Dixell/Copeland AL18 Error Code

What does Dixell/Copeland AL18 mean?

On the Dixell IC100CX iChill controller, AL18 sets the polarity of the alarm relay output and open-collector output. Set AL18 to 0 for a normally-open alarm output (output energized during an alarm condition). Set AL18 to 1 for a normally-closed alarm output (output de-energized during an alarm condition). Correct AL18 setting is essential for the external alarm circuit (e.g., monitoring panel, BMS) to detect faults properly.

Symptoms

• External alarm panel does not indicate an alarm when the IC100CX is faulted (reversed polarity).
• External alarm panel shows a permanent alarm state even when no fault is present (reversed polarity).
• Buzzer or remote alarm device behaves opposite to expected during fault conditions.

Common causes

• AL18 configured incorrectly for the external alarm circuit's expected contact polarity.
• Wiring change at the external monitoring panel without updating AL18 to match.
• Factory default AL18 setting not matching the site-specific alarm monitoring requirement.
• Commissioning error — AL18 set before confirming the external circuit wiring type.

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Diagnostic steps

1. Determine external alarm circuit type

   Identify whether the external alarm panel, BMS, or relay circuit expects a normally-open contact that closes on alarm, or a normally-closed contact that opens on alarm. Refer to the monitoring system documentation.

2. Set AL18 to match the external circuit

   Access the AL sub-menu on the IC100CX. Set AL18 = 0 if the external circuit expects the alarm output to be energized (closed) during a fault. Set AL18 = 1 if the circuit expects the output to be de-energized (open) during a fault.

3. Test alarm signal end-to-end

   Trigger a test alarm on the IC100CX (e.g., by temporarily disconnecting a probe) and verify the external alarm panel or BMS responds correctly. Restore the probe after testing.

4. Check AL17 setting simultaneously

   AL17 controls whether the alarm relay activates when the unit is in Off or standby. Confirm AL17 is set correctly (0 = disabled in standby, 1 = enabled in standby) alongside AL18.

5. Document the final configuration

   Record the AL18 and AL17 settings in the system commissioning log. Polarity settings are often forgotten during controller replacement, leading to repeat issues.

When to call a professional

AL18 is a configuration parameter — no system fault underlies it. Commissioning technicians or controls engineers routinely adjust this setting during installation. If the alarm circuit behavior is complex or integrated with a BMS, involve the controls specialist who designed the monitoring system.