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Smoke from fireplace flue being drawn down flue for furnace

Posted by Donald20 (My Page) on
Thu, Dec 6, 12 at 19:47

We have an 11"x11" flue for our fireplace and a 9"x9" flue for furnace (side by side). After installing chimney caps the smoke from the fireplace flue is being drawn down the furnace flue and into our basement. This smoke is being drawn upstairs and onto our first floor where the fireplace is. Did not have this problem before chimney caps were installed. If we open a window by fireplace the problem is solved but cold winter air comes in too. If we close the fireplace doors the problem is also solved. We have a 3" dia. air supply from louvers on the side of the chimney. We would like the doors open. How can this problem be addressed without removing chimney caps? The chimney is 2' above the ridge of the house.

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RE: Smoke from fireplace flue being drawn down flue for furnace

Soo... This stack is an exterior stack that terminates 2' above the peak? It terminates therefor at least 2' above the HIGHEST portion of the home, not just where it exits? IF NOT then that is the problem, the chimney was never built properly; even it it 2' above the highest portion of the home, that's not tall enough, a minimum of 3' is barely adequate, and 4' is minimum recommended.

Having said all that, What "chimney professional" talked you into chimney caps? What "problem" were you trying to solve with them? Have them REMOVED and solve your problem. It's likely that the second flue always had a week and occasionally reversing draft due to improper chimney height, but the caps (which are, in most cases, unnecessary) have caused this unseen problem to become visible. You have three options: 1. extend the chimney height so that it functions like a proper chimney should. 2. Remove the caps! (you have some aversion to this, but it works and will cost you less than the other options). Remove furnace connect from basement flue and disable furnace (not very likely a good choice).

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