D3 — External temperature limiter activated

What does D3 mean?

The external temperature limiter has been activated, preventing the boiler from operating. This is a safety feature to prevent overheating.

• External temperature sensor malfunction.
• System overheating.
• Faulty wiring to the limiter.

Click steps to track your progress.

1. 1

   Reset the boiler by pressing the reset button on the control panel.

2. 2

   Check that all external temperature sensors are clear of debris and properly connected.

3. 3

   If the limiter continues to trip, contact a qualified heating engineer to investigate the cause of overheating.