BoilerFaultCodesYour boiler has detected that the electrical supply coming into your home is too low for it to operate safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Low mains voltage
What causes this fault?
This fault occurs when the electrical voltage supplied to the boiler drops below the minimum level required for its internal components to function. It is often caused by a wider issue with the local power grid, though it can also be triggered by a failing internal control board that can no longer process power correctly. In some cases, poor electrical connections or a faulty spur socket in your home may be the root cause.
This fault can occasionally occur during extreme winter cold snaps when the national grid experiences high demand, leading to temporary 'brownouts' or dips in local voltage.
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 F7 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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