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295 AC
800-00158
AIR CONDITIONER MAINTENANCE CONTINUED...
17) Turn refrigerant tank right side up on charging scale (vapor charge position).
18) Start machine engine and turn on a/c system.
19) Record ambient temperature, evaporator inlet temperature, evaporator air outlet temperature,
suction pressure and discharge pressure.
20) If suction pressure is 5 psig or less, keep engine speed at idle until additional refrigerant has
been added and suction pressure exceeds 5 psig.
21) Slowly open blue valve on manifold gauge set and bleed vapor refrigerant into low side of system
in small increments (0.1 to 0.2 lbs at a time). Suction pressure should not exceed 50 psig while
charging vapor into the low side of the system or the compressor can be damaged.
22) Continue to add refrigerant in this manner in small increments until optimum a/c performance is
achieved.
23) Document total amount or refrigerant added to system and apply appropriate label near
compressor stating refrigerant charge amount.
Alternate Charging Technique:
1) Perform steps 1- 20 above.
2) With an infrared thermometer measure condenser tube temperatures from refrigerant inlet to
refrigerant outlet (typically from top to bottom).
3) The temperature will be highest at the refrigerant inlet (superheated region). Then the temperature
will decrease to the saturation temperature of the refrigerant at the operating discharge pressure
(saturation or condensing temperature). Near the outlet of the condenser the temperature should once
again decrease by roughly (10º to 14° F) (6 to 8°C) below the saturation temperature (sub-cooled
region).
4) If the refrigerant at the outlet of the condenser is not sub-cooled by (10º to 14° F) (6 to 8°C) below
the saturation temperature, continue to add vapor refrigerant in small increments through the blue (low
side) charge port.
5) When (10º to 14° F) (6 to 8°C) of condenser outlet sub-cooling is reached, verify proper a/c
operation.
6) Document total refrigerant amount added to system and apply appropriate label near compressor
stating refrigerant charge amount.
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