Mantle heat shield installed

Nick Mystic Posted By Nick Mystic, Mar 3, 2013 at 10:22 AM

  1. Nick Mystic

    Nick Mystic
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    After installing my new Jotul F 600 wood stove on my fireplace hearth extension I've been monitoring the temperature on the underside of the mantle. The clearance called for is 26" for an 11" mantle and my stove top is only 22" below my 10" mantle. When I shot it with my IR thermometer I was getting a reading around 170 F with a 400 F burn going in the stove. I could put my hand on the mantle for more than three seconds without discomfort, but I didn't have peace of mind, so I decided to install a heat shield under the mantle. I had some left over sheet metal from making my stop off plate for the fireplace, so I cut a piece 48" x 9 7/8" for the shield. I attached it with some short drywall screws and used 3/8" thick slices of bamboo for the ten spacers.

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    It is not very noticeable when viewed from the front.

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    I know a one inch air space is normally called for when installing heat shields, but since this application was so marginal I decided to keep it closer to the mantle for aesthetic reasons.
     
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  2. EatenByLimestone

    EatenByLimestone
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    That looks pretty nice! I'd be curious how much the heat was reduced by the shield and convection. Do you have a probe by any chance you could push between the shield and mantle?

    How does the masonry work with evening out temperature swings?

    Matt
     
  3. Nick Mystic

    Nick Mystic
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    Matt,
    I just took some temperature readings: Heat shield: 155 F with 375 F stove top temperature and probe reading of 122 F between heat shield and mantle. With my masonry work and temperature swings are you asking if all that solar mass from my 8' x 4' brick chimney helps store heat? If so, yes, all that solar mass stores a lot of heat. When I first got my IR thermometer I shot the backside of the chimney, which serves as a kitchen wall, and after the stove had been burning a few hours the brick was reading 78 F while the house was only about 68 F.
     
  4. ScotO

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  5. Laurent Cyr

    Laurent Cyr
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    Nice install, Nick!

    Laurent
     
  6. begreen

    begreen
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    The install looks good, but for a proper shield installation, the spacers need to be non-combustible. Bamboo is definitely a combustible.
     
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  7. Nick Mystic

    Nick Mystic
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    Yes, I know, but since the heat I'm shielding against is so marginal I'm not worried about the bamboo igniting. The mantle itself without any shielding wasn't getting too hot to place your hand on it for considerable time.
     
  8. begreen

    begreen
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    I know and I don't mean to bust your chops but safety is safety. There could be a day like in a power outage where you are running the stove 100-150F hotter for hours if not days. Prepare your system for the worst case scenario and there'll be less panicking when it happens.
     
  9. Nick Mystic

    Nick Mystic
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    I decided to heed begreen's advice on the replacing my bamboo spacers. I couldn't think of anything I readily had on hand that would fill the bill, then it occurred to me to just remove the spacers all together and just let the shield hang from the screws. I popped them out this morning and I think that will work fine. I just left the ones at the four corners, which are far enough off to the sides of the stove to meet the required clearances.
     
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  10. begreen

    begreen
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    That'll do. I was thinking thick washers or 1" cuts of 1/2" copper pipe.
     
  11. Nick Mystic

    Nick Mystic
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    Great idea! I was just about to head out to my shop to start scrounging around for something I can use for the spacers since the shield was looking a little wavy just hanging suspended. I have some scrap copper pipe from when my central AC system was replaced a couple years ago. With a pipe cutter I should be able to cut off ten spacers in a short time. Thanks for the suggestion.
     
  12. begreen

    begreen
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    Give the shield a coat of honey brown paint and it will almost disappear.
     

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