BoilerFaultCodesYour boiler is limiting its maximum output to match your heating needs, which is a normal setting adjustment rather than a breakdown.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Heating system part load
What causes this fault?
This occurs when the boiler has been manually or automatically adjusted to limit its maximum heat output to prevent wasting energy. It happens because your home doesn't require the boiler's full power to reach the desired temperature, so the system scales back to a more efficient level. This is a normal operational setting rather than a component failure.
You may see this more often during milder weather when your home requires very little heat to stay comfortable compared to the depths of winter.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like d.0 — no call-out fees, no surprises.
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