Dixell/Copeland AL21 Error Code

What does Dixell/Copeland AL21 mean?

The AL21 alarm on the Dixell IC100CX iChill controller (firmware 1.8 GRU) is a general unit block alarm triggered by a digital input activation. The alarm is enabled only when AL23=1. After a configured number of interventions, the alarm transitions from automatic to manual reset. The controller activates the open collector alarm output and buzzer when AL21 triggers.

Symptoms

• AL21 displayed on the IC100CX FW1.8 GRU screen.
• Open collector alarm output activates; buzzer sounds.
• Unit operation blocked after the alarm becomes manual.
• General alarm icon lit on the display.

Common causes

• External protection device wired to the general alarm digital input has activated.
• AL23 parameter set to 1, enabling the unit-blocking behavior for the general alarm.
• Digital input activated by a persistent fault condition on a connected safety device.
• Wiring fault holding the general alarm digital input in the active state.

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Diagnostic steps

1. Identify the triggering digital input

   Access the IC100CX digital input status screen and identify which general alarm input is active. Cross-reference with the site wiring diagram to find the connected external protection device.

2. Inspect the external device

   Locate the field device — such as a thermal protection relay, flow switch, or external alarm contact — and determine why its contact is closed. Resolve the underlying fault condition.

3. Check AL23 configuration

   Verify that AL23=1 is correct for this installation. If AL23=1 is not required and the general alarm should be signaling only, changing AL23=0 prevents unit block behavior.

4. Check AL20 count status

   Access the alarm log and check how many AL21 interventions have occurred in the current hour. If the count has reached the AL20 limit, the alarm is now manual and requires manual reset even after the fault clears.

5. Perform manual reset

   After resolving the field device fault, navigate to AlrM on the IC100CX, select AL21, and press SET to execute the manual reset. The unit will not restart automatically if the alarm is in manual mode.

When to call a professional

Call a licensed HVAC/R technician if the external device triggering AL21 is a refrigerant safety control that has tripped and requires root cause investigation, or if AL21 continues to trip repeatedly — indicating a systemic fault that the blocking protection is correctly responding to.