Carel AL016

What does Carel AL016 mean?

AL016 indicates a thermal overload alarm on LT (Low Temperature) pump 1 in the µChiller system. The pump motor protection relay has tripped, signaling that the pump drew excessive current for long enough to activate its thermal protector. The unit shuts down to prevent motor damage.

Symptoms

• LT pump 1 stops running immediately on alarm activation.
• Unit or circuit shuts down depending on pump role in the system.
• AL016 flashes on the controller display alongside the buzzer alarm.
• Thermal overload relay on the pump motor panel is tripped.

Common causes

• Pump motor thermal overload relay has tripped due to sustained overcurrent.
• Blocked or partially closed isolation valve restricting pump flow.
• Worn pump bearings causing increased mechanical resistance and motor load.
• Incorrect overload relay setting too low for the installed pump.
• Phase imbalance or single-phasing on the pump motor power supply.

Diagnostic steps

1. 01

   Locate and reset the thermal overload relay

   Find the motor protection relay in the electrical panel. Allow the motor to cool for at least 15 minutes, then press the manual reset button on the overload relay.

2. 02

   Check pump isolation valves

   Verify all isolation valves in the LT pump circuit are fully open. A partially closed valve increases head pressure, overloads the motor, and trips the overload.

3. 03

   Measure motor current on all phases

   Use a clamp meter to measure running current on each phase while the pump operates. Compare against the motor nameplate FLA rating. Investigate any phase imbalance exceeding 5%.

4. 04

   Inspect pump mechanically

   Check for seized bearings or impeller obstructions by attempting to rotate the shaft by hand with power off. Replace bearings or clear impeller blockage as needed.

5. 05

   Verify overload relay settings

   Confirm the overload relay trip current is set to match the motor nameplate FLA. Adjust within the allowable range if found incorrectly configured.

When to call a professional

Engage a licensed technician if the thermal overload trips repeatedly after reset, if you measure phase imbalance or low voltage at the motor terminals, or if the pump shaft is seized. Motor replacement, electrical supply repairs, and pump assembly work require professional tools and refrigerant system expertise to avoid water-side damage to the chiller.