BoilerFaultCodesYour boiler has shut itself down because it has become too hot inside, likely due to a circulation issue or a lack of water.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Safety switch-off: Overheating temperature reached
What causes this fault?
This fault occurs when the boiler’s internal temperature rises too quickly or exceeds a safe limit, causing the system to shut down for safety. It is usually caused by a lack of water flow, which can happen if the pump has failed, the system pressure is too low, or there is a blockage or trapped air preventing the heat from being carried away from the heat exchanger.
This issue is more common when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
DIY fix possible
Check if your radiator valves are open to allow water to flowCheck the boiler pressure gauge and top it up to 1.5 bar if it is too lowPress the 'Reset' button (represented by a flame with a line through it) to restart the system
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 F.20 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.