Dixell/Copeland AL15

What does Dixell/Copeland AL15 mean?

On the Dixell IC100CX iChill controller, AL15 is the differential parameter for resetting the condenser low-pressure or low-temperature alarm. After the probe falls below AL14 (low alarm setpoint) and triggers a low condenser alarm, the alarm does not clear until the probe rises above AL14 plus the AL15 differential value. This hysteresis prevents hunting near the alarm threshold.

Symptoms

• Low condenser temperature or pressure alarm activates when probe falls below AL14.
• Alarm remains latched after probe rises slightly above AL14.
• Alarm clears only when probe rises above AL14 plus AL15 differential.

Common causes

• AL15 set to zero, causing rapid alarm toggling as the probe oscillates near AL14.
• AL15 set too large, creating an excessive reset band that keeps the alarm active longer than necessary.
• Genuine low condenser temperature during cold ambient operation exceeding the AL14 setpoint.
• Condenser probe fault or disconnection reading artificially low values.

Diagnostic steps

1. 01

   Verify AL15 differential value

   Access the AL sub-menu and confirm AL15 is set to a practical differential — typically 2°C to 5°C (or equivalent pressure). Zero differential causes alarm chatter; excessively large values mask recovery.

2. 02

   Check current condenser probe reading

   View the condenser probe value on the IC100CX display. Compare to an independent temperature measurement at the condenser. A large discrepancy indicates a probe or wiring fault.

3. 03

   Inspect condenser probe wiring

   Check the NTC probe wiring to the analog input designated for condenser sensing. Look for open circuits, corroded terminals, or probe damage. Measure probe resistance and compare to the NTC curve.

4. 04

   Review AL13 alarm delay for analogue input

   AL13 sets the low-condenser alarm delay after compressor startup. Confirm AL13 is adequate to suppress transient pressure dips at startup before steady-state condensing conditions are reached.

5. 05

   Adjust AL14 setpoint if needed

   If genuine low-ambient conditions are causing nuisance trips, evaluate whether AL14 can be reduced. Consult the system design envelope before modifying alarm setpoints.

When to call a professional

If the condenser probe consistently reads below AL14 during normal operation, a licensed refrigeration technician should assess whether a low-ambient kit or head pressure control is required for the installation environment. Probe replacement also benefits from proper NTC calibration verification.