Service manual

6-6T-294-01
6.5 REFRIGERANT LEAK CHECKING
WARNING
Never mix refrigerants with 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.
b. Ifthesystemiswithoutrefrigerant,refertosections
6.3 and 6. 4 and, chargethe system with refrigerant
to build up pressure between 2.1 to 3.5 kg/cm@ (30
to 50 psig). Remove refrigerant cylinder and
leak-check all connections.
NOTE
It must be emphasized that only the correct
refrigerant cylinder be connected to pressurize
the system. Any other gas or vapor will
contaminate the system, which will require
additional purging and evacuation of the
system.
c. Remove refrigerant using a refrigerant recovery
system and repair any leaks.
d. Evacuate and dehydrate the unit. (Refer to section
6.6.)
e. Charge unit per section 6.7.
6.6 EVACUATION AND DEHYDRATION
6.6.1 General
Moisture is the deadly enemy of refrigeration systems.
The presence of moisture in a refrigeration system can
have m any undesirable effects. The most common are
copper plating, acid sludgeformation, “freezing-up”of
metering devicesby freewater, and formationof acids,
resulting i n metal corrosion.
6.6.2 Preparation
a. Evacuate and dehydrate only after pressure leak
test. (Refer to section 6.5.)
b. Install manifold gauges (refer to section 6.3), and
recover the refrigerant (refer to section 6.4).
c. Essential tools to properly evacuate and dehydrate
any system include a vacuum pump (8 m
3
/hr = 5
cfm volume displacement, P/N 07-00176-01) and
electronic vacuum gauge.
d. If possible, keep the ambient temperature above
15.6_C(60_F)tospeedevaporation of moisture.If
the ambient temperature is l ower than 15.6_C
(60_F), ice might form before moisture removal is
complete. Heat lamps or alternate sources of heat
maybeusedtoraisethesystemtemperature.
e. Tohelpspeed up theevacuation procedure, replace
the filter-drierwith a section of 3/8 inch ID copper
tubing.
6.6.3 Procedure
a. Remove all refrigerant using a refrigerant recovery
system.
b. The recommended method to evacuate and
dehydrate the system is to connect two evacuation
hoses,asshown inF igure 6-5,tothevacuumpum p
and refrigeration unit. DO NOT use standard
service hoses, as they are not suited for evacuation
purposes. Also as shown, connect a evacuation
manifold, with evacuation hoses only, to the
vacuum pump, electronic vacuum gauge, and
refrigerant recovery system.
c. With the manifold gauge hand valves back seated,
andt hevacuumpumpandelectronicvacuumgauge
valves open, start the pump and draw a deep
vacuum. Shut off the pum p and check to see if the
vacuum holds. This operation is to test the
evacuation setup for leaks. Repair if necessary.
d. Open the vacuum pump and electronic vacuum
gaugevalves, if they arenot alreadyopen.Startthe
vacuum pump. Evacuate unit until the electronic
vacuum gauge indicates 2000 mi crons. Close the
electronicvacuumgaugeandvacuumpumpvalves.
Shut off t he vacuum pump. Wait a few minutes to
be sure the vacuum holds.
e. Break the vacuum with clean dry refrigerant gas.
Use refrigerant specified for the unit. Raise system
pressure to approximately 2 psig, monitoring it
with the compound gauge.
f. Remove refrigerant using a refrige rant recovery
system.
g. Repeat steps (e) through (g) one tim e.
h. Remove the copper tubing and change the
filter-drier.Evacuateunitto500microns.C losethe
electronicvacuumgaugeandvacuumpumpvalves.
Shutoffthevacuumpump.Waitfiveminutestosee
ifvacuumholds.Thisprocedurechecksforresidual
moisture and/or leaks.
i. With a vacuum still in the unit, the refrigerant
charge may be drawn into the system from a