Your boiler has detected a temporary sensor problem or an unusual temperature difference, which may cause the system to pause or restart.

Temporary fault code (Refer to section 7.10)

What causes this fault?

This fault occurs when the boiler's internal sensors detect an inconsistent temperature reading or a slow rate of water flow through the system. This is often caused by a buildup of debris or lime scale within the heat exchanger, or a sensor that is starting to fail and providing inaccurate data. Much like a safety check, the boiler pauses briefly to ensure it doesn't overheat before attempting to fire up again.