F.25 High
Your boiler has shut down because the exhaust fumes have become too hot, which is a safety measure to prevent damage to the internal components.
Technical description: Safety switch off flue gas temperature too high
Typical repair cost: £120-350 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like F.25 — no call-out fees, no surprises.
*Affiliate links — we may earn a commission at no extra cost to you. Prices shown are starting prices.
Parts commonly replaced
- Heat exchanger (descaling)
- Flue gas thermostat
- STB (Safety Temperature Limiter)
- Overheat sensor
*Affiliate links — we may earn a commission at no extra cost to you.