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62-11637
8–42
Figure 8.38 Check Valves
8.9.10
Replacing Check Valve
A check valve (see
) allows flow in one
direction only.
The function of the discharge check valve is to prevent
liquid refrigerant from migrating back the compressor
during the unit off cycle.
The function of the hot gas bypass check valve is to
raise the receiver pressure (when the ambient tem-
perature is low) so that refrigerant can flow from the
receiver to the evaporator when the unit is in heating or
defrost.
NOTE
These check valves are not serviceable and
must be removed and replaced as an
assembly.
1. Remove the refrigerant charge. Refer to
NOTICE
Unit uses R404A and POE oil. The use of
inert gas brazing procedures is manda-
tory for all Carrier Transicold refrigera-
tion units; otherwise compressor failure
will occur. For more information Refer to
Technical Procedure 98-50553-00 Inert
Gas Brazing.
2. Using a pipe cutter, cut the valve stub-outs and
unbraze the remaining stub-out from the con-
necting copper.
3. Clean tube stubs so new valve fits easily. Posi-
tion new valve.
4. Wrap valve with wet rags to keep cool when
brazing.
5. Braze valve in place and cool connections with
wet rag.
6. Leak check, evacuate & dehydrate, and charge
system as required. Refer to
,
&
8.9.11
High Pressure Switch
a. Replacing High Pressure Switch
1. Pump down the compressor. Refer to
.
2. Disconnect wiring from switch, and remove
switch.
3. Install switch after verifying switch settings.
(Refer to following step b.)
4. Leak check, evacuate & dehydrate, and charge
system as required. Refer to
,
&
b. Checking High Pressure Switch
WARNING
!
Do not use a nitrogen cylinder without a
pressure regulator. Cylinder pressure is
approximately 2350 PSIG (160 bar). Do
not use oxygen in or near a refrigerant
system as an explosion may occur. (See
Figure 8.39 Typical Setup for Testing Pressure
Switch
1. Cylinder Valve and Gauge
2. Pressure Regulator
3. Nitrogen Cylinder
4. Pressure Gauge 0 to 400 PSIG (0 to 27.2
bar)
5. Bleed-Off Valve
6. Switch
- - - - -
Discharge Check Valve
Hot Gas Check Valve
Summary of Contents for Transicold X4 7300
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