Blocking fault 4/l/ (2/2/0) - Safety temp sensor shorted or over 266°F (130°C)

What does 4/l/ mean?

The contacts for the safety temperature sensor have either shorted or the sensor has detected a flow temperature exceeding 266°F (130°C). This is a critical safety fault, preventing heating and domestic hot water. This is a blocking fault.

• Short circuit in sensor wiring
• Faulty safety temperature sensor
• Extreme overheating

Click steps to track your progress.

1. 1

   Press the 'Reset' button on the BC10 basic controller after ensuring the boiler is cool.

2. 2

   Visually inspect accessible sensor wiring for any signs of damage.

3. 3

   If the fault persists, contact a qualified service technician to check the sensor and wiring.