BoilerFaultCodesWhat the manual says
Manufacturer manualDry fire protection | No water in appliance, pump cable defective, pump blocked or defective, pump output too low
What causes this fault?
This fault occurs when the boiler's internal sensor detects that the system pressure has dropped too low for the unit to heat water safely. The most common reason is a slow leak somewhere in your radiator network or a faulty expansion vessel that can no longer regulate pressure correctly. Without enough water to circulate, the boiler shuts down to prevent the heat exchanger from overheating or sustaining permanent damage.
This fault is more common in autumn and winter when the heating is first turned on, as the increased pressure of hot water can expose small leaks or reveal that the system lost pressure while sitting idle during the summer.
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 F.22: no call-out fees, no surprise bills.
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