5-11 62-11863
b. Essential tools to properly evacuate and dehydrate any system include a good vacuum pump (5 cfm = 8m-H vol-
ume displacement, P/N 07-00176-01) and a good vacuum indicator such as a thermocouple vacuum gauge
(vacuum indicator).
The use of a compound gauge is not recommended due to its inherent inaccuracy.
c. Keep the ambient temperature above 60°F (15.6°C) to speed evaporation of moisture. If ambient tempera-
ture is lower than 60°F (15.6°C), ice might form before moisture removal is complete. Heat lamps or alter-
nate sources of heat may be used to raise system temperature.
5.6.3 Procedure for Evacuating and Dehydrating System
a. Remove refrigerant using a refrigerant recovery system.
b. The recommended method to evacuate and dehydrate the system is to connect three evacuation hoses as
shown in Figure 5.7 to the vacuum pump and refrigeration unit (see note). Also, as shown, connect an
evacuation manifold, with evacuation hoses only to the vacuum pump, electronic vacuum gauge, and refrig-
erant recovery system.
Do not use standard service hoses, as they are not suited for evacuation purposes.
c. With the unit service valves closed (back seated) and the vacuum pump and electronic vacuum gauge valves
open, start the pump and draw a deep vacuum. Shut off the pump and check to see if the vacuum holds. This
operation is to test the evacuation setup for leaks, repair if necessary.
d. Midseat the refrigerant system service valves.
e. Open the vacuum pump and electronic vacuum gauge valves, if they are not already open. Start the vacuum
pump. Evacuate unit until the electronic vacuum gauge indicates 2000 microns.
f. Close the electronic vacuum gauge and vacuum pump valves. Shut off the vacuum pump. Wait a few min-
utes to be sure the vacuum holds.
g. Break the vacuum with clean dry refrigerant. Use refrigerant that the unit calls for. Raise system pressure to
approximately 2 psig.
h. Remove refrigerant using a refrigerant recovery system.
i. Repeat steps e. through g. one time.
j. Evacuate unit to 500 microns. Close off vacuum pump valve and stop pump. Wait five minutes to see if vac-
uum holds. This checks for residual moisture and/or leaks.
k. With a vacuum still in the unit, the refrigerant charge may be drawn into the system from a refrigerant con-
tainer on weight scales. The correct amount of refrigerant may be added by observing the scales (refer to
Section 5.7).
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