The electronic leak detector is sensitive to the presence of refrigerant gas in the atmosphere. When
refrigerant gas is present in the atmosphere of the work area, false indications can result. Use in a well
ventilated but draft-free area.
(1) Electronic Leak Detector. Turn the electric unit on, and slowly pass the probe around all points of the
refrigeration system at which a leak could exist. Depending upon the type of detector used, a leak will be indicated by an
audible signal, a light, or by meter deflections.
(2) Soap Solution. Brush soap solution on all possible points of leakage, and watch for bubbles. Follow a
definite sequence to avoid missing any points that should be tested. Wipe the solution from all joints, and mark any point
at which a leak is found.
c. If leaks were detected,discharge the system (paragraph 5.22. a), repair leaks and retest as directed above. If
the system is leak-tight. double evacuate and charge the system as directed below.
5.25. Evacuating The System
Before the system is charged with refrigerant, it must be completely evacuated to exhaust water vapor, non-condensable
gases and other impurities which would prevent the system from operating. Proceed as follows:
The following instructions are provided for use by refrigeration shops furnished with only the most basic
equipment,. If more sophisticated equipment, such as two-valve or four-valve service manifolds is avail-
able, it should be used by making appropriate modifications to these instructions.
to figure 5-8 for identification
of service valves.
Connect a vacuum pump
to the suction service valve
gauge port, and a vacuum gauge to the discharge service valve gauge port. Start the pump, and open both service valves.
Operate the vacuum pump until pressure in the system is reduced to not more thsn 500-microns. Close the suction service
valve, and turn the vacuum pump off. Let the unit stand in this condition for at least three hours. If the system holds the
vacuum without change of pressure. continue with step b. If the 500-microns vacuum cannot be held for three hours,
break the vacuum with dry nitrogen and retest for leaks. If 500-micron vacuum cannot be achieved, one or more of the
following reasons may account for the problem.
(1) Presence of water vapor in the system. Continued pumping will correct this condition.
(2) Leaks in the refrigeration system. Break the vacuum with dry nitrogen, and retest fcr leaks.
(3) Internal leakage of vacuum pump. Test the pump by connecting a vacuum gauge directly to the vacuum
pump intake and continue to pump. If pump still fails to reach 500 microns. the pump is faulty.
b. With the suction line service valve closed, disconnect the vacuum pump attach a cylinder of dry nitrogen.
Leave the connection to the suction service valve somewhat loose, and open the nitrogen cylinder shutoff valve slightly
for a few seconds to purge the line of air. Tighten the connection and crack the suction servicevalveopem slightly to break
the vacuum. Leave in this configuration until the system reaches atmospheric pressure (760 mm) then close the suction
service valve and the cylinder shutoff valve, and disconnect the nitrogen cylinder.
c. Reconnect the vacuum pump to the suction service valve gauge port, and start the pump. Open the suction
service valve, and again pump until a 500-micron vacuum is achieved. This double evacuation will remove all traces of
water vapor and non-condensable gas from the system. Close the suction service valve, and disconnect the vacuum
pump. Close the discharge service valve, and remove the vacuum gauge.
5.26. Charging The System
Refer to figure 5-8 for identification of service valves. Connect a cylinder of refrigerant, R22, loosely to the discharge
line service valve, and open the cylinder shutoff valve for a few seconds to purge the line of air. lighten the service vslve
connection. Charge the refrigeration system as directed in the following steps: