Heating, Air Conditioning, Fridge, HVAC/furnace venting


Hi Jim,
On inspecting a townhome for purchase, I noticed the furnace, a Carrier, gas, forced hot air unit was vented with single wall galvanized metal pipe, through the exterior wall of the utility room in which it was installed. The vent pipe exits the room at a height of about 7'6", and terminates at a metal vent installed in the vinyl siding in the exterior wall. This is not a high efficiency furnace. I wanted to know if it is proper to vent a non high efficiency gas furnace through a side wall like this.  Thank you for your attention.


The single wall galvanized metal pipe vent is OK inside as long as it has a 1/4" or more rise per foot, and is at least 6" away from combustible, the double wall vent that goes up needs to have an enclosure around it all the way up until it's above the roof line, the double wall vent needs to be 1" away from combustible and terminate at least 2' above the roof line, the connection between the single wall and double wall needs to be inside the building.  

Heating, Air Conditioning, Fridge, HVAC

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Jim Barnhart


Fifty + years conditioning the air.


Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

Hands on since 1950

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