EF 349 Medium
Your boiler is overheating because water isn't moving through the system quickly enough, forcing it to run at its lowest power to prevent damage.
Technical description: Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return.
Typical repair cost: £100-£350 (including labour)
DIY fix possible
Check that all radiator valves (TRVs) are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barBleed all radiators to remove trapped air
Protect yourself from future repair bills
A boiler cover plan would cover faults like EF 349 — no call-out fees, no surprises.
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Parts commonly replaced
- Central heating pump
- Main heat exchanger (flushing)
- Flow/Return thermistors
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