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Section XIII. MAINTENANCE OF T H E REFRIGERANT
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TM-5-4120-337-14 Air Conditioner Vertical: Compact Self-Contained Air Cooled Electrical Motor Driven Manual
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Table 4-3. Normal Operating Pressures and Currents.
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

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