Carel AL022 Error Code

What does Carel AL022 mean?

AL022 on the Carel FLSTDmSCHE screw chiller indicates a battery alarm for Circuit 1's EVD electronic expansion valve driver. The EVD evolution driver uses a backup battery or capacitor module (EVBAT) to close the expansion valve on power failure. AL022 signals that this backup power source has discharged, is absent, or has detected an abnormality. The controller logs the alarm but takes no shutdown action — it is a signal-only event with automatic reset.

Symptoms

• AL022 displayed on pCO5 terminal; unit continues operating normally
• EVD Driver 1 battery/backup module status indicator may show discharged or fault state
• Risk of incomplete valve closing on next power failure

Common causes

• EVBAT capacitor or battery module has depleted and needs recharging time after recent power restoration
• EVBAT backup module not installed on EVD Driver 1
• EVBAT module internal fault — capacitors have degraded beyond service life
• Intermittent power supply issue causing the EVBAT module to not charge fully

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Diagnostic steps

1. Verify EVBAT module presence

   Inspect EVD Driver 1 for the EVBAT00400 or EVBAT00500 backup power module. It mounts on the DIN rail adjacent to the driver. If not installed, the system is not protected against valve-open power failures.

2. Allow module to fully charge

   After a power restoration event, the EVBAT module requires 4–5 minutes to fully charge (or longer for some valve types). AL022 should clear automatically once the module reaches full charge.

3. Inspect EVBAT module condition

   Check the EVBAT module for physical damage, swollen capacitors, or discolored components. Modules have a finite service life and should be replaced per Carel's recommended maintenance interval.

4. Test backup close function

   With the system running and the EVBAT charged, perform a controlled power interruption to EVD Driver 1 and verify the expansion valve closes fully. Incomplete closing indicates a depleted or failed module.

5. Replace EVBAT module if defective

   Replace a failed or life-expired EVBAT module with a new Carel unit. Confirm AL022 clears after the replacement module has had time to charge.

When to call a professional

EVBAT module replacement is a straightforward task for a qualified controls technician. If the alarm persists after module replacement and charging, the EVD Driver 1 internal battery monitoring circuit may be faulty, requiring Carel-authorized board service.