Blocking fault 1/u/ (3/1/7) - Flue gas sensor contacts shorted

What does 1/u/ mean?

The contacts for the flue gas sensor have a short circuit. This is a safety fault that prevents heating and domestic hot water operation. A manual reset is required after the cause is corrected.

• Short circuit in flue gas sensor wiring
• Defective flue gas sensor

Click steps to track your progress.

1. 1

   Press the 'Reset' button on the BC10 basic controller.

2. 2

   Visually inspect any visible wiring connected to the flue gas sensor for damage.

3. 3

   If the problem returns, contact a qualified service technician to diagnose the sensor and wiring.