BoilerFaultCodesWhat the manual says
Manufacturer manualDEMAND ON
What causes this fault?
This fault occurs when the boiler recognizes you want heating or hot water but fails to complete its internal safety checks to ignite the flame. It is usually caused by a mechanical failure in the fan or the air pressure switch, which prevents the boiler from proving it can safely expel exhaust gases. As a result, the system stays in a 'holding' pattern and refuses to fire the burner for safety reasons.
This issue often surfaces during the first cold spell of autumn when a fan that has sat idle all summer struggles to spin up to the required speed.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Avoid the next call-out bill
A cover plan would handle faults like NEON2: no call-out fees, no surprise bills.
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