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Old 09-30-2009, 08:26 AM   #1
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downdraft problem

thanks in advance for reading my post.
the problem is that in the winter time when we are heating the house, our CO alarm (located in a small closet with the boiler and water heater) alerts us and shows high CO levels when we get a southern wind. it eventually clears up and the alarm shuts off. most of the time we open windows and doors to help clear it out. we've narrowed the problem down to only in the winter when the boiler is in use, and when there are medium to strong gusts of southern winds.

I have a hot water boiler for my heating system in my house. the exhaust vents through a 5 inch stove pipe which is met by a 3 inch pipe from my water heater. they wye together into what appears to be a 7" (outside diameter) double wall pipe that goes through the roof. it then extends 42" above the roof.

i have enclosed a picture. the garage is on the right, the house is on the left and the breezeway with the boiler room is in the middle. north is to the left, which means a southern wind would come from the right, up over the garage, past the flue and over the house. i was hoping that someone could look at this picture and diagnose the problem and offer possible solutions?

thank you very much. if i have not provided enough info. i will be glad to answer any questions. thanks again for your time.

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downdraft problem-img_0276-1.jpg  


Last edited by spyshot; 09-30-2009 at 08:28 AM.
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Old 09-30-2009, 10:23 AM   #2
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The flue(chimney pipe) is too short.
2' above any horizontal surface within 10' of it.

Measure from the top of the chimney cap straight across to the house roof. If its 10' or less, the cap must be 2' above it.

That area is being pressurized when the wind comes from a south direction.


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Old 10-01-2009, 01:56 PM   #3
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You have some interesting roof line congestion, but this is a similar situation to what many wood and pellet stove owners experience. The solutions are to extend the chimney, reroute the chimney, or force a draft. Been has already mentioned one solution that I would try first. If raising it doesn't solve the problem you could look into installing some kind of exhaust draft inducer as found on all high efficiency devices that don't need a chimney to prevent any back draft once and for all. Check with your boiler manufacturer before going that route.

Last edited by dac122; 10-01-2009 at 01:59 PM.
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