Pumping Down The Unit; Removing The Refrigerant Charge; Leak Checking The Unit; Evacuation And Dehydration - Carrier Supra 950MT Operation & Service Manual

5.4.1

Pumping Down the Unit

To service the filter drier, expansion valve, CPR valve, or evaporator coil, pump most of refrigerant into condenser
coil and receiver as follows:
a. Close (backseat) suction and discharge service valve (turn counterclockwise) to close off gauge connection
and attach manifold gauges to valves.
b. Open valves two turns (clockwise) and purge gauge line.
c. Close the receiver outlet (king) valve by turning clockwise. Start unit and run in high-speed cooling. Place
the RUN/STOP switch in the STOP position when unit reaches 1 psig (0.1 kg/cm).
d. Frontseat suction service valve and the refrigerant is trapped between the compressor suction service valve
and the manual shutoff (king) valve.
e. Before opening up any part of the system, a slight positive pressure should be indicated on the pressure
gauge.
f. When opening up the refrigerant system, certain parts may frost. Allow the part to warm to ambient tempera-
ture before dismantling. This avoids internal condensation which puts moisture in the system.
g. Open (backseat) king valve and midseat suction service valve.
h. Leak check connections with a leak detector.
i. Start the unit in cooling and check for noncondensibles.
j. Check the refrigerant charge (refer to
If the system must be opened between the compressor discharge valve and receiver, store the refrig-
erant charge in an evacuated container. Whenever the system is opened, it must be evacuated and
dehydrated (refer to
5.4.2

Removing the Refrigerant Charge

Connect a refrigerant recovery system to the unit to remove refrigerant charge. Refer to instruction provided by the man-
ufacturer of the refrigerant recovery system.
5.5

LEAK CHECKING THE UNIT

If system was opened and repairs completed, leak-check the unit.
a. Use an electronic leak detector to find leaks in the system. Testing joints with soapsuds is satisfactory only
for locating large leaks.
b. If the system is without refrigerant, charge system with refrigerant to build up pressure between 30 to 50
psig (2.1 to 3.5 kg/cm). Remove refrigerant cylinder and leak check all connections.
It must be emphasized that only the correct refrigerant cylinder be connected to pressurize the sys-
tem. Any other gas or vapor will contaminate the system, which will require additional purging and
evacuation of the high side (discharge) of the system.
c. Remove refrigerant using a refrigerant recovery system and repair any leaks. Evacuate and dehydrate the unit
(refer to Section 5.6). Charge unit with refrigerant (refer to
5.6

EVACUATION AND DEHYDRATION

5.6.1

General

Moisture can seriously damage refrigerant systems. The presence of moisture in a refrigeration system can have
many undesirable effects. The most common are copper plating, acid sludge formation, "freezing-up" of metering
devices by free water, and formation of acids resulting in metal corrosion.
5.6.2

Preparation

a. Evacuate and dehydrate only after pressure leak test (refer to
62-11863
Section
Section 5.6)
5.7.2).
NOTE
NOTE
Section 5.7).
Section 5.5).
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