Why do chiller fault codes vary by brand?
Each manufacturer uses its own control board and software. So a given code may indicate high pressure on one brand and a completely different alarm on another. Instead of giving a code-by-code list in this article, we explain what the codes indicate: alarm groups and their likely causes. After you find what the code means on your unit from the manual or the on-screen description, the table below will guide you.
Chiller alarm groups and likely causes
| Alarm group | Likely causes | First thing to check |
|---|---|---|
| High pressure (HP) | Dirty condenser, condenser fan failure, high outdoor temperature, excess refrigerant, non-condensable gas, low tower water flow on water-cooled units | Condenser cleaning and fans |
| Low pressure (LP) | Low refrigerant/leak, clogged filter drier, expansion valve failure, low water flow | Water flow, sight glass, leak |
| Water flow (flow switch) | Pump stopped, strainer clogged, valve closed, air in the line | Pump and strainer |
| Freeze / low water temperature | Low flow, wrong setpoint, sensor drift, insufficient glycol | Flow and setpoint |
| Compressor current / thermal | Mechanical wear, low voltage, phase imbalance, overload | Current and voltage measurement |
| Oil pressure / level | Low oil, oil return problem, oil filter | Oil level and pressure |
| Phase protection | Phase loss, phase sequence, voltage fluctuation | Supply and phase protection relay |
| Sensor fault | Broken cable, faulty sensor, moisture in the connection | Sensor resistance and cable |
Is your chiller giving an alarm?
Send us the code on the screen, the brand and the model; we will get back to you for a measured fault diagnosis.
How do you fix a chiller low pressure fault?
For a low pressure alarm, the water side is checked first: if not enough water is passing through the evaporator, the refrigerant cannot evaporate and the pressure drops. Is the pump running, is the strainer clean, are the valves open? If the water side is normal, the refrigerant circuit is measured: bubbles in the sight glass, low subcooling and high superheat point to low refrigerant. In this case the leak is found and fixed first, then the circuit is evacuated and charged with the correct amount. A clogged filter drier and an expansion valve failure give similar symptoms.
Chiller high pressure fault
The most common causes are a dirty condenser and condenser fans that are not working. Combined with high outdoor temperatures in summer, the alarm becomes more frequent. Detailed explanation: chiller high pressure alarm: 6 causes.
Compressor faults
Compressor current alarms, abnormal noise, oil problems and frequent starting and stopping show that the compressor is under strain. For early signs, see chiller compressor failure symptoms; for repair, see our compressor overhaul page.
Chiller service by brand
We analyze alarms and carry out repairs on chillers of Carrier, Daikin, York, Trane, Clivet, Alarko Carrier, Rhoss and other brands. For brands other than LG, we are an independent technical service: Carrier, Daikin, York, Trane, Clivet, Alarko Carrier, Rhoss.
Frequently asked questions
Is there a list of chiller fault codes?
Codes vary by brand, model and control board; the correct list is in the unit's own manual. We focus on finding the alarm group the code indicates and its cause through measurement.
Is it right to reset a chiller alarm?
Resetting once is possible; but if the alarm repeats, continually resetting without finding the cause can damage the compressor.
Why does a chiller drop to low pressure?
Low water flow, low refrigerant or a leak, a clogged filter drier and expansion valve problems are the most common causes.
Why does a chiller give a high pressure fault?
A dirty condenser, a condenser fan failure, high outdoor temperature, excess refrigerant or non-condensable gas in the circuit lead to high pressure.