BoilerFaultCodesTechnical description
Non - Volatile Lockout / Reset O/H or in 'standby' mode
What causes this fault?
This fault occurs when the internal safety sensors detect that the water inside the unit has reached a dangerously high temperature or if the system has failed to ignite properly. The most common reason is a lack of water circulation, often caused by a failing pump or a blockage in the pipework that prevents heat from moving away from the boiler. It can also be triggered by a faulty control board incorrectly reading the system's temperature.
This issue often appears when the heating is first turned on in autumn, as pump components can seize up after being inactive during 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.