EVCO AL61

What does EVCO AL61 mean?

AL61 on the Evco C-PRO RACK controller is a liquid level alarm indicating that the liquid refrigerant level in the receiver or liquid header has dropped below the monitored threshold. The controller reads a liquid level sensor (float switch or electronic level sensor) and triggers AL61 when liquid level falls below the set point. The alarm is visualization-only per the rack manual — it is a warning rather than a shutdown — with a configurable delay before activation.

Symptoms

• AL61 displayed on the C-PRO RACK controller.
• Liquid level sensor is indicating a low-level condition.
• Sight glass on the liquid receiver or liquid line may show bubbles or be empty.
• System may show symptoms of refrigerant starvation — low suction pressure and high superheat.
• Alarm does not automatically shut down compressors but signals a developing problem.

Common causes

• Refrigerant leak in the system has reduced total charge, dropping receiver level.
• Refrigerant migrated to another part of the system — particularly to evaporators or low spots during off-cycle.
• Liquid level sensor float is stuck or sensor has failed, producing a false-low reading.
• Receiver liquid outlet valve is partially closed, trapping refrigerant.
• System is operating with an insufficient initial refrigerant charge.

Diagnostic steps

1. 01

   Check the sight glass on the liquid receiver

   Inspect the receiver sight glass with the system running. Bubbles in a fully open sight glass indicate low charge; a clear, full column confirms adequate liquid level.

2. 02

   Inspect the liquid level sensor and wiring

   Check the float switch or electronic level sensor for physical damage, fouling, or a stuck float. Verify sensor wiring to the controller is secure. A faulty sensor produces false AL61 events without an actual refrigerant shortage.

3. 03

   Check all manual liquid line valves

   Confirm the receiver outlet service valve and any liquid line service valves are fully open. A partially closed valve can cause the receiver to appear full while starving the downstream circuit.

4. 04

   Perform a leak search

   Use an electronic refrigerant detector or UV dye inspection to check all joints, valves, and brazed connections for leaks. Low receiver level combined with AL61 is a strong indicator of refrigerant loss.

5. 05

   Record system pressures and superheat

   Attach manifold gauges and measure suction superheat at the compressor. High superheat with low suction pressure alongside AL61 confirms refrigerant undercharge requiring recovery and recharge by a technician.

When to call a professional

AL61 combined with signs of low refrigerant — bubbles in the sight glass, high superheat, or low suction pressure — requires a licensed refrigeration technician. Leak detection, refrigerant recovery, system evacuation, and recharge must be performed by an EPA Section 608 certified technician. Do not add refrigerant without first identifying and repairing the leak source.