Carel AL029 Error Code

What does Carel AL029 mean?

AL029 is a Low Temperature alarm on the µChiller system, triggered when the monitored chilled water or refrigerant temperature falls below the configured low-temperature threshold for a sustained period. This alarm protects the evaporator from freeze-up and the refrigerant circuit from abnormally low suction conditions.

Symptoms

• AL029 displayed on the controller with buzzer active.
• Chilled water outlet temperature or evaporator temperature below alarm setpoint.
• Circuit may shut down or reduce compressor capacity depending on configuration.
• Frost or ice formation visible on evaporator surfaces in severe cases.

Common causes

• Chilled water flow rate too low, causing excessive temperature drop across the evaporator.
• Low temperature alarm threshold set too high relative to design operating conditions.
• Refrigerant overcharge causing unusually low evaporation temperatures.
• Expansion valve malfunction allowing excessive refrigerant flow.
• System operating below design ambient conditions in cold weather applications.

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Diagnostic steps

1. Verify chilled water flow rate

   Check that the pump is running at design speed and that all isolation valves are open. Low flow is the most common cause of evaporator freeze-up leading to a low temperature alarm.

2. Review alarm setpoint parameters

   Access the service level and compare the low-temperature alarm threshold to design operating conditions. Adjust the threshold within the allowable range if it was set incorrectly.

3. Check evaporator for ice formation

   Inspect the evaporator visually or via temperature probes. Ice on the water-side or refrigerant-side indicates insufficient flow or incorrect refrigerant charge.

4. Inspect the expansion valve operation

   Monitor superheat via the EVD driver display. Abnormally low or negative superheat confirms excessive refrigerant flow from a stuck-open or oversized valve.

When to call a professional

Contact a licensed refrigeration technician if the low temperature alarm persists after restoring adequate water flow, or if evaporator icing is confirmed. Refrigerant charge adjustment, expansion valve replacement, and evaporator defrost procedures require system recovery equipment and EPA 608 or equivalent certification.