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power vent design

TomM Posts: 233
Question on exhaust design:


If an appliance has a 6" exhaust, and you are using a 4" power vent, which is better:


1)  bush down the exhaust pipe immediately to 4" and use a 4" barometric


2) use a 6" barometric and 6" exhaust pipe until you get close to the power vent, and then bush down to 4"


Which is better, and why?


(disclaimer - i am NOT building my own exhaust, but the contractors i've spoken to say to use 6" as far as possible, but can't explain why)

beautiful Conshohocken PA


  • icesailor
    icesailor Member Posts: 7,265
    Power Venters:

    You go with the larger pipe for the "Plenum Effect". The "Plenum Effect" slows the velocity  of the gasses.

    It's like those steam boiler headers. If you have a single 1 1/2" riser coming off the boiler into the system, you could have incredible velocity. But if you ran two, 2" risers out of the boiler, the same amount of steam will be traveling slower, and have less surface area to cause resistance.

  • TomM
    TomM Posts: 233

    thanks man!
    beautiful Conshohocken PA
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