BoilerFaultCodesYour boiler has detected an issue with the quality of the electricity supply coming into your home, meaning it cannot 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: Internal error with the mains voltage – frequency may be inconsistent
What causes this fault?
This fault occurs when the boiler's control system detects that the electrical supply from your home is unstable or outside of safe operating limits. It is typically caused by a failure in the boiler's main control board sensing the wrong electrical frequency, or external issues like a power surge or a faulty household circuit. Because the boiler requires a precise voltage to run its internal safety components, it will stop working to prevent damage.
This fault can sometimes be more common during stormy weather or high winds, when external power lines are prone to fluctuating or temporary 'dirty' electricity supplies.
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 328 — no call-out fees, no surprises.
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