EVCO COH

What does EVCO COH mean?

COH on Evco EV3-series and EVK-series controllers stands for Condenser Overheated warning. It activates when the condenser probe temperature exceeds the threshold set in parameter C6 for the warning level. Regulation continues normally at this stage, but if temperature keeps rising to the higher limit C7, the controller escalates to a CSd (Compressor Shut Down) alarm and stops the compressor to protect it. The COH alarm resets automatically once the condenser cools below C6.

Symptoms

• COH displayed on the controller screen.
• Alarm relay may activate depending on alarm output configuration.
• Condenser probe is reporting a temperature above the C6 threshold.
• Refrigeration regulation continues — compressor is still running at COH stage.
• If temperature rises further to C7, display escalates to CSd and compressor stops.

Common causes

• Condenser coil is dirty or blocked with dust and grease, reducing heat rejection.
• Condenser fan not running or running at reduced speed due to capacitor or motor fault.
• Ambient temperature is too high — unit sited in a poorly ventilated room or near a heat source.
• Condenser airflow is recirculating — discharge air re-entering the condenser inlet.
• Condenser fan control parameter C6 is set too low for the installation environment.

Diagnostic steps

1. 01

   Inspect and clean the condenser coil

   Power down and use compressed air or a condenser brush to clean lint, dust, and grease from the condenser fins. Dirty coils are the most common cause of condenser overheat alarms.

2. 02

   Verify condenser fans are operating

   Confirm all condenser fans spin freely when energized. Check fan capacitors with a capacitance meter — a weak or open capacitor causes slow-start and overheating. Replace failed capacitors.

3. 03

   Assess room ventilation and airflow clearances

   Check that the unit has the manufacturer-specified clearance on all sides and that the room ventilation rate is adequate. Measure ambient temperature — if above the unit's design limit, improve room cooling.

4. 04

   Check parameter C6 threshold

   Access the configuration menu and confirm C6 is set appropriately. If the installed environment genuinely runs warm, C6 may need to be adjusted upward — but verify against the compressor's maximum discharge temperature rating first.

5. 05

   Confirm alarm auto-reset after condenser cools

   Once the condenser temperature drops below C6, COH should clear without user input. If it reappears quickly after clearing, the root cause has not been resolved.

When to call a professional

Call a licensed refrigeration technician if the COH alarm escalates to CSd (compressor shutdown) or if cleaning the condenser and verifying fan operation does not bring condenser temperatures back to normal. A refrigeration technician can check high-side pressures with a manifold gauge set to determine whether an overcharge, non-condensables, or refrigerant-side restriction is contributing to the overtemperature condition.