BoilerFaultCodesWhat the manual says
Manufacturer manualfrost protection active (Priority 4)
What causes this fault?
This code appears when the internal temperature sensor detects that the water inside the boiler has dropped below a safe threshold, usually around 5°C. To protect itself from damage, the boiler automatically fires up to circulate warm water until the internal temperature reaches a safer level. It is a built-in safety feature rather than a mechanical failure.
This status is almost exclusively seen during the winter months when external temperatures drop near or below freezing.
DIY fix possible
Check that your home heating is turned on at the thermostatEnsure any radiator valves in cold rooms are open to allow water to circulateWait for the boiler to finish its cycle; the code will disappear once the temperature rises
Avoid the next call-out bill
A cover plan would handle faults like S.34: no call-out fees, no surprise bills.
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