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rvegab00 12-06-2009 10:48 PM

furnace combustion air from attic
I have a goodman 93% high efficency natural gas furnace located in my single story home in the utility room. Utility room is not closed off in any way to the rest of the house.

Original installers used pvc to vent the furnace to the roof but combustion air for the furnace is pulled from inside the house.

Could the combustion air for the furnace be piped in with pvc pipe from my attic area? Of course routed well above attic insulation. The attic has 1 vent on the north side of the home, and 1 on the south side of the house, and 3 roof vents.

just wondering if this is acceptable practice.

beenthere 12-07-2009 04:19 AM

Its done, but instructions want both intake and exhaust in same area. To prevent nusiance trips of the pressure switches.

If you have trouble on windy days. Cut it open in the furnace room again.

rvegab00 12-07-2009 07:30 AM

Thanks for your reply.

I know the prefered setup has them both on the roof, but if one is in the attic, what difference in pressure would there be, not sure I understand.

Currently the furnace pulls air for combustion from in the house. So there is already a difference in pressure, no?

Just wondering.
Thanks again.

beenthere 12-07-2009 08:18 AM

Sudden change in wind direction could make the attic a positive pressure compared to the outside where the vent is. And then go back to normal, or even negative. Sudden changes like this can cause the pressure switch to open and drop out the burners. If this happens 3 to 5 times(depending on brand) the board will lock out the burner.

With it in the furnace room. There is no sudden change of pressure from the inside air.

What you want to do. Works in many houses. But not in all. Depends on where the exhaust is located. And how the attic is vented. And which way gable vents face.

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