Blocking fault 4/u/ (2/2/2) - Safety temp sensor contacts shorted

What does 4/u/ mean?

The contacts for the safety temperature sensor have shorted. This is a safety fault that prevents heating and domestic hot water. This is a blocking fault, requiring a manual reset.

• Short circuit in sensor wiring
• Faulty safety temperature sensor

Click steps to track your progress.

1. 1

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

2. 2

   Visually inspect accessible sensor wiring for any signs of damage or wear.

3. 3

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