Checking Refrigerant Charge

The refrigerant charge should be checked during pretrip and routine maintenance inspections. A low charge of refrigerant will cause the container temperature to rise due to the lack of liquid refrigerant at the expansion valve even though the unit is operating in a cooling mode. All units are charged with 4.0 kg (8.0 lbs) refrigerant at the factory. The refrigerant charge can be checked by inspecting the receiver tank sight glass.

  1. Inspect the receiver tank sight glass with the unit operating in cool or modulation cool. If the ball floats in the bottom receiver tank sight glass when the compressor is engaged, the refrigerant charge level is correct.

      2. Notice
    • Cargo Loss
    • When adjusting the controller setpoint to check refrigerant charge, return controller to the setpoint indicated on the shipping manifest.

  2. If the ball is not floating in the sight glass, the unit may be low on refrigerant charge. Adjust the controller setpoint to operate the unit on cool. Operate the unit on cool for five minutes. If the ball floats in the receiver tank sight glass, the refrigerant charge level is correct.

  3. If the ball in the receiver tank sight glass does not float after operating the unit on cool for five minutes, the unit is low on refrigerant charge. With the unit operating on cool, add liquid refrigerant charge. With the unit operating in cool, add liquid refrigerant until the ball in the receiver tank sight glass floats in the sight glass.

    Note Inspect the unit for refrigerant leaks with a reliable leak detector if the unit is low on refrigerant charge.

Parent topic: Refrigeration Maintenance