BoilerFaultCodesYour boiler is not receiving the correct amount of electrical power to operate safely and has shut down as a precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Fault – supply voltage
What causes this fault?
This fault occurs when the boiler’s electronic control board detects that the incoming electrical supply is outside of the safe operating range required to power the internal components. The most common reason is a fluctuation in the mains power or a physical failure within the boiler's internal wiring or control unit that prevents it from processing electricity correctly. Because the system cannot guarantee safe operation under these power conditions, it shuts down to prevent damage to the sensitive electronics.
This fault is more common during periods of severe stormy weather, when power surges or local grid instability are more likely to affect the home's electrical supply.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like E4 — no call-out fees, no surprises.
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