Applies to:
TWH.581.TTJ low-load chiller units, including 600kW applications.

Issue / Symptom:
Compressor body or suction area is sweating during operation. Site may report visible condensation on one or more compressors, particularly when the unit is running for extended periods or under low thermal load conditions.

Example site:
600kW TWH.581.TTJ low-load chiller at Oasis Shopping Centre, QLD.

Background

Some compressor sweating can occur depending on the operating conditions of the chiller. However, excessive sweating may indicate that the compressor is drawing in liquid refrigerant or that the evaporator refrigerant level is too high.

Factory advice is that the first step is to confirm the chiller is operating within its intended working range before making any refrigerant or control adjustments.

Checks Required

Before adjusting refrigerant charge or controls, verify the following:

  • Chilled water flow rate is within specification.
  • Entering and leaving water temperatures are within the expected operating range.
  • The unit is operating under suitable load conditions.
  • The compressor operation is stable and not excessively cycling.
  • Refrigerant charge is correct, especially for units supplied NI / without refrigerant.
  • The evaporator sight glass refrigerant level is within the acceptable range.

Important Refrigerant Level Guideline

The refrigerant level in the evaporator must not exceed 50% of the sight glass indicator.



If the level is above 50%, refrigerant may need to be removed.

In the attached reference image, the red line indicates the approximate maximum acceptable refrigerant level. The refrigerant level should remain at or below this point during normal operation.

Likely Cause

Visible compressor sweating may be caused by liquid refrigerant returning to the compressor.

This can occur when:

  • The evaporator refrigerant level is too high.
  • The unit is overcharged with refrigerant.
  • The unit is operating under low thermal load.
  • The compressors are starting and stopping frequently.
  • The chiller does not reach steady-state operating conditions.
  • Refrigerant level control in the evaporator becomes unstable under low-load operation.

Notes on Low Thermal Load Operation

TT units are not ideal for very low thermal load operation.

When the thermal load is low, the compressors may frequently start and stop. This prevents the unit from reaching steady-state conditions and may result in sub-optimal evaporator refrigerant level control.

Where this occurs, the compressor response should be stabilised according to the actual site load. Factory may be able to optimise some control algorithm parameters during site attendance.

Recommended Action

  1. Confirm operating conditions

    • Check water flow.
    • Check entering and leaving water temperatures.
    • Confirm the site load condition at the time of operation.
    • Confirm whether one or both compressors are sweating.

  2. Check refrigerant charge

    • Confirm the correct refrigerant quantity was charged during commissioning.
    • This is especially important if the unit was supplied NI / without refrigerant.

  3. Inspect evaporator sight glass

    • Confirm refrigerant level does not exceed 50% of the sight glass.
    • Use the attached image as a reference.

  4. Remove refrigerant if required

    • If refrigerant level is above 50%, recover refrigerant until the level is within the acceptable range.
    • Ensure this is carried out by appropriately qualified personnel.

  5. Monitor compressor operation

    • Check whether compressors are cycling frequently.
    • Confirm whether the chiller can reach stable operating conditions.

  6. Escalate for factory support if issue remains

    • If compressor sweating continues after confirming operating range and refrigerant level, escalate to factory / GI technical support.
    • Control parameter optimisation may be required to improve compressor response under low-load conditions.