High pressure trips
The chiller cannot reject heat fast enough. On air-cooled chillers, look for dirty or blocked condenser coils, failed condenser fans, or hot air recirculating around the unit. On water-cooled chillers, the usual causes are fouled condenser tubes, low condenser water flow, or a cooling tower that is not doing its job.
Low pressure trips
Low suction pressure often means the chiller is short of refrigerant, which means a leak somewhere. Topping up without finding the leak only delays the next trip. It can also be caused by low chilled water flow or a faulty expansion valve.
Flow switch trips
Chillers will not run without proven water flow through the evaporator and, on water-cooled machines, the condenser. Check that the pumps are running, valves are open and strainers are clean. Air in the system can also cause flow switches to drop out.
Freeze protection trips
If the water leaving the evaporator gets too cold, the chiller stops to avoid freezing and splitting tubes. Low flow, a low setpoint or a faulty sensor are the usual causes. Do not keep resetting this alarm: evaporator damage is expensive.
Compressor and electrical faults
Motor overloads, phase faults, oil pressure faults and drive faults stop the compressor directly. These need a technician, and repeated resets can turn a small fault into a compressor failure.
Before you call
Write down or photograph the exact alarm, the time it happened and how often it repeats, along with the make, model and serial number from the nameplate. Send those with your enquiry so the technician can come prepared.
Chiller repair
Breakdowns, fault trips, leaks and compressor failures on air-cooled and water-cooled chillers. See chiller repair →
Updated 2 November 2026. General information only; your specialist will advise on your plant.