F8 High
Your boiler's temperature sensor for the hot water storage tank has developed a fault, meaning the system cannot safely monitor or heat your hot water.
Technical description: Tank thermistor fault
Typical repair cost: £120-£210 (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 F8 — no call-out fees, no surprises.
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Parts commonly replaced
- Domestic Hot Water (DHW) NTC Sensor
- Sensor Wiring Harness
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