Your boiler is currently set to run at a lower power level than its maximum capacity to save energy or match your home's heat demand.

Partial heat load (Diagnostics menu)

What causes this fault?

This status appears because the boiler’s maximum output has been manually limited during installation or a service to better suit the size of your property. It is not a mechanical failure, but rather a configuration setting that ensures the unit doesn't use more gas than necessary to heat your radiators. It prevents the system from 'short cycling,' which occurs when a boiler is too powerful for the home it is heating.