EVCO AH Error Code

What does EVCO AH mean?

The AH alarm on Evco EV3-series and EVK-series controllers signals that the cabinet or room temperature has risen above the high-temperature alarm threshold. The controller evaluates the measured temperature against the setpoint plus parameter A4 (high alarm differential) and triggers AH after the configured delay expires. Refrigeration regulation is not interrupted; the alarm resets automatically once the temperature falls back within limits.

Symptoms

• AH displayed on the controller screen.
• Alarm relay output activates, triggering audible or visual notification.
• Cabinet temperature reading exceeds the setpoint by more than the A4 differential.
• Compressor is running but unable to bring temperature down to setpoint.
• Alarm self-clears when temperature returns within the alarm band.

Common causes

• Parameter A4 (high alarm differential) set too narrow for the application, causing nuisance alarms.
• Condenser is dirty or airflow is blocked, reducing cooling capacity.
• Door or lid left open, allowing warm ambient air to raise cabinet temperature.
• Refrigerant charge is low, limiting system capacity.
• High ambient temperature exceeds the unit's design rating, reducing heat rejection.

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Diagnostic steps

1. Verify cabinet temperature and compare to setpoint

   Confirm the displayed temperature is genuinely above setpoint by comparing it with an independent thermometer inside the cabinet. Rule out a false reading from a failing probe.

2. Check condenser and ensure adequate airflow

   Inspect the condenser coil for dust and grease buildup. Clean with compressed air or a condenser brush. Confirm condenser fans are running and airflow is not blocked by nearby walls or stored goods.

3. Inspect door seals and ensure doors are fully closed

   Check all door gaskets for tears or compression failure. Confirm door heaters are not over-heating the gasket area, and that doors latch and seal under normal spring tension.

4. Review parameter A4 and alarm delay

   Access the controller configuration and verify A4 is set to an appropriate differential for the cabinet type and product load. Increase A4 only if the alarm consistently triggers during normal loading or defrost recovery.

5. Monitor compressor run time and system pressures

   If the compressor runs continuously but the cabinet cannot reach setpoint, this indicates a capacity issue. Have a technician connect a manifold gauge set to check suction and discharge pressures.

When to call a professional

Call a licensed refrigeration technician if the AH alarm recurs after cleaning the condenser and confirming door seal integrity, if the compressor runs continuously without reaching setpoint, or if manifold gauge readings reveal low suction pressure suggesting a refrigerant leak. These findings require EPA-certified technician work — leak detection, refrigerant recovery, and recharge must be performed by a certified professional.