Oil Furnace and wood stove with a tee to the same chimney flue...

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jwl

New Member
Nov 24, 2013
1
CT
Hi all,

I already know this is a bad idea and that it may be against code. However, I know a lot of "old timers" that tell me they do it and have been for years without a problem. I want to hook up my wood stove to the same chimney as my hot air oil furnace. I'm in a pinch financially and don't have the cash for a new chimney or triple wall pipe up the side of the house. I have a few cord of 2 year old wood ready to go. I need to know if this will be an immediate safety problem or not. I plan to burn a little this year to see how it goes. If things go well, I'll line the chimney next year then get serious about burning more often.

My chimney is in pretty good shape and seems to pull a great draft with the furnace going. See the attached pics and let me know your opinions.
 

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Jags

Moderate Moderator
Staff member
Aug 2, 2006
18,395
Northern IL
I can honestly state that I cringe at posts that start out with "I already know that this is a bad idea". If you are looking for confirmation that this is a bad idea, consider it confirmed. I understand your situation, but I doubt if you will find many that will condone what is CLEARLY a safety issue. Your house, your stove, your family. Do what you are gonna do, but I sincerely hope you reconsider.
 

Seasoned Oak

Minister of Fire
Oct 17, 2008
7,217
Eastern Central PA
If you have no other choice, i would suggest that you simply disconnect the oil furnace when you want to run the wood stove. You could leave the tee in there and put a cap in it. It only takes a few minutes, In other words only have one or the other connected at any one time NOT both.When you want to run the oil furnace disconnect the wood stove and move the cap to that side. Always a possibility of back feed with BOTH connected.
 
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Seasoned Oak

Minister of Fire
Oct 17, 2008
7,217
Eastern Central PA
It seems your flue pipe could use an adapter where it enters the chimney flue. They are inexpensive and available at most hardware stores. You should not have big gaps around your stove pipe where it goes into the chimney. It looks like your using a 6" flue pipe in an 8" flue nipple.
You would need a 6x8 adapter. Measure to be sure.
 
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kingston73

Member
Feb 10, 2011
172
SE MA
Think of it like this, if you did have a fire would your insurance cover you? You already said you think it's against code, so you basically answered your own question.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,251
South Puget Sound, WA
I don't understand why one would come here and asking for a blessing to install against code and safety rules? It's not going to happen. That would not be helpful or responsible. Check into installing a power vent on the furnace and sealing off it's chimney hole.
 

CenterTree

Minister of Fire
Sep 15, 2008
1,050
SouthWest-Central PA
I agree that the OP's idea is NOT the thing to do.

I have a question for those who may know.
How is it possible that the PSG CADDY WOOD/OIL furnace is setup from the factory to use the SAME CHIMNEY/FLUE.????
_g:confused:


3.4.3.1 DRAFT AND CHIMNEY
The chimney must conform to the rules of the authorities having jurisdiction and
the CAN/CSA B139 & NFPA 31 standard regarding installation of oil burning
heating appliances. The installation of the connecting pipes to the oil unit must
be done and approved by a professional.
NOTE: The barometric damper provided with the appliance must be
properly installed on the flue pipe of the oil burning unit. The purpose of
the damper is to adjust the draft in the evacuation pipe of the oil burning
unit to the recommended level. Since the evacuation pipe of the oil burning
unit is connected on the evacuation pipe of the wood burning furnace,
the
minimum draft to be respected is 0.04 IN.W.C. in the evacuation pipe of the
wood burning side, at all times. In fact, a barometric damper that would be
opened too wide could cause an important loss of draft in the evacuation
pipe of the wood burning furnace.


upload_2013-11-25_11-16-3.png

upload_2013-11-25_11-16-55.png
 

Jags

Moderate Moderator
Staff member
Aug 2, 2006
18,395
Northern IL
How is it possible that the PSG CADDY WOOD/OIL furnace is setup from the factory to use the SAME CHIMNEY/FLUE.????_g:confused:

Because is was designed and built and tested to do so. Unlike the stove in question.
 

Seasoned Oak

Minister of Fire
Oct 17, 2008
7,217
Eastern Central PA
Check into installing a power vent on the furnace and sealing off it's chimney hole.

That would be a good permanent solution,especially if there is a need to run both stoves at the same time.
 

Toploader

Burning Hunk
Sep 28, 2013
190
Nova Scotia
It's potentially deadly if creosote builds up on the inside of the flue and falls down blocking of the flue exit for the furnace. This is the reason my furnace service man stated for the rule. I'm not sure if there is any other reason it can be unsafe. My grandfather ran his oil furnace and cook wood stove on the same flue for almost 40 years until the insurance company made us disconnect the wood stove. We never had to clean the chimney because the cook stove couldn't be run airtight and the furnace kept the flue warm. I think like so many rules we have to live with it exists to guard against stupidity and neglect.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,251
South Puget Sound, WA
I think there are a few issues with a double connection. They can get worse with a modern EPA stove hookup. One is the fact that the draft is constantly diluted by another opening in the chimney. Many EPA stoves rely on a stronger draft to pull air through the secondary manifold and tubes. They don't work well with just a mild draft. That can lead to faster plugging of the chimney and possible CO or CO2 spillage out of the lower outlet. Another bad scenario would be the furnace firing off as a woodstove caused chimney fire happens.

These "rules" are not arbitrary. They are pushed for by fire departments, mechanical inspectors and architects that get tired of and grieve over the many post-mortem tragedies they have to investigate. We fought seat belts for many years in this country too, but they do save lives.
 

Toploader

Burning Hunk
Sep 28, 2013
190
Nova Scotia
I think there are a few issues with a double connection. They can get worse with a modern EPA stove hookup. One is the fact that the draft is constantly diluted by another opening in the chimney. Many EPA stoves rely on a stronger draft to pull air through the secondary manifold and tubes. They don't work well with just a mild draft. That can lead to faster plugging of the chimney and possible CO or CO2 spillage out of the lower outlet.
Yeah, so it probably worked so well for my grandpa because his stove was an old style cook stove. You could get overnight burns if you only slept for an hour and a half.
 
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