- (a) List FOUR reasons for a refrigeration compressor to stop unexpectedly, after running for a short period.(4)
(b) Describe the faults which lead to TWO of the reasons for the stoppage, listed in part (a).(6)
(a) FOUR reasons for a refrigeration compressor to stop unexpectedly after a short period (4 marks)
- High pressure cut-out operated.
- Low pressure cut-out operated.
- Motor overload trip activated.
- Oil pressure safety switch trip.
(b) Faults leading to TWO of the reasons in part (a) (6 marks)
1. High Pressure Cut-out:
- Faults:
- Condenser cooling water failure (blocked sea water strainer, pump failure, or insufficient flow).
- Air or non-condensable gases present in the condenser.
- Overcharge of refrigerant increasing system pressure.
2. Low Pressure Cut-out:
- Faults:
- Refrigerant leakage leading to undercharge.
- Expansion valve stuck closed or restricted, starving evaporator.
- Evaporator fan failure or iced-up evaporator coils restricting refrigerant flow.