Expert: James Ball - 9/29/2008

Question
QUESTION: Why is it considered unsafe to run gas furnace and wood stove in same flue? Especially if monthly inspections are done to check creosote buildup?
thanks
Mark

ANSWER: Hello Mark, It is in NFPA 211 code book (do not mix liquid and solid flues), second Creosote is very corrosive and so is the natural gas that produces a ton of moisture and hydrochloric acid and then my guess would be that if you had a problem and your house burned down, some one died/got hurt your home owners insurance company may not pay if they find it like that. I wont even clean a system  like you describe even if the  home owner signed a waver. Its kind of like cleaning with Clorox and ammonia I have heard of people using and done it but I would never take that chance.
I say do not do it.you can always look into a power vent (this is a fan that just blows the gases out the side of the house and the furnace must be rated for it and be oked by your local building department) for your gas furnace and use the chimney for your wood stove.
Or just run a new Class "A" chimney for the wood stove up the out side of your house.
hope this helped
James Ball

---------- FOLLOW-UP ----------

QUESTION: That makes sense. I wasn't sure of the code either, I'll look up the NFPA code at work, we have a copy. The easiest option is to install a new 95+ efficient and vent it outside, but that will have to wait a year. The next option is to run a B vent up along the existing chimney. Are B vents rated for running through floors?
thanks
Mark

Answer
Welcome back Mark, depending on the pipe you will have to speak to the manufacturer (B-vent is a brand name but it is like Comet or Fantastic). B-vent is for inside if I am not mistaken, you must follow all manufactures installation instructions when installing.
hope this helps
James Ball