Dixell/Copeland AL27

What does Dixell/Copeland AL27 mean?

On the Dixell IC100CX iChill controller, AL27 is the condenser water flow alarm delay parameter. It sets the time in seconds that the condenser water flow switch must be continuously active (indicating no flow) before the controller signals a condenser flow alarm. This delay prevents nuisance trips caused by momentary flow interruptions during condenser pump startup or system transients.

Symptoms

• Condenser water flow alarm trips immediately on pump startup (AL27 = 0 or too short).
• System locks out from condenser flow alarm despite flow recovering quickly after transient (AL27 too short).
• Real flow loss takes too long to alarm (AL27 set too long, delaying protection of heat exchanger).

Common causes

• AL27 set to zero — any momentary flow switch activation triggers the alarm immediately.
• Condenser water pump taking longer than AL27 to establish flow on each startup.
• Air in the condenser water circuit causing intermittent flow switch activation.
• Flow switch calibrated at too high a threshold relative to actual condenser flow rate.

Diagnostic steps

1. 01

   Verify current AL27 setting

   Access the AL sub-menu on the IC100CX. Confirm AL27 (seconds) is appropriate for the condenser pump startup time. A typical value is 10–60 seconds to cover pump priming and flow establishment.

2. 02

   Measure condenser pump startup time

   Time how long the condenser pump takes to establish adequate flow after startup. Set AL27 to slightly exceed this time to suppress nuisance startup alarms.

3. 03

   Check for air in condenser water circuit

   Air pockets cause intermittent flow switch trips. Bleed air from the condenser water circuit at automatic air vents and high points. Confirm system fill and pressurization are correct.

4. 04

   Verify flow switch calibration

   Confirm the flow switch setpoint is matched to the actual condenser water flow rate in the system. A switch set too close to minimum design flow generates nuisance trips.

5. 05

   Review AL28 maximum duration parameter

   AL28 sets the maximum time the condenser flow alarm can persist before it becomes a manual-reset lockout that also stops the condenser pump. Confirm AL28 is set appropriately relative to AL27.

When to call a professional

If condenser flow alarms persist despite correct AL27 settings and system priming, a licensed HVAC/R technician should investigate the condenser water circuit for pump performance issues, flow restrictions, strainer blockages, or hydraulic imbalance problems that are preventing adequate and stable condenser water flow.