F.23 - Safety switch-off: Temperature difference too great

What does F.23 mean?

The boiler has performed a safety shutdown because the temperature difference between the flow and return was too large, indicating circulation problems or incorrect sensor readings.

• The pump is blocked or has insufficient output.
• Air is present in the boiler or heating system.
• Flow and return NTC sensors are connected the wrong way around.

Click steps to track your progress.

1. 1

   Press the reset button on the boiler display up to three times to try and clear the fault.

2. 2

   Check for trapped air in the heating system and bleed radiators if necessary to release air.

3. 3

   Contact customer service. This safety shutdown indicates issues with the pump, air in the system, or incorrectly installed flow/return NTC sensors that require professional attention.