1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

duct work wrapped in the ASTM E84 foil insulation.

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Fsappo, Feb 11, 2011.

  1. Fsappo

    Fsappo New Member

    Joined:
    Apr 9, 2008
    Messages:
    3,551
    Loc:
    Central NY
    Is this a good idea for a plenum above a furnace? I have a customer with a caddy furnace (I posted pics of his install before) who claims when his plenum temp gets up towards 250 degrees the surface of that foil is very hot to the touch.

    What say you, gurus of the boiler room?

    Helpful Sponsor Ads!





  2. offroadaudio

    offroadaudio New Member

    Joined:
    Dec 17, 2007
    Messages:
    365
    Loc:
    South Central Pa.
    I would think the best thing to do is check the manufacture's spec on the insulation - they certainly will have an "up to" temp.
  3. muncybob

    muncybob Minister of Fire

    Joined:
    Apr 8, 2008
    Messages:
    1,974
    Loc:
    Near Williamsport, PA
    yep, check the specs. That's what I did before wrapping my 6" pipes....temps anywhere from 375 to 550 when in full burn but insulation is never hot to the touch. I beleive what I used was rated to 1200.
  4. laynes69

    laynes69 Minister of Fire

    Joined:
    Oct 2, 2006
    Messages:
    1,809
    Loc:
    Ashland OH
    How is he seeing those temperatures? The highest I have ever had our ductwork was 115*f. Maybe he is doing something different like blower speeds, draft, etc? If you could ask him for I am curious.
  5. ronoz

    ronoz Member

    Joined:
    Aug 15, 2008
    Messages:
    37
    Loc:
    CT
    It is my furnace that Frank is referring to. Matt, when the draft is fully open after reloading, the temps on my thermodisc easily reach the 250 degree shut off point at which time the draft door automatically closes. It is then that the front of my hot air plenum just above the clean out door gets very hot and the entire plenum is wrapped in the ASTM E84 insulated foil. This area of foil wrap just above the clean out door gets really hot but, that's the only area that gets that hot. I'm just concerned that it may be too hot for the foil insulation in that area. I believe you actually asked me this very same question after I sent you the pics of my install a while back. I have considered cutting the foil insulation off of the lower front of the hot air plenum just to be safe but wanted to get Frank's opinion before I did so. Thanks for starting the thread Frank! Hopefully we'll get some good advice on this.

    Here are the pics that Frank posted of my install. I couldn't figure out how to post them here so I emailed them to Frank.

    http://www.hearth.com/econtent/index.php/forums/viewthread/70265/

    The PATS will come back stronger next year. Watch Out! In the mean time, "Let's Go Red Sox"
  6. laynes69

    laynes69 Minister of Fire

    Joined:
    Oct 2, 2006
    Messages:
    1,809
    Loc:
    Ashland OH
    Okay, that makes sense. I've seen 300 at that location. I would cut it back because I believe it's plastic in-between those foil sheets right? Either that or remove the wrap on the plenum and install foil faced fiberglass. Does that foil insulation you have do a good job otherwise? Now that you have a little time with the furnace how has it performed?
  7. ronoz

    ronoz Member

    Joined:
    Aug 15, 2008
    Messages:
    37
    Loc:
    CT
    Yes, I believe the insulation does a good job everywhere else except this area which gets really hot. Maybe I could try to find some higher rated insulation to replace the front area of the hot air plenum. As far as the furnace's operation, I really like it so far. I'm a little concerned about low stack temps. It burns at about 100 degrees or so after it dampers down. I use a Rutland magnetic flue thermometer which is attached to the single wall flue pipe about 2 feet above the rear evacuation point of the furnace. I have a 40' outside chimney so I'm not sure that enough heat is reaching the top of the chimney with those temps. Just had my chimney cleaned last week and so far, so good. What are your flue temps Matt when your furnace is dampered down? What type of thermometer do you use to measure stack temps? Have you had any creosote issues? I can say though that I only load this furnace 3 times/day and it heats my 2200+ sq. ft. home easily. In the morning, I load it before work and set the thermostat to 74 degrees. When I get home, there are plenty of coals to restart it and I usually get the first floor to 76-78 degrees easily while the second floor reaches around 70 degrees. Before bed, I load it again and set the thermostat to 74-76 degrees and it keeps the house nice and warm overnight. Nice easy restart with plenty of coals left over in the morning again.
  8. laynes69

    laynes69 Minister of Fire

    Joined:
    Oct 2, 2006
    Messages:
    1,809
    Loc:
    Ashland OH
    Our flue temps range between 125-175 external when the damper is closed on the firebox. The higher side with a food hot fire and lower with the coaling stage. I have swept the chimney 2 times and both times pulled a couple cups of dust. I did eliminate our barometric damper because of flue temps. I tried a key damper then eliminated that. In the end I reduced the primary and secondary ports to mimic a shorter chimney and have good results. No smoke spillage and total control of the furnace. I wasn't going to do it, but with out 32' chimney I had to do something. Our wood usage this year has been lower so that's nice.

Share This Page