TM 9-4120-357-14
(a) Electronic Leak Detector. Turn the electronic unit on, and slowly pass the probe around all points of the re-
frigeration 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.
(b) Halide Torch. Turn on the gas from the cylinder and light the torch. Adjust to obtain a stable light-blue flame.
Pass the open end of the sensing tube slowly around all locations at which a leak could exist. A small leak will be indi-
cated by the flame turning from blue to indigo with a red tip, or the torch may be extinguished.
(c) Soap Solution. Brush soap solution on all possible points of leakage, and watch for bubbles. Follow a definite
sequence from all joints, and mark any point at which a leak is found.
(5) Discharge the system in
accordance with paragraph 5-6. If
leaks are detected, repair and retest as
directed
above. If system is leak-tight, proceed as follows:
(a) Connect a vacuum pump to the suction service valve gage port, and a vacuum gage to the discharge service
valve gage port. Start the pump, and open both service valves. Operate the vacuum pump until pressure in the system
is reduced to not more than 500-Microns. Close the suction line 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, continue with step
(b) . If 500-Micron 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 problem.
2. Leak in the refrigeration system. Break vacuum with try nitrogen, and retest for leaks.
3. Internal leakage of vacuum pump. Test pump by connecting the gage directly to the vacuum pump intake and
continuing to pump. If pump still fails to reach 500-Microns, pump is faulty.
(b) With the suction line service valve closet, disconnect the vacuum pump and attach a
cylinder of
dry nitrogen.
Leave the connection to the suction line service valve loose, and open the cylinder shutoff valve for a few seconds to
purge the line of air. Tighten the connection, and crack the suction line service valve open slightly to break the vacuum.
Leave in this configuration until system reaches atmospheric pressure (760 MM) , then close the suction service valve
and cylinder shutoff valve. Disconnect the nitrogen cylinder.
(c) Reconnect the vacuum pump to suction line service valve gage port, and start the pump. Open the suction line
service valve, and again pump until a 500-Micron vacuum is achieved. This double evacuation will remove all traces of
water vapor from the system. Close the suction line service valve, and disconnect the vacuum pump. Close the dis-
charge line service valve, and remove the vacuum gage.
(d) Connect a cylinder of refrigerant, R22, loosely to the discharge line service valve, and open the cylinder shut-
off valve for a few seconds to purge the line of air. Tighten the service valve connection. Charge the refrigeration sys-
tem as directed in the following steps:
1. Place the refrigerant cylinder on a scale of sufficient capacity, with the shutoff valve down, or suspend the
cylinder from a spring scale or beam scale, with the valve end down.
NOTE
If cylinder is equipped with both liquid and gas (vapor) valves, connect the line to the liq-
uid valve.
2. Weigh the cylinder, and record the weight.
3. Open the discharge line service valve, and slightly open the refrigerant cylinder shutoff valve. Liquid refriger-
ant will be sucked into the refrigeration system rapidly at first, then more slowly as pressures begin to equalize. When
25 pounds (11.4 KG) of refrigerant have flowed into the refrigeration system, as indicated by the scale, close the dis-
charge line service valve and the cylinder shutoff valve.
g. Assembly and Operating Check. Prepare the air conditioner for an operating check by installing the junction box
and control panel assembly in the following manner:
(1) Place the junction box and control panel assembly in the air conditioner, and secure with six screws (7, Figure
4-3) through the casing and into the mounting flange, and two screws (8) and washers (9) through the mounting
bracket.
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