Dixell/Copeland AL12

What does Dixell/Copeland AL12 mean?

On the Dixell IC100CX iChill controller, AL12 is the condensing temperature or pressure differential parameter used to reset the high condenser alarm. After the condenser probe value rises above AL11 (high alarm setpoint) and triggers the high alarm, the alarm does not reset until the probe drops below AL11 minus the AL12 differential. This hysteresis prevents rapid alarm on/off cycling near the setpoint.

Symptoms

• High condenser temperature/pressure alarm (HA condenser) activates when probe exceeds AL11.
• Alarm remains active even after condenser temperature drops slightly below AL11.
• Alarm only clears when condenser probe falls below AL11 minus AL12 differential.

Common causes

• AL12 set to zero, causing the alarm to flicker on and off as the probe oscillates near AL11.
• AL12 set too large, delaying alarm reset well below the high alarm setpoint when system has recovered.
• Actual high condenser temperature condition — dirty condenser coil, fan failure, or high ambient.

Diagnostic steps

1. 01

   Verify AL12 differential setting

   Access the AL sub-menu on the IC100CX. AL12 should be set between 1°C and 5°C (or equivalent pressure differential) to provide stable hysteresis around the AL11 setpoint without excessive reset delay.

2. 02

   Check for genuine high condenser temperature

   If the alarm is active during normal operation, measure condensing temperature or pressure with instruments. Compare to the system design specification for current ambient conditions.

3. 03

   Inspect condenser coil and fans

   A fouled condenser coil or failed condenser fan is the most common cause of genuine high condensing temperature. Clean the coil and verify all fans run at correct speed.

4. 04

   Check ambient conditions

   Verify that ambient temperature around the condenser is within the design range. Blocked airflow recirculation or adjacent heat sources can elevate condensing temperature even with a clean coil.

5. 05

   Adjust AL11 setpoint if appropriate

   If the system is operating correctly but high ambient conditions push condensing temperature close to AL11, consult the system design documentation before adjusting the setpoint upward.

When to call a professional

If high condensing temperatures persist despite clean coils and properly operating fans, a licensed refrigeration technician should evaluate refrigerant charge, non-condensable gases in the system, and whether the system is correctly sized for the operating ambient. Refrigerant-side investigations require proper certification.