NATIONAL BUREAU OF STANDARDS REPORT

6524

A STUDY OP THE TEST PROCEDURES IN

INTERIM FEDERAL SPECIFICATION AA-R-002lld (Army QMC)

DOMESTIC TYPE, SELF-CONTAINED, ELECTRIC REFRIGERATORS

by

W. F. Goddard and C. W. Phillips

Report to

Mechanical Engineering Division

Headquarters,

Quartermaster Research and Engineering Command

Natick, Massachusetts

<nb|>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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,

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problems; invention and development of devices to serve special needs of the Government; and the

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the National Bureau of Standards (#1.25) and its Supplement (#0.75), available from the Superintendent of Documents, Go\ eminent Printing Office, Washington 25, 1). C.

Inquiries regarding the Bureau’s reports should be addressed to the Office of Technical Information, National Bureau of Standards, Washington 25, D. C.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003-20-4832 August 27, 1959 6524

A STUDY OP THE TEST PROCEDURES IN

INTERIM FEDERAL SPECIFICATION AA-R-002lld (Army QMC)

DOMESTIC TYPE, SELF-CONTAINED, ELECTRIC REFRIGERATORS

by

w. F. Goddard and C. W. Phillips

Air Conditioning, Heating, and Refrigeration Section

Building Technology Division

to

Mechanical Engineering Division

Headquarters,

Quartermaster Research and Engineering Command

Natick, Massachusetts

IMPORTANT NOTICE

NATIONAL BUREAU OF SI

intended for use yvithin the

to additional evaluation and

listing of this Report, either the Office of the Director, N however, by the Government

to reproduce additional copi

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

jrogress accounting documents

rmally published it is subjected

reproduction, or open-literature

sion is obtained in writing from Such permission is not needed,

prepared if that agency wishes

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

A STUDY OF THE TEST PROCEDURES IN

INTERIM FEDERAL SPECIFICATION AA-R-^00211d (Army QMC

)

DOMESTIC TYPE, SELF-CONTAINED, ELECTRIC REFRIGERATORS

by

W. F. Goddard and C. W. Phillips

1„ INTRODUCTION

In accordance with the request on March 13, 1957 •> of Mr, J. W.

Millard, Research Director, Mechanical Engineering Division,

Quartermaster Research and Development Command, U. S. Army, performance tests were made on four nominal twelve cubic foot household refrigerators in accordance with test procedures as set forth

in Interim Federal Specification AA-R-00211d (Army QMC). These

tests were made to furnish information on the suitability of the

test procedures now included in the Interim Federal Specification

AA-R-211. Since regular commercial items of an acceptable quality

that will assure efficient expenditure of government funds are

desired in response to contracts, it was requested that the tests

finally recommended should reflect industry practice while still

establishing the minimum quality that acceptable commercials items

must provide. It was further requested that the four refrigerators

procured for test should approximate Type I, as defined in the Interim Specification AA-R-00211d; should be purchased for test through

conventional civilian retail sources without disclosure of intended

use. Also, to support the final test requirements, the following

four areas of investigation were identified for study;

1. Special equipment required for the tests and/or

procedures that may not conform to industry practice.

2. Recommendations for changes of test requirements

and/or procedures that conflict with industry

standards

.

3. Time to perform each test.

4. Total time for complete test series.

This report presents the results of the four areas of investigation as stated above. The tests were performed in accordance

with the interim specification in all cases except those where.
.

-

.

.
2 -

fo r some reason^ exact conformity was not possible. In these

cases, the necessary changes to be made and incorporated in the

test procedure were discussed with Mr. Paul Vogel, the project

officer representing the Quartermaster Research and Engineering

Command. This procedure for revising the tests as the problems

presented themselves eliminated the necessity for repeating certain tests.

By agreement with the project liaison officer, this investigation covered only the areas of the specification relating directly to performance tests listed under Section 4.4.

2. DESCRIPTION OF THE TEST SPECIMENS

The four refrigerators used for the tests were all Type I

units - units having no frozen food storage compartments as defined for Types III and IV, and equipped for manually-initiated

defrost. Each had an ice storage or low temperature storage compartment. The four makes and models are listed below together

with descriptive information from the manufacturer’s literature.

Adm. i ra 1 DA .1360 , as described in Admiral Form A 6412, list price

$359. 95 j rated at a gross storage volume of 13 cubic feet;

full-width ice storage freezer chest and drawer; four fullwidth shelves; twin porcelain crispers; butter and cheese

chest in door; four door shelves (l egg); "Lifeguard" and

"Touch-O-Magic" door handle - a means of opening the door

from inside in the event of accidental imprisonment and an

easy opening outside handle; push button auto-defrost (electric

defrost); two ice trays. Fig. 1 and Fig. 2 show the front

and back, respectively, of this refrigerator.

Coldspot L 12-A , as described in Sears-Roebuck Form No. RG46-100380,

manufactured by the Whirlpool Corporation, Evansville, Indiana; list price $219.00; rated at a gross storage volume of

12.9 cubic feet; full-width ice storage freezer chest and

drawer; three full-width shelves; one crisper; four door

shelves (.1 egg); porcelain enameled interior; safety door

.'latch; on-off-defrost switch; two ice trays. Fig. 3 and Fig. 4

show the front and back, respectively, of this refrigerator.

Pig. 1

Fig. 2

Fig 3

Fig . H-

-3-

Frigidaire S-124-57 :? as*-/ described in Frigidaire Bulletin HA-4616;

list price $329-95; rated at 12.4 cubic feet storage volume

(NEMA); full-width ibe storage freezer chest and drawer; four

full shelves and a partial shelf; two porcelain-finished hydrators; butter compartment on door; five door shelves (2 egg);

porcelain-finished interior; "Safety-Seal” latch; semiautomatic defrost; three ice trays. Fig. 5 and Fig. 6 are

views of this refrigerator.

Westinghouse SK 115 , as described in Westinghouse Bulletin 7 DR-0606;

list price $299-95; rated at a gross storage volume of 11.53

cubic feet (NEMA); full-width ice storage freezer chest and

drawer; three full shelves; two porcelain-enameled "Humidrawers"; butter keeper in the door; four door shelves (l

egg); titanium-porcelain enamel interior; on-off thermostat

(no defrost position); two ice trays. Fig. 7 and Fig. 8 are

views of this refrigerator from front and back, respectively.

As procured, from conventional civilian retail sources without disclosure of intended use, the purchase price for each refrigerator was the list price as given above except for the Admiral,

in which case the purchase price was $201, a reduction of $ 158.95

below the list price. This reduction was made by and at the insistance of the seller at the time of pickup when it became known

to the seller that the purchaser was the U. S. Government.

The refrigeration systems for all four units were probably

typical of current design and construction. All were hermetically

sealed. The Admiral and Westinghouse refrigerators used a single

refrigeration circuit - compressor, condenser (outside of unit),

capillary tube and one evaporator. The Coldspot and Frigidaire

refrigerators had, in addition to this circuit, a second refrigerantcooling circuit. On the Coldspot, it was identified as a "Precooler", and consisted of a 1/4" O.D. copper line running from the

discharge side of the compressor, through the upper first four tubes

of the condenser and back to the high pressure side of the compressor

shell. This "Pre-cooler" tubing can be seen in Fig. 4. On the

Frigidaire, a "Superheat Coil", mounted in the compressor compartment under the refrigerator, was connected into a 1/4" O.D. copper

line running from the compressor discharge to the high pressure side

of the compressor shell. Fig. 9 shows this coil in place as viewed

from the front of the refrigerator. These differences in construction

of the condenser part of the refrigeration circuit probably affected

the length of time involved in the condenser overload test.

Fig 5

Pig . 6

Fig. 7

Fig . 8

Fig 9

-4-

The several units differed in the method of defrost. Although

the defrosting operation in each was manually-initiated, two were

equipped with off-defrost-on switches, one with a push button defrost switch, and one had an on-off switch with no marked defrost

position. Only one unit, the Admiral, had a means of accelerating

the defrost operation - an electric heater element on the evaporator. Three of the specimens were equipped with a means for automatically returning to at least limited operation after defrosting.

These refrigerators were all competitive models intended to

represent a cross-section of current industry production. None

were ’’floor” models or ’’demonstrators.” Each unit was removed

from existing warehouse stock at the time of purchase. The units

were chosen by an NBS representative from the stock available in

accordance with recommendation of QMR&E Command as to type. The

government was not identified as the purchaser at the time prices

were solicited so they probably did not represent normal cost to

the government.

3. PROCEDURES AND TEST RESULTS

a. Review of industry practice to determine special

equipment or procedures required by the interim

specification that may not conform to industry

practice

The formal review of Industry practice, upon which the NBS

recommendations for the present specification were predicated, was

made in 1954, and an informal check made at the time of the work,

covered in this report, indicated no outstanding change in industry practices concerning testing equipment or procedures. Nonconformities that do exist between industry practice and the interim specification will probably be found in the method or means

of doing the drop test, the door liner test, the test for moisture

content of the refrigerant, and the gasket compression test. The

need still exists for standardizing these various tests throughout

the refrigerator industry.

b. Study to determine what major areas of non-compliance,

if any, exist between test requirements of the interim

specification and the performance of typical stock

refrigerators
'
-5-

The main purposes of testing the four refrigerators were to

determine the suitability of the test procedures incorporated in

the interim specification with regard to laboratory techniques and

to identify whether or not stock models of current production would

comply with the performance requirements of the specification.

Table I summarizes the test results for the four refrigerators

and compares these results with the present requirements of the

interim specification. An analysis of these test results follows.

Table I shows that all four refrigerators tested were in compliance with part or all of each of the following requirements of

Interim Federal Specification AA-R-00211d.

1. Paragraph 4. 4. 1.2 - Run-in test, 24 hours.

2. Paragraph 4.4. 2.1 - No Load Operating Test. Fixed thermostat setting with general food compartment temperature

at 39°Nj ambient temperature 90 0 F.

3. Paragraphs 4. 4. 2.1., 4. 4. 2. 2., 4. 4. 2.3 - No Load Operating

Tests in ambient temperatures of 70°F, 90°F, and 110°F.

Minimum permissible food compartment temperature, 33 °F.

4. Paragraph 4. 4. 2.3 - No Load Operating Test at 110 °F

ambient temperature. 'Two of the units did not hold the

general food compartment temperature below 43 °F as required, but all four units operated considerably less

than the maximum of 90 percent of the time.

5. Paragraph 4.4.3 - Ice Making Test. Only one unit had the

required ice storage capacity. All units froze the required amount of ice in 6 hours.

6. Paragraph 4.4.5. 1 - Temperature Change during Cyclic

Operation. All units provided less than 6°F change in

general food compartment temperature during no-load tests

in ambient temperatures of 70°F, 90°F, and 110°F.

7. Paragraph 4. 4. 5. 2 - Minimum Adjustable Range of Refrigeration Temperature Control, 37°F to 43 °F. Four of the units

provided adjustment below 37 °F. Two units could not be

adjusted for cyclic operation as high as 43°F.
’

'
SUMMARY

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8 . Paragraph 4. 4.7.1 - Motor Overload Protective Device.

Operation with condenser blocked. All complied,

9. Paragraph 4. 4.7. 2 - Motor Overload Protective Device.

Operation with failure of starting mechanism. All

complied.

10. Paragraphs 4.4.10.1* 4.4.10.2* 4.4.10.3 - Quality of

porcelain enamel on interior liner. Ail complied on

maximum enamel thickness, minimum reflectance* and acid

resistance

.

11. Paragraph 4.4.11.1 - Thermal Tests of Door Liner. All

units were undamaged at a temperature of l40°F. All of

the original liners failed at a temperature of 0°F.

All four refrigerators tested failed to comply with the following requirements:

1 . No-load operation at 110 °F ambient temperature . The

four refrigerators did not maintain the general food compartment

temperature below 43 °F as required. Observed temperatures ranged

from 44.1 to 47.0 C F. This failure was probably due to an inadequate* improperly adjusted* or improperly located thermostat* or

inadequate air flow through the manually-adjusted refrigerator

temperature control baffles* because none of the refrigerating

systems operated more than 68^ of the time during this particular

test although the specification allows a maximum of 90^ operating

time

.

In literature supplied with each refrigerator* three of the

four manufacturers of the specimens tested suggested that the temperature control baffles be used to restrict air flow only at low

ambient temperatures. One manufacturer suggested that the baffle

be used to restrict air flow at all times except during high ambient temperature. None of the instructions furnished* defined

low or high ambient temperatures. The baffles were set to restric

air flow in the no-load tests at 70 °h ambient only.

2 . Thermal Tests of Door Liner at temperatures of l40°F

and 0°F . Although no failures were observed in the door liner of

any of the four refrigerators at a temperature of l40°F* all four

of the liners failed at 0°F because of cracks which developed and

progressed mainly from the holes for the screws used to hold the

-7-

liner in place on the door. Fig. 10 through 13 show the failed

liners from the Admiral, Coldspot, Frigidaire ar.d Westinghouse

refrigerators, respectively.

A new liner was installed in each of the four refrigerators

and the test was repeated. Again, no failures were observed at

a temperature of l40°F. Three liners failed at a temperature of

0 °F . The liner which did not fail, in the Coldspot refrigerator,

was installed by a representative from Whirlpool-Seeger Corp.,

manufacturer of the refrigerator, using screws of a different design from the ones used in the original test. The new screws had

a shoulder which prevented excessive pressure on the liner when

tightened.

One or more, but not all, of the four refrigerators failed

to comply with the following requirements:

1. Ice tray capacity . Only the Frigidaire refrigerator was

supplied with sufficient Ice tray capacity.

2. Defrosting test . The Westinghouse refrigerator was not

equipped with a temperature control having a designated defrost

setting. According to the manufacturers' printed instructions,

the procedure for defrost was to turn the control switch to "off".

Although complete defrosting could be obtained by allowing sufficient time in any room temperature above freezing, the control

did not automatically return the system to at least limited operation after defrosting. The Frigidaire refrigerator did not release

or melt more than an estimated one-third of the frost; on the evaporator before the thermostat returned the system to limited operation 2 3/4 hours after being turned to the defrost setting. The

Admiral refrigerator was equipped with a push button defrost switch

which did not require changing the normal temperature control setting of the thermostat to defrost the evaporator. It was also

equipped with an electric heater on the . evaporator to shorten the

time required for defrost. The defrost switch returned the refrigerator tON normal temperature operation in less than 25 minutes

from the time of manual initiation of the defrost operation, leaving

a very slight trace of ice at the left front edge of the evaporator.

The Coldspot refrigerator defrosted completely in about two hours

and returned to limited operation automatically.
-
Fig. 10

Fig. 11
I
Fig. 12
>


-8

3. Adjustable Refrigeration Temperature control range . All

four refrigerators tested held general food compartment temperatures well below 37 °F i- a 90°F ambient temperature as required

but only the Westinghouse and Coldspot models could be adjusted

to hold a temperature above 43 °F. The Frigidaire and Admiral

refrigerators failed this requirement^ with general food compartment temperatures at the highest thermostat setting of 4l.5°F

and 38.9 °Fj respectively.

4. Exterior condensation . The Coldspot refrigerator failed

this requirement. Condensation was observed on the refrigerator

surface between the hinges. Condensation was also observed on the

lower right side near the gasket closure. This latter condensation

was probably caused by failure of the gasket to seal because of a warped door.

5. Drop test . The Frigidaire refrigerator failed this requirement. A permanent twisting of the hinges was observed as a

consequence of the drop test. No failures were observed in the

other refrigerators.

It is possible that refrigerant system leaks were caused in

three refrigerators by the drop test. The Frigidaire refrigerator

lost its charge sometime prior to the test for moisture in the refrigerant , which was the last test in the series. The Westinghouse

and Admiral refrigerators appeared to contain less than a complete

charge of refrigerant at the time of the moisture test. Because

of interruptions in the test program., the elapsed time between the

drop test and the moisture test for the four refrigerators ranged

from three months to more than a year. This elapsed time and the

fact that no specific check for refrigerant leaks was made before

and after the drop test; make it impossible to state whether or not

leaks were caused by the drop test.

6. Compression set of door gasket material . A sample of the

door gasket from each of the four refrigerators was tested in accordance with Method B of ASTM D395° For each sample, flat specimens approximately one square inch in area5 cut from the gasket s were piled atop one another until a thickness of 0.395 inch was

obtained. The test determined the compression set of the material

of which the gasket was formed rather than that of the extruded

design of the gasket. Three samples failed with a compression set

of 25/^<. The gasket material from the Admiral refrigerator was the

only one which complied,, having a compression set of 10$.
,* .
-9-

7 . Door Gasket Seal , The Coldspot refrigerator failed this

test. The lower edge of the door opposite the hinges did not close

sufficiently to effect a gasket seal. Adjustment of the hinges and/

or latch did not remedy the situation. After a new liner was installed for the door liner test with special attachment screws,

and after readjustment of the latch and hinges, a continuous gasketseal was attained.

Test procedures described in the Interim Specification, which

had to be modified in order to conduct the required tests were;

1 . Temperature measurement in ice tray* compartment . The

four refrigerators tested each had a compartment containing the ice cube trays which was identified by the

respective manufacturers as a ’’freezer chest”, etc. In

a Type I refrigerator, this compartment is not required

to be suitable for frozen food storage. Accordingly,

the temperature of this compartment was measured by placing

two thermocouples in air in the center of the compartment

instead of in packages of simulated frozen food as required for Type III and IV refrigerators.

2. Motor overload protective device test . In the test

for operation of the motor protective device with the

condenser air blocked (Paragraph 4. 4.7.1)* the overload

device on the Frigidaire refrigerator did not function

even after several hours of test. The temperature of the

windings was determined by measuring their resistance at

the time of manual shutdown, repeated at about 30-minute

intervals, until four repetitive measurements were obtained.

The temperature of the windings was 254°F as determined by

this procedure. The Interim Specification does not describe

the procedure to be used in the event the overload device

does not trip out.

3. Compression set of gasket . The tests for determination

of compression set of the door gaskets was made in a manner

which determined the characteristics of the material rather

than the extruded form of the gasket. Due to a misinterpretation, this was contrary to the test procedure in paragraph 4.4.11.2, which says, ”A one-inch section of the gasket shall be compressed ; *... . . in a device described in

Method B of ASTM D395 . . . .

The tests, as -performed, were
,* . <
- 10-

in non-compliance with two parts of this requirement:

(l) a section of the gasket as installed on the refrigerator was not used; and ( 2 ) all of Method B of ASTM D395

was used for the test procedure instead of just the device described in Method B of ASTM D395 as stated in the

Interim Specification.

4. Taste contamination test for plastics . No tests were

made for taste contamination of plastics during this study.

Paragraph 3.^.5 requires that none of the plastics used

in the refrigerator shall impart odor or taste to food

or water. There are many items inside the ref rigerators

,

all of which may be made from different plastics. The

test requirement in Paragraph 4.4.11.3 calls for use of

a "standard sample" of the plastic to be tested. In view

of the fact that these refrigerators were obtained from

retail sources, not from the manufacturer direct, no standard samples were available for this test.

5 . Time to perform each test . The total time required

to complete each performance test on the refrigerators

may be divided into three component time periods:

1 . Stabilizing the room

2 . Stabilizing the refrigerator

3. Test run

These periods ran consecutively. The length of time required

to stabilize the room was a function of the equipment used, the room

construction, and the degree of condition change required] the time

required to stabilize the refrigerator was a function of the refrigerator as a composite unit and the degree of change in ambient

conditions required; the test run time was a function of the number

of on-off cycles or the time required to assure representative values

of the variables observed.

Table 2 presents a break-down of the time required to perform

the various phases of the test series on one refrigerator. The

order of testing and the time periods involved are not necessarily

those listed in the present specification. They are believed to

be representative of an average test setup.

-lilt can be seen from Table II that about 262 hours were required to test one refrigerator for compliance with the performance

tests in the interim specification which required operation or use

of the complete refrigerator. This does not include those secondary

tests listed under general performance tests which must be done by

means other than actually operating or involving the assembled .refrigerator; nor does it include preparation or setup time. These

will be discussed under "Time for complete test series."

The time used in stabilizing the various refrigerators varied

some from the reported value. However, since there was some overlapping between the time used for room stabilization and refrigerator stabilization, the values reported in Table II are considered

representative. The time required for stabilizing room condition

would vary with the effectiveness of automatic controls used. The

values in Table II were based on automatic control of temperature,

manual control of humidity.

6. Time for complete test series . The time required for

a complete series of performance tests of one refrigerator under Section 4.4 of the interim specification is

summarized in Table III. The time required for complete

tests, which includes all phases of performance testing,

is divided into three parts:

1. Set-up time

2. Primary performance testing time

3. Secondary testing time

Setup time is defined as that period required to make the

specimen ready for a test condition. It includes such items as

placing thermocouples, preparing and connecting, electrical instruments for the various tests, setting up the moisture determination

apparatus, etc. A summary of these items and the time to perform

each task is shown in Table IV. Of the total of 32 hours of setup time shown in Table IV, all but 7 were combined with room or

refrigerator stabilizing periods. The variation in set-up 'time for

the several specimens depended on such factors as the degree of

access to components in the refrigerators, handle design, thermostat response time, and capability of the person doing the job.

The times as listed are representative values. For example, the

time required to adapt a door-opener for the defrost test was two

hours for one refrigerator with a positive latch as compared to less

than an hour for refrigerators with magnetic or easy opening doors.
>
- 12 -

Table III

Time Required for Complete Test Series*

Observer

Required

Hours

No

Observer

Required

Hours

Total

Time

Hours

Set Up 7

- 7

Run In - 24 24

Stabilize Room 18 58 76

Stabilize Refrigerator 23 38 61

Actual Test Time 107 - 107

Total Hours 155 120** 275

* Based on Section 4.4 of Interim Federal Specification

AA-R-00211d.

** Does not include 168 hours required for test of gasket

compression set; includes estimated time for taste contamination tests.

The primary performance testing time was discussed in the previous section (Table II ) and is included ir, this section as part of

the time required for a complete test. The 262 hours of primary

testing time consisted of two main parts

:

1. Time requiring data observation - 101 hours

2. Time necessary for stabilizing, pull-down, etc. - 161 hours

Secondary testing time was that period used in testing those

items which did not require operation of the refrigerator as a part

of the test. Table V lists the secondary test items and the time
.
-13-

required for each. The greatest percent of the time was that required for the test of the gasket compression set* and was the time

required for the gasket to set in the testing device, a period during

which no labor charges and minimum overhead charges were involved.

This time, 168 hours, is not included in the total time shown in

Table III.

Table IV

Set--Up Time for Tests

Item

Time Required,

Task Hours

Installation in room Placing, leveling, shielding, 5

installing thermocouples, etc.

Drop test Inserting weights on shelves, 2

etc

.

Defrost Defrosting and/or drying between 8*

condition changes, total for

several tests

Thermostat set Changing settings between con- 7*

dition changes in temp, range,

90°NL, and ice making tests,

total for several tests

Handle adapter

(Defrost test)

Designing, fabricating, & con- 1*

necting opener on door handle

Sweat test observation Wiping unit dry & checking for 1*

condensation before actual test

Water for ice making Preheating water, filling, 1*

weighing and placing trays

Overload preparation Covering & blocking air to con- 1*

denser

Starter Overload Disconnecting starter windings 1*

Moisture determination Connecting sampling tubes and 1*

instruments

Gasket compression Setting up testing instrument 4*

Total 32

* Can be done during stabilizing periods
1
- 14 -

Table V

Time Required for Secondary Tests

Test

Thickness of

Porcelain Enamel

Reflectance

Ac id-Resi stance

Compression Set

Taste Contamination

Item

Cabinet & Interior Liner

Cabinet & Interior Liner

Interior Liner

Door Gasket

Butter Dish & Liner

No

Observer Observer

Required Required

Hours

1

1

1

1

2

*

0

0

0

168

2

Total 6 170

* estimated

4 . DISCUSSION AND CONCLUSIONS

The conclusions based on this study of four refrigerators are

limited specifically to requirements referenced in Section 4.4 of

Interim Federal Specification AA-R-00211d. Other requirements of

the specification were not considered in determining points of compliance, and the times reported for testing do not include times

which would be required for determining compliance with these other

requirements

.

The conclusions are presented in two parts:

1. Time required to perform the tests on a refrigerator.

2. Recommended changes and additions to the specification

based on this study.
<}
-15-

1. Time required to perform the tests on a refrigerator

The time for the complete series of performance tests for one

refrigerator was 275 hours based on the order of testing shown in

Table II. It includes 155 hours which required an observer and

120 hours during which conditions were maintained by automatic

control. It does not include 168 hours for the test of compression

set of the door gasket. It does not include supervisory time or

preparation of the test report. It does not include time spent on

maintenance or repair of test facilities. The tests were conducted

on an around-the-clock basis where necessary.

The order of testing shown in Table II,, is recommended to reduce to a practical minimum the num.ber of times conditions must be

changed and the abruptness of these changes. It makes use of the

drop test first to determine whether or not failure occurs at this

point before the other more complex tests are run on the unit. If

the run-in test follows., it may be used to check operation of the

refrigerator after the drop test.

Use can be made of the stabilizing periods to accomplish tasks

which are necessary prior to the tests themselves. The times shown

in Tables II through V for the room and refrigerator stabilizing

periods are the average values for the four refrigerators used in

this study. As test facilities are improved,, the time required for

stabilizing can probably be reduced somewhat.

For 155 hours of the 275 hours required for testing an observer

is needed. In most cases this observer would be one or more persons

capable of taking and recording readings; in other cases it would

be a person capable of preparing the specimen or changing a condition

of the room or specimen. The number of man hours involved will depend on the test facilities, instrumentation, and capabilities of

test personnel.

For 120 hours of the 275 hours required for testing, reasonable

automatic control can be used to maintain test conditions without

personnel in attendance.

Such special equipment as is needed for these tests can be

found in any well equipped appliance testing laboratory. The more

efficient the test room and equipment is, the sooner proper conditions can be attained, and therefore, both time and cost of the

16 -

test will be reduced. Accuracy commensurate with this specification

is a part of the normal procedure of any good appliance test setup.

2. Recommended changes or additions to Section 4.4 and referenced requirements of Interim Specification AA-R-002lld

based on this study

It should be noted that, of all the tests under Section 4.4,

in only two cases did all four of the refrigerators tested fail to

comply. One case was the no-load operation at 110 °F, where general

food compartment temperatures of 44.1°F, 44.4°F, 45.9°F and 47.0°F

were observed as compared to a requirement of 43 °F maximum. A companion requirement for this test was that the machines should not

operate more than 90$ of the time. The refrigerators operated, in

the same order, 58$, 68$, ^ 1 %, and 42$ of the time during this test.

Since it is probable that a minor change in the temperature control

mechanism would bring these units into compliance without exceeding

90$ operating time, no change in the requirement is believed necessary.

Fig. 14 and Fig. 15 show operating characteristics of the four

refrigerators tested during the no load tests in ambient temperatures of 70°F, 90°F and 110°F. Fig. 15 also shows the effect of

the manually-adjusted baffles which were closed in each refrigerator

for the no-load tests at 70°F ambient temperature and opened for the

no-load tests at 90 C F and 110 °F ambient temperature.

The second case where all four refrigerators failed to comply

concerned the door liners. Although none of the liners failed at

a temperature of l40°F during the test outlined in Paragraphs 4.4.11.1,

they all cracked around the supporting screw holes as the liners approached a temperature of 0°F. Redesign of the liners, or change

of materials, or change of methods by which the liners are attached

to the door could probably solve this problem. In a retest of new

liners installed in the same refrigerators only three failed. The

Coldspot liner did not fail, and, according to the manufacturer’s

representative who installed the replacement, the only change was in

the design of the screws used to fasten the liner to the door. In

view of this, and unless it can be shown that storage temperatures

of 0°F will not be encountered, the requirement should not be changed.

Since all of the other test requirements were met by one or more

of these typical refrigerators, major changes to meet industry practice

may not be necessary.
’

.
sanoH

FRIGIDAIRE

„

ADMIRAL

WEST1NGHOUSE

COLDSPOT

d© 1 3dm.VU3dN31 INBMXUVdMOO QOOd 1VW3N30 39VW3Atf
«
-17-

Changes or additions to the specification which may clarify

or improve the specification are discussed in the following paragraphs in the order in which they appear in Section 4.4. No review

of the other sections of the specification is included, except where

items are specifically referenced in Section 4.4.

4. 4. 1.7 Typographical. Fourth line of first paragraph should

read, "...... between front and....."

If a temperature requirement is to be included in the specification for the low temperature (ice tray) compartment for Type I

and II refrigerators, the means for determining the temperature of

this compartment should be included in this paragraph.

4. 4. 1.8 Add at the beginning of this paragraph, ’’This test

requirement applies to Type III and IV refrigerators only.”

4. 4. 1.9 Typographical. Second line of second paragraph should

read, ".....time-integrator.”

4.4.2

Instructions for positioning of the temperature control

baffles, if used, should be included in this paragraph.

It is our recommendation that the baffle positions remain unchanged throughout the three no-load tests required in 3. 5. 1.1.

The second sentence in paragraph 3.5. 1.1 should be changed to read,

"Without any change in refrigeration control settings or in temperature control baffle positions, the average 110°F.”

4. 4. 2.1 Change last sentence to read, "Normal ice loads for all

types of refrigerators and frozen food loads, prefrozen, for Type III

and IV refrigerators shall be...... is determined."

4. 4. 2.

2

Change last sentence to read, "The refrigeration temperature control and temperature control baffle shall be set at the

same position as for the test at 90°F ambient temperature."

4.4.

2.3

Change last sentence to read, "The refrigeration temperature control and temperature control baffle shall be set at the

same position as for the test at 90 °N ambient temperature."

the

4. 4. 4.1 Change the sixth sentence to read, "At the end.... in

defrost position recommended by the manufacturer. "
.

.
-18-

4.4.5. 1 Change the first sentence to read, "The general,. ... in Figures 1 through 5j and, for Types III and IV, the frozen. ....

4. 4. 2.1 to 4 . 4 . 2 . 3 •

V

4.4.5. 2 Change the second sentence to read, "In two successive

tests, with the temperature control set in the first test at the

lowest and in the second test at the highest settings ...... thermostat cycles."

4.4.7. 1 Change the first sentence to read, "Each sample .. .with

the heat transfer from the air-cooled condenser and other heat rejecting surfaces restricted to function.’/ Add to end of paragraph, "If the compressor motor overload device does not function

with the condenser air circulation blocked while the unit is operated continuously for four hours, the resistance of the windings

shall not indicate a winding temperature exceeding the specified

limit of 302 °F at the end of the four-hour period."

4.4.8 Moisture content of refrigerating system. Additional

Investigation in the general field of moisture measurement may devel o p more suitable means for this type of determination. Some

manufacturers are using small amounts of methanol. A requirement

covering this development should be prepared. Until this is done,

no change is recommended in the requirement. In paragraph 3.6,

the second sentence of the second paragraph should be changed to

read, "The refrigerant system. .... in excess of 25 ppm by weight as

determined ...... of 4.4.8."

4.4.9 Drop test. Insert a sentence under 4.4 Performance Tests,

as follows: "The drop test described in 4.4.9 shall be performed

before the run-in period specified in 4. 4. 1.2 and before any of the

performance tests specified in 4.4.2 to 4.4.11 inclusive."

The requirement listed under 3.4.1 should be clarified by

changing the last sentence of 3*^.1 to read, "In addition, the refrigerators subjected to this test shall not show any evidence of refrigerant leakage after the drop test or any malfunction in subsequent testing as required in Section 4."

Paragraph 4. 4. 1.2 should be changed to read, "After the drop test

and before starting other performance tests, the...... 24 hours."

4.4.10.1 and 4.4.10.2 Either delete the reference to Paragraph

3. 8. 4. 2.1 or add 3 . 8. 4. 3 and 3 . 8. 4. 4.
.. ,

.

t-..

•
-19-

4.4.11.1 Typographical. Title should read, ’’Styrene and

laminated . .. . .plastics . "

This paragraph, 4.4.11.1, as written, deals only with the

test of door liners. The test as performed under the study covered

in this report did not necessitate removal of the door from the

refrigerator and as a result, the other plastic components of the

refrigerator were also subjected to the ambient conditions of

l40°F and 0°F during the door liner test. A permanent warping and

deformation of some of the parts such as baffles, door jambs, low

temperature compartment doors, etc., was noted at the l40°F temperature. Thermal deformation of plastics is not covered in the

tests required under Section 4.4 of the interim specification but is

covered by a requirement in Paragraph 3.^.5. It is suggested that

the refrigerator be tested as a complete unit under the test conditions required for the door liner. This can be accomplished by

changing Section 4.4.11.1 to read, ’’Thermal Tests. Styrene and laminated thermosetting plastic door liners (see 3*8. 4. 4) and plastic

parts (see 3.4.5) shall be tested as follows:

1. The assembled refrigerator, empty but with all trays, etc.,

in place, with the door open, shall be permitted to come to thermal

equilibrium at l40°F, and then at 0°F. The compressor shall be inoperative for this test.

2. The door shall then be closed and the interior refrigerator

temperature permitted to come to steady state at the lowest temperature obtainable with continuous operation of the refrigerating unit

in an ambient temperature of 110 °F.

3. The door liner and other plastic parts shall be examined

for cracks, crazing or permanent distortions."

Change last sentence of paragraph 3.^.5 to read, "Plastics....

0°F to l40°F.!' Add new sentence, "Plastic parts shall not craze,

crack or permanently distort when tested in accordance with 4.4.11.1."

Change next to last sentence of Paragraph 3. 8. 4. 4 to read,

"Styrene ...... 4. 4. 11.1."

4.4.11.2 Change the title to read, "Compression set of

rubber door gaskets."

Remove last sentence from 4.4.11.2 and insert in a suitable

place in paragraph 3.8.6. Note that it is referenced in the fourth

sentence of 3.8.6.
.
- 20.

4.4.11.3 Typographical. Title should read_, "Taste Contamination . V

The wording of this section implies that the test shall be done

on all plastic materials in the refrigerator. If this is so, a

standard sample as required must be obtained frorrrthe manufacturer.

The number of tests will vary. The test itself will be difficult

because the degree of taste differentiation will vary in an individual and between individuals.

4.4.11.3 Taste contamination. Standard samples of plastic

materials shall be given the following taste contamination tests:

a. A standard sample shall be immerged in water in a glass

vessel and closed for a period of two hours. A second glass vessel

shall be filled with water from the same source and closed. At the

end of the two-hour period^ there shall be no taste difference in

the water from the two vessels.

b. A standard sample,, smeared with butter, shall be placed in

a glass container and closed for a period of two hours. Some butter,

from the same source, shall be placed in a second glass container

and closed. At the end of the two-hour period., there shall be no

taste difference in the butter from the two containers.

USCOMM-NBS-DC

U.S. DEPARTMENT OE COMMERCE

t-'r.-ilniik II. Mueller. Secretary NATIONAL BUREAU OE STANDARDS

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

The scope of activities of the National Bureau of Standards at its headquarters in Washington, D.C., and its major

laboratories in Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work. In general, each section carries out specialized research, development, and engineering in the

field indicated by its title. A brief description of the activities, and of the resultant publications, appears on the

inside of the front cover. WASHINGTON, D.C.

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