Venting appliances into masonry chimneys
cocteau3
| Posted in Energy, Heating & Insulation on
I am considering installing a wood stove in my living room, which will have a code-compliant stove pipe extended through the fireplace and up through the masonry chimney to the outside via the top of the chimney. It will be done just like Vermont Castings recommends. My question is what to do with the venting for the 2-year old 80% efficiency furnace. It is currently using the masonry chimney as well, and had a “flue liner” installed. The water heater probably is vented through it too. Since the stove would be entering the chimney on the ground floor, and the appliances entering it in the basement, is it possible or safe to vent all three considering the useage of the stove pipe for the stove?
Replies
Will the Vt Castings stove flue be "inside" the flue for the furnace and water heater? you mentioned a "flue liner" so it's not clear.
If the existing chimney is merely a chase for 2 metal separate, side by side flues, it could be OK.
You should check with Vt Castings, though. There may be an issue with their stove pipe back drafting flue gases from the furnace. I was at a lecture today on Vt Castings gas fireplaces, and they are using some fancy pipe technolgy which draws combustion air from the top of the chimeny - I don't know if they're doing the same with their wood stoves, but suspect they are because the same issues are involved.
Bob and Cocteau3,
"A solid fuel-burning appliance or fireplace shall not connect to a chimney passageway venting another appliance."
That is a direct quote from the mechanical code that applies to most of the areas that I work. The International Mechanical Code, 1996, section 801.11.
You have to run wood burning appliance vents separately from gas and oil burning appliance. If the chimney is merely achase that contains separate flues, as Bob mentioned, it is ok. Otherwise, you'll have to find another way.
The manufacturers recommendations is a good place to start, but the applicable code in your area is the law. Find it and follow it to save yourself any future compliance problems.
Tim
Thanks, I think that is what Vermont Castings said in their manual . . .I would have to backtrack and read it again. There are not two separate flues. So my only task is to re-vent the 80% appliances with their own pipes out the side of the house and up above the roofline. Looks bad from the outside, but would free up the masonry chimney. Or, would cold air outside cause condensation in the 80% appliance vents due to rapidly cooling air?
j.
Or, would cold air outside cause condensation in the 80% appliance vents due to rapidly cooling air?
In my area (NW Ohio) and, I believe many other places. you'd have to build an insulated chase to run the flue vents in for the very reaon you mention.
Edited 10/24/2002 7:40:44 PM ET by Bob Walker
The condensation of the furnace and the water heater is an issue. I had an unlined chimney (maybe I should say poorly lined) encased behind plaster in my 1910 home. It was fine with the old octopus furnace. But when I went to the 80 percent efficient furnace it got ugly.
The 80 % furnace generated so much humid exhaust gas that it started condensing on the inside of the chimney. The second floor started to effluresce then shag off chunks of plaster. The solution was to go to the local timsmith and have 30 foot of Stainless steel sheetmetal tubing formed. I then slid it down the chimney, cut in the furnace inlet and mortared the new tubing into the cap. Final stage was to knock off the old loose plaster and resheath it with greenboard. I have a separate flue for the masonry fireplace
If you have a high efficiency rig then (92%+) run it out the sidewall. Buy a high efficiency Water heater and do the same if you can swing it. Then you can use the Vermont castings unit. That would be my approach.
I am getting a new furnace (I hope) starting Monday. My heating/plumbing guy suggested I install a flue liner, since my old furnace is a 46 yr. old gas burning, converted oil furnace. Probably 45% efficient. The gas hot water tank is vented into the same chimney.
Lots of heat there to keep the bricks & mortar in good shape. When I told him I was going to add a 450 cfm range hood into the same chimney, he told me that he could not do it - the backdraft would end up killing us.
So, into the sheet metal shop for 2 liners ...At my age, my fingers & knees arrive at work an hour after I do.
Aaron the HandymanVancouver, Canada
Yes I wouldn't mess with using a chimney flue for a range hood vent pipe. Number one it would be a poor range vent as air likes to move in smooth bends. It kinds piles up in the 90 degree corners. In the world of compressed air it is the equivalent of adding 6 foot of pipe when you put in a 90 degree bend. Think friction.
It's a pain in the aQQ (as my mother used to say) to run it in separate flues but you gotta. Can't you dig up the ceiling and snake thru a Range hood vent pipe to the outdoors? Possibly you don't want to disrupt the insulation (sometimes that is best left unspoken) Or drop it to the basement and vent the fan outdoors that way.
Wet air from the new furnace is imperitive to keep from the old brick. Probably best to send that out the side of the house as well. My ss tubing ran over 300 clams about 10 years ago. 10 bucks a foot.
Edited 10/25/2002 9:04:59 PM ET by Booch
There's another possible solution for you and that is to simply install a forced vent fan on ech of these lines for the 80% appliances. Then you wouldn't have to run those pipes above the roofline, but rather just outside with a ell pointing downward or a vent flap-style hood. These must termninate miniumum distances from the ground, windows, doors and fresh air inlets of any type, but this shouldn't be all that difficult.
If the WH is nearly toast anyway, you could buy a new one that comes equipped with forced vent.Knowledge is power, but only if applied in a timely fashion.
There's another possible solution for you and that is to simply install a forced vent fan on ech of these lines for the 80% appliances. Then you wouldn't have to run those pipes above the roofline, but rather just outside with a ell pointing downward or a vent flap-style hood.
Ahh, can you give any authority for that proposition? I am not aware of any 80+ furnace which can be vented that way.
Bob,
While no furnace manufacturer provides a unit with forced exhaust from the factory for 80+ units, if you investigate the matter, you'll discover that some of them sell booster draft units for their equipment and approve the installation of said device while others do not.
Rudd, for example, sells and approves the draft booster, but Heil does not and installation of such a device on their units will void their manufacturer's warranty.
Just thought it might offer a solution for COCTEAU3.
Edit.....no furnace manufacturer provides a unit with forced exhaust from the factory.....that I'm aware of.
Knowledge is power, but only if applied in a timely fashion.
Edited 10/26/2002 11:19:01 AM ET by GOLDHILLER
Thanks for the info, I haven't seen any, I'll have to check them out.
No, you should not use the same vent for a solid fueled fireplace and for gas fire appliances. In most jusrisditions this is against code.