BoilerFaultCodesWhat the manual says
Manufacturer manualSafety valve is prompted to relieve excess pressure from the primary circuit
What causes this fault?
This fault occurs when the water pressure inside your heating system rises above safe levels, often because the expansion vessel has lost its air charge or failed. The boiler triggers this code as it uses a safety valve to eject water and protect internal components from being crushed by the high pressure. It can also happen if the filling loop was left slightly open, causing the system to overfill unintentionally.
This fault is more common in winter when homeowners turn their heating on for the first time, as the rapid heating of water puts the most strain on the expansion vessel.
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 23: no call-out fees, no surprise bills.
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