6-3
T-292
6.3.3 Refrigerant Leak Checking
WARNING
Never use air for leak testing. It has been
determined that pressurized, air-rich mix-
tures 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/cm
@
(30 to 50 psig). To ensure complete
pressurization of the system, refrigerant should be
charged at the compressor suction and economizer
service valves and the liquid line service valve. Also,
the area between the suction modulating valve and
evaporator expansion valve may not be open to these
charging points. Pressure between these compo-
nents may be checked at the low side access valve
(item 15, Figure 2-2) or by checking that the suction
modulating valve is more than 10% open at controller
function code Cd01. The suction modulating valve
may be opened by use of the controller function code
Cd41 valve override control (refer to paragraph 6.17).
Remove refrigerant cylinder and leak-check all con-
nections.
NOTE
Only refrigerant 134a should be used to pres-
surize the system. Any other gas or vapor will
contaminate the system, which will require
additional purging and evacuation of the sys-
tem.
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 paragraph
6.3.4.)
e. Charge unit per paragraph 6.3.5.
6.3.4 Evacuation and Dehydration
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.
Preparation
a. Evacuate and dehydrate only after pressure leak test.
b. Essential tools to properly evacuate and dehydrate
any system include a vacuum pump (8 m
3
/hr = 5 cfm
volume displacement) and an electronic vacuum
gauge. (The pump is available from Carrier Trans-
icold, 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 sys-
tem pump down by replaceing the filter-drier with a
section of copper tubing and the appropriate fittings.
Installation of a new drier may be performed during
the charging procedure.
6
4
5
D
S
2
3
11
9
10
1
7
8
1. Liquid Service Con-
nection (if equipped)_
2. Receiver or Water
Cooled Condenser
3. Compressor
4. Discharge Service
Connection
5. Economizer Service
Connection
6. Suction Service Con-
nection
7. Vacuum Pump
8. Electronic Vacuum
Gauge
9. Manifold Gauge Set
10. Refrigerant Cylinder
11. Reclaimer
Figure 6-4. Refrigeration System Service Connec-
tions
Procedure - Complete system
NOTE
Refer to Partial System procedure for informa-
tion pertaining to partial system evacuation and
dehydration.
a. Remove all refrigerant using a refrigerant recovery
system.
b. The recommended method to evacuate and dehy-
drate the system is to connect evacuation hoses at
the compressor suction, compressor economizer
and liquid line service valve (see Figure 6-4). Be sure
the service hoses are suited for evacuation purposes.
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