F.23 High
Your boiler has shut down because the water is heating up too quickly or unevenly, suggesting a circulation problem.
Technical description: Safety switch-off – temperature difference too great (NTC1/NTC2)
Typical repair cost: £120-350 (including labour)
DIY fix possible
Ensure all radiator valves (TRVs) are turned to the highest settingCheck that the boiler pressure is between 1.0 and 1.5 bar on the displayGently bleed air from your radiators using a radiator key
Protect yourself from future repair bills
A boiler cover plan would cover faults like F.23 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation Pump
- NTC Temperature Sensors
- Main Heat Exchanger (De-scaling)
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