Venting configuration (direct vent or non-direct vent)

What is going on

The furnace can go in as a Direct Vent or a Non-Direct Vent unit, and the choice changes where the combustion air comes from. With Direct Vent the air is drawn from outdoors through its own pipe. With Non-Direct Vent the furnace takes air from the room, so the space has to have enough of it. Either way, the flue gases leave the house through the exhaust pipe. Figure 2 in the manual shows roof termination layouts, so decide before you start cutting pipe.

Likely causes

• Tight house or finished basement with limited indoor air, which favors Direct Vent
• Corrosive vapours, dust or chemicals indoors that make indoor air a poor choice
• Existing vent layout that decides which option fits
• Code requirements for combustion air in the mechanical room

Check in this order

1. Choose Direct Vent or Non-Direct Vent before installing, because the piping differs.
2. For Direct Vent, bring combustion air from outdoors through the intake pipe.
3. For Non-Direct Vent, supply combustion air from indoors per the National Fuel Gas Code or CSA-B149.
4. Use Figure 2 for roof termination layouts.
5. After install, run a full heating cycle and look for flue gas leaks at every joint.
6. Make sure intake and exhaust terminations are clear of snow, leaves and obstructions.

More furnace guides

• Annual planned service inspection
• Annual service checklist
• Blower access panel and carbon monoxide hazard
• Burner assembly cleaning
• Change blower speed tap
• Check temperature rise and adjust blower speed