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Thread: Distance to Combustible

  1. #1
    Join Date
    Feb 2020
    Location
    Intervale, NH
    Posts
    32

    Default Distance to Combustible

    Hi All,


    I am converting an old building into a Maple Sugar house. It will have a wood-fired evaporator (with blower) vented with 10" stainless steel single wall stove pipe. I expect some pretty darn high flue gas temps. The roof of the building is framed with trusses, 24" o.c. The nature of this setup makes it so that the stovepipe passes about 6" from the 2x4 truss members in a few spots, which is too close for my comfort. Any suggestions on a solution?


    - Attach ceramic fiber insulation to the trusses where the pipe passes closely by?
    - Fab up small heat shields to attached to the trusses at the questionable points?
    - Combination of the above too?
    - I already have all the single-wall pipe, but should I buy a few short pieces of double-wall pipe for the trouble spots? Can I go back and forth from single to double-wall? I'd say this is my least preferred choice, but I'd obviously do it if it means not burning the place down.

    Thank you for any thoughts.

  2. #2
    Join Date
    Jan 2017
    Location
    Williston, VT
    Posts
    615

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    Dundee:

    I used tin roofing attached to the wood framing as a reflective shield where the stove pipe passes by combustible materials.

    I also wanted to comment on the stove pipe temperatures. I don't measure it but I find the pipe isnt as hot as I'd expect. I think it's because the raised flue in my evaporator is pretty efficient. Obviously the idea is to make use of that heat coming off the fire and converting into heat applied to the sap. In a perfect system, the fire exhaust would be almost the same as the sap boiling in the flue section. My point is that fire up the chimney is wasted heat.
    Ken & Sherry
    Williston, VT
    16x34 Sugarhouse
    1,500 taps on high vacuum, Electric Releaser & CDL Sap Lifter
    Wood-Fired Leader 30"x10' Vortex Arch & Max Raised Flue with Rev Syrup Pan & CDL1200 RO
    https://www.facebook.com/pumpkinhillmaple/

  3. #3
    Join Date
    Apr 2013
    Location
    Northeast Vermont
    Posts
    648

    Default

    i used a combination of what you are describing for my chimney. i put tin on my rafters that are near the stack. the tin is held off the rafters 1 1/2" with some steel tubing. you don't want to attach it directly to the wood. i also used 1" ceramic insulation around my chimney where it goes close to the wood. i wrapped the insulation with 29 ga coil stock. after running my rig for 2 hours, the wood is not even warm to the touch!
    Awfully thankful for an understanding wife!

    “The only place success comes before work is in the dictionary.”
    - Vincent “Vince” Lombardi

    Good luck to all!

  4. #4
    Join Date
    Jan 2015
    Location
    Catskill Mts, Ulster County NY
    Posts
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    You could make a heat shield, but do you really want to be worried about it after boiling for several hours? My chimney passes pretty close to the roof framing, and goes through a wood roof deck. I didn't want any issues at all with the heat, so used insulated chimney pipe (3 - 3 ft sections of 8" SS Class A) to pass by the framing and through the roof. This was after reading a few threads on fires started by inadequately insulated chimneys. Now five years later and I couldn't be happier with it, and never had a worry about it. My single wall stove pipe temps before the transition to the insulated pipe range between 600-1000 degrees F - depending on how aggressive I fire the arch.
    Last edited by Ghs57; 02-17-2020 at 01:21 PM.
    Gary / Zena Crossroads / 42˚ 00' 24" N / Hobby in Early '70s, Addiction since 2014

    175+ taps on 3/16 (60 of which are on two Lunchbox Vac/Releasers)
    12x34 timber framed sap house w/attached 10x34 shed roof for storage
    2 x 6 Smoky Lake hybrid pan on Corsair arch with AUF/steam hood/preheater/concentric exhaust
    7.0 KW Sun Power PV System, Smokey Lake Filter Press/Steam Bottler, Modified NGMP RO - 2 4x40 posts 200 gph

  5. #5
    Join Date
    Jan 2006
    Location
    Oneida NY
    Posts
    11,544

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    I do measure mine, before I added air over fire (AOF) it hit temps up to 1500F, with AOF it on ocassions gets to 1050F. Any temperatures at 300F can in time make the wood ignite at 300F, once the heat turns it into charcoal. To protect it any of those methods will do the job. 1 layer of tin, spaced on non combustible spacers cuts the needed distance in half. With none you need 36", so 1 makes it 18", 2, each spaced an inch makes it 9" and 3 cuts it to 4.5". An inch of ceramic blanket will do the same. Remember, this not only means the trusses or rafters but also roof boards.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  6. #6
    Join Date
    Mar 2005
    Location
    Albion PA
    Posts
    5,099

    Default

    Yes do as much as you can to be safe. Add the blanket and some tin also. Insulated pipe is probably the best. I have done all of those and more to keep the heat contained. My stack temps are not nearly as high as they used to be. But you cant be too safe with the pipe going through the roof.
    Regards,
    Chris
    Casbohm Maple and Honey
    625 roadside taps + Neighbors bring some sap too!
    3x10 King, WRU, AOF and AUF
    12" SIRO Filter Press.
    2015 Ford F250 PSD sap hauler
    One Golden named Maggie, Norwegian Forest Cat named Lucy
    Too many Cub Cadets
    Ford Jubilee and several Allis WD's, and IH tractors
    1932 Ford AAB ton and a half, dump truck

    www.mapleandhoney.com

  7. #7
    Join Date
    Feb 2020
    Location
    Intervale, NH
    Posts
    32

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    [ATTACH=CONFIG]20873[/ATTACH

    This is the area in question.
    Attached Images Attached Images
    Last edited by Dundee Ridge; 02-17-2020 at 06:25 PM.

  8. #8
    Join Date
    Mar 2011
    Location
    Potsdam in far northern New York
    Posts
    775

    Default

    Build a 1" spaced sleeve around your pipe. Build another 1" spaced sleeve around that. Now you have triple wall pipe. Put a spaced covering over or around anything combustible that's nearby, and then install one of those cheap chimney surface thermometers on your triple wall. My stack runs at 900 degrees sometimes, but the outer layer of the triple wall never gets above 80. Peace of mind is the most valuable thing you can get.

  9. #9
    Join Date
    Jan 2006
    Location
    Oneida NY
    Posts
    11,544

    Default

    I've made my own triple wall pipe twice in the past, On my last one the stack was 12", I bought a 14" (I think I had to use 2x7") made some 1" Z shaped spacer to hold the spacing, put that around the stack, then I added a second another 2" larger, the same way. My first one was on 7" stack and I used the same method. Where I am, we need a fire dept inspection or fire insurance will not cover any losses, the fire inspector liked what I had done.
    My current one I used a different method, this one is 12" stack then I made a sleeve 14.5" diameter. with 3/4" flanges and a row of bolt holes. Then I wrapped 1" ceramic blanket around the 12" pipe and clamped the larger sleeve around it. On the bottom I slit and folded about 1" inward tabs about 1" wide all around to help conceal the blanket. Then the sleeve has wires attached which suspend it from the rafters (top cord of the trusses. Both methods worked well, this later method looks far neater though.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  10. #10
    Join Date
    Jan 2015
    Location
    Catskill Mts, Ulster County NY
    Posts
    602

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    Since this may help someone else, I'll include a few pictures of my setup. I happened to hit Lowes at the right time and got the pipe at a discount - it was the end of the heating season. You can also find second hand pipe online, that many times is like new. The only pieces I had to find were the ceiling hanging bracket, flashing/storm collar, which was easy. I later extended the chimney another foot and added a rain cap.

    The SS Selkirk SuperVent/ProVent pipe is rated for 2" to combustibles, 1,000 degrees F. This season I replaced the standard single wall black stove pipe between the funnel and the insulated chimney with double wall, SS adjustable pipe (about 70"). The old single wall pipe had rusted through. I definitely recommend SS for all piping. The other stuff will not last.

    15A6F5C1-A171-4FE0-ADC2-DE4E3CB870D4.jpg
    7CFB17BE-0B30-4C0C-9742-56FFE31486C9.jpg
    Last edited by Ghs57; 02-19-2020 at 10:52 AM.
    Gary / Zena Crossroads / 42˚ 00' 24" N / Hobby in Early '70s, Addiction since 2014

    175+ taps on 3/16 (60 of which are on two Lunchbox Vac/Releasers)
    12x34 timber framed sap house w/attached 10x34 shed roof for storage
    2 x 6 Smoky Lake hybrid pan on Corsair arch with AUF/steam hood/preheater/concentric exhaust
    7.0 KW Sun Power PV System, Smokey Lake Filter Press/Steam Bottler, Modified NGMP RO - 2 4x40 posts 200 gph

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