IMPORTANT: Troubleshooting of heaters should only be carried out by qualified Gas Safe engineers or Electricians.

There are two types of lockout on a CTU: a burner lockout and an overheat lockout.

Burner Lockout

If the heater attempts to light 3 times, but fails to maintain a flame, it will go into burner lockout mode as indicated by the red light at the front of the heater being on. 

To reset it, on the back of the heater, press and hold the reset button for 3 seconds. Most controllers also have a remote reset button; see the FAQ section relevant to the controller. If the red light goes off, the heater has reset. 

If the green light is on, it shows the controller (thermostat) is calling for heat. 

Make sure the valves on the gas supply are open (open: handle parallel to the gas pipe; closed: perpendicular to the gas pipe).

If the red light does not go off after pressing the reset button, there is a technical issue with the heater.  Contact our Technical Support Team for assistance.

Overheat Lockout

If the heater isnt turning on and the red light is off, it means the heater is in overheat lockout. In this state, if the green light is on, this indicates that the controller (thermostat) is calling for heat, confirming that they system is requesting operation. To reset the heater safely, please contact our Technical Support Team or a Gas Safe-Registered Engineer for further assistance.