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Fireplace vent sealant ? Please Help

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by cohomeowner, Dec 12, 2007.

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  1. cohomeowner

    cohomeowner New Member

    Joined:
    Dec 12, 2007
    Messages:
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    Loc:
    CO
    Hi! I'm new and I'm hoping someone can help with my question.

    We pulled out our old wood firebox and just had a new gas fireplace installed in the same enclosure.
    The new fireplace vents out the back, it does not use the old chimney that has since been blocked off.
    The installers used red caulk around the new venting inside the enclosure, to seal where the metal meets the
    wall, etc.

    I had noticed there were gaps where the sealant hadn't filled in so when they came out again to fix the new
    gas line (they had pressurized the line and the pressure had dropped) we had them add more caulk. But after
    the guy left I had been looking at it again and found new gaps I didn't notice before and therefore, hadn't been
    brought to his attention. I didn't want to keep bugging them to add more caulk (I'm not sure how critical it is to
    seal all the gaps) and we were concerned that it would need drying time before they finish the install (inspection
    was today) so...I went to HD and asked for heat safe caulk to seal between the vent pipe and the wall. I filled
    in the gaps but now I'm convinced I've used the wrong product (different consistency than what the installers
    used) and my whole house will go up in flames :red:.

    I don't know what they used but it's red. It was smelly when they first applied it. And it is shinier and smoother
    in consistency than my stuff...silicone maybe.

    I used 3M Fire Barrier Sealant. It is indeed red but not really smelly. It's rated for 4 hours. It's latex and
    intumescent. But I can't find any info on it's temperature rating.

    Is my stuff okay to use? And if not, can it be fixed?

    Sorry for the rambling. I blame the late (early!) hour. Thanks!

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  2. Metal

    Metal Minister of Fire

    Joined:
    Nov 18, 2005
    Messages:
    681
    Check the manual for your stove to see what they recommend for sealing around the vent (you didn't state what brand/model you have).

    I don't know anything about the 3M product you used, but the installer most likely used High Temp RTV Silicone Sealant. The RTV part stands for room temperature vulcanizing. When the silicone vulcanizes it releases acetic acid (the vinegar smell you smelled). It usually has a temperature rating of ~650º, if the 3M product has a similar rating, you should be fine. I am not completely sure what type of pipe they sealed. If you have a direct vent stove, the casing doesn't get very hot and you could just use pure silicone, they might have just used the high temp because it is what they had in the truck. Once again, check your manual to see what is recommended.
  3. cohomeowner

    cohomeowner New Member

    Joined:
    Dec 12, 2007
    Messages:
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    Loc:
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    More info might help. The fireplace is a Heat & Glo 6000GLX-IPI-R. It is indeed direct vent. The only mention of caulking
    material I can find in the manual says "hi temp caulking material". I can't find any info on what temperature the 3M
    product is rated for. The product I used is "3M Fire Barrier Sealant CP 25WB+". Anyone know if this is going to be a problem?

    Thanks!
  4. webbie

    webbie Seasoned Moderator Staff Member

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  5. cohomeowner

    cohomeowner New Member

    Joined:
    Dec 12, 2007
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    Thanks for the silicone product info. They definitely didn't have that at HD.

    But is the stuff I did use going to cause a problem?
  6. webbie

    webbie Seasoned Moderator Staff Member

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    Loc:
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    Probably fine to use certain fire blocks, but it is not as flexible, etc. - the fireblock stuff is really for sealing up between areas so that fire does not spread - oversize holes for plumbing, etc.

    Ideally, you would use the silicone on the exhaust pipe - because of both the temp rating and the flexibility. The other stuff is certainly fine for elsewhere, but again there is a big difference between a fire barrier and a heat resistant material......in your case, it is probably not a big deal, but in general people should use the silicones and furnace cements when working with stoves. That fire barrier stuff is for different applications.
  7. jtp10181

    jtp10181 Minister of Fire

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    Loc:
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    You should not use fire barrier stuff, some of it actually expands when heated to prevent fire spread. What areas have the red silicone on them? The only part that really needs silicone is where the flue penetrates through the outside wall. If they siliconed the joints where the pipe comes together it is overkill. Also they did not need to use the HT red silicone, the clear or aluminum colored stuff works just fine. Any high temp rated silicone caulk from the hardware store will do the job.

    We install Heat & Glo units every day and follow standard practices that are proven to give great results and are approved and taught by HHT (parent of Heat & Glo). If you have any other questions about your fireplace or installation I would be happy to help.
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