Dixell/Copeland AL02

What does Dixell/Copeland AL02 mean?

On the Dixell IC100CX iChill chiller controller, AL02 is the configuration parameter that sets the maximum number of low-pressure alarm events allowed within one hour before the controller switches from automatic to manual reset mode. When the count of low-pressure trips within a rolling 60-minute window reaches this threshold, the unit latches and requires technician intervention to clear.

Symptoms

• Low-pressure alarm trips multiple times within one hour.
• After reaching the AL02 count limit, the unit locks out and does not restart automatically.
• General alarm icon illuminates on the controller display.
• Compressor(s) remain off until manual reset is performed.

Common causes

• Refrigerant leak causing suction pressure to drop below the low-pressure switch setpoint repeatedly.
• Faulty or sticking low-pressure switch generating nuisance trips.
• Expansion valve stuck closed or plugged distributor starving the evaporator.
• Severely dirty or blocked evaporator coil reducing heat absorption.
• Ambient temperature extremes causing rapid pressure cycling near the alarm threshold.

Diagnostic steps

1. 01

   Record alarm history

   Access the AL sub-menu on the IC100CX and note frequency and duration of low-pressure events. This helps distinguish a nuisance switch problem from a genuine refrigerant issue.

2. 02

   Check refrigerant pressures

   Connect manifold gauges to suction service port. Compare suction pressure to the refrigerant saturation temperature for current operating conditions. Low pressure confirms undercharge or restricted flow.

3. 03

   Inspect and test the low-pressure switch

   Verify the switch cut-out setpoint matches the system design. Check for mechanical sticking or contact welding that could cause false trips. Replace if suspect.

4. 04

   Inspect evaporator coil and expansion valve

   Check for ice build-up, dirt blockage, or restricted airflow/water flow across the evaporator. Confirm the expansion valve responds correctly to superheat.

5. 05

   Perform manual reset

   After resolving the root cause, access the AL menu and perform the manual reset procedure (enter function menu per IC100CX service manual) to re-enable automatic compressor operation.

When to call a professional

If low-pressure trips persist after checking pressures and the switch, a refrigerant system issue such as a leak, blockage, or expansion valve failure requires a licensed refrigeration technician. Refrigerant handling and leak testing must comply with local regulations and require EPA 608 certification in the US.