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  1. #1
    Join Date
    Aug 2003
    Posts
    471

    80% sidewall venting

    Was on a call yesterday for a water heater changeout and the homeowner asks me to change the filter a quick look in the attic and there is a 2 year old 80% forced air funace sidewall vented with b-vent out the side of the home and terminated.i did not see a power venter on it either and told the owner it didnt seem right.question is i have installed 82% boilers that can be sidewall vented which are draft induced wondering why you cant with forced air.

  2. #2
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    502
    ???? theres draft induced then theres power vented in 1 its(the heat exchanger) in a negitive the other is a poitive (actually pushed or pulled) through though I guess it would be up to how such oem is aproved 4 venting though I 2 am with u its probly not right

  3. #3
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,050
    B-vent is approved for CAT I non-positive vent pressure venting only and must terminate vertically.

  4. #4
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    502
    Ive done some checking and the only way is with a negitive static pressure vent which would only be possible with a side wall vent kit (power venter)at the exit creating a nonpositive vent conector with a tempature above 140'f as to not condense

  5. #5
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    502
    the boilers would have to follow the same rules

  6. #6
    Join Date
    Jan 2011
    Posts
    21
    Most 80% equipment is not power vented, ie the motor doesn't create any pressure in the flue (not much more than a chimney would pull). The inducer motor just pulls air through the heat exchanger. That furnace isn't right until it has a power vent kit installed. They're just asking for trouble.

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  7. #7
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,050
    There are aftermarket power vent wall terminations that do induce negative vent pressure throughout the vent and appliance. Their use is slightly questionable because you are modifying the appliance from its listed configuration. You would need test data and a listing report to show your AHJ why it should be allowed. These devices use a pressure sensing switch to verify air movement through the vent, which closes a circuit to allow the burners to fire. This is some level of safety but not a guarantee and the fan will have to be tuned to the unit with a combustion analyzer.

  8. #8
    Join Date
    Jan 2010
    Posts
    5,812
    I removed two identical 80% furnaces last week. Both from the same house. Both had draft inducers on the furnaces. They were sidewall vented in b-vent. The short run had no power vent but the one with the 25' vent was power vented at the wall. The power vented heat exchanger looked like new. The non power one had numerous cracks.

  9. #9
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    502
    could'nt you just put a stack through the roof???

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,759
    Quote Originally Posted by mechanical'al View Post
    the boilers would have to follow the same rules
    Most 80% boilers that list side wall venting require SS vent pipe. And the inducer on them is actually a blower designed to do a positive vent system.
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