Dixell/Copeland AL19

What does Dixell/Copeland AL19 mean?

On the Dixell IC100CX iChill controller, AL19 allows selection of the probe used for the anti-freeze heater alarm. AL19 = 0 uses the automatic selection based on Ar16 (chiller mode) or Ar17 (heat pump mode) parameters. AL19 = 1 through 4 fixes the anti-freeze alarm to Pb1, Pb2, Pb3, or Pb4 respectively, regardless of operating mode. This alarm protects the evaporator water circuit from freezing when water temperature falls below the anti-freeze setpoint.

Symptoms

• Anti-freeze alarm triggers on a probe that does not represent evaporator water temperature (incorrect AL19 probe selection).
• Anti-freeze heaters activate in wrong operating mode because probe reading does not reflect actual water temperature.
• Anti-freeze alarm not triggering despite dangerously low water temperature (AL19 pointing to wrong probe).

Common causes

• AL19 set to a probe that is not measuring evaporator water temperature (e.g., set to Pb3 condenser probe instead of Pb1 water inlet).
• System modification changing probe roles without updating AL19.
• Controller replacement without restoring the correct AL19 setting from commissioning records.
• AL19 = 0 with Ar16/Ar17 pointing to a probe that has been disconnected or moved.

Diagnostic steps

1. 01

   Identify the evaporator water temperature probe

   Determine which physical probe (Pb1 through Pb4) measures the evaporator water temperature most relevant for anti-freeze protection. Typically this is the evaporator outlet water probe.

2. 02

   Set AL19 to the correct probe

   Access the AL sub-menu on the IC100CX. Set AL19 = 0 to use the automatic Ar16/Ar17 selection, or set AL19 = 1, 2, 3, or 4 to fix the anti-freeze alarm to Pb1, Pb2, Pb3, or Pb4 respectively.

3. 03

   Verify Ar16 and Ar17 if using AL19 = 0

   If AL19 = 0, access the Ar sub-menu and confirm Ar16 (chiller mode anti-freeze probe selection) and Ar17 (heat pump mode selection) point to the correct probes.

4. 04

   Test anti-freeze alarm activation

   Verify the anti-freeze alarm triggers when the selected probe temperature drops below the Ar anti-freeze setpoint. Test by temporarily lowering the setpoint and confirming correct behavior.

5. 05

   Confirm probe readings are valid

   Verify all probes referenced by AL19 and the Ar parameters are connected, reading correctly, and positioned appropriately. A faulty probe renders anti-freeze protection ineffective.

When to call a professional

Anti-freeze protection configuration is critical for evaporator water circuit safety. If anti-freeze alarms are not triggering correctly during cold conditions, a licensed HVAC/R technician should verify the complete anti-freeze protection system — including heater elements and the Ar parameter group — before winter operation.