Dixell/Copeland AL24

What does Dixell/Copeland AL24 mean?

The AL24 alarm on the Dixell IC100CX iChill controller indicates an inlet water temperature alarm. The probe measuring inlet water temperature to the evaporator has exceeded the AL24 threshold. The alarm is disabled for a programmable delay period (parameter AL26) starting from compressor activation to avoid nuisance trips at start-up when inlet water temperature may be temporarily outside the operating band.

Symptoms

• AL24 displayed on the IC100CX controller screen.
• Inlet water temperature probe reading above or below the AL24 setpoint.
• Alarm relay activated and buzzer on.
• General alarm icon illuminated on the display.

Common causes

• Building chilled water supply temperature out of range due to upstream HVAC fault.
• Inlet water temperature sensor (probe) failed or wired incorrectly.
• Low water flow causing excessive temperature rise across the evaporator.
• Condenser or heat source contaminating the chilled water loop.
• AL24 threshold incorrectly configured for the application water temperature range.

Diagnostic steps

1. 01

   Check inlet water temperature at the probe

   Use a clamp-on thermometer or insertion probe to measure inlet water temperature at the evaporator inlet and compare to the value displayed on the IC100CX. A large discrepancy indicates a probe fault.

2. 02

   Inspect the inlet temperature probe

   Check the probe wiring connections at the IC100CX terminal block. Measure probe resistance with a multimeter and compare to the NTC characteristic — a reading of 0 Ω or open indicates failure.

3. 03

   Evaluate upstream water supply conditions

   If inlet temperature is genuinely out of range, investigate the upstream system supplying water to the chiller — check for upstream equipment faults, heat loads, or bypass conditions.

4. 04

   Verify AL24 setpoint parameter

   Access the service menu and confirm the AL24 threshold is set to match the application's design inlet water temperature range. Adjust only per commissioning documentation.

5. 05

   Reset and monitor

   After correcting the inlet temperature or probe fault, navigate to AlrM on the IC100CX, select AL24, and reset the alarm. Monitor the inlet temperature reading to confirm stability.

When to call a professional

Call a licensed technician if the inlet water temperature remains out of range despite verifying upstream supply conditions, if the chilled water loop requires chemical treatment or system balancing work, or if probe replacement involves isolation and draining of pressurized water piping.