Pressure switches - TM-5-4120-337-140050

detector is the preferred method of testing for leaks

p r e s e n t and continuous observation should be made

in the refrigerant system if an electronic halogen

f o r incresase in moisture content. A definite yellow

tester is not available. Pass the exploring tube

c o l o r indicates the presence of excessive moisture in

s l o w l y over all sweat fittings, mechanical couplings

t h e system. The air conditioner should be taken out

and valves. If refrigerant is leaking from the

of service immediately and referred to DS

system, the flame of the halide torch will change

Maintenance for correction.

from blue to green when the leak is small. If the

(2) R e f r i g e r a n t c h a r g e . The presence of a clear

leak is large, the flame will be dense blue with a

sight glass when the air conditioner is on the cooling

reddish tip; or a large leak may extinguish the

cycle indicates that there is an adequate charge of

torch. Mark all spots where leaks are noticed.

r e f r i g e r a n t . The presence of bubbles or foam in the

glass indicates a shortage of refrigerant which

4-56. Pressure switches

should be referred to DS Maintenance for

a . General. The air conditioner is equipped with

correction. Bubbles and foaming will occur upon

three pressure switches. Low pressure cutout S6 is

initial start-up and following change-over between

provided to prevent harmful effects due to ex-

t h e cooling and by-pass cycles of operation so that

t r e m e l y low refrigerant pressure. It is set to open at

observation for a clear sight glass should be made

2 5 10 PSIG. High pressure cutout S5 is provided

after stable operation has been established.

to prevent harmful effects due to extremely high

4-58. Compressor

refrigerant pressure. It is set to open at 460 10

P S I G . Switches S5 and S6 are wired in series with

a . General. The function of the compressor is to

the compressor control circuit and automatically

deliver refrigerant to the condenser coil at a

deenergize this circuit upon opening. S5 and S6

pressure and temperature at which the condensing

must be reset manually by depressing the reset

process can readily be accomplished. The com-

buttons located at the top rear of the air con-

p r e s s o r raises the pressure of the refrigerant suction

gas to the condensing discharge pressure.

ditioner. The switches are found in a metal en-

b. Inspection. Inspection of the compressor

closure located in the top rear section of tbe air

includes checking for refrigerant leaks particularly

conditioner. Pressure switch S8 is provided to

where the suction, pre-cooler and discharge lines

s w i t c h the fan motor from Low to High speed when

enter and leave the compressor. Inspect the pre-

the refrigerant pressure reaches 405 17 PSIG.

c o o l e r coil for dents, cracks or other damage. When

When the pressure drops to 285 17 PSIG the

inspection of the compressor is accomplished, the

switch opens and the fan motor automatically goes

compressor mounts should be inspected for secure

f r o m High to Low speed. This switch is located in

mounting. The four nuts which fasten the com-

t h e discharge refrigerant line close to the fan motor.

pressor to the base panel of the air conditioner

b. Test of Pressure Switches S5 and S6.

should be tightened securely. Tbe eight rubber

(1) Remove the top panel (para 4-11).

resilient mounts located at the top and bottom of

(2) Remove the four screws which secure the

e a c h of the four holes in the base panel under the

pressure switch enclosure to the rear panel and

compressor feet should be inspected to insure that

remove the enclosure.

there is no undue deterioration. Defective rubber

(3) Using a multimeter check for continuity

resilient mounts should be reported to GS Main-

from terminal 1 of S6 to terminal 2 of S5. Con-

tenance for replacement.

t i n u i t y should exist if the pressures are in the range

c. Test. Test of the compressor consists of

from 25 to 460 PSIG.

observation for normal operating pressures under

(4) Check the capillary tubes leading to the

n o r m a l r u n n i n g current a n d

load,

cooling

two pressure switches for kinks or breaks.

measurement of the winding and winding in-

4-57. Sight Glass

s u l a t i o n resistance of the internal motor. Insulation

a . G e n e r a l . The sight glass provides a means of

resistance between the windings and the com-

determining the moisture content and adequacy of

p r e s s o r frame should be not less than 60 megohms.

t h e refrigerant charge of the system. The sight glass

The main winding (terminal pin A to C) should

is located in the top rear of the air conditioner.

range between .6 to .8 ohms and the auxiliary

b. Inspection.

winding (terminal pin A to Pin B) should be be-

(1) Moisture content. The center disc of the

tween 5 and 7 ohms. The current and pressures

g l a s s is green when the refrigerant system is dry. A

should be as shown in table 4-3.

chartreuse color indicates that some moisture is

4-18