Your boiler is taking longer than expected to heat up your hot water tank, causing the system to stop as a precaution.

Maximum charging time for a storage without own controller

What causes this fault?

This fault happens when the boiler fails to heat your hot water cylinder within a set time limit, usually because the internal sensors haven't detected a sufficient rise in temperature. The most common cause is a faulty sensor giving an incorrect reading, or a mechanical failure in the diverter valve which prevents heat from actually reaching the water tank.