Pumping Down The Unit; Refrigerant Leak Checking - Carrier 69NT40-561-019 Operation And Service Manual

7.3.2

Pumping Down the Unit

To service the filter drier, economizer, expansion valves, economizer solenoid valve, digital unloader valve or evap-
orator coil, pump the refrigerant into the high side as follows:
The scroll compressor achieves low suction pressure very quickly. Do not use the compressor
to evacuate the system below 0 psig. Never operate the compressor with the suction or dis-
charge service valves closed (frontseated). Internal damage will result from operating the com-
pressor in a deep vacuum.
a. Attach manifold gauge set to the compressor suction and discharge service valves. Refer to
b. Start the unit and run in the frozen mode (controller set below -10°C (14°F)) for 10 to 15 minutes.
c. Check function code Cd21 (refer to
continue to run until the valve opens.
d. Frontseat the liquid line service valve. Place start-stop switch in the OFF position when the suction reaches
a positive pressure of 0.1 bar (1.4 psig).
e. Frontseat the suction and discharge service valves. The refrigerant will be trapped between the compressor
discharge service valves and the liquid line valve.
f. Before opening up any part of the system, a slight positive pressure should be indicated on the pressure
gauge. Remove power from the unit before opening any part of the system. If a vacuum is indicated, emit
refrigerant by cracking the liquid line valve momentarily to build up a slight positive pressure.
g. 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.
h. After repairs have been made, be sure to perform a refrigerant leak check (refer to
evacuate and dehydrate the low side (refer to
i. Check refrigerant charge (refer to
7.3.3

Refrigerant Leak Checking

Never use air for leak testing. It has been determined that pressurized, mixtures of refrigerant
and air can undergo combustion when exposed to an ignition source.
a. The recommended procedure for finding leaks in a system is with a R-134a electronic leak detector. Testing
joints with soapsuds is satisfactory only for locating large leaks.
b. If the system is without refrigerant, charge the system with refrigerant 134a to build up pressure between 2.1
to 3.5 bar (30.5 to 50.8 psig). To ensure complete pressurization of the system, refrigerant should be
charged at the compressor suction valve and the liquid line service valve. Remove refrigerant cylinder and
leak-check all connections.
Only refrigerant 134a should be used to pressurize the system. Any other gas or vapor will contami-
nate the system, which will require additional purging and evacuation of the system.
c. If required, remove refrigerant using a refrigerant recovery system and repair any leaks. Check for leaks.
d. Evacuate and dehydrate the unit. (Refer to
e. Charge unit per Section
T-359
CAUTION
!
Section 4.2.2). The economizer solenoid valve should be open. If not,
Section
Section 7.3.5).
CAUTION
!
NOTE
Section
7.3.5.
7–4
7.3.4).
7.3.4.)
Section 7.2.
Section 7.3.3), and