Select a fault code

Flow NTC thermistor has short-circuited.

Flow NTC thermistor disconnected or failed open.

Primary circuit overheated and the safety thermostat tripped. Caused by pump failure, blocked heat exchanger, or very low flow.

System pressure has dropped below the minimum operating level (typically 0.5 bar). Common in systems with small leaks or after bleeding radiators.

Return temperature sensor fault or reverse flow in the system.

Boiler failed to light within the safety period. Common causes: gas supply interrupted, air in gas pipe after supply outage, faulty igniter or gas valve.

Flame detected initially but then lost — low gas pressure, faulty flame sensor, or draught across the burner.

Fan not reaching minimum speed — worn fan motor bearing or faulty Hall sensor.

Fan speed sensor reading above expected range — faulty fan or PCB.

Communication error between boiler PCB and external controls via the eBUS protocol.

Pump not running on start-up or pressure sensor not detecting flow. Faulty pump, jammed impeller, or pressure sensor failure.