Carel AL30

What does Carel AL30 mean?

AL30 on Carel µChiller and pCO chiller controllers indicates that the thermal overload protection device on one or both electric heaters (heater 1 or heater 2) has tripped due to overcurrent. This protection prevents heater element burnout when the heater draws more current than its rated value. The alarm requires manual reset after the heater cools down and the fault cause is identified.

Symptoms

• AL30 displayed on the Carel controller.
• Heater 1 or heater 2 output is de-energized.
• Anti-freeze or supplementary electric heating is unavailable.
• The thermal overload relay in the heater circuit has tripped.

Common causes

• Heater element partially failed, causing unbalanced current draw.
• Supply voltage too high, increasing heater current above rated value.
• Thermal overload relay sized incorrectly for the installed heater element rating.
• Heater operating in a poorly ventilated space causing thermal overload of the overload relay itself.

Diagnostic steps

1. 01

   Allow the heater and overload relay to cool

   Wait at least 15 minutes before attempting to reset. Thermal overload relays require cooling before they will reset.

2. 02

   Inspect the heater element

   With power isolated, visually inspect the heater element for burn marks, discoloration, or physical damage that indicates an element failure.

3. 03

   Measure heater element resistance

   Disconnect the heater element and measure resistance across each element. Infinite resistance (open circuit) or zero resistance (short) confirms element failure.

4. 04

   Check supply voltage

   Measure supply voltage at the heater terminals. Overvoltage (more than 10% above rated) increases heater current proportionally.

5. 05

   Reset the overload relay and AL30

   After cooling and corrective action, reset the thermal overload relay manually in the panel, then reset AL30 at the Carel controller.

When to call a professional

Call a licensed electrician if the heater element requires replacement, if supply voltage is found out of tolerance, or if the overload relay trips immediately on restart. Working on heater circuits involves exposure to mains voltage and must be performed under proper isolation procedures by qualified personnel.