BoilerFaultCodesWhat the manual says
Manufacturer manualNO HW BUT CH ON
What causes this fault?
This fault occurs when the boiler's internal sensors do not detect enough water movement to safely heat the system, causing it to shut down to prevent overheating. The most common reasons are a failed circulation pump that can no longer push water through the pipes, or a blockage caused by a build-up of debris and sludge. It can also be triggered if the water pressure is too low or if air is trapped inside the heat exchanger.
This fault often appears when the heating is first turned on in autumn, as pumps can seize up after sitting idle throughout the summer months.
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 4.12: no call-out fees, no surprise bills.
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