BoilerFaultCodesYour boiler is not receiving enough electrical power from the property's mains supply 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 supply from your home to the boiler drops below the minimum level required for the internal components to function. It is usually caused by an external issue with the local power grid or a fault within the boiler's control board that prevents it from processing electricity correctly.
This fault is more common during winter or heatwaves when the national grid is under heavy load, causing temporary 'brownouts' or voltage drops in certain areas.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like F7 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.