Check the following:
- Is the flue system permissible?
- Are there any blockages?
- Is the appliance and flue correctly adjusted (air inlet guide, restriction slide, throttling ring)?
- Has the correct gable/roof pass-through been used (DRU brand)?
- Does the gable/roof pass-through discharge into the prescribed areas (free from any interference from walls and roofs)?
More information on the above can be found in the manual.
! PowerVent®? Check that the pressure setting unit is correctly adjusted (see manual).
Pilot light burner
Is the pilot light too weak (dirty)? And does igniting the main burner pull it away from the thermocouple?