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Combustion Air for PV equipment or Atmospheric Equipment

markotah
markotah Member Posts: 36
A new house is being constructed to meet the code which

now makes the house "unusually tight construction" according the the IRC and NFPA54



Option 1 is use a 40 gal gas atmospheric heater into a chimney.



Option 2 is use a 40 gal  and power vent 

Both models have 40K BTU and require room air for combustion



It would seem to make sense that a  PV (power vented unit) would require more air as it needs air for not only combustion but also air to dilute the exhaust so you can vent with PVC. If the buildings are now tighter where is this additional air coming from?

Anything I find seems to show the cubic feet of air required is less with a PV unit.

Anyone know why?

Comments

  • Robert O'Connor_12
    Robert O'Connor_12 Member Posts: 728
    Why?

    New house = tight construction.

    IMHO, I'd go will 100% direct vented appliance(s).
  • markotah
    markotah Member Posts: 36
    because

    I too would use a DV unit. The problem is since they are more money PV units are more desirable.

    The question still is is why does the code seems to indicate that a PV unit would need less  cu ft air?  This is what doesn't make sense.
  • Tim McElwain
    Tim McElwain Member Posts: 4,504
    It needs less cubic fett of air

    because the draft hood needed 15 Cubic Feet of dilution air added at the draft hood and when you do not use a draft hood you only need for every 1 cubic foot of gas 10 cubic feet of air and 4 cubic feet of excess air hence for PV only 15 cubic feet of air required.
  • markotah
    markotah Member Posts: 36
    thank you

    I would have thight a PV unit with a blower would have used more air than an atmospheric drat hood.



    Thanks Again
  • markotah
    markotah Member Posts: 36
    thank you

    I would have thight a PV unit with a blower would have used more air than an atmospheric drat hood.



    Thanks Again
This discussion has been closed.