TM 9-4120-357-14
h. Charging the System. Prepare the refrigeration system for charging by attaching a pressure gauge to the high-
pressure service valve gauge port, and a pressure hose and drier-strainer, loosely, to the suction service valve gauge
port. Leave both valves closed. Proceed as follows:
WARNING
Avoid contact with liquid refrigerant or escaping refrigerant gas. Ir-
reversible tissue damage can result from sudden freezing. Be especially
careful to protect the eyes. Avoid inhaling high concentrations of refrig-
erant gas, and prevent gas coming into direct contact with flame or hot
metal surfaces; lethal phosgene gas can be formed.
(1) Connect a cylinder of refrigerant, R22, to the pressure hose. Open the cylinder shutoff valve slightly to purge
the hose of air, then tighten the hose connection to the suction service valve gage port.
(2) Open both service valves and the cylinder shutoff valve. Charge the system with refrigerant gas until the gage
on the discharge (high-pressure) service valve registers 70 PSI (5 KG/CM2). Close the suction service valve and the
cylinder shutoff valve.
(3) Transfer the charging line to a cylinder of dry nitrogen. Open the cylinder shutoff valve and the suction service
valve. Let nitrogen flow into the refrigeration system until the discharge pressure gage reads 350 PSI (21.4 KG/CM2).
Turn off the suction and discharge service valves and the cylinder shutoff valve. Disconnect the charging line from the
suction service valve.
(4) Test the refrigeration system for leaks, using an electronic leak detector, Halide torch or soap bubble method.
Discharge the system by attaching a hose to the discharge valve gage port, and discharging the gas slowly to avoid
blowing oil out of the system. If leaks are detected, repair and retest as directed above. If system is leak-tight proceed
as follows:
(5) 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 (6).
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:
(a) Presence of water vapor in the system. Continued pumping will correct this problem.
(b) Leaks in refrigeration system. Break the vacuum with dry nitrogen, and retest for leaks.
(c) Internal leakage of vacuum pump. Test the pump by connecting gage directly to vacuum pump intake and
continuing to pump. If pump still fails to reach 500-Microns, pump is faulty.
(6) With the suction line service valve closed, disconnect the vacuum pump and attach a cylinder of dry nitrogen.
Leave the connection to the suction 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 the system reaches atmospheric pressure (760 MM), then close the suction service valve and
cylinder shutoff valve, and disconnect the nitrogen cylinder.
(7) Reconnect the vacuum pump to the 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 gage.
(8) 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:
(a) Place the refrigerant cylinder on a scale of sufficient capacity, with the shutoff valve down, or suspend the
v cylinder from a spring scale or beam scale, with the valve end down.
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