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  1. #1

    Air leaving cooling equipment always 90% ???

    Is the air leaving cooling equipment always considered to be at 90% RH?

  2. #2
    Join Date
    Mar 2003
    no,there can be many configurations to change that. one example would be hot gas reheat.

  3. #3
    Join Date
    Aug 2006
    Or gas fired, or electric reheats.

  4. #4
    Join Date
    Jan 2004

    The air leaving the evap coil, is always a high RH%.
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  5. #5
    Join Date
    May 2000
    In the classroom...
    Quote Originally Posted by guitarboyled View Post
    Is the air leaving cooling equipment always considered to be at 90% RH?
    Yes, even after condensing moisture out of the air, the cold air has contracted (think ice cube on a t*tty) so the moisture that is left takes up a "relative" high amount of
    space in the cold air - the supply air has moved close to
    the Saturation Point Curve of the Psychrometric Chart.
    Prof. Koldenhott
    HVAC Instructor

    "Those that CAN...teach...

  6. #6
    Obviously I was referring to the air leaving the cooling coils before any type of reheat.

    From a calculation point of view, do we consider that it's almost always at 90% RH.

    For instance is the Bypass factor always between 100% saturation and 90% RH?

  7. #7
    From ACCA Manual P (First Edition) pg. 29 it says "In actual practice, a supply air condition which falls on the RSHR (Room Sensible Heat Ratio) line and has a relative humidity between 85% and 95% is a good choice". Also, "A supply condition that falls below the RSHR line can be used, but the room humidity will be lower than the desired design humidity and If a supply condition that falls above the RSHR line is used, the room humidity will be higher that the desired design humidity". I hope this helps.

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