BoilerFaultCodesTechnical description
Safetyswitch-off:Temperaturelimiter | Incorrectearthconnectionbetweencableharnessandproduct,flowor returnNTCdefective(looseconnection),straysparkviaignitioncable, ignitionplugorignitionelectrode
What causes this fault?
This fault occurs because the boiler's internal sensors have detected that the water temperature has risen too quickly or exceeded a safe limit. It is usually caused by a lack of water flow, often due to a pump failure or a blockage, which prevents the heat from being carried away from the heat exchanger. In some cases, the sensor itself may have become detached or faulty, sending an incorrect reading to the control board.
This fault is more common in autumn when heating systems are first turned on after summer, as circulation pumps can seize due to months of inactivity.
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.