Chiller Fault Diagnosis: The 8 Most Common Problems and an Emergency Response Guide

A chiller system failing can endanger an entire building, a production line or patient safety. For this reason, rapid diagnosis and correct prioritization are vital in chiller faults. In this guide we share the 8 most commonly encountered chiller faults, their symptoms and the emergency response steps.

1. Low Refrigerant Pressure

Symptoms: a drop in cooling capacity, a low-pressure alarm, ice formation on the evaporator. Cause: a refrigerant gas leak or a blocked expansion valve. Emergency measure: put the system into 'manual reset' mode; keep the low-pressure alarm active and call for service. Gas should not be charged before the leak point is located.

2. High Condenser Pressure (High Discharge Pressure)

Symptoms: a high-pressure alarm, compressor safety shutdown, insufficient cooling. Cause: dirty or blocked condenser tubes, a cooling-tower problem, or the ambient temperature rising too high. Emergency measure: check whether the condenser fans are running; in air-cooled systems, clear the area in front of the coil.

3. The Compressor Won't Start

Symptoms: a loud noise or silence on the start attempt, a compressor alarm on the control panel. Cause: low oil pressure, high discharge temperature, a start-capacitor fault, or the overload relay. Emergency measure: record the control panel's alarm history and identify the cause before resetting.

4. Chilled-Water Temperature Goes Out of Control

Symptoms: the outlet water temperature deviates from the target setpoint, with excessive swings. Cause: a change in water flow, dirty evaporator tubes, or a control-system problem. This situation adversely affects all connected fan-coils and air handling units.

5. Abnormal Noise and Vibration

Symptoms: metallic knocking, whistling, continuous vibration. Cause: liquid refrigerant entering the compressor (liquid slugging), worn bearings, or air in the system. Liquid slugging can destroy the compressor instantly; when you hear this sound, shut the system down immediately.

6. Cooling-Tower Failure (Water-Cooled Systems)

When the cooling-tower fan stops or the fill section becomes blocked, the condenser water does not cool sufficiently; this shuts the chiller down with a high-pressure alarm. The water level in the tower basin, pump operation and biological contamination must be checked regularly.

7. Control System / Communication Fault

Symptoms: the chiller does not appear in the BMS, the sensors read incorrect values. Cause: a control-board fault, a broken communication cable, or a software error. As chiller control systems become ever more sophisticated, these faults may require the manufacturer's authorized service.

8. Freeze-Protection Alarm

In the winter months or under low-load conditions, if the water temperature approaches the freezing point, the system shuts down automatically. Adding glycol to the water circuit or correctly setting the freeze-protection setpoint prevents this problem.

The Most Effective Way to Prevent Faults

More than 70% of chiller faults can be prevented with regular maintenance. Comprehensive annual maintenance that includes tube cleaning, oil analysis and a refrigerant gas check dramatically reduces unexpected shutdowns. Call our 24/7 service line for our chiller maintenance and emergency response services.