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Hi-
4″ flexible chimney liner runs from basement up 1st floor and out to roof. Only thing hooked up to it is a 75,000 btu gas furnace with a powervent blower or “direct vent”. Want to add a 40,000 btu gas hot water heater to same 4″ chimney duct. Can it handle the additonal 40,000 btu exhaust (so I have 115,000 going into a 4″ chimney duct) Does that work??? Remember, furnace is power vent- does that make any difference on what 4″ can handle…?
Thanks for the advice- B
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Replies
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Is the furnace really a "power vent", or is it an induced draft?
My understanding is that a power vent furnace actually pressurizes the flue, the induced draft doesn't.
Different rules for different furnaces/appliances.
*Yes on power vent- there is definetly a blower running that kicks on and spools up the whole time the furnace is running...-B
*Brian, that blower is present on both power vent and induced draft.I need to know the Brand, model number, and whether it is an 80+% or a 90+% furnace. I will look it up in my code book and answer you if possible.
*The furnace pressurizes the 4" flex whether its an 80+ or 90+. So if you wanted to "tee" into the run before the flex runs up the chimney then I would say you are headed for trouble. A large portion of the exhaust from the furnace will take the path of least resistance and exit into your basement via the WH stack. Am I missing something here?
*Right on Eric- makes sense to me now that you mention it...better get back to the physics of it...-Brian
*"The furnace pressurizes the 4" flex whether its an 80+ or 90+."Do you have authority for that statement? I've taken several classes and talked to countless heating contractors who have told me the opposite."So if you wanted to "tee" into the run before the flex runs up the chimney then I would say you are headed for trouble. A large portion of the exhaust from the furnace will take the path of least resistance and exit into your basement via the WH stack. Am I missing something here?"In practice, I see a lot of furnaces with induced drafts and a standard draft water heater Wye'd into it and the furnace flue gases almost always go where intended. (& I've checked many of them with a draft guage.) Probaly a combination of the Wye and the natural, constant flow of air up the chimney (the stack effect) get's things off on the right foot.Now a T'd connection .... Fargretare chance to back draft through the water heater.Where's Tim when we really need him!
*Bob - I had an 80+ induced draft furnace in a former home that required it's own type B vent and nothing else. Different locales - different codes. Was there pressure in the flue? Sure, maybe an inch of water or so and then progressively lower as the gases made their way out. Would a y be "better" than a t - sure but still not good in my book. A 90+ furnace typically uses PVC for intake and exhaust and, for sure, my installation book for my existing furnace says "dedicated" lines.
*Please leave venting issues to professionals who know what they are doing. This is dangerous stuff to be giving advice on when you don't know what you are talking about.And Eric, I am sorry to say you don't know what you are talking about here. Sorry, but that is the truth. I have multiple codebooks and all of them prove you wrong. UPC, IPC, UMC, and the IMC
*For Wet Head Warrior - I accept your response (and sincerely thank you) because I do not have ready access to the code books you mention but still would like to know where, in my response, am I wrong.
*First I want to aplogize for the rude way I posted. I am sorry. You did not deserve that. I had a really bad afternoon and I fear it reflected in my post.The main thing you were wrong on was this."A large portion of the exhaust from the furnace will take the path of least resistance and exit into your basement via the WH stack."With an induced draft (80+) furnace you can hook the water heater in with the draft and it will not spill into the room IF the main vent is sized right. Now to be fair to you I kina doubt that this 4" is sized big enough... but it may be... I didn't size it out... partly because I never did get enough info.Again, please accept my apologies for my rude post.If you have any other questions feel free to ask and I'll do my best to answer.BTW, what you said is what seems would happen but is doesn't.