Your boiler has shut down because electronic interference or a faulty internal circuit board is preventing the burner from starting safely.

Burner blocked. Strong interference (EMC) field nearby; alternatively boiler coding card or main PCB faulty. Cause: Remove EMC interference. If the equipment will not restart, check the boiler coding card and replace, or replace the control unit.

What causes this fault?

This fault occurs when the boiler's internal computer receives garbled or 'noisy' signals that prevent it from safely managing the burner. It is typically caused by electronic interference from a nearby appliance or a physical defect in the PCB or its unique coding card. Essentially, the boiler has lost its ability to verify its own settings and shuts down as a safety precaution.