EVCO AL31

What does EVCO AL31 mean?

AL31 on the Evco C-PRO RACK controller (144RACKNUE05) indicates a high discharge pressure alarm on circuit 1. The controller monitors discharge pressure via a transducer on the compressor pack and triggers AL31 when pressure on circuit 1 exceeds the configured high-pressure limit. When active, all condenser fans are switched ON at full speed to maximize heat rejection. The alarm resets automatically once pressure returns below the threshold.

Symptoms

• AL31 displayed on the C-PRO RACK controller.
• All condenser fans on circuit 1 run at full speed.
• Discharge pressure reading is above the programmed high-pressure setpoint.
• Compressors may continue running with fans at maximum until pressure drops.
• Alarm clears automatically once discharge pressure falls within limits.

Common causes

• Condenser coil fouled with dirt, grease, or debris, reducing heat rejection.
• One or more condenser fans failed or running below rated speed.
• Ambient temperature exceeds the unit's design rating.
• System refrigerant overcharged, leaving excess liquid in the condenser and reducing condensing surface.
• Non-condensable gases (air) in the high-pressure side displacing refrigerant vapor in the condenser.

Diagnostic steps

1. 01

   Verify all condenser fans are running

   Confirm every condenser fan on circuit 1 is spinning at full speed. A stalled or slow fan motor dramatically reduces condenser capacity; replace failed motors or capacitors immediately.

2. 02

   Inspect and clean the condenser coil

   Shut down the rack and clean condenser coils using compressed air or a coil cleaning solution. Even partial blockage on a multi-circuit rack significantly raises head pressure.

3. 03

   Check ambient temperature and rack enclosure ventilation

   Measure ambient temperature at the condenser inlet. Confirm that hot air discharged from the condenser is not recirculating back to the inlet. Improve room ventilation if ambient exceeds design limits.

4. 04

   Connect a manifold gauge set and read high-side pressure

   Attach refrigeration manifold gauges to circuit 1 service ports. Record high-side pressure and corresponding saturation temperature. Compare to the expected condensing temperature for current ambient conditions to identify overcharge or non-condensable contamination.

5. 05

   Confirm alarm auto-clears after corrective action

   After addressing condenser or fan issues, monitor discharge pressure. AL31 should clear automatically once pressure drops below the limit. If it returns repeatedly, escalate to refrigerant system diagnostics.

When to call a professional

Contact a licensed refrigeration technician if AL31 returns after cleaning the condenser and confirming all fans operate correctly. High-side pressure diagnostics requiring manifold gauges, refrigerant recovery for overcharge correction, and purging of non-condensables are EPA Section 608 regulated tasks that must be performed by a certified technician to avoid refrigerant release violations and compressor damage.