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Furnace Roof Vent Ice Dam and Resuilting Roof Leak - HELP!!!

HVAC_Rookie
HVAC_Rookie Member Posts: 4
Hello folks - I'm really hoping someone can help me with this problem I've been trying to solve since last winter. As you can see I from the pictures I had a vertical ice damn being formed by the furnace roof exhaust vent. First I thought it was a roof problem but the roofer of the recently installed roof rightfully pointed out that there is no water leaking even after the heaviest rain. And then we saw theses vertical ice dams. Problem seems to be that none of the HVAC people I've spoken to seem to know how to address this. Two claim its a roof problem, while the last one side I should saw off the exhaust vent so that it is vertical pointing upwards which he feels means there will be nothing dripping out of it and thus no ice dam accumulation... ANY THOUGHTS PLEASE??

Comments

  • Zman
    Zman Member Posts: 6,959
    What model equipment is that venting.
    Straight up is a good idea provided the manufacture approves.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HVAC_Rookie
    HVAC_Rookie Member Posts: 4
    Zman thanks for the comment.. it is a Comfortmaker furnace - can't seem to find anything that looks like a model name or number.
  • Zman
    Zman Member Posts: 6,959
    I would cut it off and go straight up, just like in the manual. https://www.utcccs-cdn.com/hvac/docs/1011/Public/0C/44001201003_ICP_5970.pdf
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    HVACNUTDZoro
  • DZoro
    DZoro Member Posts: 1,048
    The exhaust should go straight up, keep elbow on the intake. They should be a minimum of 18" apart.
  • Jamie Hall
    Jamie Hall Member Posts: 17,011
    Go straight up. If you are concerned about the possibility of rain getting into the pipe -- which is a very minor problem and one I wouldn't worry about (the top cap on chimneys for fireplaces which you often see is there to keep the birds out, not the rain) -- you can put a lid over the top opening -- a flattish cone (tip up!) about twice the diameter of the pipe and set the diameter of the pipe above the top of the pipe. If that makes any sense.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Leonard
    Leonard Member Posts: 903
    Looks to me like it's an ice stalactite. Formed either by dripping water or cold steam vapor condensing on roof.

    Just curious, have you ever seen it grow so tall it meets the pipe?

    If I didn't have the installation manual I might have installed a Tee fitting on the vertical pipe ( as they like to do in England)
  • captainco
    captainco Member Posts: 502
    It should be straight up. I don't believe a flue should ever be 180 degrees back down. Rain is good because it helps neutralize the condensate in the furnace. Birds can get in any vent pipe. Can't cover them or they will freeze shut.
    Steve Minnich
  • HVAC_Rookie
    HVAC_Rookie Member Posts: 4
    Guys thanks very much for all of the great comments. I took the advice and had the vent cut so that it goes straight up. However as you can see now there is ice somehow accumulating along the based of the vent/flashing. Any ideas on what can now be causing this?? Could the cap somehow be causing the problem??
    Thanks in advance for any help!

  • KC_Jones
    KC_Jones Member Posts: 4,813
    It looks like they put a cap on it, I am pretty sure that isn't necessary and probably causing the issue.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    Canucker
  • Harold
    Harold Member Posts: 241
    My two cents. If the new roof is properly installed and the two pipes properly installed with appropriate materials at the base; the ice should not matter. I would guess it is possible for melt and remelt could affect the roofing. But it should not cause damage.

    I have a question: should the exhaust pipe be below the intake? Or does it matter. It would seem to me that in the new configuration the intake would inhale some of the exhaust.
  • DZoro
    DZoro Member Posts: 1,048
    That's wrong, should not be a cap on it, it should be higher than the intake pipe, and at least 18" away from the intake pipe. That ice will push up on the shingles and find its way in. Keep the exhaust pipe straight up no tee's , 90's, caps.
    HVACNUT
  • HVAC_Rookie
    HVAC_Rookie Member Posts: 4
    Guys so is the cap a problem because air going up is being forced back down to the roof and then freezing?
    Thanks.
    DZoro
  • SuperJ
    SuperJ Member Posts: 605
    edited November 2018

    Guys so is the cap a problem because air going up is being forced back down to the roof and then freezing?
    Thanks.

    It's a problem, because the moisture in the flue gases (steam) hits the cold cap, condenses, and then drips down and freezes on your roof. Without a cap any condensation will flow back down the vent pipe and be dealt with thru the condensate drain at the bottom.
  • DZoro
    DZoro Member Posts: 1,048
    Don't forget that that condensate is VERY CORROSIVE. Not something you want running down your roof, gutters, siding....
  • NeverDone
    NeverDone Member Posts: 4
    Point the exhaust straight up, no cap. Its done like that here in WI all the time. The cap is the cause of the condensate dripping.
  • NeverDone
    NeverDone Member Posts: 4
    Also it might be a good idea to put a reducer on the end of the pipe to drop 1 size, for example 1-1/2 -to- 1-1/4. Lennox calls this an 'accelerator' and it increases velocity to help blow the exhaust further away from the termination point to prevent exhaust from being drawn into the intake.
    DZoro
  • John Mills_5
    John Mills_5 Member Posts: 935
    Yup, blow straight up. There's a drain in the furnace if a little bit of rain gets in it. I see these elbowed over all the time. Like DZoro said, you don't want that stuff on your roof. I have a picture somewhere of one that blew on an adjoining chimney and the mortar is totally gone between the bricks.