EXT COM (green) LED not lit - No communication with indoor module/control module

What does EXT COM LED off mean?

The green EXT COM LED on the base board (AA2) is off, indicating that there is no communication between the Heat Pump and the NIBE indoor module or control module. This prevents control and status updates.

• No communication with the indoor module/control module.
• Communication cable not correctly connected or damaged.
• Issue with the indoor module/control module itself.

Click steps to track your progress.

1. 1

   Check that the S2125 is correctly installed and paired with the indoor module or control module.

2. 2

   Verify that the communication cable (three-core cable to terminal block X22:1–4) is securely connected at both the Heat Pump and the indoor/control module.

3. 3

   Inspect the communication cable for any visible damage. If damaged, it may need to be replaced.

4. 4

   If the problem persists, contact a qualified NIBE service technician to diagnose the communication link.