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Poor Man's Block off plate - II

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by EJL923, Oct 8, 2011.

  1. EJL923

    EJL923 Feeling the Heat

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    This is an extension of another thread, but i wanted to show how you can make a simple block off plate which is quick, effective, and doesn't require drilling into masonry. Its not the prettiest, but it is out of the way anyway and will last. Ive been burning two seasons with the block off plate the installers put in. I finally went in myself and found how ineffective it really was, so after i did this im looking forward to an improvement in heat retention.

    I should add how it is done. Stuff with Roxul above the damper plate. Cut a 1/8 thick piece of steel and drill a hole for a long threaded rod. Two separate pieces of sheet metal, cut to the size of the damper area and made to fit around the liner. Slide the steel into place, and tighten the sheet metal up to the damper with wing nuts. Probably about a 30-45 minute job.

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  2. begreen

    begreen Mooderator Staff Member

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    Nice job and good pictures. I changed the title to include block off plate so that folks will find it in the future. Thanks for posting!
  3. cowtown

    cowtown Member

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    I started the initial "Poor Man's Block off Plate" - nice job, question where did you get the metal for this project? Can you give me details on the metal components as I would like to get some myself.
  4. Danno77

    Danno77 Minister of Fire

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    Sheet metal should be available at any hardware store. ANY gauge of steel should work as it's not anything structural, just needed to keep the Roxul covered and in place.

    The little metal strips need to be heavy enough to hold the weight of everything, if your sheet metal is heavy enough to cut them out of that stock, then great, but you can buy 1"+ wide strips of steel at the hardware store, too, then cut it to the appropriate lengths.
  5. mhrischuk

    mhrischuk Guest

    Very smart. I may do the same.
  6. cowtown

    cowtown Member

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    Might be a dumb question, but could some sheet metal "off gas" as the temp increases; hence, the sheet metal needs to be made of specific metal (e.g. aluminum or something like that ?)
  7. Danno77

    Danno77 Minister of Fire

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    Straight steel. Not any of the galvanized stuff for sure.
  8. cowtown

    cowtown Member

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    I am not playing dumb here, but if I were to go to the harward store and ask for "Straight Steel" they know what I would be talking about?
  9. Danno77

    Danno77 Minister of Fire

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    No, just say "steel"...I said straight to make sure it's understood that it doesn't need to be stainless, not galvanized, not expanded, nothing. Just some plain old sheet steel.
  10. begreen

    begreen Mooderator Staff Member

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    It most likely will be galvanized. That is ok for a block off plate. It doesn't get that hot.
  11. JeffT

    JeffT Member

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    My existing damper opening was 6'' so i saved my damper plate and did basically the same thing.Had to notch my damper frame for the flex(6 1/2'' for a 6'' i.d.) then cut a 6 1/2'' hole in my original damper plate.worked like a champ.I would like to post pics but there is a five hundred pound stove in the way.
  12. cowtown

    cowtown Member

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    Okay - thanks for the help, really appreciate it.
  13. cowtown

    cowtown Member

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    I thought about doing this as well - my issues is that I am the store do the install, so they don't want to fuss with doing this, nor a block off plate. So the solution is to simply put up some roxul. My plan is then to have some steel cut into bars and simply place these bars in a North/south fashion to hold up the insulation.
  14. Danno77

    Danno77 Minister of Fire

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    At what temp does the zinc outgas and how hot will it get? I have a big sheet of galvanized I could use, but I figured that at 700 degrees on the stovetop and having my block off plate just a hair over a foot over the stove would heat it up enough that I should be worried... Actually, my black pipe transfers to the class A just after where I would use the block plate, so the plate would likely be in contact with the black pipe.
  15. JeffT

    JeffT Member

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    You would have to get your stove hotter than 700* at that part of the flue to off gas,and if it did it would only be maybe 1/2'' around the block off.
  16. EJL923

    EJL923 Feeling the Heat

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    The sheet metal used was galvanized. I used the piece that my installers used, and it has shown no signs of overheating after two years of burning. Galvanized should be good up to 400-500°, and that area should not get that hot. You could use unfinished, it just might get some surface rust overtime. Another thing that is hard to see, but my installers left about a 1.5" wide strip on the sheet metal to be bent down and secured around the liner with a large band clamp, not too tight. From my engineering background, i usually wouldn't want to secure disimilar metals, but again, after two seasons it has shown no issues.

    Home depot, lowes, any hardware store should have all of these materials, very common.
  17. fire_man

    fire_man Minister of Fire

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    EJL923: Great ideas.

    Another maybe dumb question, what is the purpose of the Roxul? If the block of plate prevents warm air from rising into the clay liner, what does the Roxul do? If the liner were not insulated, it might act as a liner islulator, but only as far up as you can stuff the Roxul.
    How far did you stuff the Roxul?
  18. EJL923

    EJL923 Feeling the Heat

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    The roxul creates an air seal, as it is stuffed real tight and stops heat from leaving your house. Without it, you will have to seal other ways to stop the air flow. This would negate the point of the poor mans block off, and would require more precise cuts and silicone to seal the edges, and another way to seal around the liner.
  19. fire_man

    fire_man Minister of Fire

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    Makes sense, thanks.
  20. stejus

    stejus Minister of Fire

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    EJL923 - This looks great and far better than just stuffing insulation up there like my current situation. One question, can this be done with the stove in place? I had some reach issues with stuffing insulation up there so I'm trying to figure a way to do it like yours, without pulling the stove out.
  21. rakuz66

    rakuz66 New Member

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    Is that spray foam insulation?
  22. begreen

    begreen Mooderator Staff Member

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    Packed Roxul.
  23. EJL923

    EJL923 Feeling the Heat

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    I did mine with the stove in place. Without pics I have no idea whether or not you can. It was tight, but I managed.
  24. tickbitty

    tickbitty Minister of Fire

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    Hmmm... makes me wonder if it could be held up with magnets, that's how I did my mantel shield. A metal sculptor gave me a thick blanket of kaowool, but I haven't put it up there yet, and I'm certain it would be a bad idea in my particular situation to have it in there without a plate of some sort. (I have an insert, but no surround panel, so I feel like it would be dropping junk on my stove as well as blowing out...) We will see.
  25. DanCorcoran

    DanCorcoran Minister of Fire

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    Not sure, but I think heat causes a loss of magnetism. Someone on this site will know for sure....

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