4-8. LEAK TESTING THE REFRIGERANT SYSTEM
Supplies: Dry nitrogen gas (item 2, Appendix E)
Refrigerant 22 (item 8, Appendix E)
a. The entire repair area should be thoroughly leak tested after repair or replacement of any component, before it is
recharged with Refrigerant-22. Leak testing is also the method for troubleshooting when a system has lost all or part of its
refrigerant charge through an undetermined cause.
b. Testing Method. There are two acceptable methods for leak testing the refrigeration system.
(1) Refrigerant gas leak detector. If an electronic refrigerant gas leak detector is available it should be used in
accordance with the procedures contained in TM -4940-435-14, "Leak Detector, Refrigerant Gas".
The electronic refrigerant gas leak detector is highly sensitive to the presence of a
minute quantity of gas in the air, and due to this factor is quite effective in the
detection of small leaks. However, due to the rapid dispersion of refrigerant gas
into the surrounding air, difficulty may be encountered in pinpointing large leaks.
The detector must be used in a well ventilated but draft-free area.
(2) Soap solutions. In this method, a strong solution of a liquid detergent and water is brushed onto all points of
possible leakage while closely observing for the formation of bubbles.
If the soap solution testing method is used, thoroughly rinse with fresh water after
testing is completed. A residual soap film will attract and accumulate an excessive
amount of dust and dirt during operation.
c. Testing procedures. To perform leak testing by use of the electronic detector, it is necessary that the system be
pressurized with a proportion of refrigerant gas. To perform leak testing by use of the soap solution method the system
may be pressurized with dry nitrogen alone.
(1) To pressurize a system that has some refrigerant charge, for either leak testing method:
(a) Remove the caps from the high and row pressure service valves.
(b) Connect the hoses from a charging manifold to the service valve.
If it is possible that the problem may not be a leak and that you may not have to
replace a refrigeration system component Refrigerant-22 may be substituted for
the nitrogen in the following test. If nitrogen is used, you will have to discharge,
evacuate and recharge the system after this test is completed.
(c) Connect a nitrogen pressure regulator and nitrogen bottle to the center hose connection of the charging
(d) Open the unit service valves and the charging manifold valves.
(e) Open the nitrogen tank valve and pressurize the system to 350 psi (24.7 kg/cm ).
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