Refrigerant Leak Checking; Evacuation And Dehydration; General; Preparation - Carrier 69NT40-541-001 Operation And Service

a. Attach manifold gauge set to compressor service valves. Refer to
b. Start the unit and run in a cooling mode for 10 to 15 minutes. Frontseat the liquid line service valve. Place
start-stop switch in the OFF position when the suction reaches a positive pressure of 0.1 kg/cm² (1.0 psig).
c. Frontseat the suction service valve. The refrigerant will be trapped between the compressor suction service
valve and the liquid line valve.
d. Before opening up any part of the system, a slight positive pressure should be indicated on the pressure
gauge. If a vacuum is indicated, emit refrigerant by cracking the liquid line valve momentarily to build up a
slight positive pressure.
e. 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.
f. After repairs have been made, be sure to perform a refrigerant leak check (refer to
uate and dehydrate the low side (refer to
g. Check refrigerant charge (refer to
7.5

REFRIGERANT LEAK CHECKING

Never use air for leak testing. It has been determined that pressurized, air-rich mixtures of
refrigerants 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 kg/cm² (30 to 50 psig). 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.
d. Evacuate and dehydrate the unit. (Refer to
e. Charge unit per Section
7.6

EVACUATION AND DEHYDRATION

7.6.1

General

Moisture is the deadly enemy of refrigeration 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.
7.6.2

Preparation

a. Evacuate and dehydrate only after pressure leak test. (Refer to
b. Essential tools to properly evacuate and dehydrate any system include a vacuum pump (8 m
volume displacement) and an electronic vacuum gauge. (The pump is available from Carrier Transicold, P/N
07-00176-11.)
c. If possible, keep the ambient temperature above 15.6°C (60°F) to speed evaporation of moisture. If the
ambient temperature is lower than 15.6°C (60°F), ice might form before moisture removal is complete. Heat
lamps or alternate sources of heat may be used to raise the system temperature.
d. Additional time may be saved during a complete system pump down by replacing the filter-drier with a sec-
tion of copper tubing and the appropriate fittings. Installation of a new drier may be performed during the
charging procedure.
Section
Section 7.7).
WARNING
!
NOTE
Section
7.7.
7–5
Section
7.6).
7.6.)
Section 7.5.)
7.3.
Section 7.5), and evac-
3
/hr = 5 cfm
T-316