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PE Increased clearances How Much Closer 1" Air Space

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by michiganwinters, Sep 4, 2013.

  1. michiganwinters

    michiganwinters Member

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    So we decide to go back to the ol PE Summit for its quality, and ease of use. I think our last one was 6" from the back to combustible using double wall pipe. This one now states 71/2". It does seem like they made a few changes with the stove....hopefully it wasn't in quality!

    My great room isn't big so I would like to get the stove closer to the wall and use a veneer cobblestone for the hearth. My question is how much closer can I get the stove? Also, I would love some pics of a completed hearth with the air space...I'm just not envisioning how this is going to look. If it doesn't look good I'm not sure what I will do.

    Lastly, because my livingroom is vaulted up to a office in the loft and master bedroom..I can tell already where the heat will become trapped. I have a cold air return at the highest point and am playing with the idea of tying my OAK into my CAD so I dont have to run the furnace fan. Im thinking this light draw of air will help circulate the heat into the areas that become too warm and to areas down a hallway. This is me brainstorming...thoughts?

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  2. begreen

    begreen Mooderator Staff Member

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    What is CAD? The oak is for outside air only.
  3. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    I think he is talking about central air ducts. If so, no way in hell. That blower comes on for some reason and that stove becomes a forge. If the stove is cold the room it is in becomes known as Ashland.
  4. begreen

    begreen Mooderator Staff Member

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    Agreed, that would be a extremely bad, unsafe idea. A ceiling fan would help here and would be much safer.

    The improvements to the stove look good. I see no exceptions for clearance reduction from the specs in the manual. You must work with the 7.5" rear clearance with double-wall pipe. Note that this is measured from the studs behind the wall and not from the stone veneer on cement board.
  5. webby3650

    webby3650 Master of Fire

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    An NFPA approved wall protection is intended to be used with an old stove that doesn't have listed clearances. It reduces the distance to combustibles by 2/3, from 36" to 12". If the stove manufacturer lists clearances, then these must be followed, they cannot be reduced. The exception would be if the stove manufacturer gives a listed clearance but then gives closer clearance with an NFPA approved wall protection. Only then will the wall protection be of any help in reducing clearances.
  6. michiganwinters

    michiganwinters Member

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    Your right if the furnace turned on that wouldn't be a good thing. We typically just shut ours off during the winter but theres always a what if!

    So based on what your saying I cannot move the stove any closer. It was actually the mechanical inspector who I pulled the permit with who said if I do this I can reduce the mfg clearances, and handed me the code book. Well thats scary!

    But the good thing is I thought it was 7.5" to whatever was closest...meaning the stone veneer. But if Im understanding you correctly my stone may only be 4" from stove....but its built out with metal studs and the actual wood studs are 8" away with drywall, metal studs, durock and stone we are good!!? That really helps!
  7. begreen

    begreen Mooderator Staff Member

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    The clearances are to the nearest combustible, be it sheetrock paper or studs. If you have metal studs with cement board and then the veneer you should be fine at 6" to the stone.
  8. thechimneysweep

    thechimneysweep Minister of Fire

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    Not necessarily so, BG. Wall shielding is accomplished by using a non-combustible material to create a ventilated airspace between it and the wall. It is the ventilated airspace that cools the wall, not the material used for the shield. For example, If brick or stone is applied directly to the combustible material (and sheetrock is considered a combustible material), clearance is measured from the outer (room-side) surface of the brick or stone.

    There might be an out here, though: if the durock and stone are held off the sheetrock with the metal studs, and 1" holes can be drilled across the top and bottom of the wall behind the stove so the air between the metal studs can rise when it heats up and flow into the room, pulling cooling air from the floor into the space, the new Summit can stand 7-1/2" from the sheetrock.
  9. begreen

    begreen Mooderator Staff Member

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    The point being that the clearance is to the nearest combustible. If a combustible wall sits behind a metal stud wall that is cement board covered, isn't the clearance measured to the combustible wall sitting behind and not the new cement board wall with the stone veneer? He is not trying to get a clearance reduction with a ventilated wall. He has 6" to the stone and much more than that to the original combustible wall. Well over the required 7" at least.

    This is important because it has come up many times. For example a 3" thick brick wall on cement board on wooden studs. Do you measure clearance to the face of the brick or to the wood studs? My understanding is that it is to the wooden studs which are the nearest combustible surfaces. Sure hope that is correct. It is the way I remember if from NFPA 211 and is repeated here in this article:

    http://hearth.com/econtent/index.php/articles/wood_stove_clearances_installing_it_safely

    "An Example of clearance reduction from this code states that a piece of 24 gauge sheet metal installed on spacers 1” from an existing wall will reduce stove clearances by 66% - or from 36” to 12”. The clearance reduction is usually measured from the rear of the stove to the original combustible wall, not to the sheet metal."
    Last edited: Sep 10, 2013
  10. thechimneysweep

    thechimneysweep Minister of Fire

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    The issue is, unless there's a ventilated airspace between the shield and the combustible wall, the shield is considered to be part of the combustible wall. You can't further reduce UL clearances with wall shielding unless allowed in the installation manual, but you can measure from the wall as if the shielding wasn't there, so long as the airspace is ventilated.
  11. webby3650

    webby3650 Master of Fire

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    Are you saying that if there is 3"s of brick sitting in front of a stud wall, the measurement to the nearest combustible is the face of the brick? Not the studs behind the brick?
  12. begreen

    begreen Mooderator Staff Member

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    This doesn't make sense. How can 4 or 6" of non-combustibles be considered part of the combustible wall? An NFPA brick wall has no air space yet qualifies for clearance reduction.
    webby3650 likes this.
  13. begreen

    begreen Mooderator Staff Member

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    I trust Tom like a brother and he has a lifetime of experience with stoves, so if you want to have perfect peace of mind, ventilate the wall space as suggested.

    But I still want to see the documentation supporting this. I would hate to be giving any person here misinformation. ;sick
  14. webbie

    webbie Seasoned Moderator Staff Member

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    I think in a case like this, it is to the original combustible wall. We are not talking about any airspace reduction.

    Other than that, webby above is correct that you cannot reduce this stove more unless stated in the manual. If it says 7.5 to combustibles, it's exactly that. A ceramic plate hanging on the wall would not make it have to go further out, IMHO.

    If we were talking about the engineering inside a jet engine at 42,000 ft, I'd be a bit more exacting. But a case like this seems OK.

    Of course, those cobblestones are a waste of money and time because they are NOT allowing you to get any closer. You may as well paint them on.....
  15. thechimneysweep

    thechimneysweep Minister of Fire

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    Correct, at least in all five code jurisdictions we work in. As it has been explained to me, heat from the stove will eventually penetrate the brick and transfer to the combustibles behind it. Over time, pyrolysis can rear its ugly head. A ventilated airspace (NFPA 211 calls for at least 1") between the bricks (or whatever non-combustible material is used) and the wall prevents the trapped-heat situation.

    BG, the respect is mutual. As has already been mentioned above, NFPA clearance reductions don't apply here, as the Summit is already UL listed for 7-1/2" clearance, which is closer than the NFPA minimum shielded wall clearance of 12". Ventilating the airspace will simply take the shielding material out of the equation, and allow clearance to be measured from the original wall.
  16. begreen

    begreen Mooderator Staff Member

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    Here is the confusion - NFPA 211-39 table 12.6.2.1 - lines a & b take heat transference into account.

    a) 3 1/2" (90mm) masonry wall without air space = 33% reduction.

    Line b) also indicates a non-ventilated wall.

    The brick wall only needs ventilation if a 66% reduction is desired. (line d)

    My thought was that this Summit's installation most resembled line b's requirements. There is xx thickness of stone masonry, then 1/2" thick non-combustible board (he has durock nexgen @R=.49) over 1" of glass or mineral fiber batt (he has 3.5" of trapped air space) without ventilated air space. We are agreed that clearance reduction is not the question here. He has over 7" to the original combustible wall. In this specific case I think the concern over heat transfer is moot.

    Ultimately this is up to the inspecting authority. Tom's suggestion of just eliminating the question by ventilating the wall to essentially bring it out of the equation is a good one if it's an issue for the inspector.

    nfpareductions.gif
    Last edited: Sep 11, 2013
  17. thechimneysweep

    thechimneysweep Minister of Fire

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    I'm very familiar with this table, used to refer to it all the time back in the days when we sold unlisted stoves. Note that although lines (a) and (b) allow a maximum clearance reduction of 33% and 50% respectively, the next column limits the actual clearance minimum to 24" and 18". This table doesn't apply to UL listed stoves, which have specific clearance requirements determined by the test lab: you can't apply a clearance reduction to a UL listed stove by shielding the wall, unless the manufacturer has tested with that technique and specifically allows for it in the installation manual. Nor can you apply NFPA shielding techniques (a) and (b) to locate any stove any closer than 24" and 18", respectively.

    SO... the OP cannot use the existing shielding to reduce the Summit's 7-1/2" rear clearance requirement, even if he ventilates it. However, there would be an advantage to drilling the air holes: by ventilating the airspace, he gets to measure from the original wall instead of the surface of the stone.
  18. begreen

    begreen Mooderator Staff Member

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    Understood. The concern you brought up was heat transfer. That is why I posted the table to indicate NFPA took it into account. The user doesn't need a clearance reduction to the nearest combustible. He already has that.
  19. thechimneysweep

    thechimneysweep Minister of Fire

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    Ah. Gotcha. As you've probably noticed by now, I systematically destroyed several million brain cells in my younger days, and am sometimes a little slow on the uptake.

    Anyway, this thread provided an opportunity to reiterate an important point that hasn't come up on the forum for awhile: NFPA 211 rules are generic, and were created for unlisted stoves. They don't apply to UL listed stoves, which have specific rules defined by the test lab.
  20. begreen

    begreen Mooderator Staff Member

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    Right on!
    Last edited: Sep 11, 2013
  21. Jags

    Jags Moderate Moderator Staff Member

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    I dun learnt something today. Can I go home now?
  22. begreen

    begreen Mooderator Staff Member

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    Not until you finish writing on the blackboard "I will not burn wet wood" one hundred times.
  23. Jags

    Jags Moderate Moderator Staff Member

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    Already did that for Tom, years ago.
  24. akbear

    akbear Member

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    well, I'm thoroughly confused now since this seems to contradict what my manual says in two different places (the only clearances they do list are to combustibles) and it is a UL listed stove.

    1st instance:
    CLEARANCES TO NFPA 211
    PROTECTED SURFACES
    .
    You can reduce the clearances to combustible
    surfaces by using any National Fire Protection
    Agency (NFPA) approved wall protection
    system.
    Please refer to NFPA 211 for
    specifications and complete details. You can obtain this information directly from NFPA.

    2nd instance:
    CLEARANCES TO COMBUSTIBLES
    Use this section to plan the layout for
    your stove. Consider clearance of pipe
    to combustibles and cook stove to
    combustibles.

    You must follow minimum clearances for the
    Deva 100 cook stove to combustibles such as
    walls and ceilings. You may reduce the general
    clearances if installing the stove near Protected
    Surfaces.


    I'd be thoroughly screwed if this information was in error
  25. Jags

    Jags Moderate Moderator Staff Member

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    Your manual is the law of the land for your stove. Period. NFPA 211 was designed as a catch all for everything else. Follow the manual - produce the manual for inspection - and burn on brother.
    akbear likes this.

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