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  1. #1

    Thermostat for 2 furnaces and AC and flue sharing

    Hello this is my first post and hope to gain some knowledge here.

    I have been having trouble finding an installer for my Brunco 150 add on furnace since I did not purchase it from a dealer. I recently found a co worker thats a licensed HVAC and he said hes willing to take a stab at it.

    I have a central AC unit, an oil furnace thats 7 years old, and now have the add on furnace (burns coal and wood).

    question 1 : Can the oil and wood/coal furnace share the same flue? Its all mason from the basement to the second story.

    question 2 : whats a good thermostat to handle these 3 units? Im trying to find a honeywell but I am not sure which one to go with.
    The wood furnace is going to be my primary and the oil is going to b used as backup when Im away for a few days.

    Thank you for your time, have a great day.

  2. #2
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,294
    no, you cannot share solid fuel chimney flues with other fuel types or even other appliances of the same fuel type. You would need a factory chimney listed to UL 103HT or a suitable spare chimney flue with a liner listed to UL 1777 installed with the maximum insulation for the 2,100F rating.
    HTH,

  3. #3
    So the chimney is concrete block and brick with clay tile lining. It just has the 5 " flue hooked into it and sealed for the oil furnace. With that being said, can I run an 8" lining down the chimney directly to the wood furnace with the oil flue still attached?

    Basically the wood vapors would be eliminated through the 8" metal flue and the oil vapors would be eliminated through the chimney around the wood flue. The total chimney cavity is 12" x 12".

    The oil furnace would be used very seldom if any at all...and any advice on a good 8" flue for a wood/coal furnace would be appreciated.

  4. #4
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by Procyrus View Post
    So the chimney is concrete block and brick with clay tile lining. It just has the 5 " flue hooked into it and sealed for the oil furnace. With that being said, can I run an 8" lining down the chimney directly to the wood furnace with the oil flue still attached?

    Basically the wood vapors would be eliminated through the 8" metal flue and the oil vapors would be eliminated through the chimney around the wood flue. The total chimney cavity is 12" x 12".

    The oil furnace would be used very seldom if any at all...and any advice on a good 8" flue for a wood/coal furnace would be appreciated.
    IMC 801.17 Space around lining

    The space around a flue lining system or other vent installed within a masonry chimney shall not be used to vent any other appliances. This shall not prevent the installation of a separate flue lining in accordance with the manufacturer's installations instructions and this code.

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,505
    For the thermostat a simple dpdt switch could do the job for coal\oil. You could automate it with a 2 stage thermostat, but would require creative wiring\relays.

  6. #6
    Just an update for everyone here. I ended up doing everything myself. Ordered a 25 ', 5.5" diameter 316ti flextube liner, with a double t attachment. The Brunco exhaust is 8" and I reduced it at the chimney to 5.5". Keep in mind that the chimney is 25' in height. That produces a strong enough draft to make the stove work just fine. Also the 8" exhaust is only 5' in length before it enters the chimney with two 30 degree turns. So at the end of the flue I have the 2 t's, the top one is for the wood, the bottom is for the oil. The oil furnace will only be used when the wood furnace is not in use. Also the 2 stage thermostat was easy to install for both units. The Brunco needed a switching relay for the digital thermostat.

    The first time I fired it up, no smoke, no issues except it got warm enough to open the windows a bit. Now its just trial an error, and finding better wood that what I have now and/or coal.

    And the insurance guy came out, he said everything is A-ok, so I am fully covered, with 2 units on one flue.

  7. #7
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    518
    not correct !!!!

  8. #8
    Join Date
    Oct 2004
    Location
    So Cal
    Posts
    3,609
    This venting is unsafe & NOT approved. You are gambling with your family's lives.

  9. #9
    Join Date
    Jul 2006
    Location
    Georgia
    Posts
    406
    This has to be a test or joke.

    Sent from my XT907 using Tapatalk 2

  10. #10
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,928

  11. #11
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,589
    Wow what a week, first I see a guy hauled out of a house in a body bag from CO poisoning then I'm seeing crazy threads like this one.


    Sent from my iPhone using Tapatalk

  12. #12
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,589
    Quote Originally Posted by Joehvac25 View Post
    Wow what a week, first I see a guy hauled out of a house in a body bag from CO poisoning then I'm seeing crazy threads like this one.
    Last I checked my CA didn't have say smoke or no smoke as its only measurement lol


    Sent from my iPhone using Tapatalk



    Sent from my iPhone using Tapatalk

  13. #13
    Join Date
    May 2006
    Location
    Austin, Texas
    Posts
    303
    The insurance guy approved it.

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