Carel AL49

What does Carel AL49 mean?

AL49 on Carel µChiller and pCO chiller controllers indicates that EEV driver 1 detected the expansion valve failed to complete its close-on-power-off sequence. At power-down, the Carel EVD driver steps the valve fully closed to prevent refrigerant migration into the compressor crankcase during the off period. If this sequence fails, circuit 1 is locked out on the next startup until the alarm is manually reset.

Symptoms

• AL49 displayed on the Carel controller.
• Circuit 1 is locked out at startup following a power interruption.
• EEV driver 1 reports a valve position fault.
• Manual reset required before circuit 1 can restart.

Common causes

• EEV valve motor coil failed, preventing the valve from stepping closed during power-down.
• Power was lost too quickly for the EVD driver to complete the close sequence.
• EEV wiring harness disconnected during the power-off stroke.
• EVD driver 1 capacitor bank insufficient to complete the close stroke before power fully drops.

Diagnostic steps

1. 01

   Check EEV valve wiring harness continuity

   Inspect the wiring from EVD driver 1 to the EEV valve. Verify all conductors are intact and connectors are fully seated.

2. 02

   Test EEV motor winding resistance

   Disconnect the valve from the driver and measure winding resistance. Compare against specification; open windings confirm motor coil failure.

3. 03

   Power-cycle the EVD driver and observe startup

   Switch off the driver and restore power. The driver should perform a valve homing sequence on startup. Listen for the valve stepping through its full stroke.

4. 04

   Manually open the valve via driver manual mode

   Using the EVD driver 1 manual control, command the valve to a partially open position, then allow the driver to re-close it automatically. This verifies motor and driver output stage functionality.

5. 05

   Reset AL49 at the Carel controller

   After confirming the valve closes correctly, reset AL49 and restart circuit 1. Monitor the next power-off cycle to confirm the issue does not recur.

When to call a professional

If EEV valve replacement is required, the circuit must be evacuated of refrigerant before the valve can be removed — an operation requiring F-Gas certification. An engineer should also investigate whether the power supply arrangement provides adequate hold-up time for the EVD driver to complete the close sequence; this may require adding a UPS or buffer capacitor to the driver supply.