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  1. #1
    Join Date
    Aug 2006
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    I keep hearing different info on whether various HVAC manufacturers recommend using screens on PVC flue vents.

    One guy says they're prone to freeze up - don't use them.

    The next guy says birds, etc get inside & cause trouble.

    Which mfgs require them that you know of????????????

  2. #2
    Join Date
    Nov 2001
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    Some mfg's ship a small round screen with the unit.
    It has about 1/4" opening squares on the screen.

    Don't use the type like your windows have, It will freeze.
    If you put anything on it, make sure the openings are big enough to get exhust out.

    I had 2 units that chip monks would get in the pipe,
    I had to use the 1/4" material and wrap it around the pipe.
    I had it stick out passed the pipe about 8".
    So if it did start to freeze, it had other areas to pull from.

    Don't just cover over the egde and expect to be safe.
    If you try to fail, and succeed.
    Which have you done ?

  3. #3
    Join Date
    Apr 2004
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    I am not aware of any that allow any screening on the exhaust side, you may in some cases put it on the inlet. You need to read the venting tables and rules for every furnace, there is no one venting table for all 90+ furnaces. If they dont mention screening, dont use it. Even 1/2" hardware cloth will freeze.

  4. #4
    Join Date
    Dec 2002
    Rochester, MN
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    Where are you from?

    Here in Minnesota, I have more problems with the screen in than out, even the 1/4" ones. We get our winter thaw in the day where the humidity is high, then at night air is cold, the screen freezes over from the high humidty in the air.

    If you are worried about something going in, look into the BAYVENT that trane uses.

  5. #5
    Join Date
    May 2004
    Rapid City, SD
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    I never use em (screens).

    If I want to keep birds out or other stuff I'll use a Tee, 45, or just cut the end and an angle.

    "If you call that hard work, a koala’s life would look heroic."

  6. #6
    Join Date
    Feb 2004
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    Seems a natural opening for them to get in, but I don't think I've ever seen birds, bird nests, mice, or any similar critters in PVC vents. What I have seen are wasps nests and thick spider webs, and they'd have got in through the 1/4 " mesh anyhow. Have seen lots of leaves in intakes, so keep shrubs well cut back. Have also seen gravel, golf balls, and even a toque tassle put in by kids. As well I saw 1 furnace severely damaged from the HO setting his sprinkler under the intake in the summer, found in the fall that he'd wrecked his furnace.

    I recall water heater mfgrs using 1/4" mesh on their PVC vents for awhile, but they stopped that. That mesh would thicken with moisture and household dust after awhile, and the vent pressure switch would shut down the unit for safety. That was not even a freeze-up problem. We'd just yank the screens out and throw them away, solved.
    Question authority!

  7. #7
    Join Date
    Apr 2006
    South West Ohio
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    In Ohio We had a problem with birds getting in the intake.
    And a mesh will freeze up on very cold nights.

    We drill a hole thru the end of the pipe or elbow and slide a nail thru it, bend it so it wont work its way out. Since then (2years) we have not had a bird or a freezing condition.

  8. #8
    Join Date
    Sep 2001
    Vancouver Canada
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    I always drill a hole in both sides of the pipe and put a piece of 14 gauge wire through it. Local building inspector insists on it. Won't block the vent but will certainly keep the birds out. Other option as stated is A/S BayVent kit.
    "Go big or Go Home"

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