Ash pan fills very quickly and ash is unusually coarse or contains unburned fuel

Safety: Empty ash only when the furnace is cold. Use metal containers for ash disposal.

• Clean the burner grate thoroughly, ensuring all air holes are open.
• Reduce the fuel feed rate slightly in the controller and/or increase combustion air within allowed limits.
• Verify that the fuel type and size match Defro's specification for your burner.
• Monitor the flame; it should be bright and stable, not dark and smoky.

Continued poor combustion may require professional tuning of the controller parameters.