Your boiler has paused operation because it cannot safely clear waste gases or discharge wastewater produced during the heating process.

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.