BoilerFaultCodesWhat the manual says
Manufacturer manualMains High Voltage or Low Voltage Error
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the incoming electrical power is outside the safe operating range of 230 volts. The most common reason is a fluctuation or surge in the local power grid, or a failing component on the control board misreading the incoming voltage.
This fault is more common during severe winter storms, as falling branches or high winds can cause power surges and fluctuations in the local electrical grid.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Avoid the next call-out bill
A cover plan would handle faults like H7: no call-out fees, no surprise bills.
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