EVCO AL41 Error Code

What does EVCO AL41 mean?

AL41 on the Evco C-PRO RACK controller indicates a low discharge pressure alarm on circuit 1. The controller detects that discharge pressure has dropped below the low-pressure limit for the discharge circuit and responds by switching all condenser fans OFF to allow head pressure to build back up. The alarm has a configurable delay and resets automatically once discharge pressure recovers above the threshold.

Symptoms

• AL41 displayed on the C-PRO RACK controller.
• All circuit 1 condenser fans are commanded OFF by the controller.
• Discharge pressure reading is below the low discharge pressure setpoint.
• Condensing temperature is unusually low for ambient conditions.
• Alarm self-resets once discharge pressure rises back within range.

Common causes

• Ambient temperature is very low — cold weather operation drives head pressure below the minimum limit.
• Condenser fan speed is too high for current ambient conditions, over-condensing the refrigerant.
• Refrigerant undercharge causing reduced high-side pressure across the system.
• Discharge pressure transducer fault or wiring issue producing a falsely low reading.
• Low discharge setpoint parameter is configured too high for the installation environment.

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Diagnostic steps

1. Check ambient temperature at the condenser

   Measure outdoor or machine-room ambient temperature. Low discharge pressure alarms are common in cold weather operations; if ambient is below 5 °C (41 °F), the alarm may be a normal low-ambient response.

2. Verify discharge pressure transducer and wiring

   With the rack running, compare the controller's displayed discharge pressure to a manifold gauge reading on the same circuit. A significant discrepancy indicates a faulty transducer or wiring fault — inspect connections and replace the transducer if necessary.

3. Review the low discharge pressure setpoint

   Access the rack controller parameters and check the low discharge pressure trip point. Adjust the setpoint downward if the installation regularly operates in cold ambient conditions that legitimately produce lower head pressures.

4. Check refrigerant charge with manifold gauges

   If ambient conditions cannot explain the low discharge pressure, connect manifold gauges and check suction pressure and superheat to determine whether the system is undercharged. An undercharged system shows low suction and low discharge simultaneously.

5. Confirm fan lockout behavior and alarm reset

   Observe that condenser fans have switched OFF per the alarm response. Once discharge pressure recovers, AL41 should clear automatically and fans should resume normal control. If fans do not restart, check fan relay and controller output wiring.

When to call a professional

Engage a licensed refrigeration technician if low discharge pressure persists after confirming the setpoint and ambient temperature are reasonable. A technician with manifold gauges can determine whether refrigerant undercharge or a system restriction is causing the condition. Adding refrigerant requires EPA Section 608 certification and must be performed by a certified professional.