor cuts off in a normal cycle, in not less than

three or more than six equal intervals per gallon of required

draw-off capacity. The water must be drawn off at a rate of

not less than 1/2 gallon per minute per bubbler. It was assumed that in accord with general requirements of paragraph F-3a,

60^ of the cooled water should be allowed to flow through the

precooler as water was being drawn.

For this test, the specimen was equipped with a selfclosing, hand-onerated stop valve adjusted to permit water

to flow at a rate of 1/2 gallon per minute when opened.

Water was drawn off in 54 equal samples, each consisting of

a 40^ portion, drawn first, and a 60^ portion, drawn second.

The kOfo portion, representing water consumed, was poured into

a container for subsequent weighing. The 60fo portion was poured into a vessel of low thermal mass immediately prior to each

subsequent draw. This vessel allowed the 60% portion to flow

into the precooler during the time required for the entire subsequent draw.

A second thermostat v/as installed in the specimen cooler

by representatives of Frigidaire Division in connection with

the thermostat requirements. Peak draw tests were made with

each of the two thermostats furnished, and compliance with

peak draw requirements was observed in both cases. Using

thermostat ^1, a temperature rise of ^.5°F was observed, the

initial outlet drinking water temperature being 46.5°F. Using

thermostat §2^ a temperature rise of 5.5°F was observed, with

the initial outlet drinking water temperature being 49.9''F,

(3) Maximum Operating Test (Paragraphs D-lb, F-3b)

The specification required that the cooler should start

and operate satisfactorily, and should be tested for at least

^ hours of continual operation under conditions of 110°F

ambient temperature, 100°F inlet water temperature, 50°F outlet water temperature, and, it was assumed in accord with

paragraph F-3&, with o0% spill through the precooler.

The cooler was operated for eight hours under the above

conditions. At the conclusion of the test, the cooler was

turned off and left idle for five minutes and then restarted

to determine whether or nit would start satisfactorily without

causing the motor overload mechanism to operate. The cooler

- 5 -

started and operated satisfactorily during this test.

TahJ£ 2 shows the avera?^e conditions maintained during

•fhe maximum operating test.

TABLE 2o MkXimn OPERATING TEST OF SPECIMEN NBS 96-52

Performance Characteristics

op

op

Ambient Tem.perature , °F

Electric Power Input, watts

Terminal" Vbltage

Total Current, amps

Drinking Water, Inlet Tem.p.,

Drinking Water, Outlet Temp.,

Drinking Water, Temp. Diff . , °F

Spill through precooler, %

Drinking Water Flow Rate, observed, gph

Drinking Water Flow Rate, corrected for

50°F temp, difference, gph

ired

rmance

Observed

Performance

110 109,4

-- 29^

115 115 — 3,9

100 101 ol

50 50.0

50 51,1

60 60.

g

— 6,6

M — 6.7

(4) Jet of Water (Para?rraph D-6a)

The position of the Jet of water relative to the orifice,

guard, and cooler basin was observed and was found to be in

compliance with the specification requirements.

(5) Water Regulator and Valve Test (Paragraph D-6d)

The specimen cooler was equipped with an adjustable,

automatic water-pressure regulating valve and a foot-pedal

actuating an electric switch which opened the bubbler solenoid

valve. The adjustment for the pressure regulating valve was

accessible after removal of the front panel. The foot pedal

switch also vras accessible after removal of the front panel;

however the basin top of the cooler had to be removed if service on the solenoid valve became necessary. The solenoid

valve could be removed from the cooler without breaking the

cooling unit insulation.

Observations were made of the stream height, through distance, and rate of water discharge on the specimen cooler for

inlet water pressures of approximately 20 psig and 75 psig.

At 75 psig inlet pressure, the solenoid valve did not open

properly on the cooler. A representative of the manufacturer

found the valve to be out of adjustment and corrected the difficulty. After the adjustment, the valve operated satisfactorily. The results of the observations are summarized in

Table 3 below.
f
- 6 -

Water did not spurt from the bubbler of the cooler

specimen when the stop valve was opened except when purging; air during initial filling of the cooler. Mo objectionable spashing of the drinking water on the cooler top was

observed

,

TABLE 3. WATER PRESSURE REGULATOR PERFORJIANCE

COOLER SPECIMEN N3S 96-52

Supply Water Pressure, psig

Stream Height above nozzle, in.

Stream Height above guard, in.

Throw Distance from nozzle, in.

Flow rate, gph

20

3-1/2

1/4

3 - 1/2

26.7

75

5

1-3/4

5-1/2

36.9

(6) Refrigeration Control Test (Paragraph D-lOd)

The cooler specimen was equipped with a thermostat which

controlled the operation of the compressor motor. The thermostat was readily accessible for adjustment and servicing when

the front panel of the cooler was rem.oved, and could be replaced without breaking the main insulation of the cooling

unit housing.

Adjustment of the thermostat could be affected by turning a knob. The therm.ostat caused the cooler to deliver

colder water when this knob was turned in a clockwise direction,

and caused delivery of warm.er water if the knob was turned in

a counterclockwise direction. In addition, a small adjusting

nut located on top of the thermostat casing could be used to

change the range of the thermostat.

The specification requirem.ent as miodified in Amendment 2

stated in part:

''Unless otherwise specified, the temperature control of the water shall be adjustable between 45°F

and 55°F and shall have a differential of not more

than plus or minus 5°".

This sentence has been interpreted by this Bureau for all

water coolers tested for the Office of the Quart erm.aster General to require that the adjustment of the thermostat shall

cover a range large enough to result in delivered water at

control point temperatures ranging from 45°F or lower to 55°F

or higher. Since the rate of water withdrawal for v/hich these

control points should result is not given in the specification,

the rate of l/2-hourly capacity has been selected with the

water being drawn at equal intervals of time in batches of

12 f1 . oz . each

.

_ 7

-

In the light of this interpretation, the cooler specimen did not meet the requirements of paragranh D-lOd. For

the rate of withdrawal m.entioned above, and using the original thermostat furnished with the cooler, the average delivered water temperature at the lowest setting was 40,7°F

with a maximum deviation from this average of 0,9®F, and

for the highest setting of this thermostat, the average

temperature was 41o^°F with a maximum deviation of 0,4°F

from this average. In testing this thermiostat, only the

knob in front of the thermostat, and not the adjusting nut

located on top of it, was used to change the range of thermostat operation.

After this thermostat was reported in non-compliance,

a representative of the manufacturer installed a second

therm.ostat. Tests of this thermostat indicated that at its

lowest setting the average delivered water temperature was

41..4°F with a maximum deviation from this average of 1.1°F,

and at its highest setting the average temperature was

4^.2°F with a maximum deviation of 3*2°F from the average.

In testing this thermostat, the knob as well as the top adjusting nut was used to change the range of thermostat operation. The representative of the manufacturer requested that

the performance of the cooler specimen be judged on the basis

of the second thermostat tested. As can be seen from these

results, the cooler did not meet the requirements using either

the first or the second therriostat.

(7) Freezing Test (Paragraph D-lOd (1), F-7 modified)

The cooler specimen had a temperature-sensitive switch

in the condenser fan circuit, which would stop operation of

the condenser fan when the ambient temperature dropped below

a predetermined point. This switch, in conjunction with the

automatic expansion valve used as refrigerant flow control,

served as protection against feezing by assuring a sufficiently high entrance pressure to the expansion valve so that it

would always operate at above-freezing temperatures.

Three freezing tests, each of 4^ hours duration, were

made, the first in an ambient of 50 °F, the other two in an

ambient of 35°F. The drinking-water thermostat was shunted,

and the cooler was operated under the above conditions. No

freezing was observed during any of the three tests and drinking water could be drawn from the cooler at the conclusion

of each test.

{^) Motor Overload Protection Test (Paragraph D-llb

modified

)

Paragraph D-llb states in part: ^’Motors shall be protected in case of failure of the starting mechanism or excessive

overload by a thermal protective device of proper current rating.
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which shall open the circuit before the motor windin/^s reach

a temperature that will injure the motor.”

The cooler specimen was equipped with such a device. To

determine the protection afforded, two tests were made, both

in a 90°F ambient temperature, with supply water flowing

steadily through the cooler at a rate slightly in excess of

30 gallons per hour. First , the power lead to the starting

winding of the compressor motor was disconnected. The cooler

was then energized electrically, and measurements were made

of the motor running-winding resistance immediately following

each cutout of the overload protector. The overload protector

was allowed to function until successive resistance measurements at the time of cutout were no longer increasing and the

temperature of the winding was com.puted on the basis of the

highest resistance observed. The highest motor-winding temperature computed under these conditions was 206®F. Second . the

condenser fan was disconnected, the air flow over the condenser

was blocked, and the cooler was allowed to continue in operation. Under these conditions, the highest motor-winding temperature computed from resistance observations was 210°F.

Based on pipesent accepted practice in the design of herm.etic raotor-com.pressor units, it is the opinion of this Bureau

that the compressor-motor of the cooler was adequately protected against overload and against excessive tem.peratures caused

by motor overload.

(9) Operation at Varying Water Pressures (Paragraph D-13a)

After adjustm.ent of the bubbler solenoid valve, discussed

under Section 5 of the Test Results, the cooler operated satisfactorily when connected to a water supply system at pressures

ranging from 20 psig to 75 psig. The capacity test described

under Section 1 of the Test Results was made with a water supply

pressure of approximately 25 psig. The performance of the

water regulator under supply water pressures of 20 psig and 75

psig is discussed under Section 5 of the Test Results.

(10) Drain Capacity (Paragraph D-13b)

The drainage system of the cooler specimen was apparently

free of internal trappings and did not cause stoppage of water

in the bubbler basin.

( 11 ) Overload Test (Paragraphs F-3c, D-lla modified)

The cooler specimen was tested in accordance with the requirements of paragraph F-3c of the specification, which calls

for 4 hours of continuous operation in 100°F ambient temperature

with water drawn at the rate of 300 percent of the required

hourlv capacity and 60% spill through the pre-cooler. The inlet

water temperature was held at approximately ^0®F. The results

of this test are summarized in Table 4, which follows.

- 9

-

The cooler operated satisfactorily and without any indication of breakdown. The temperature rise of the motor running

winding was determined by the resistance method and computed by

the formula given in paragraph 4.2.3 of Federal Specification

CC-M-636a, dated October 29, 1951. Table 4 shows that the

temperature rise of the motor winding was well below the permissible rise for totally-enclosed motors in this specification.

It is pointed out that Federal Specification CC-M-636a

does not carry any reference to motors integral to a hermtically-sealed refrigeration comipressor. It is believed that

the coil-winding temperature rise limits for totally-enclosed

type motors should serve as a guide to assist in judging hermetic motors.

The overload test, for which the results are summarized

in Table 4, was inadvertently made in an am.bient tem.perature

of 90°F instead of 100°F as required by the specification.

However, since the temperature rise of the motor windings

was more than 30C below the permissible maximum, it is very

unlikely that a rise of lOF in the ambient temperature would

cause the specim.en to fail the overload test.

TABLE 4. OVERLOAD TEST OF SPECIMEN 96-52

Performance Characteristics

Required Observed

Performance Performance

Ambient Temperature, °F

Drinking Water, Inlet Temp., °F

Drinking Water, Outlet Temp., °F

Ratio of Drinking Water Flow to

Required Capacit 3^, %

Spill through precooler, %

Electric Power Input, watts

Terminal Voltage

Temperature Rise of Motor Windings,

100 ^9.^

.

79.9 — 6^.3

300 300

60 60.0

262

115 115

65^= 33.?^

(maximum)

Permissible temperature rise for totally-enclosed

fractional-horsepower motors in Federal Specification

CC-M-636a.

V. CONCLUSION

The cooler specimen, as submitted, met all, the specification requirements of the performance tests, with the exception

of the thermostat test and part of the water regulator and valve

test. Adjustment of the bubbler solenoid permitted the specimen to meet, the water regulator and valve test. However, installation of a second thermostat did not result in compliance

with the requirements of the thermostat test.
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THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

Tlie 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

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consistent with these standards; the determination of physical constants and

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

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Bureau of Standards (25 cents). Both are available from the Government Printing Office. Inquiries regarding the Bureau’s reports and pubhcations should be

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