BoilerFaultCodesWhat the manual says
Manufacturer manualIrregular mains frequency – electric supply problem
What causes this fault?
This fault occurs when the boiler's internal computer detects that the incoming electrical supply is fluctuating outside of the standard 50Hz frequency required in the UK. The most common reason is a temporary instability in the National Grid or a local power surge, though it can also be triggered by a degrading main control board failing to read the power correctly.
This fault may be more frequent during periods of extreme weather, such as heavy storms or lightning, which can cause temporary fluctuations and interference in the local electrical grid.
Engineer required
This fault requires 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 F35: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.