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Barometric Damper and EPA Wood Furnace Questions

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Tinder, Jan 13, 2012.

  1. Tinder

    Tinder Member

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    Long time lurker, first time poster.... 2 related questions about using a barometric damper with a wood furnace:

    #1: I'm currently awaiting a finished installation of a wood furnace. The installer doesn't think a barometric damper is necessary because he's never installed on on a wood stove before. In the manual for my furnace, it mentions that a barometric damper is only necessary outside a particular range - 0.04 to 0.06. Let's say he measures it within tolerance on the day of install, which is a non windy day. Without a baro, isn't the draft going to extend outside that range on a 20-25MPH windy day?! (~6' of 6" double wall exhaust with 3 bends to a ~24' of 6" class A, AKA not a really short chimney)

    I've never taken draft measurements myself, so I don't know how easily it fluctuates, but it would seem as though the wording in the manual should state that a baro should be installed to reduce the variable effects of the temperature and wind, doesn't it? Should I be concerned and install a baro even if it's within tolerance on the day of installation?


    #2: So let's say I purchase one to have installed besides his previous wood-fuel appliance experiences, does the 'T' need to be between the furnace and the class A stack, or could I 'T' off the back of the furnace with the exhaust to the stack on one end and the baro on the other, provided that it's a sealed system with the exception of the stove/baro/stack? (Hopefully this second question makes sense).

    To add some background, the exhaust between the furnace and the stack will be on an angle for a good portion of it, having a 90 and a couple 45s, so if incorporating a baro should be done, it'd be easiest when it's being installed rather than having to possibly reroute the piping at a later date.

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  2. flyingcow

    flyingcow Minister of Fire

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    I knew my chimney had good draft, so i choose not to put it in. My boiler works excellent. I figured if i did have problems i would install later. Not much help, just my experience.
  3. Tinder

    Tinder Member

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    I appreciate you sharing your experience. If I had to pick an ending, I'd hope mine to be the same. I just thought windy days/cold nights might be too much of a variable.
  4. taxidermist

    taxidermist Minister of Fire

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    Tinder,

    Welcome!

    I have a baro on my boiler you can see it in my video at the bottom of this post. I live in Fowlerville north of town. If you want to check it out let me know.

    Rob
  5. chuck172

    chuck172 Minister of Fire

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    I put one on my tarm. Set it with a manometer which I also permanently installed.
    Worked great, but I got constant noxious odors in my basement. I had to remove it. Seems like it was leaking some fumes back into the basement.
    If I had an outdoor setup, I would use one.
  6. Tinder

    Tinder Member

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    Thanks for the great offer! I did check out your video a couple weeks ago when I was first researching this. For right now I think I'm set, but I'll keep your offer to check out your installation in mind.
    Thanks for the input. Fumes are a concern of mine since my basement is partially finished.

    I think I'll just see how things go without one first, but get a manometer and if the draft/wood consumption gets excessive I'll come back to adding one then.
  7. laynes69

    laynes69 Minister of Fire

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    What furnace are you installing? Keeping it within draft range or close will help ensure proper operation.
  8. Tinder

    Tinder Member

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    PSG Mini-Caddy; BTW I appreciate all the Caddy information you've posted on here throughout the years. Couldn't quite follow whether you stayed with using a baro on yours or switched it back.
  9. RobC

    RobC Minister of Fire

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    Dampers do leak smoke and dust.
    I installed one for efficiency and will be redoing flue piping at some point this season.
    I will be putting the damper on a Tee, upstream of the boiler to chimney connection. So the smoke doesn't pass by the damper on way to chimney. Similar set up to Rob's video, his is just below smoke path.
    I will also try to put damper in a Tee and position it so I can remove damper and have a clean out strait through to chimney so I don't have to remove any pipe to clean out ash. If damper still lets in smoke / ash I can put a cap on where damper is. I have problems in summer with down draft with cold chimney so I may just use a plug for summer burns.

    Rob
  10. maple1

    maple1 Minister of Fire

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    I have never had smoke or dust come out my damper. It may have to do with individual situations. My chimney is 30' tall, I always have a good draft. Way too good when the wind blows, which is why I'll always have a damper - and I'm on top of an open hill.

    But, if someone is in a sheltered place that doesn't get a lot of wind exposure, and has a marginal chimney height, I could see not using a baro - although they do make for an easy access point to stick an arm in and scrape when cleaning.
  11. chuck172

    chuck172 Minister of Fire

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    I really liked using the damper. It steadied out the draft. I think I got longer burn times, but I did get a faint but noxious odor. I removed the damper and no more smells.
  12. pybyr

    pybyr Minister of Fire

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    The "old wisdom" with low-tech wood units was that barometric dampers were a hazard, in that if creosote deposits in the chimney caught fire, the baro damper would fly open and supply even more air to the runaway flue fire.

    Modern efficient units (gasification boilers or true gasification furnaces) will simply not leave creosote in the chimney, so that rationale ceases to apply.

    If you have a chimney with strong draft, you'll definitely be pulling combustion through your heat exchangers faster than the heat can be efficiently captured, so there is definitely an efficiency advantage to the damper (although you'll also be getting more air up the chimney through the damper when the boiler is out, pulling cold "makeup air by random drafts" in to the rest of the house, so one can contemplate or debate overall full-cycle efficiency effects)

    I have been running a Field Controls baro damper with my Econoburn 150, and have a real love-hate thing going with the arrangement

    My 30 foot tall round flue chimney pulls enough draft that, especially on cold nights, draft would substantially exceed the amounts recommended for best efficiency for my Econoburn. When I temporarily cover the damper with scientifically-precise heavy duty aluminum foil, stack temperatures definitely rise. This confirms that the damper's moderation and steadying of the draft is helping the boiler extract more heat than it would be able to with unregulated draft.

    But... my boiler will "puff" and "whoomp" under certain conditions such that the baro damper (near where the flue pipe meets the chimney) takes a beating (it gets blown back against its own flimsy stop) and sometimes emits dust (fine fly ash) and, briefly, combustion fumes (the cellar is so drafty it dissipates rapidly). The pivots in the damper and its stop are getting pretty beat up from this and I am unimpressed both that it is happening and that the baro damper is as fragile as it turns out to be. My cellar is and will always be an old farmhouse cellar, so it does not freak me out, but that still doesn't make me pleased about it.

    What I really wish I could have, if price were no object, is one of the Euro-style baro dampers, where, when the flue experiences positive pressure, the door swings affirmatively shut against a "frame" thus no strain on a hinge (the US type baro dampers have just a wimpy thick wire pivot and thin sheet metal stop, with no frame to stop the door from swinging bacwards), and no "exhaust" of fly ash or fumes.

    The nifty-est one I've spotted yet:

    http://www.tigerholm.com/en/hvac/Draught-stabiliser-Tigex50.htm

    Alas, they are not sold here, and the basic cost of the item is expensive even before trying to get it to the US

    PS in terms of adding a damper after your flue's tinwork is in, it is possible to get a "collar tee" type adapter (they come with the Field Controls baro dampers) and then you can install that by drilling a hole and using a sheet metal nibbling tool to make an opening to fit the collar over.

    For any boiler that experiences puffing (not sure how much it is found among the various makes and designs) that is going to be in a finished or even semi finished space, I would NOT want a baro damper unless it is a Euro-design type that affirmatively seals in the event of brief flue pressure.
  13. Tinder

    Tinder Member

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    I appreciate all the input from everyone on this topic!
    Is it possible that the stack temperature is lower with the damper because the damper is letting cooler room-temperature air into the stack?
    I agree that the more common baros here look kind of flimsy with regards to the stop/seal, though I haven't actually had one in my hands. The one you linked to looks interesting. At the very bottom of their list of distributors there is one USA company at the very bottom: http://www.tigerholm.com/en/Tigerholm_Distributors-heating.htm . I can help but wonder what the pricing is, but am going to wait to contact them.
    That's what I'm basically leaning towards to start things out. I'm trying to get in a 'T' piece of piping so it can be installed when the stove exhaust is installed. I'll cap it for the time being, but it'd be really easy to add the damper at a later date if needed and the cost of the piece verses the cost of a straight piece is relatively insignificant. I've also got a Dwyer manometer on order, so I'll collect some data once everything finally gets installed at some point and decide what course of action to take with regards to a baro.

    With regards to my #2 question - does placement of the barometric damper matter? I see a lot of installation manuals saying it must be 18" beyond any manual damper, though I won't be installing one of those. I've seen some recommendation that having it near the ceiling means it'd draw in warmer air than if it was near the floor, decreasing stack temperatures less. At the same time it seems to me that putting a 'T' right off the stove and running the baro somewhere the smoke should never go (see Taxidermist's video) seems to make the most sense because it seems it wouldn't get any build-up on itself then. Thoughts on placement?
  14. taxidermist

    taxidermist Minister of Fire

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    I never get any smoke out of my BD. Even when my boiler has a smoke explosion when the fan kicks on from idle I dont get any.


    Rob
  15. RobC

    RobC Minister of Fire

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    That's good info Rob. Keeping dampers out of the smoke stream may help.
    Rob

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