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Blocker PLate?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by YZF1R, Mar 6, 2009.

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  1. YZF1R

    YZF1R New Member

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    First off, let me say thank you for all the excellant advice I see posted on this site. Second, about us, we are not new to wood heat as we used it 20 plus years ago in another home. Now the question. We are having an insert installed (see sig.) in our full masonary, raised hearth, outside chimney fireplace. Home was built in 1966, bilevel. Flue will be about 24 feet from family room downstairs to chimney exit. (Installer was already here to look it over.) Installer will seal the top around the cap, use a liner with insulation installed. Will need to ovalize slightly to get down the chimney. As it will be sealed at the top, do we still need a blocker plate at the bottom? I'm sure it wouldn't hurt, but is it still needed as no drafts can go anywhere in the chimney with it sealed at the top? So far as heat givin off into it, the inserts are insulated around themselves inside I think? Please tell me if I'm missing something. Maybe it should just be done anyway?

    Thank you,
    Steve

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  2. AbeAinPa

    AbeAinPa Member

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    There are lots of threads that discuss this exact issue, but the bottom line is; Do you HAVE to have one -> No, but it's highly recommended by most on this sight. Even with a top plate you'll still lose heat up the chimney, and should the top plate not stay completely sealed, you'll be losing lots of heat. I put a block off plate in and the plate itself is not that big a deal, but it does lock the liner in place somewhat so installing the insert can be a bit more difficult, but not prohibitively so.
  3. YZF1R

    YZF1R New Member

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    Thanks for the reply. I read some other threads on it before posting but didn't see a definative answer on it. Judging by what everyone is saying, I'll have one installed. It just looked a bit of a pain to get it exactly fit so when you slide the insert back in it lines up.

    Thanks,
    Steve
  4. YZF1R

    YZF1R New Member

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    Did more reading further back on a search of the forums. Blockoff Plate = Flashback Protection. Got it. 'nuff said!

    Steve
  5. AbeAinPa

    AbeAinPa Member

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    You're welcome, I think you made the correct decision, and you won't have to second guess yourself later.
  6. YZF1R

    YZF1R New Member

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    "Another over-thinking engineer" I remember that. And once again thank you. You're also right about about always wondering in the back of my mind if I should have.

    Steve
  7. Lanningjw

    Lanningjw Feeling the Heat

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    In my case, I also have an insert but installed a insulation (Soft block off). It makes a huge difference in the performance of the insert. I live in a cold climate, so far Minneapolis has had 34 days this winter of at or below 0.

    The insulation, designed for high heat, was stuffed around the 6 inch stainless steel tube in the damper area. This keeps the heat in the living room rather than having it go up the chimney flue. The Chimney will leak air and draws the warm air up into it. The heat stays were you want it.
    All kinds of good things happen as a result!
    Jim
  8. DBoon

    DBoon Minister of Fire

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    Hi Lanning, what kind of insulation did you use for the "soft" block off plate, and where did you get it?
  9. burntime

    burntime New Member

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    C'mon hunting season!
    I did the same thing with rockwool, the next year I did a sheet metal block off plate and insulated the liner...WOW what a difference!
  10. Lanningjw

    Lanningjw Feeling the Heat

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    I went down to my local wood stove dealer. They do alot of insert installs and had the insulation in the back room. I am not sure what kind it is but its the high heat kind and was about 2 foot by 4 foot and 2 inches thick, for $20.

    The stove shop said that they use it when they install inserts for there customers. He said they cut a 6 inch hole in the insulation and stuff it up in the damper. I mentioned that I would like to also put a steel block off plate and he had never heard of this but thought it was a great idea.

    I put on a long sleeve shirt and leather gloves with a N95 mask during the install. Its nasty stuff because it doesnt have any paper backing on the insulation.
  11. DBoon

    DBoon Minister of Fire

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    I think some rockwool and a block off plate is on the list of summer projects.
  12. czorbach

    czorbach Member

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    I am obtaining estimates for an insert for my fireplace.
    The one installer said I don't need a block off plate - just stuff with insulation.
    I think they just don't want to do the work.
    They also said they just use regular Pink Panther insulation - is this ok?
    Everything I have read on this site recommends rock wool.

    charlz
  13. North of 60

    North of 60 Minister of Fire

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    Pink/standard fiberglass insulation is not considered a non-combustible. Even around your class a chimney you are supposed to maintain the 2" minimum clearances. Certainly not a good item to use up tight against a liner above a block off plate. People use it but does not meet any of the ratings it could be exposed to. A ceramic fiber insulation such as Kao-wool or rock wool is the way to go. This stuff is used on boiler breaching and access gaskets witch is part of a standard spec in the mechanical industry.
    N of 60
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