NATIONAL BUREAU OF STANDARDS REPORT

2506

A STUDY OF TWO 3/4 HP STERLING

AIR CONDITIONERS

by

R. L. Dillard

Henry Karger

C. W. Phillips

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

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

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003-40-4700 May 18, 1953 2 506

A STUDY OF TWO 3/4 HP STERLING

AIR CONDITIONERS

by

R. L. Dillard

Henry Kar.ger

C. W. Phillips

Heating and Air Conditioning Section

Building Technology Division

for

Headquarters

United States Marine Corps

Department of the Navy

Washington, D. C.

The publication, rep

unless permission is

i

25, D. C. Such pern

cally prepared If th

Approved for public release by the

" 03,11 ls prohlblted

„ , ,

. „ indards, Washington Director or the National Institute or

iort has been specln- Standards and Technology (NIST) port for own use . on October 9, 201 5.

A Study of Two 3/4 HP Sterling

Air Conditioners

Abstract

Calorimeter tests were made of a specimen

3/4 HP console-type Sterling air conditioner

as received and in several steps as modifications were made to reduce the air leakage between the condenser air circuit and the evaporator air circuit in the cabinet . Two air

conditioning units were submitted because

capacity tests of the first compressor unit

showed that it was defective. Subsequent

inspection revealed a ruptured cylinder-head

gasket which caused one of the two cylinders

to be ineffective in producing refrigeration

.

Inspection showed that both test specimens

submitted had poor cabinet construction. The

total net cooling capacity of the specimen

that was tested as a unit was increased from

an as-received value of about 400 Btu/hr

(with a defective compressor) to about 64OO

Btu/hr after modification and with a good compressor. Detailed instructions for making

similar improvements in the 150 units of the

same model purchased by the U. S. Marine Corps

are given and a field test for evaluating the

results is described.

I. INTRODUCTION

In accordance with a request by Headquarters,

United States Marine Corps, dated June 3, 1952, tests

and inspections were made of two specimen air condition

ing units manufactured by Sterling Equipment Company,

Columbus, Ohio, to determine the reasons for the poor

performance of these units and whether or not enough

improvements could be made in similar units in the

field to warrant their installation. This report is

a summary of the tests made of the two specimens both

before and after modification and contains recommendations for sealing and other changes to -the cabinets of

the units so that their cooling capacity can be increased. A simple field test to determine approximate

capacity is explained.

2

II. DESCRIPTION OF TEST SPECIMEN

Two air conditioning units were supplied by the

United States Marine Corps for the tests. The second

unit was supplied after tests showed that the compressor of the first unit was defective. The majority

of tests were made with the cabinet of the first unit,

the defective compressor having been replaced with the

compressor of the second unit. The first unit submitted

was identified as follows:

(NBS Test Specimen 56-52)

Sterling Equipment Company, Columbus, Ohio

Serial O.E. 2265

3/4 Horsepower

The specimen was a console-type air conditioning

unit, designed for placement near a window or other

suitable wall opening. Ducts for the condenser air

supply and discharge were furnished with the unit and

were intended to communicate with the outside air through

-the window or wall opening. The unit was enclosed in

a sheet steel housing, with the front and rear panels,

as well as the top panel, removable to provide access

for repairs and adjustments.

A 10nxl6 fT xl tT filter of the throw-away type was

provided in the return air circuit of the evaporator.

It was mounted between the return air grill and the

evaporator coil face, and could be replaced by removing the return air grill.

The electrical controls for operation of the air

conditioning unit were located on the right side of

the unit, underneath a small metal flap. Operation

of fans and compressor could be controlled by means of

a selector switch located there. The unit was built

for operation on alternating current, 115 volts, single

phase, 60 cyclb'.

A small damper, 2-3/4 tT x5 tf

, was located on the side

of the unit, several inches below the electrical control switch. The opening in which this damper was

located provided communication with the low-pressure

side of the condenser fan, and enabled the user to

exhaust some air from the room to the outside.

Both condenser and evaporator fans were of the

centrifugal type. The evaporator fan was located

in the top section of the unit, behind the cooling

coil, and discharged its air through the top of the

unit. The condenser fan was located in the lower section of the air conditioner, next to the compressor.

Each fan was driven by a separate motor. A thermostatic expansion valve was used as the refrigerant

flow control.

A side view of the unit showing the small sheet

metal flappers mentioned above, as well as the front

panel and the condenser shroud, is shown in Fig. 1.

Fig. 2 shows a side view of the evaporator air intake

grille, as well as the evaporator air outlet, located

in the top section of the air conditioner. A front

view of the unit with the front cover removed is

shown in Fig. 3. The arrangement of the major components can be seen clearly in this view.

The unit was equipped with a Tecumseh compressor,

Model B-7616, nominal 3/4 horsepower. The condenser

fan motor was a Wagner Type RB motor, rated at 1/4

horsepower, 4.4 amperes and 115 volts, 1000 rpm. The

evaporator fan motor was a Wagner Type TM, 1,5 amperes

and 115 volts, 1725 rpm. The expansion valve was a

Detroit, Model 673. Dichlorodifluoromethane was the

refrigerant employed.

III. TEST PROCEDURE AND RESULTS

The capacity of the air conditioning unit was determined by the calorimeter method. The testing procedure and method is outlined in detail in National

Bureau of Standards Report $223$ entitled "Performance

of a York 3/4 HP Window Air Conditioning Unit, Model

24“l n

, submitted to the United States Marine Corps

under date of February 2, 1953.

All capacity tests of the unit were made at the

standard ASRE rating conditions of 95°F DB, 75°F WB

temperature at the condenser inlet of the unit, and

$0°F DB, 67°F WB temperature on the room side of the

unit. Measurements were also made of the air circulating capacity of the evaporator and condenser fans.

The air circulating capacity of the evaporator fan

was found to be 270 cfm, and of the condenser fan,

500 cfm.

- 4

-

The first unit furnished for test Jiad a total net

cooling capacity of approximately 400 T3tu/hr as received,

compared to $000 Btu/hr for a well-desighed unit of

similar size. The net cooling capacity, as the term is

used here, is the amount of latent and sensible heat that

the unit will remove from the space in which the unit is

installed, not the amount that the unit is able to extract from the air passing through it. This air circuit often includes unwanted ventilating air which is

exchanged between the evaporator (room side) and condenser (ambient) portions of the unit. The cooling required to lower the latent and sensible heat content

of this unwanted ventilating air to that of the conditioned space does not result in cooling of the conditioned space but does utilize a portion of the refrigerating effect produced by the unit.

The penalty imposed by unwanted ventilating air,

for example, is of the following order: Each 100 cfm

of air introduced at 95°F DB and 75°F WB requires a

cooling capacity of approximately 3000 Btu/hr to reduce

it to 80°F DB and 67°F ¥B.

The unwanted ventilating air exchanged between the

outside and the conditioned space by this first test

was found to be in excess of 150 cfm, or more than 55

percent of the^totaf circulating capacity of the evaporator fan. After inspecting the unit, steps were taken

to reduce the undesired ventilating air as much as

possible by sealing the cabinet with masking tape and

by other means. A capacity test subsequent to the sealing revealed a total net cooling capacity of approximately 2600 Btu/hr for the unit.

From these results it was concluded that the compressor of the unit might be defective. The compressor

was removed from the air conditioner, and a capacity

test of the compressor was made with a secondary refrigerant calorimeter. The capacity of this compressor, at

conditions of temperature and pressure approximately

equal to those observed when the compressor was in the

air conditioning unit, was found to be approximately

6100 Btu/hr. A normal capacity of 11,000 to 12,000

Btu/hr is indicated by the manufacturer^ rating for

this compressor. The compressor was dismantled, and

an examination revealed that a head gasket had ruptured

and a portion of the gasket was jammed between seat

and disc of one of the discharge valves, preventing

closure of this valve. Consequently only one of the

two cylinders of the compressor was doing useful compression work. The valve plate with the ruptured

. 5 -

gasket can be seen in the center of Fig. 4. The

valve from the other cylinder is also shown on the

right of Fig. 4 indicating the proper position of

the section of the gasket which provides the seal

between the suction and discharge sections of the

heat assembly. The head assembly shown on the left

in Fig. 4 is from the cylinder with the defective

gasket

.

A second Sterling air conditioning unit of the

same model was then supplied by the United States

Marine Corps for test. The compressor of this second

unit was removed and its capacity determined on the

secondary refrigerant calorimeter. The capacity was

approximately 11,500 Btu/hr at conditions nearly

equal those observed during actual operation of the

air conditioner with the defective compressor.

The compressor of the second air conditioner

was then installed in the original air conditioner

and capacity tests were resumed. The unit was recharged with 5 lbs. of dichlorodifTouromethane , the

amount shown on the unit nameplate. The net cooling capacity was approximately 5300 Btu/hr, and the

unwanted ventilating air amounted to 23 cfm during

this test.

It appeared during this test that the condensing

temperature was higher than should be expected during

normal operation of the unit under the ASRE standard

conditions. To determine if this was due to an excessive refrigerant charge, the refrigerant was discharged from the unit, and the unit was recharged with

3-1/2 lbs. of dichlorodiflouromethane (instead of

5 lbs. as shown on nameplate). This smaller charge

proved to be adequate. In addition, the expansion

valve superheat was reduced to the lowest value that

appeared possible without causing flooding of refrigerant into the compressor. Further sealing was made of

the unit ^cabinet. A capacity test then indicated a total net cooling effect of approximately 5$00 Btu/hr.

The undesired ventilating air during this test averaged

about 15 cfm. A final capacity test was made after

installation of a baffle on the condenser shroud to

prevent short-circuiting of condenser discharge air

into the intake duct, and after removal of the filter

from the evaporator air circuit. Under these conditions the totalnet cooling capacity of the unit was

approximately 6400 Btu/hr, and the undesired ventilating air averaged about 9 cfm. It appeared that this

was the maximum capacity which could be obtained from

the unit without a major redesign of the refrigerant

circuit

.

- 6 -

IV. RECOMMENDATIONS

Based on the test results outlined in Section III

of this report, it appears that the net cooling capacity of this model of air conditioning unit can be increased by reducing the amount of air exchanged between warm and cool sections of the unit.

The following procedures are recommended for

the field repair of these units and it, is suggested

that the steps in such field repairs be carried out

in the order listed below so unnecessary labor may

be avoided.

No special tools are required to effect the work

required. An electric drill will be advantageous in

drilling holes for #$ and #10 sheet metal screws but

a hand drill can be used. The two drill bit sizes

needed are l/$Tt (for #$ sheet metal screws) and 9/64"

(for #10 sheet metal screws). Hand tools required are

1

- Drill (electric, or hand)

1 - Drill bit - 1/3"

1 - Drill bit - 9/64"

1 - 6” or x l/4" screwdriver

1 - Center punch

1 - Small machinists hammer

1 - Knife

$ oz. Solvent (benzine, naptha, or gasoline)

for cleaning surfaces to which selfadhesive sponge rubber is to be attached.

List of Materials Required to

Process One Air Conditioning Unit

Item

No . Quantity Description

1 1 Sheet metal collar for evaporator air

discharge, in accordance with Fig. 16

2 1 Wood filler strip, in accordance with

Fig. 9.

3 2-1/2 lbs Mastic-Type sealing compound, such as

Permagum #545.2, made by Presstite

Engineering Co., or equal.

- 7

-

Item

No . Quantity

4 1

5 17 ft.

6 13 ft.

7 5

3 2

9 2

10 9

11 150 cu.in.

Description

Air baffle for condenser shroud, in

accordance with Fig. 20.

Self-adhesive sponge rubber, 5/32”

thick x 5/3" wide

Self-adhesive sponge rubber, 3/4"

thick x 5/$" wide

#3 x 1/2” Sheet metal screws, selftapping, binding head, (3 for

condenser air baffle, 1 for wood

filler strip, 1 for condenser shroud)

#3 x 1" Sheet metal screws, selftapping, binding head, (for wood

filler strip)

ft10 x l

fT Sheet metal screws, selftapping, binding head (for side panels)

#10 x 1-3/4" Sheet metal screws, selftapping, binding head (for front and

rear panels)

Hairfelt, or other filler material

The outline of steps, which follows, refers to

various figures (photos and drawings) which are a part

of this report. Item numbers refer to the preceding

list of materials. The outline is divided into two

major sections - Part A, which suggests certain cabinet

modifications and explains how to seal the cabinet to

reduce unwanted air exchange, and Part B, which describes

a test which will show, after the repairs have been complted, the approximate capacity comparison between the

field-repaired unit and the test unit described in

Section III of this report after the latter was repaired.

Part A - Sealing of Cabinet

1. See Figs. 1 and 2. Remove front panel, rear

panel, top panel and condenser shroud from unit.

2. See Figs. 5, 6 and 7. Fig. 5 is a front view

of the machine compartment with all panels removed,

and otherwise in the condition as received. Fig. 6

is a rear view of the machine compartment. Mastic

sealing compound (Item 3) should be applied generously at all points indicated in Figs. 5 and 6. Note

that these are interior openings which require sealing. After application of the sealer the cabinet

should appear as shown in Fig. 7. The condensate

drain should be checked at this time.

3. See Figs. 7, $ and 9 . The wooden filler strip

(Item 2) as shown in Fig. 3 should be installed below

the condenser as shown in Fig. 7 and should be secured

by means of 2 - #3x1" sheet metal screws (Item 8) at

points marked ”b Tt in Fig. 7 and 1 - ##xl/2 fT sheet metal

screw (Item 7) located at point marked "a" in Fig. 7.

This wooden filler strip should be covered with the

5/32 TT x5/$tT self-adhesive sponge rubber (Item 5), as

shown in Figs. 7 and $. Dimensions for the wooden

filler strip (Item 2 \ may be found in Fig. 9.

4. See Fig. 7. The 5/32 Tt x5/3Tf sponge rubber

material (Item 5) should be applied to the edges of

the machine compartment on the rear side of the unit

cabinet, as shown at points marked ,r c" in Fig. 7.

The sponge rubber seal should not extend higher than

the wooden filler strip, and a l/$ n space must be left

on the sides as indicated in Fig. 7 to provide clearance

for the metal sides of the rear panel.

5. The rear panel should now be installed on the

cabinet. Note that the interior surface of this panel

is fitted with l/2 TT fiberboard type sound-deadening insulating material. In addition, a separate sheet of

this material ( 29-3/4 n x26-l/2”xl/2 TT

) is recessed into

the rear surface of the machine compartment. If either

of these insulating surfaces are broken or missing they

should be replaced and installed at this time. The insulating board in the panel is necessary for satisfactory sealing of the panel.
•

'
- 9

-

6. See Figs. 10 and 11. The large void between

the condenser air duct and the side of the cabinet, as

shown in Fig. 10, should be filled with hairfelt or

other suitable filler material (Item 11) to within approximately l/2 inch of the surface of the condenser

air duct. On top of the filler material mastic sealer

(Item 3) should be applied to a thickness of about

l/2 inch. Attention should be given to good bonding

of the mastic material to both the condenser air duct

and the cabinet side, top, and condensate pan. The

finished treatment of this point can be seen in Fig. 11.

Additional sealing with mastic against the back panel

should be applied at points "a TT

, Fig. 11, and at the

power cord, point "b fT

, Fig. 11.

7. See Fig. 12. Sponge rubber gasketing material,

3/4 inch thick and 5/8 inch wide, (Item 6) should now

be applied around the machine compartment in the front

of the unit, as shown at points ,T a

tf

, Fig. 12. A l/8

inch space must be left on the sides as shown in Fig. 12

to provide clearance for the metal sides of the front

panel

.

8 . As can be seen from Fig. 13, the front cabinet

panel has two ears at its bottom, which hook over the

bottom cabinet channel. These ears should be cut off.

9. A sheet metal collar (Item 1) with 3/4 inch

thick x 5/8 inch wide self-adhesive sponge rubber

(Item 6) in place is shown in Fig. 8 9 Dimensional data

for construction of this collar are given in Fig,. 16.

It should be installed over the evaporator fan discharge

as shown at point TT c" in Fig. 11. The collar is intended to slip into the fan opening. It is expected that

some fitting will be necessary due to normal production

variations of the aid conditioning units.

10. Install top panel on the unit.

11. Install front panel on cabinet. Note that the

interior surface of this panel is fitted with l/2 inch

fiberboard type sound-deadening insulating material. In

addition, a separate sheet of this material (29-3/4 x 26

x 1/2") is recessed into the front surface of the machine

compartment. If either of these insulating surfaces are

broken or missing they should be replaced and installed

at this time. The insulating board in the panel is

necessary for satisfactory scaling of the panel.

- 10 -

12. See Figs. 14 and 15. Five #10x1-3/4” sheet

metal screws (Item 10) should now be installed to secure the front and rear panels to the cabinet at the

points marked f, a

,T in Fig. 14 and 15, in addition to

the existing screws. At the locations marked n b

,T in

both Figs. 14 and 15, a screw (Item 3) should be installed to secure each side panel to the condensate

pan. The fastening of the front, rear, and side

panels to the condensate pan should be done in a careful manner, so as to minimize the air flow between

condenser and evaporator compartments. It is important that these screws always be replaced after any

servicing of the air conditioning units.

13. Fig. 17 shows the cabinet side of the condenser shroud. The sheet metal edges of the shroud,

if bent, should be straightened, and 5/32 inch thick

by 5 /$ inch wide sponge rubber (Item 5) should be applied along these edges as shown in Fig. 17 at points

tr an

. Sponge rubber should not be placed across the

center dividing strip of the shroud, since sealing at

this surface will be effected by the sponge rubber attached to the wooden filler strip previously installed.

14. The condenser shroud should then be installed on the cabinet. An additional sheet metal screw

(Item 7) should be used approximately at the center of

the lower flange, as shown by point M b

TT

, Fig. 17.

15. A sheet metal baffle (Item 4) should be installed between the discharge and intake plenum of the

condenser shroud at the dividing strip, as shown in

Fig. 1$. Three #$xl/2 TT sheet metal screws (Item 7)

should be used at points marked n a

TT in Fig. 1$.

NOTE: IMPORTANT If a particular air conditioner is

located so that the condenser air baffle would be hazardous to passersby, it is recommended that it be eliminated

or suitably guarded.

16. All of the preceding 15 steps outlined are

important if the maximum results are to be realized.

If this work has been done carefully, the unit is

now ready for the test described in Section B below.

- 11 -

Part B - Test of Air Conditioning Unit

1. The purpose of the test described herein is

to enable the United States Marine Corps to determine

(after modifications described, previously) whether

other Sterling air conditioning units of the same

model have sufficient capacity to compare favorably

with the test unit, or whether additional repair of

the refrigeration systems by qualified refrigeration

personnel is needed to bring the capacity of the

units up to a satisfactory value.

The results of the test should be checked against

Fig. 19, which shows, for various temperatures of inlet evaporator and condenser air, the maximum evaporator air discharge temperatures that should be observed

if the capacity of the unit is to be as large as that

of the test unit after it was repaired.

The test results shown in Fig. 19 were obtained

with the unit submitted for test and are based on an

air delivery of approximately 270 cfm from the evaporator fan, with filter removed and a clean evaporator.

It is believed that other units of the same model will

have approximately the same air delivery for the

evaporator fan.

2. The assembled unit, with all panels and the

condenser shroud in place should be set up for test

in a room, or other enclosed space, such as a garage,

hall, or shop. The evaporator air and the condenser

air should both be drawn from within the enclosed

space, i.e., the unit should not be installed at a window but should be free-standing in the enclosed

space. The filter should be removed for the test unit

and the evaporator and condenser surfaces should be

free from dust or other obstructions to normal air

flow. The air conditioning unit should be turned on

by setting the selector switch in the "Cool" position.

3 o The only equipment needed for the test is a

sling psychrometer (wet- and dry-bulb thermometer) and

two mercury-in-glass or alcohol-in-glass thermometers.

- 12

4. All thermometers, including those in the sling

psychromet er , should be calibrated against each other in

an ice bath, containing a mixture of crushed ice and

water. Any deviation of the thermometers from the icepoint (32°F) should *be carefully noted for each individual

thermometer. This deviation is approximately linear for

other parts of the scale on most thermometers, hence if

a thermometer reads 34°F when immersed in the ice bath,

it would mean that 2°F -.should be subtracted from any

reading on this thermometer; for example, if a subsequent measurement on this thermometer shows 68°F, the

true temperature would be 66°F. If a thermometer should

read lower than 32°F when immersed in ice, the amount of

error should be added to the reading, of course.

5. After calibration, one of the thermometers should

be laid over the evaporator air outlet of the unit. The

other should be suspended in front of the evaporator air

inlet. The sling psychrometer should be used as follows:

The wick should be wetted well with distilled water, and

the psychrometer revolved rapidly in a vertical plane

parallel to and approximately 1 foot away from the evaporator air inlet. After whirling the psychrometer for

about 15 seconds, the temperature of the thermometer with

the wick should be read. Then the psychrometer should

be whirled for another 10 seconds, the temperature read

again, whirled again for 10 seconds, and the temperature

read for a third time. If, during any one measurement,

any temperature reading of the thermometer with the wick

has risen after a prior reading, the wicfc should be wetted

again, and the procedure described should be repeated.

The lowest temperature read on the wet bulb thermometer

should be considered as the wet bulb temperature of the

air. This temperature will always be lower than the dry

bulb temperature of the a.ir_ observed on the thermometer

without a wick.

6. The following readings should be recorded at

10-minute intervals during the test of the unit: The

wet bulb temperature of the air entering the evaporator,

the dry bulb temperature of the air entering the evaporator, and of the dry bulb temperature of the air leaving

the evaporator. The test should be continued for 40

minutes or longer, after readings become steady. These

recorded readings should be averaged after the test and

compared with Fig. 19.
.

.

. .

.
- 13 -

7. Fig. 19 shows the maximum dry-bulb temperature

of the evaporator discharge air which the unit should

produce under certain inlet wet- and dry-bulb temperatures. Curves are shown for a range of wet-bulb temperatures for three inlet dry-bulb temperatures, 70°F,

$0°F, and 90°F. The use of Fig. 19 is illustrated by the

following example: Assuming that the dry-bulb temperature of the evaporator inlet air is $0°F, and the wet-bulb

temperature is 70°F, enter the graph at the bottom, follow

the 70 degree wet-bulb line up until the curve marked $0°F

D.B. Inlet is reached. From this point of intersection

proceed horizontally to the left to read the expected

dry-bulb outlet temperature. For this example, the drybulb outlet temperature should be 65°F or lower.

If inlet dry-bulb temperatures between 70°F and $0°F,

or between $0°F and 90°F are encountered, a curve can

easily be approximated between these limits on Fig. 19.

3. If the dry bulb temperature of the evaporator

discharge air during the test is the same as or lower than

the dry-bulb outlet temperature shown in Fig. 19, the

unit is suitable for installation. If the dry bulb

temperature of the evaporator discharge air is higher

than shown in Fig. 19 by as much as two degrees it indicates a capacity reduction ranging from' 10 to The

greater loss of capacity corresponds to the higher ambient temperatures. Under these conditions, it is likely

that the refrigerating system of the air conditioning

unit needs servicing or that there are additional significant air leaks not sealed by the procedures described in

Part A of this report, and appropriate arrangements should

be made in that case for further examination of the unit.

V. CONCLUSION AND DISCUSSION

Both of the two sample Sterling air conditioning

units submitted for examination by the United States

Marine Corps were of poor cabinet construction in that

excessive air exchange between the condenser and evaporator sections lowered the net cooling capacity to such a value that the units would not warrant installation.

In addition one of the units had a defective compressor. Representatives of the compressor manufacturer

stated that the particular type of failure was quite rare.

- H -

A thorough sealing of the cabinet is necessary to

increase the net cooling capacity of the unit. Detailed steps outlined under the "Recommendations" Section

of this report show how this can be done. A relatively simple test procedure to be followed after sealing

is completed is also described which will determine

whether the unit is of sufficient net cooling capacity

to warrant installation.

Based on calorimeter tests of the sample unit,

after sealing of the cabinet had been completed, and

assuming that units in the field are similar, a net

cooling capacity of approximately 6000 Btu/hr (at

A.S.R.E. Standard Test condition of 95°F DB, 75°F WB

ambient and $0°F DB, 67°F WB room) can be expected

from these units if they are sealed as outlined.

If a unit in the f'ield, after sealing is completed,

fails to indicate a satisfactory capacity based on the

test procedure outlined, it must have air leaks not

found in the specimens tested here or the refrigeration

system must be faulty and in need of skilled attention.

Materials required to effect the sealing of one

unit are listed under the "Recommendations" section of

this report. Item 1, a sheet metal collar, Item 2, a

wood filler strip, and Item 4, an aluminum baffle, require fabrication and dimensional drawings are included.

It is suggested that a sufficient number of kits of

this material, packaged on a unit basis, be prepared

at a central source for the number of units to be

serviced. This method should be economically advantageous as compared to local procurement of the necessary items, and should not exceed $£ per kit, exclusive

of packaging and distribution costs.

The on-the-job time required to seal and test one

unit should not exceed one man-day for the sealing and

other modifications and one-half man-day for the test.

This is exclusive of the time required to remove a

unit from the window, or reinstall it, or uncrate a

unit, etc.

Photographs and Drawings

Figure 1. Front right quarter view of assembled air

conditioning unit as received for test,

with all panels in place.

- 15 -

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure £.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

Figure 13.

Figure 14.

Front left quarter view of assembled unit,

showing evaporator air inlet grill on left

side

.

Front view with front and top panels removed

showing arrangement of internal components.

Two valve plate assemblies and one cylinder

head from motor-compressor of first test

unit, showing ruptured cylinder-head gasket.

Front view of the machine compartment.

Arrows indicate certain places where mastic

sealing material is to be applied.

Rear view of the machine compartment. Arrows

indicate certain places where mastic sealing

material is to be applied.

Rear view of unit showing wood filler-strip

and self-adhesive gaskets in place on rear

surface of machine compartment.

Wood filler-strip and evaporator air discharge

collar, each with self-adhesive gasket attached.

Dimensional drawing of wood filler-strip.

Front view of evaporator section. Arrow designates void to be filled and sealed.

Same as Fig. 10, but showing mastic sealer in

place and evaporator air discharge collar installed . Front view of unit showing self-adhesive

gaskets in place on front surface of

machine compartment.

Inside surface of front and rear panels,

showing mounting ears which are to be

cut off.

Right front quarter view of assembled unit

showing points where additional sheet metal

screws are to be installed in the front and

right hand panels.

- 16 - Figure 15. Right rear quarters view showing where additional sheet metal screws are to be installed in the rear and left panels. The

air filter, behind the evaporator air inlet grill, can be seen clearly in this

picture.

Figure 16. Dimensional drawing of the sheet metal collar

for the evaporator air discharge opening.

Figure 17. View of the machine-end of the condenser

shroud, showing where self-adhesive gasket

is to be applied.

Figure IS. View of the outdoor-end of the condenser

shroud showing air baffle in place.

Figure 19. Graph of capacity check curves.

Figure 20. Dimensional drawing of condenser air

baffle.

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FIG. 3

FIG

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EVAPORATOR AIR DISCHARGE COLLAR

(Item I )

20 GAUGE GALVANIZED IRON

FIG, 16

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musnst

Dun

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J

1AI

CAPACITY CHECK CURVES

76

74

72

70

68

66

J 64

LlJ- 62

D

5

0 60

3

58

56

54

52

50

50 60 70 80 9 0

W.8. INLET TEMPERATURE

CONDENSER

AIR

BAFFL OZ

'9

Id

THE NATIONAL BUREAU OF STANDARDS

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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

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