Carel AL06

What does Carel AL06 mean?

AL06 on Carel µChiller and pCO chiller controllers signals a high ambient temperature alarm. The controller monitors outdoor or machine-room air temperature and activates AL06 when it exceeds the configured upper ambient limit. High ambient temperature reduces refrigeration system efficiency and can push compressor discharge pressure and temperature beyond safe operating limits, potentially causing other protective alarms to cascade.

Symptoms

• AL06 displayed on the Carel controller.
• Outdoor or machine-room air temperature is above the maximum ambient design limit.
• System cooling capacity is reduced due to elevated condensing temperature.
• Compressor high-pressure protection alarms may also appear concurrently.

Common causes

• Ambient air temperature genuinely exceeds the chiller's rated maximum (often 45–50 °C).
• Condenser discharge air is recirculating back to the inlet in a confined installation.
• Insufficient clearance around the unit causing heat buildup in the machine room.
• Ambient temperature probe fault reporting false high readings.

Diagnostic steps

1. 01

   Verify ambient temperature with an independent thermometer

   Measure air temperature at the unit's air intake using a calibrated thermometer to confirm whether the ambient is genuinely above the alarm setpoint.

2. 02

   Check for discharge air recirculation

   Inspect the installation to ensure warm condenser exhaust air is not returning to the air intake. Add baffles or increase clearances if needed.

3. 03

   Improve machine room ventilation

   If the unit is installed indoors, confirm ventilation is adequate. Machine rooms require sufficient fresh-air intake and exhaust airflow for rated ambient conditions.

4. 04

   Check the ambient temperature probe

   Inspect the ambient probe wiring and placement. Verify the probe is positioned in free air away from heat sources, and test probe resistance to rule out a sensor fault.

5. 05

   Reduce load or schedule operation for cooler periods

   If ambient conditions routinely exceed design limits, consult the chiller manufacturer about de-rating or operational scheduling.

When to call a professional

Consult a refrigeration engineer if AL06 occurs alongside HP alarms or if the chiller is being operated in an environment that regularly exceeds its ambient design rating. Persistent high-ambient operation damages compressor windings and oil. An engineer can advise on de-rating, additional ventilation, or the need for a high-ambient condenser upgrade.