Carel AL46 Error Code

What does Carel AL46 mean?

AL46 on Carel µChiller and pCO chiller controllers indicates that EEV driver 2 has exceeded the Low Operating Pressure (LOP) timeout. The Carel EVD driver's LOP protection opens the expansion valve when evaporating temperature drops too low, preventing the compressor from operating in a liquid-starved, excessively low-pressure condition. When evaporating temperature stays below the LOP limit longer than the permitted timeout, AL46 activates and circuit 1 is shut off.

Symptoms

• AL46 displayed on the Carel controller.
• Circuit 1 is shut down following a LOP timeout.
• Evaporating temperature on circuit 1 was running abnormally low.
• Suction pressure is below normal for the current operating conditions.

Common causes

• Refrigerant undercharge causing insufficient suction pressure and excessively low evaporating temperature.
• EEV valve stuck closed or failing to open, starving the evaporator of refrigerant.
• Suction line filter/dryer partially blocked, restricting refrigerant flow.
• EVD driver 2 LOP setpoint configured too close to normal operating conditions.

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Diagnostic steps

1. Connect refrigerant gauges to circuit 1 suction

   Verify actual suction pressure and convert to saturation temperature for the refrigerant type. Confirm whether the evaporating temperature is genuinely below the LOP limit.

2. Check for refrigerant undercharge

   Inspect the system for refrigerant leaks using an electronic leak detector at all joints, valve stems, and brazed connections on circuit 1.

3. Test EEV valve operation

   Using the EVD driver 2 manual mode, fully open the EEV valve and observe whether suction pressure rises. If pressure stays low with the valve fully open, refrigerant charge or a filter blockage is the cause.

4. Inspect the suction filter/dryer

   Check the moisture indicator sight glass on the suction dryer. Replace a discolored (yellow/brown) dryer and investigate moisture ingress if indicated.

5. Review LOP setpoint in EVD driver 2

   Verify the LOP setpoint (evaporating temperature) is correct for this refrigerant and application. Adjust if it is set too high relative to normal low-load operating conditions.

When to call a professional

Refrigerant leak detection, recharge, and dryer replacement on a live refrigerant circuit all require F-Gas certification. Contact a licensed refrigeration engineer. Do not restart circuit 1 repeatedly with a suspected undercharge; operating a compressor in a vapor-starved condition causes rapid compressor oil carbonization and bearing failure.