BoilerFaultCodesYour boiler is not receiving enough electricity from your home's power supply to run safely and has shut down as a result.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Supply voltage under 170v – electric supply problem – the electrical system needs checking
What causes this fault?
This fault occurs when the electrical current reaching the boiler's internal components drops below a safe operating level. The most common reason is a fluctuation or brownout in the local grid supply, but it can also be triggered by a failing main circuit board that can no longer process electricity correctly.
This fault may be more frequent during periods of extreme weather or high local demand when the National Grid experiences temporary voltage drops.
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 F15 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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