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Single wall to double wall

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by jarvis, Jan 8, 2010.

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  1. jarvis

    jarvis New Member

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    I'm finally finishing up my wood furnace installation and have a question on the black pipe. I have about 17" clearance between the joists and the chimney pipe, so I bought an 8" double wall 90 degree elbow to stay within the required safe distance. This elbow will connect to the class A to smoke pipe adapter, but I don't know how to connect the other end. I wanted to join it to a single wall pipe running the rest of the way down to the furnace, but I'm not sure that's possible because of the way the other end of the elbow is designed. It has a smaller crimped end about 7" diameter which is surrounded by the outer pipe and will not join on to either end of a regular 8" single wall pipe. I wish I could describe it better but it's hard to explain without pictures. I'm using Supervent pipe...is there some kind of adapter I need to connect the two or do I have to run double wall all the way to the furnace?

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  2. WRVERMONT

    WRVERMONT New Member

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    I would guess that Supervent makes an adapter to get to regular single wall smoke pipe? Check a catalog. Good luck.
  3. jarvis

    jarvis New Member

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    I did look through their catalog but couldn't find anything specific like that. They do have a stove pipe adapter which I found here: http://www.shopwiki.com/_Selkirk+Metalbestos+268210+Stove+Pipe+Adapter+8"+DS-DSP?o=1032604453&s=3885& but I'm not sure if that will work because it says it connects old style double wall to new style. I don't have any outside access to the cleanout, so I need to be able to remove the pipe from the wall periodically for cleaning which is why I would prefer to use a single wall elbow on the furnace end because it isn't rigid like the double wall.
  4. john26

    john26 New Member

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    I had a similar issue when i hooked up my wood furnace. What I ended up doing was I took my class A adapter came with through wall kit and slide it inside my double wall 90. The other end of my 90 was hooked to a 12" piece of double wall (for clearance reasons) I then took my single wall shrunk the end a little with sheetmetal crimping pliers and slid it inside the double wall pipe. When I was finished I screwed all the joints together with sheet metal screws. Here a pic it might help.

    Attached Files:

  5. jarvis

    jarvis New Member

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    Thanks...not sure if I can do that with my pipe though the way it's designed. The lower end is sealed so I can't insert a single wall very far into it. I'll try to post some pictures tonight when I get home from work.
  6. john26

    john26 New Member

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    My elbow is like that I put the class adapter insde the inner piece on the double 90 and the single wall went inside the inner piece on the 12" piece open end. It was hard to get it to fit I had to shrink the single wall a little then smack them together by a mallet and a couple of boards.
  7. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    <>do I have to run double wall all the way to the furnace?<>

    If you want to do it correctly, & MORE IMPORTANTLY code compliantly,
    use double-wall for the entire run.
    Single-wall & double-wall connector are not meant to be
    interchangeable & used together.
    Should something (Gawd forbid!) go amiss, your system fails,
    & you incur damage to your property (& FAMILY!) your homeowner's
    insurance may not have to pay you for your loss.
    Then again it's YOUR life & YOUR home...
  8. jarvis

    jarvis New Member

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    Thanks, that pretty much answers my question. I guess I'm left with two options, either buy more double wall and finish the run to the furnace, or put a piece of cement board above the chimney connection to protect the joist and use single wall. I don't think with the way my furnace is located, that I'll be able to make the two ends meet using 90 degree elbows. Here's what it looks like:
    [​IMG]
    With a 90 hooked to the chimney pipe, the lower end of that elbow is not in line with the furnace to run a straight piece of pipe down with another 90 degree elbow to connect on that end...and the double wall elbows are not adjustable. To further complicate matters, I have no outside access to the cleanout plug so the only way I can clean is by removing the smoke pipe from the chimney connection (blame the plumbing contractor for that wonderful idea). I'm thinking it would be a whole lot simpler to insulate the joists with cement board and run single wall the whole length.
  9. john26

    john26 New Member

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    I bought my double wall from a local stove shop who does a lot of installs he showed me a factory made adapter to go from double wall to single wall. He told me they typically don't use it on thier install because they have the shrinker pliers to shrink the single wall and its esentially the same thing. All thier installs are inspected. If you look on simpsons web site they sell an adapter called "8: singlewall stove pipe snap-lock adapter" part # 6889. I emailed simpson on the issue since thier installation instructions mention nothing on the subject.
  10. Gooserider

    Gooserider Mod Emeritus

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    I think they make adjustable length double wall - presumably you could use two adj. length double wall sections and the fixed 90's to make everything line up - but I agree it might be easier to put up a heat shield and use single wall...

    Gooserider
  11. jarvis

    jarvis New Member

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    They do make adjustable double wall sections which would make disassembly easier, but I'm not sure how long they would remain moveable after heat and soot do their thing. I don't think with the way my furnace is located, that I can run the pipe straight with two 90 degree elbows and a 45 won't be enough either. I don't think I have a whole lot of choice other than a single wall with two adjustable elbows.
  12. Gooserider

    Gooserider Mod Emeritus

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    The same thing applies with single wall adjustable stuff - including the elbows - once they've been used for a while and have some heat and creosote built up in the seams, they don't adjust very well any more... usually it's a case of setting stuff up when assembling, and then wiggling apart the ends later to clean...

    What I was thinking in terms of your picture and the earlier post, and I may be misjudging things - it is easy to do since photos don't give much scale - is a 90 at the wall, an adjustable leading at an angle to behind the furnace and a second 90, then an adjustable to make up the difference between the furnace and the 90 (or possibly a fixed length piece in either place if the numbers work out right...)

    However, I do tend to agree, just from a cost standpoint if nothing else, you'd be better off with a clearance reduction barrier and using single wall all the way.

    Gooserider
  13. Tony H

    Tony H New Member

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    I also used supervent pipe and at the local menards found several adapters to go from single 8" 7" and 6" and it turned out one of them fit just perfect into the double wall pipe. I think we had to pry the internal to external baffle so the pipe could slide in between the two. I don't think the pipe I found was listed as a single to double adapter but it did fit.
    I my most cases double wall all the way would be my choice but I was trying to fit parts for a draft blower in an open space with no fire hazards.
  14. john26

    john26 New Member

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    I recieved an email from simpson duravent today they said it is ok to connect single wall to double wall with a connector or sliding the single wall inside of the double wall. They said this will be a very tight connection but should be secured with screws.
  15. Gooserider

    Gooserider Mod Emeritus

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    That is good to hear, sounds like it makes for an easy solution to your setup problem...

    Just remember to install the pipe so that it faces in the correct direction - a lot of people that aren't used to stove piping do it backwards, which can get messy... The key thing is to make sure the small end always points towards the fire... This is counter intuitive because most people just think about the smoke, and have it the other way to "funnel" the smoke out - which is good in an auto exhaust, and most other ducting / plumbing type situations. But in a wood burner you can get condensation and / or liquid creosote and other crud in the pipe, which will want to drip back down towards the fire. If you install the small end away from the fire, the liquid will escape between the joints and make a mess on the outside of the pipe. If you put the small end towards the fire, it will act as a funnel and direct the crud back into the firebox...

    Gooserider
  16. john26

    john26 New Member

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    Yeah i know you are supposed to put the little end towards the fire box, but I set mine up backwards so any liquid cresote would leak out because the first 90 from the furnace is a low point and I didn't want creoste puddling in the 90. My furnace is a rear exit with that big round heat exchanger in it so it would never make it into the fire box just puddle in the pipe. My setup is in an unfinished basement so the mess isn't a big deal.
    Jarvis's furnace looks like a wood chuck so its probably made the same way depnding on the model. What do you think gooserider about a reverse setup in that situation?
  17. Gooserider

    Gooserider Mod Emeritus

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    If you don't care about the mess, probably doesn't make a lot of difference, especially since the newer stuff shouldn't be making much creosote to begin with... However - if one is actually doing stuff per code, your elbow coming out of the stove should have a little bit of upwards slope - I think its supposed to be something like 1" in ten feet minimum - which is supposedly enough to prevent the puddling. Add to this the fact that you are going to have pretty hot flue temps coming out of the furnace, and it should be plenty to evaporate the crud or burn it, without it necessarily having to actually reach the firebox...

    For whatever it's worth in not directly comparable experience - my VC creosote factory stove is connected to the chimney via a rear exit exhaust, going into the snout of a Tee, with the top going into the liner, and the bottom being capped. For various reasons, the snout has a slight downward angle, so I would have a hard time getting a more puddling conducive setup if I tried... When I take things apart for cleaning however, I find that I have just a small amount of dry creosote in the cap, with the rest of the tee and the first few feet of liner being very clean... (I only get the major buildup in the last 8-9 feet where the chimney goes out of the roof)

    Gooserider
  18. jarvis

    jarvis New Member

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    John26,
    How do you like your Woodchuck 2900 and what kind of flue temperatures do you see? If you search my posts you'll find the thread about mine...my *former* plumbing contractor gave me a lot of static about the design, claiming I would have fire going up the chimney because of the way the heat exchanger is designed since the inlet is located directly over the fire. He refused to hook up the pipe inside unless I ran class A insulated all the way to the connection on the furnace because he truly believed I would have flames shooting right up into the chimney. Legal action is pending against said plumber for some other unfinished issues he left me sitting with and the house is currently unliveable until I get that mess straightened out...but I'd love to hear what other model 2900 owners have to say about theirs since I haven't been able to fire mine up yet.
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