BoilerFaultCodesTechnical description
Fluenon-returnflapclosed | Fluenon-returnflapresponseblocks burneroperation (onlyinconjunctionwithaccessoryVR40)orcondensate pumpdefective;heatrequirementisblocked
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that waste fluids or gases are not being cleared from the system correctly. The most common reason is a failure in the pump that removes wastewater, or a communication error with the components that manage the exhaust gases. To prevent potential flooding or unsafe operation, the boiler automatically disables the burner until the blockage or electrical fault is resolved.
This fault is more frequent during extreme winter cold, as the external pipe that carries away wastewater can freeze and cause the internal pump to fail.
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.