Dixell/Copeland AL2 Error Code

What does Dixell/Copeland AL2 mean?

On the Dixell XR70CX digital controller, AL2 is the condenser low temperature alarm setpoint parameter. When the condenser probe (connected per the AP2 probe selection parameter) reads below the AL2 value, the controller triggers the LA2 low condenser temperature alarm after the Ad2 delay expires. Parameter bLL controls whether the compressor shuts down when this alarm is active.

Symptoms

• LA2 alarm displayed on XR70CX controller.
• Alarm relay activates (if configured).
• Compressor may stop depending on bLL parameter setting.
• Condenser probe reading below the AL2 setpoint.

Common causes

• Ambient temperature too low for the application, causing condenser temperature to drop below the minimum setpoint.
• Condenser probe (P3 or P4) failed, reading incorrectly low values.
• AL2 setpoint configured too close to normal operating temperature range.
• Loss of compressor load reducing heat rejection to condenser.
• Faulty or disconnected condenser probe wiring.

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Diagnostic steps

1. Check the condenser probe reading

   View the condenser temperature on the XR70CX display. Compare to an independent thermometer placed near the condenser. A large discrepancy indicates a probe or wiring fault.

2. Inspect probe wiring and connections

   Check the NTC probe connected to the terminal designated by AP2 (P1, P2, P3, or P4). Look for loose terminals, open circuits, or damaged cable. Replace probe if resistance measurement is out of spec.

3. Verify AL2 setpoint

   Access AL2 in the parameter menu and confirm the setpoint matches the design intent. The range is -55 to 150°C. If actual winter ambient conditions are dropping below this value legitimately, adjust AL2.

4. Check Ad2 alarm delay setting

   Verify Ad2 (condenser alarm delay, 0–255 min) to prevent nuisance trips during startup transients. Increase Ad2 if the alarm trips only briefly during pull-down.

5. Review bLL and AC2 parameters

   Confirm whether bLL (compressor off on low condenser alarm) and AC2 (compressor off on high condenser alarm) are set correctly for the application. Incorrect bLL=Y causes unnecessary compressor shutdowns.

When to call a professional

If the probe consistently reads abnormally low despite correct wiring, replace the NTC sensor — probe calibration requires accurate reference measurement equipment. If the system operates in a cold ambient and condenser temperatures are genuinely below design minimums, a refrigeration engineer should assess whether a head pressure control modification is needed.