TM 9-4120-357-14
(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 serv-
ice 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 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, breaks 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.
Leaks in
the refrigeration system. Break vacuum with dry nitrogen and retest for leaks.
3. Internal leakage of vacuum pump. Test pump by connecting gage directly to the vacuum pump intake
and continuing to pump. If pump fails to reach 500-Microns, pump is faulty.
(b) With the suction line service valve closed, disconnect the vacuum pump and attach a cylinder of dry nitro-
gen. 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 vacuum.
Leave in this configuration until system reaches atmospheric pressure (760 MM) , then close the suction service valve
and cylinder shutoff and 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 then remove vacuum gage.
(d) Connect a cylinder of refrigerant, R22, loosely to the discharge line service valve, and turn the cylinder
shutoff valve on for a few seconds to purge the line of air. Tighten the service valve connection. Charge the refrigera-
tion system 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
liquid 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
refrigerant 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
discharge line service valve and the cylinder shutoff valve.
g. Assembly and Operating Test. The air conditioner must be partially re-assembled to permit an operating test to
be made. Proceed as follows:
(1) Place the motor mounting bracket and rear panel assembly upright on blocks just behind the panel opening.
(2) Push the circuit breaker operating cable through the hole in the panel. Install lock washer, jam nut and outer nut
on ferrule. Pull the cable all the way out, grip the shaft with a brass or copper strip held in a pair of pliers, and screw
knob onto shaft.
(3) Position pressure cutoff switch housing against inside of panel. Secure with four screws.
(4) Install the motor mounting bracket and the rear panel assembly on casing. Secure with nine screws through
each side flange. Remove blocks, and install six screws through bottom flange.
(5) Position the deflector door assembly over the coil opening. Secure with six screws. Attach lid support mounting
feet to casing, and secure with two screws and nuts through each foot.
(6) Install condenser intake screen, and secure with 12
screws.
5-59