Dixell/Copeland AL13

What does Dixell/Copeland AL13 mean?

On the Dixell IC100CX iChill controller, AL13 is the low-pressure alarm delay for the analogue condenser input probe. After a compressor starts, the low condenser pressure alarm from the analogue probe is suppressed for the time set in AL13. This prevents nuisance low-alarm trips during the pull-down phase when condensing pressure transiently drops before stabilizing at steady-state operating conditions.

Symptoms

• Low condenser pressure alarm trips at every compressor startup (AL13 = 0 or too short for the pull-down transient).
• Alarm log shows low condenser alarm events always coinciding with compressor starts.
• No low-pressure alarm during startup despite genuine undercharge (AL13 too long, masking real fault).

Common causes

• AL13 set to zero — alarm fires immediately when condensing pressure dips below AL14 at startup.
• AL13 too short for the specific refrigerant and system startup transient duration.
• AL13 too long — genuine refrigerant shortage during startup goes undetected for extended period.
• Low-ambient startup conditions causing unusually long pressure pull-down, exceeding even a correctly set AL13.

Diagnostic steps

1. 01

   Check AL13 current value

   Access the AL sub-menu on the IC100CX. Confirm AL13 (in seconds) is set to cover the normal condensing pressure pull-down duration from compressor start to steady state.

2. 02

   Measure pull-down duration

   With manifold gauges connected, time how long it takes for condensing pressure to stabilize above AL14 after compressor start in typical operating conditions. Set AL13 slightly longer than this.

3. 03

   Verify AL14 setpoint appropriateness

   Check AL14 (low condenser pressure/temperature setpoint). If AL14 is set too close to the normal startup condensing pressure, even a properly set AL13 may not be sufficient. Lower AL14 if appropriate.

4. 04

   Monitor startup in cold ambient conditions

   Cold ambient temperatures cause slower condensing pressure rise at startup. If the system operates in cold environments, increase AL13 to cover longer pull-down periods in low-ambient conditions.

5. 05

   Check refrigerant charge if alarm persists after AL13

   If the low condenser alarm fires after AL13 expires during steady-state operation, check refrigerant charge. Low charge causes condensing pressure to remain below AL14 even at steady state.

When to call a professional

If low condenser pressure alarms occur at steady state after the AL13 bypass period expires, a licensed refrigeration technician must investigate the cause. Typical root causes include low refrigerant charge, a refrigerant leak requiring repair, or an expansion valve malfunction. All refrigerant system service requires proper certification.