BoilerFaultCodesTechnical description
If burner lockout is reset 5 times in one demand period using the fascia reset button the controls will lockout with a new code: 9F 856. This is to protect the burner components against over use of the reset and requires a power down of the appliance to reset.
What causes this fault?
This fault occurs when the boiler's safety system permanently locks itself to prevent damage after the manual reset button has been pressed too many times. It is triggered by an underlying failure in the burner system, such as a blocked oil nozzle or a faulty ignition component, which prevents the flame from lighting correctly. Once this specific code appears, the boiler will no longer respond to simple resets and requires a professional intervention to clear the memory.
This fault is frequently seen in autumn and winter when the oil in the tank or supply lines becomes more viscous due to the cold, potentially leading to blockages that trigger the initial burner failure.
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.