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Thread: Gravity Furnace

  1. #1
    Join Date
    Nov 2005
    Posts
    13

    Gravity Furnace

    Hi,

    I have one of those old old green monster gravity furnaces w/ asbestos ductwork. The homeowner is going to remove all the asbestos and leave the boots intact and a 12" section at the furnace for each run. My question is, can I replace all the ductwork w/ wireflex or would it be too hot and possibly melt it? Some people say I can some say it won't last long at all. Should I use alum flex instead?

  2. #2
    Join Date
    Dec 2005
    Location
    Virginia Beach, Va.
    Posts
    250
    If that furnace was compared to a car, we would be talking model T at best. And if you’re a tenant it’s not your equipment . Abatement is not 100 o/o anyway, so you’ll be playing around asbestos dust? There is no improvement worth the effort, expect selling that thing to the Smithsonian institute. I do think there neat to look at . There is definitely a point of reasonable liability. Half a century old residential equipment?

  3. #3
    Join Date
    Nov 2004
    Posts
    1,030
    replace everything

  4. #4
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    asbestos ductwork?
    or
    metal ducts covered with asbestos sheeting?

    if the latter, the sheeting can be cut into sections, removed with as little disturbance as possible, then double bagged. [small asbestos particles draw into the lungs are B A D]

    your message implies that you are just changing the ductwork ?
    if so, the furnace will NOT keep the house warm!
    the gravity system needs LARGE piping to get the air exchanged/ moved.
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  5. #5
    Join Date
    Nov 2005
    Posts
    13

    Wireflex or not?

    No I am not a hack. I sold the homeowner 2 furnaces at 2 other properties already, but w/ this particular unit he just wants the ductwork replaced. So again the question is can I use wireflex duct work. Also, since this is an extremely old furnace, the existing ductwork is sloped upward (for gravity purposes i assume), he wants the wireflex to be run tight up against the ceiling in a joist bay, straight and tight. The ducting size is going to be the same but I just need to know if wireflex would work.

    thanks

  6. #6
    Join Date
    Feb 2003
    Location
    pittsburgh,pa
    Posts
    727
    I would suggest getting some liability issues in writing. All assessable should be removed and the rest should be sealed. Not an uncommon job for my area but you should do it right. We use outside pro's for abatement. Start with heat loss calc , select your system, design ductwork. Chances are you will need return added. Gravity used central return with open grates to upper floors (not very efficient). Adding a box plenum and flex will not be very efficient as well.This has the potential for legal issues in future if all bases are not covered. good luck

  7. #7
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,677
    I wouldn't use flex, I would hard pipe it, but would not run it any differently than it is now. Unless you add a blower housing to it(seen it done) But the blower looked to be added like 45 yrs ago. Guy must not be paying for the fuel, wouldn't think it would take long to recoup costs on a new furnace. Only seen 1 fire resulting from a gravity furnace, it was easier to remove the old pig that way, picked it out of the hole with an excavator
    You can't fix stupid

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