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  1. #1
    Join Date
    Oct 2011
    Location
    Minneapolis, MN
    Posts
    780

    Default gravity furnace vent thingy

    Saw this today on an old monster of a furnace. Never saw anything like it before, and I'm wondering if/why it's necessary. It's a open-bottomed box on the vent, just before it joins with the water heater vent.

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    Do not think of knocking out another person's brains because he differs in opinion from you. It would be as rational to knock yourself on the head because you differ from yourself ten years ago.
    - James Burgh, 1754.

  2. #2
    Join Date
    Mar 2007
    Location
    Lake Barrington, IL
    Posts
    1,363

    Default Re: gravity furnace vent thingy

    Draft hood.

    Eric Barker, ACI
    Lake Barrington, IL

  3. #3
    Join Date
    Oct 2011
    Location
    Minneapolis, MN
    Posts
    780

    Default Re: gravity furnace vent thingy

    Thanks, Eric! Feel like I should have known that. Geez, seems odd there somehow, but I know little about HVAC, especially these ancient furnaces.

    Probably unrelated, and I can't say with absolute certainty it was coming from this house, but I noticed in the back yard quite strong combustion fumes, though it was vented through the chimney. Strange. Couldn't see where else it might have been coming from.

    Do not think of knocking out another person's brains because he differs in opinion from you. It would be as rational to knock yourself on the head because you differ from yourself ten years ago.
    - James Burgh, 1754.

  4. #4
    Join Date
    Mar 2007
    Location
    Philadelphia PA
    Posts
    3,177

    Default Re: gravity furnace vent thingy

    Looks like asbestos duct wrap, but you knew that...

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  5. #5
    Join Date
    Oct 2011
    Location
    Minneapolis, MN
    Posts
    780

    Default Re: gravity furnace vent thingy

    Yup, but thanks anyway! Never seen a gravity furnace without asbestos.

    Do not think of knocking out another person's brains because he differs in opinion from you. It would be as rational to knock yourself on the head because you differ from yourself ten years ago.
    - James Burgh, 1754.

  6. #6
    Join Date
    Mar 2007
    Location
    Near Philly, Pa.
    Posts
    1,643

    Smile Re: gravity furnace vent thingy

    Unlisted horizontal draft hood. They were often added on when the heater was converted to gas. Of course, I have a bunch of boilers in my area still set up for mfd. gas, which burns totally different from NG or LPG. No approved way to convert them so these units really should be replaced.

    The problem with draft hoods is they function exactly as designed: they disconnect the chimney from the appliance. They should be outlawed. Safer solution is to replace them with a bullhead tee to double acting barometric damper with spill switches. A lof of debate on whether this modification is approved or not but I can assure you it is one helluvalot safer and works.

    Keep the fire in the fireplace.

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