BoilerFaultCodesWhat the manual says
Manufacturer manualInsufficient primary flow
What causes this fault?
This fault occurs when the water inside the boiler heats up too quickly because it isn't being pumped away into your radiators or cylinder fast enough. The most common reasons are a failing external pump, a blockage caused by sludge in the pipework, or air trapped within the system preventing a steady flow.
This issue is more frequent in autumn when heating systems are switched back on after a long summer break, as pumps can seize and debris can settle while the system is inactive.
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 27: no call-out fees, no surprise bills.
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