Carel AL22

What does Carel AL22 mean?

AL22 on the Carel pLoads controller (source document 040000131) indicates that analogue input probe B8 is reading outside its valid range or has lost continuity. The pLoads Large model supports analogue inputs B1 through B8 for current, voltage, or temperature measurements. A faulty B8 probe triggers an alarm relay activation and flags the associated measurement as unreliable.

Symptoms

• AL22 displayed on the pLoads pGD1 terminal with the alarm relay activated
• Probe B8 reading absent or displaying an out-of-range value on the pLoads display
• Any load scheduling or energy measurement function depending on B8 data may be disrupted

Common causes

• Probe B8 cable has an open circuit — wire break or loose screw terminal
• Probe B8 sensor has failed — resistance or voltage output outside the configured input range
• Wrong probe type connected to B8 input vs. the type configured in pLoads parameters
• Moisture or contamination at the B8 analogue input connector causing signal degradation

Diagnostic steps

1. 01

   Identify what is connected to B8

   Review the pLoads installation records or wiring diagram to confirm the sensor type connected to analogue input B8 (NTC temperature, PT1000, current transformer, or voltage input).

2. 02

   Inspect B8 wiring and terminals

   With pLoads powered down, inspect the cable connected to B8. Check for loose terminal screws, broken wire strands, and correct wire connection to the appropriate analogue input terminals per the pLoads wiring diagram.

3. 03

   Measure probe output

   Reconnect power and measure the signal at the B8 terminal with a multimeter. Compare the reading against the expected output for the installed probe type at the current measurement condition.

4. 04

   Verify probe type configuration

   Navigate to the pLoads analogue input configuration screens and confirm B8 is set to match the installed probe type. A misconfigured input type causes the controller to flag a valid signal as a fault.

5. 05

   Replace the probe if defective

   If the probe output is absent or incorrect, replace it with a compatible sensor of the correct type and range. Reset AL22 after replacement and verify B8 reads correctly.

When to call a professional

If AL22 persists after probe replacement and configuration verification, the pLoads analogue input circuit may be damaged. Board-level repair or replacement requires a Carel-authorized service technician. Current transformer inputs at B8 in high-current measurement applications should only be worked on by a qualified electrician.