# Wood and Oil on one flue--Yes, you can (or in Maine at least)



## Hakusan (Nov 11, 2009)

Augusta (the Capital of Maine) now allows more than one heating device on one flue. There are some limitations, but it is possible under code.


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## albertj03 (Nov 11, 2009)

I don't know the exact reason that makes this dangerous but common senses tells me there are probably multiple things that could go wrong. Seems dicey to me. I know a guy who just bought a house in Gorham. When he first looked at it there was an old cool looking woodstove in the basement and loved it. When he bought the house and went to move in the woodstove was disconnected and he was told the bank made the original owner disconnect it because it was a single flue chimney and there was also an oil furnace attached to it. He was pretty PO'ed!


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## webby3650 (Nov 11, 2009)

I find it hard to believe that they allow a wood burning appliance to vent into a chimney with anything else! You can vent multiple appliances into one flue if it is not wood burning. This is an International Code, are you sure about this?


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## theheatelement (Nov 11, 2009)

Are you sure they don't mean you can have two liners in one flue


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## littlesmokey (Nov 11, 2009)

Multiple appliances with same type of fuel, maybe, but you can not safely vent gas and wood in the same flue. It is flat deadly. International fire standards are very clear about it. Best recheck the language of the ordinances.


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## webbie (Nov 11, 2009)

It was legal under code for a decade or more in Ma....and in Maine as I remember. The only reason that it stopped was because people stopped burning wood in central heaters and it was not relevant any longer! Also, the ETLM (Energy Testing Lab of Maine) had done a lot of the approval work and that lab stopped operating in the same capacity....

Back in the 80's and 90's when this was OK, the requirements were something like this.....

Only OIL and wood/coal...no nat. gas or LP.
Chimney had to have enough capacity to vent both appliances at full boat......

In their testing of such scenarios, ETLM found that the chimney stayed warmer, worked better and produced less creosote than with a single unit!

BUT, I think this could present more of a problem these days.....because back then lots of boilers were natural draft as opposed to all being fan forced......but that is probably as much of an issue with a single flue too!


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## LLigetfa (Nov 11, 2009)

I think it is a really bad idea to vent oil and wood into the same flue.  The barometric damper that the oil furnace needs will cool the flue too much for wood.  I know... I had a chimney fire.


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## webbie (Nov 11, 2009)

Every multi-fuel furnace and boiler made - and UL approved - does just that - vents multiple fuels into one flue.


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## CowboyAndy (Nov 11, 2009)

Webmaster said:
			
		

> Every multi-fuel furnace and boiler made - and UL approved - does just that - vents multiple fuels into one flue.



yup.


we have a dual fuel unit and they share a flue. the oil burner has a sensor that if the temp is so many degrees or above in the firebox it wont ignite.


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## Fsappo (Nov 11, 2009)

I can understand the danger of a wood fired applinace blocking a flue and an oil burner kicking on and backing up into the house.  What I always have a hard time explaining to folks is why a wood/oil combo furnace is ok, but two seperate units into the same flue isnt.  The EPA Certified Caddy furnaces we sell have the barometric damper down wind from the wood exhaust and it does create low flue temps.


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## tiber (Nov 11, 2009)

It's also legal in Pennsylvania BUT the union of the flues has to occur at the furthest point from the source of ignition.

This means that you still end up with two flues, just one hole in your roof.

(rolling eyes).


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## k3c4forlife (Nov 11, 2009)

How about if you have a fireplace and a wood stove back to back in adjoining rooms sharing the same chimney?  The fireplace can be closed off to give the stove full chimney.


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## tiber (Nov 11, 2009)

I'm not familiar with NJ code but for the sake of discussion we should disambiguate chimney from flue. A chimney is a device which holds one or more flues.


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## k3c4forlife (Nov 11, 2009)

Ya, I'm sorry, its a 1-flue chimney.


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## Northern NH Mike (Nov 11, 2009)

When I was having my home inspected for purchase here in NH a few years ago, the bank would not finance unless the woodstove that was sharing the single flue with the oil burner was disconnected and the thimble sealed.  When I had the furnace cleaned after moving in, there was quite a bit of ash at the elbow where the horizontal furnace exhaust heads vertically up the flue.


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## firefighterjake (Nov 12, 2009)

Hakusan said:
			
		

> Augusta (the Capital of Maine) now allows more than one heating device on one flue. There are some limitations, but it is possible under code.



Actually, this has been allowed for several months . . . the change was initiated last Fall however when a citizen in the County found out that his woodstove would not be allowed as it was hooked into the same flue shared by his oil furnace. As you no doubt recall, the prices last Fall were crazily high and folks were concerned about people freezing to death so a certain Legislator in the County brought this legislation forward.

Me, I have mixed feelings. After listening to several folks it seems as though this may not have as many negatives as one would think . . . but that said, I don't like the idea of nixxing standards that were created on a consensus based system (i.e. the NFPA way) because some thing is not economical or convenient. To me, it would have been far better to initiate these changes on the national level.


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## jjs777_fzr (Feb 10, 2010)

I have a natural gas forced hydronic burner vented to a 1 flue chimney (its a brick chimney with nothing inside but air and brick 

Is it possible to vent a pellet stove into the same chimney ?   

Just from what I have seen and observed first hand - that pellet stove venting is by far safer than other solid fuels ?
So maybe it is treated differently than other wood/coal boilers sharing the same flue where codes are concerned.

The nat gas burner setup I have (that has a sticker of inspection) has no baro/mano in the pipes...just goes right into chimney.
I also added a vent to the outside to allow fresh air intake to be safe.

I believe I practice safety wisely - and I cant see anything wrong with making this type of connection - but I am not an expert so...thats why I am asking.

Thx for any advice.

ps I know I could vent directly outside...but I have seen first hand what pellet vent gases do to the exterior siding...and also I do not wish to have neighbors complaing about the smell - as I live in a densely populated location - the vent would be going straight at their driveway.


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## Leonard (Feb 10, 2010)

Sure code may accept this but I am sure the insurance company will definately have something to say about it.


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## gyrfalcon (Feb 10, 2010)

luv2burnwood said:
			
		

> Sure code may accept this but I am sure the insurance company will definately have something to say about it.



Interesting.  It's code here to not do dual appliances in a one-flue chimney, and one of the few bits of code this land of devil-may-care DIYers generally abide by, but the insurance co's sure don't give a darn.  The standard form asks only if you have a wood stove, nothing about type, install, chimneys, other heating source, etc.  And no government or insurance inspectors of any kind to approve or disapprove.


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## raybonz (Feb 10, 2010)

My Dad's stove and oil hot air system have been in the same flue for around 30 yrs.. Back then it was allowed.. I wonder if this would help to keep the chimney cleaner due to the oil preventing creosote from getting a good foothold onto the liner? I have 2 flues one for the oil furnace one for the woodstove and the oil flue never needs cleaning and only gets a little black soot.. 

Ray


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## NH_Wood (Feb 10, 2010)

k3c4forlife said:
			
		

> How about if you have a fireplace and a wood stove back to back in adjoining rooms sharing the same chimney?  The fireplace can be closed off to give the stove full chimney.


This is exactly my setup. Cheers!


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## NH_Wood (Feb 10, 2010)

[quote author="raybonz" date="1265827853"]My Dad's stove and oil hot air system have been in the same flue for around 30 yrs.. Back then it was allowed.. I wonder if this would help to keep the chimney cleaner due to the oil preventing creosote from getting a good foothold onto the liner? I have 2 flues one for the oil furnace one for the woodstove and the oil flue never needs cleaning and only gets a little black soot.. 

My dad = same deal - wood stove in cellar and oil burner venting to same flue (but for ~ 41 years now) - had the chimney cleaned in the fall for the first time in I don't know how long (just a clay flue) - at least 10 or 15 years - the sweep check the flue and didn't even sweep - said it was spotless.  But....one good story doesn't mean other bad stories aren't out there........Cheers!


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## fluemasterjr (Feb 10, 2010)

An Act To Permit the Use of a Common Flue 
for Oil and Solid Fuel Burning Equipment 
Be it enacted by the People of the State of Maine as follows: 
Sec. 1. 25 MRSA §2465, sub-§1-A, as enacted by PL 2005, c. 571, §1, is amended to read: 
1-A. Routine technical rules. The Commissioner of Public Safety shall adopt rules pertaining 
to the construction, installation, maintenance and inspection of chimneys, fireplaces, vents and solid 
fuel burning appliances. Rules adopted pursuant to this subsection may include rules pertaining to 
maintenance and inspections, except as provided in subsection 1-B. Rules adopted pursuant to this 
subsection may not prohibit the continued use of an existing connection of a solid fuel burning appliance 
to a chimney flue to which another appliance burning oil or solid fuel is connected for any chimney 
existing and in use prior to February 2, 1998 as long as sufficient draft is available for each appliance, 
the chimney is lined and structurally intact and a carbon monoxide detector is installed in the building 
near a bedroom. Rules adopted pursuant to this subsection are routine technical rules as defined in Title 
5, chapter 375, subchapter 2-A. 


this is the bill that was adopted, what it say is that. they can not prohibit the continued use prior to 1998. being part of the maine chimney sweep guild we have had many decisions about this topic.


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## JP11 (Dec 11, 2011)

Dragging up an old post here..

But looking to do two appliances, but electrically limited to one at a time in the same flue.

My setup would only allow one to work at a time.  The vigas closes the flue completely on shutdown, so it's essentially a closed end.

My questions.

1.  Is it really that bad?  Like others have said.. the multi fuel units run both in one.
2.  I have the flue auto damper in the oil side..  I've got plenty of draft, chimney is about 40' tall.  All set with just the 1, correct?
3.  Where do I put the wood one in.  I have lots of room.  I can probably be anywhere from 1 foot below the oil (opposite side of chimney from oil) to 6 or 7 feet above oil (top access I could get to is about 12' up the chimney (utility room has 10'4 bottom of truss height and 2 foot of open trusses)

Thanks for the input.

JP


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## firefighterjake (Dec 12, 2011)

Biggest thing is to check with your insurance company to see what they have to say before going too far with this idea . . . some may have no issues, some may have a real problem with it.


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