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

Permanently on (LED on Burners) - Means the burner is locked out,and troubleshooting is required. Check for oil pump or gas valve inlet & burner pressure, head and air settings.  If everything is as per the manual, check the photocell (Flame Rectifier) in the burner. If it keeps locking out contact Technical Support for further troubleshooting 

Inlet Pressure for all gas heaters is 17mbar to 25mbar