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  1. #1
    Join Date
    Feb 2013
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    Psychometrics Question


    I have a quick question regarding the design of an AHU. I have been using a psychometric chart and have come up with these numbers :
    OAT= 95 DB, 78 WB
    MAT= 73 DB, 61.5 WB
    Room Temp= 68 DB 57 WB

    The question I have is how do I get my leaving coil air temp?


  2. #2
    Join Date
    Feb 2012
    New York City
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    1. Use a psychrometric chart with the protractor looking thing sitting above the saturation curve with sensible heat ratio markings on it.
    2. You take your space sensible heat ratio and plot that from the room set point to about what you want your diffuser supply temp to be. If you've got more reheat off the saturation curve than you'll get from your fan (typically 2-3 F) you'll probably need to look at reheat or a desiccant wheel downstream of the cooling coil. Alternatively look at higher space humidity set points (55%).
    3. Always check the AHU design with your 1% dew point climate conditions for OA and infiltration.

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