Component Removal and Replacement
The first step in the removal of any component in a
refrigeration system for repair and/or replacement is to
pump down the system. As you have learned, this
LO
HI
procedure traps practically all of the refrigerant in the
condenser and receiver and, by the proper positioning
of the valves, the evaporator, expansion valve, and
compressor (with connecting lines) can be removed
with a minimum loss of refrigerant.
REMOVING E X PA N S I O N O R F L OA T
VALVES.--To help ensure good results when remov-
ing expansion or float valves, pump the system down to
a suction pressure of just over zero. Then, remove the
expansion valve, and plug the opened end of the liquid
line and evaporator coil to prevent air from entering the
system. Repair or replace the expansion valve, and
VACUUM PUMP
COMPRESSOR
connect it to the liquid valve. Crack the receiver service
ASf11026
valve to purge air from the liquid line and the expansion
Figure 11-26.--Connections for drawing a vacuum.
valve. Connect the expansion valve to the evaporator
coil inlet and tighten the connection. Pump a vacuum
into the low side of the system to remove any air and
4. Tighten the gland nuts of the manifold gauge
moisture.
set at the manifold and at the compressor suction and
discharge ports.
REMOVING THE EVAPORATOR.--When it
is necessary to replace an evaporator, pump down the
5. Open the compressor suction and discharge
system and disconnect the liquid and suction lines.
valves by turning them clockwise one to two turns (mid
Then, remove the expansion valve and the evaporator.
seat) from the back seated position.
After making the necessary repairs, reinstall the
6. Plug in the vacuum pump, and turn it on.
evaporator. Replace the expansion valve, and connect
the liquid and suction lines. Remove moisture and air
7. Monitor the gauge set to ensure that a vacuum
by pumping a deep vacuum in the system. Check for
of no more than 2.5 mmHg, absolute, registers on the
leaks and correct them, if found. After fixing any leaks,
gauge. The length of time to reach this reading will
pump a deep vacuum again. Repeat the process until no
vary, depending upon the amount of moisture in the
more leaks are found.
system and the efficiency of your vacuum pump.
REMOVING THE COMPRESSOR.--As was
8. After the system has been evacuated, attach a
the case in removing the evaporator, the first step in
source of dry nitrogen to the liquid charging line.
removing the compressor is to pump down the system.
9. Slowly break the vacuum with the dry nitrogen
To remove it from service, the compressor must first be
to a maximum of 300 psi, as read on the high-pressure
isolated by closing the suction and discharge service
gauge on the control panel and on the regulator of the
valves. Then, pressure within the compressor must be
nitrogen cylinder.
equalized. Both suction pressure in the crankcase and
head pressure can be equalized to atmospheric pressure
NOTE: Check your technical manual to confirm
by either positioning the service valves to the vent
the correct pressure for your system.
position or cracking the connections to the compressor.
10. Repeat steps 6 and 7. This double evacuation
When the lines to the compressor are disconnected, be
should remove all traces of water vapor from the
certain to cover or block them to prevent dirt and
system.
moisture from entering them until the compressor can
be reinstalled. After reinstalling the compressor, the air
11. Let the system stand, under vacuum, for at least
must be evacuated by drawing a vacuum on the system.
1 hour. If no noticeable rise in pressure has taken place
Then, the system must be recharged.
after 1 hour, the system is ready for charging.
11-27
