Q&A low pressure condition/cold air return

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QandA

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Staff member
Nov 27, 2012
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Question:

I'm reading in my wood stove manual that i should "avoid creating a low pressure condition in the room where the stove is operating. Operating an exhaust fan or clothes dryer could create a low pressure area, causing poisonous gases to come out..." following this line, i'm wondering if i need be concerned with the proximity of the cold air return for my forced air furnace to my woodstove (the woodstove is secondary heat). I imagine that the furnace will not run when the stove is fired excepting when it's being lit... if this is a potential problem, can i overcome it by supplying adequate combustion air? if so, where do i find the numbers on the quantity of air that must be supplied?



Answer:

I believe (not positive) that the International One and Two Family Dwelling code calls for a cold air return to be at least 10 ft away from a woodstove. It seems to me that you would also want to make sure that if your woodstove and cold air return are in the same room, that the room not have a tight closing door on it. The cold air return needs to get air from a relatively large common area, not just one room.

As far as overcoming a reversal by providing outside combustion air, that will certainly help but it would still be possible to get a reversal under very extreme conditions. If your cold air return can get adequate air from a large common area, (IE: Rec. room hallway, kitchen..dining, family..dining, etc.) I wouldn't worry much about the reversal. Go ahead and install outside combustion air to the stove. Most stoves take a 4" air inlet but you'll need to confirm that in your stove installation instructions. In any event, Make sure and get a good quality CO detector. Good luck!
 
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