80% sidewall venting

[splus]

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.

[mechanical'al]

???? 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

[hearthman]

B-vent is approved for CAT I non-positive vent pressure venting only and must terminate vertically.

[mechanical'al]

the boilers would have to follow the same rules

[beenthere]

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.

[mechanical'al]

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

[MJG]

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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[hearthman]

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.

[VTP99]

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.

[mechanical'al]

could'nt you just put a stack through the roof???