Thread: Sharing a flue... oil, wood..

I have a question to throw out there. We know that flues should not be shared between oil and gas appliances - ok. What about oil and wood? Can a wood stove and an oil burner share a flue?

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No they cannot,!!
Wood burning flue cannot be shared.

Gas and Oil can be shared, but the acid created by their gases mixing deteriorates the flue liner.
We see many older homes with oil boilers and gas water heaters in use in the NE.

That's what I thought too! But the Carson Dunlop training materials says that oil and wood can share a flue as long they are on the same level and local codes allow it. Somehow this doesn't make sense...

Prohibited by IMC and NFPA 211. Can you cut and paste the passage quoting C D ?

If its a combination oil/wood burning furnace they can be on the same flue.

Sure - here it is

Following from 2011 NFPA 31, (Standard for the Installation of Oil-Burning Equipment)


6.5.25 Solid fuel-burning appliances shall not be connected to a chimney flue serving another appliance burning other fuels, unless specifically listed for such connection.

It was way back in 09, but I saw this oil/wood combination setup in a 100 year old farmhouse. The chimney was a brick-lined affair in pretty bad shape.

The impression I got was that it had been installed this way many years ago. The chimney appears to have been patched where a second opening may have been added below the original.

The oil burner pipe is above the wood burner.
If the other way around, fumes could enter the room thru an open woodstove door, eh?

It was done professionally from the look of it. With the condition of the flue, I called for it all to be replaced.

From the 2006 IRC is M1801.12. " A solid-fuel burning appliance or fireplace shall not connect to a chimney passageway venting another appliance".

From the 2009 IRC: " M1801.12 Multiple solid fuel prohibited. A solid-fuel-burning appliance or fireplace shall not connect to a chimney passageway venting another appliance. "

This is one goofy area in the codes. As referenced in M1802.12, separate multiple appliances: one oil fired and one solid fuel fired, can NOT share the same flue. That means the code only addresses multiple appliances.

However,........There is the problem of central furnaces listed to UL 391, which though not specifically referenced in the IRC, is nonetheless, a valid listing. Personally, I think it is a BS listing but who am I? This is ONE appliance listed for dual fuel.

So, where does this leave us? You take this information to your AHJ. If you have ONE appliance that is listed to 391 for multiple fuels (oil, gas, solid fuel) then he has the right to approve or disapprove PROVIDED the installation can meet ALL the requirements of the listing. I use that emphasis because the listing is very strict on these units.

I picked at random the Yukon product line because it is sold in my area. It specifically states the chimney must comply with NFPA 211 or use a factory chimney listed to 103HT installed per the listing. That means no masonry chimney will comply since there are virtually no 211 compliant chimneys in America. Some come close but they are not "compliant", which means 100%. Also, the barometric damper must be set precisely on this particular unit for at least -0.03 wci draft but no more than -0.03wci. That's a rather tough requirement given the extremely variable nature of solid fuel burning, much less gas or oil. There are some considerable clearances to combustibles on these units as well as the warm air ducts. You are referenced to NFPA 90b for those installation details.

Regardless, there is NO circumstance where two separate appliances, one fired with solid fuel and the other with liquid or gaseous fuels can be common vented-period.

HTH

The correct answer is maybe it all depends on when it was installed or the type of appliance.
With that clear as mud I will see if I can correct most of the misinformation already in this post.
Though well meaning I see codes quoted that are not valid. Codes vary greatly from state to state and even city to city in some states. All posts should contain a location and reply's based on codes should be for that location.
Because the poster did not give a location I can only assume his question applies to the state of Maine (his profile location).

My answers are based on the following qualifcations and experiance.
I hold the following State of Maine licenses- Masters in Oil, Solid Fuel, Gas, Propane and EPA Universial A/C
I have over 35 years experence.

The State of Maine uses the following NFPA chapters 31, 54, 58, 70, 90A, 90B, 211 plus there own books.
All of the above have been modified by the State of Maine.and can vary greatly from the base NFPA chapters

Now lets go through the posts one by one

Originally Posted by wayne soper

No they cannot,!!
Wood burning flue cannot be shared.

As a blanket statement this would be false.

Originally Posted by John Lindley-Howard

That's what I thought too! But the Carson Dunlop training materials says that oil and wood can share a flue as long they are on the same level and local codes allow it. Somehow this doesn't make sense...

As pictured this would not meet Maine codes.

Originally Posted by Raymond Wand

If its a combination oil/wood burning furnace they can be on the same flue.

Approved combination wood/oil furnace or boiler may be used if the chimney, location, and clearances meet code. Approvel may be by UL, ETL etc. You must also follow the manufacturer instructions even if they go against code.

Originally Posted by H.G. Watson, Sr.

Following from 2011 NFPA 31, (Standard for the Installation of Oil-Burning Equipment)
6.5.25 Solid fuel-burning appliances shall not be connected to a chimney flue serving another appliance burning other fuels, unless specifically listed for such connection.

This applies to post 1996 installs and not to combination units. Installs from 1996 or before and have been in continuous use are grandfathered

John Kogel talks of an old farmhouse and it's oil/wood setup well here in Maine we have thousands of them and they are perfectly legal due to the 1996 exemption.

The last two post codes that do not apply to the State of Maine.

Remember it's the local laws and codes that are important in judging the fitness of any heating system.

Not uncommon to see them in Ontario too.

Yukon - Your Wood Furnace Company - Efficient indoor wood burning and multi fuel furnaces since 1970
Benjamin Heating :: Wood Oil Combination Furnaces

Hello Mort Short, and welcome to the forum.

I found what you had to say interesting, regarding furnaces and boilers which were installed and in continuous use since prior to 1996.

However, the OP's question and their follow-up with the page from training materials have to do with an oil burning furnace and a wood stove.

Since a Wood stove cannot be confused with either a furnace or a boiler, I'm not sure that you have actually addressed the question specifically. Nor have you shared with the rest of us, the basis for your statements. Please share with us the source of same and how that applies to the OPs question and example (and thank you in advance for doing so!).

You indicated "as pictured" in the diagram "it would not meet Maine Codes". This seems to imply that in some way it could be made to meet Maine codes, or that the answer to the Original Poster is *maybe" to his question pertaining to the diagram from his course. Explain how the wood stove (not furnace, not boiler) would be allowed to share the chimney of the oil burning furnce.

I note that both the wood stove and the oil burning furnace in the diagram the original poster (OP) ask about are in the basement below grade in a multi-story home in the diagram and although there is diagramed a barometric damper for the oil burning furnace, there is no diagramed damper for the wood stove chimney connector, nor between, nor is there any WH or boiler diagramed either.

Your point about local code ammended language is a valid one regarding code inspection. Home Inspection is not code inspection.

I'm not sure why went so far as to say the NFPA 211 citation I provided did not apply to a singularly installed combination fuel listed appliance when the topic of discussion is not same. It does apply to the OP's question and the OP's followup post & diagram, which is two separate appliances, one oil burning, and the other a wood burning stove. Please explain.

Originally Posted by Mort Short

The correct answer is maybe it all depends on when it was installed or the type of appliance.
With that clear as mud I will see if I can correct most of the misinformation already in this post.
Though well meaning I see codes quoted that are not valid. Codes vary greatly from state to state and even city to city in some states. All posts should contain a location and reply's based on codes should be for that location.
Because the poster did not give a location I can only assume his question applies to the state of Maine (his profile location).

My answers are based on the following qualifcations and experiance.
I hold the following State of Maine licenses- Masters in Oil, Solid Fuel, Gas, Propane and EPA Universial A/C
I have over 35 years experence.

The State of Maine uses the following NFPA chapters 31, 54, 58, 70, 90A, 90B, 211 plus there own books.
All of the above have been modified by the State of Maine.and can vary greatly from the base NFPA chapters

Now lets go through the posts one by one



As a blanket statement this would be false.



As pictured this would not meet Maine codes.



Approved combination wood/oil furnace or boiler may be used if the chimney, location, and clearances meet code. Approvel may be by UL, ETL etc. You must also follow the manufacturer instructions even if they go against code.



This applies to post 1996 installs and not to combination units. Installs from 1996 or before and have been in continuous use are grandfathered

John Kogel talks of an old farmhouse and it's oil/wood setup well here in Maine we have thousands of them and they are perfectly legal due to the 1996 exemption.

The last two post codes that do not apply to the State of Maine.

Remember it's the local laws and codes that are important in judging the fitness of any heating system.

Welcome to the Forum Mort! We appreciate your participation. It may help you to know that since we reference codes and standards so much here, it is understood by regulars that you should ALWAYS reference state and local codes and stds. such as I referenced in my post.

We you post corrections here, it is customary to provide either a link or the actual verbiage cut and pasted. We would appreciate it if you did that for us so we can understand your references here in this matter.

BTW, are you using a pseudonym or is that your real name?

Thanks in advance,

Would have to be a pseudonym, as none listed as Master with that name or begins with active or other.

My understanding is that the date is in 1998(Feb 2), and not 1996, and that there are additional conditions which must be met to ascribe to all the standards and rules.

I believe "Mort Short" was referring to:

Title 32, §18107: Installations to conform to standards

§18107. Installations to conform to standards

1. Board standards and rules. Installation of oil, solid fuel, propane and natural gas burning equipment and chimneys may not be made in this State unless the installation complies with all the standards and rules adopted by the board. These standards and rules may not prohibit:

A. 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:

(1) Sufficient draft is available for each appliance;
(2) The chimney is lined and structurally intact; and
(3) A carbon monoxide detector is installed in the building near a bedroom; or [2011, c. 225, §2 (NEW).]

B. The 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 on or after February 2, 1998 as long as:

(1) Sufficient draft is available for each appliance;
(2) The chimney is lined and structurally intact;
(3) A carbon monoxide detector is installed in the building near a bedroom;
(4) The solid fuel burning appliance has been listed by Underwriters Laboratories or by an independent, nationally recognized testing laboratory or other testing laboratory approved by the board; and
(5) The solid fuel burning appliance is installed in accordance with the manufacturer's installation specifications. [2011, c. 225, §2 (NEW).] [ 2011, c. 225, §2 (NEW) .]

2. Technician responsibility for ascertaining total conformance to the standards and rules. Whenever oil, solid fuel, propane and natural gas burning equipment, accessory equipment or its installation are separately contracted, the master oil and solid fuel burning technician or the propane and natural gas technician in charge of the installation is responsible for ascertaining total conformance to the standards and rules adopted by the board. [ 2011, c. 225, §2 (NEW) .]

3. Proof of license. Whenever a state fuel inspector authorized under section 18110 finds a person installing or assisting in an oil, propane, natural gas or solid fuel burning appliance installation, that person shall, on request of the state fuel inspector, provide evidence of being properly licensed when required by this chapter and, if unable to provide the evidence, shall furnish the state fuel inspector with that person's full name and address and, if applicable, the full name and address of the master oil and solid fuel burning technician or the propane and natural gas technician in charge. [ 2011, c. 225, §2 (NEW) .]


SECTION HISTORY 2009, c. 344, Pt. C, §3 (NEW). 2009, c. 344, Pt. E, §2 (AFF). 2009, c. 652, Pt. A, §46 (AMD). 2011, c. 225, §2 (RPR).