Dixell/Copeland AL03

What does Dixell/Copeland AL03 mean?

On the Dixell IC100CX iChill controller, AL03 controls whether the low-pressure alarm from the digital input remains active when the compressor is off or the unit is in standby. Set AL03 to 0 to disable low-pressure monitoring when the compressor is off (preventing trips during pump-down or standby). Set AL03 to 1 to keep low-pressure monitoring active continuously regardless of compressor state.

Symptoms

• Low-pressure alarm triggers even when compressor is off (if AL03 = 1 and pressure drops below switch setpoint in standby).
• Unit remains tripped in standby with a persistent low-pressure alarm.
• No low-pressure alarm generated when compressor is off (if AL03 = 0, even when LP switch is active).

Common causes

• AL03 = 1 but the low-pressure switch activates during standby due to refrigerant migration or pump-down cycle completing.
• AL03 = 0 but engineers expect the alarm to protect against system leaks during standby — risk of unchecked refrigerant loss.
• Refrigerant migrating to low side during off cycles, reducing suction pressure below LP switch cutout.
• LP switch wired incorrectly — normally-closed vs. normally-open polarity mismatch.

Diagnostic steps

1. 01

   Determine the intended system behavior

   Review the system design specification. For pump-down systems (CO31=1), AL03 = 0 prevents nuisance standby alarms. For sealed systems without pump-down, AL03 = 1 provides leak detection protection.

2. 02

   Set AL03 correctly for the application

   Access the AL parameter menu on the IC100CX. Set AL03 = 0 for pump-down equipped systems. Set AL03 = 1 for systems where monitoring during standby is required by the application or regulation.

3. 03

   Verify LP switch wiring polarity

   Confirm the digital input configured for low pressure uses the correct contact type. Check the IC100CX digital input polarity setting matches the LP switch (normally-open or normally-closed).

4. 04

   Check for refrigerant migration

   If LP switch trips during standby on a non-pump-down system, check for refrigerant migration to the compressor crankcase or low side. Install a crankcase heater if not already present.

5. 05

   Verify pump-down configuration

   If CO31 (pump-down control) is enabled, confirm the pump-down solenoid valve operates correctly and the system is pumping down fully before compressor shutdown.

When to call a professional

If refrigerant migration is suspected during standby periods, a licensed refrigeration technician should assess whether a crankcase heater is required and whether the refrigerant charge is correct. Commissioning pump-down configurations and validating low-pressure switch behavior on chiller systems also requires a qualified technician's involvement for safe and compliant refrigerant handling.