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TM 5-4120-270-15
d.
Installation. Replace a defective coil
assembly and install in reverse order of removal as
illustrated in figure 5-13. Test, evacuate and recharge
refrigerating system (para 28, 29, 30).
6-25.
Systems Access Valves
a.
General. Two angle-type access valves
(suction line and discharge line) provide access to the
refrigerant system.
b.
Removal.
Discharge
the
refrigerant
system and refer to figure 5-11 and remove the access
valves.
c.
Installation. Replace a defective valve and
install valves in reverse order of removal as illustrated in
figure 5-11. Test, evacuate and recharge the unit
refrigeration system (para 628, 29, 80).
6-26. Compressor and Motor Assembly
a.
General. The sole
purpose
of
the
compressor is to raise the pressure of refrigerant gas
from evaporator pressure to condensing pressure. The
function of the compressor i ’to deliver refrigerant to the
condenser at a pressure and temperature at which the
condensing process can readily be accomplished. The
motor/compressor is a hermetically sealed unit and is not
repairable in the field. An inoperative compressor is
usually due to a mechanical failure causing the
compressor to freeze, a control failure, or a motor
burnout. If the motor/compressor is mechanically frozen
or there has been a motor burnout, the compressor must
be removed and replaced. When the motor of a
hermetic compressor fails, high temperatures may
develop within the compressor causing a breakdown of
the oil and refrigerant, resulting in formation of acid,
moisture, and sludge. All these are extremely. corrosive
and must be flushed from the system. Repeated
burnouts will occur if all of the contaminants are not
removed.
b.
Cleaning and Inspection. The immediate
area around the compressor mounting should be
thoroughly cleaned and dried. Examine all connections
for foreign matter of any kind. Inspect area thoroughly.
Warning:
Avoid
bodily
contact
with
the
refrigerant, especially eye contact. Avoid inhalation of
refrigerant fumes.
c.
Removal.
Discharge
the
refrigerant
system, refer to figure 5-6, and remove the compressor.
If there has been a burnout, flush system as described in
e below prior to installation of new compressor.
d.
Installation.
Install
a
replacement
compressor in reverse order of removal, as illustrated in
figure 5-6. Pressure test, evacuate and recharge
refrigerating system (para 6-28, 29, 30).
e.
Flushing The System. After compressor
motor burnout, flush the system as described below:
(1)
Refrigerant-11, along with a small amount
of dry nitrogen to force the refrigerant through the tubing,
is recommended for flushing the system.
(2)
Remove the dehydrator as described in
paragraph 5-31.
(3)
Flush the refrigerant tubing to remove all
contaminants.
(4)
The liquid line bypass and the hot gas
bypass valves are normally open when deenergized.
These valves must be open to allow the flushing
refrigerant to flow through the tubing.
6-27.
Compressor Crankcase Heater
a.
General. The compressor crankcase
heater is designed to prevent refrigerant sludging. It
,provides heat to prevent sludging and oil pumping
problems when the compressor is exposed to low
ambient temperatures. It is a 208 volt, 120 watt
resistance heater enclosed within tubing and protected
by a thermally insulated cover.
b.
Removal. Refer to paragraph 5-24, and
remove the compressor. Refer to figure 6-12 and
remove the crankcase heater.
c.
Installation. Replace defective heater and
install in reverse order of removal as illustrated in figure
6-12. Refer to paragraph 524, and install the
compressor.
Test,
evacuate
and
recharge
the
refrigerant system (para 6-28, 29, 30).
6-15
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