Plenum Height

Discussion in 'HVAC Heating & Cooling' started by patelhe, Jun 6, 2011.

  1. patelhe

    patelhe New Member

    Jun 6, 2011
    I have a bryant 353BAV 92.5eff 80K furnace and 116BNA/CNPV AC codenser coil being installed in my attic. The prior installation was incorrect as the installer pointed out because the supply of the plenum were taking off the height of the coil. Now with an encased coil, how high should the plenum be.

    I have 12", 10" and 7'' duct takeoffs from the plenum. Currently the 12" and 10" takeoffs will sit 2" above the coil case.

    Thank you,
  2. TheycallMeDave

    TheycallMeDave New Member

    Jul 9, 2011
    Retired HVAC Owner/Tech
    Northern Florida
    If i were doing it, Id run an insulated supply plenum length of at least 24" and have all the duct takeoffs as far away from the Cooling Coil as possible so the air comes out of the Cooling Coil and mixes well before it gets diverted down each branch takeoff. And id install an adjustable damper for each branch duct right at the connection off the supply plenum for air balancing once the installation is complete.

    Also, if this 92% condensing gas Furnace is being put in the attic , you will run the chance of the condensate freezing up inside the furnace during the winter in N.J. during prolonged heating cycles i hope the Installer is taking some kind of precaution from that occuring. Generally, you put non condensing 80% efficient gas furnaces in attic spaces because theres no condensate to worry about freezing up inside the furnace .
    Last edited: Jul 9, 2011
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