Select a fault code

The boiler has detected a mismatch between the configured gas type and what it is detecting. This is a commissioning or configuration fault.

The fan speed is outside the acceptable operating range — either too fast or too slow. This prevents safe combustion.

A fault has been detected with the gas valve. The boiler cannot safely control gas flow.

The relay controlling the gas valve on the PCB has detected a fault.

There is a problem with the wiring or signal from the room thermostat or programmer to the boiler.

The boiler has detected a problem with the fan or flue system. This may be a blocked flue, faulty fan, or a wiring issue.

The flow temperature sensor has detected a fault or is reading an abnormal temperature. This sensor monitors how hot the water is as it leaves the boiler.

The return temperature sensor is reporting a fault. This sensor monitors water temperature returning to the boiler from the heating system.

The domestic hot water temperature sensor has failed or is reading incorrectly.

The boiler has reached an unsafe temperature and the high limit thermostat has cut out. Common causes include a blocked heat exchanger, poor water circulation, or a faulty pump.

The safety temperature limiter has tripped, meaning the boiler exceeded safe operating temperature limits. This is a protective shutdown.

The boiler attempted to ignite but failed to detect a flame. This can be caused by low gas pressure, a faulty igniter, dirty flame sensor, or a closed gas valve.

The boiler's PCB (printed circuit board) has detected an internal error. This is usually a component failure on the control board.

Water pressure in the heating system has dropped below 0.5 bar. This is one of the most common boiler faults and is usually straightforward to fix.

The boiler is detecting a flame signal when the burner should be off. This indicates a faulty gas valve or flame detection circuit.

The fan is not reaching the required speed for safe combustion. A faulty fan, wiring problem, or blocked flue can cause this.

The boiler has locked out due to a detected fault. This code appears when no specific fault code is stored.