BoilerFaultCodesTechnical description
CH system pressure less than 0.5 bar or faulty water pressure switch.
What causes this fault?
This fault occurs when there isn't enough water circulating through your pipes and radiators to allow the boiler to operate safely. The most common reason is a slow leak somewhere in the system or because you recently bled your radiators, which lowers the overall pressure. In some cases, the internal expansion vessel may have lost its charge, causing water to escape through the safety valve.
This fault is more common in autumn when homeowners turn their heating back on for the first time after summer, revealing pressure losses that occurred while the system was idle.
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.