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Calculating 100% outside air latent loads

James Day_2
James Day_2 Member Posts: 191
in A-C, Heat Pumps & Refrigeration
I have a customer who wants me to take 2-   5 ton air handlers and pull fresh air from outside( either 50-100 %) to pressurize and slightly dehumidify his commercial building.  I know how to calculated the sensible load of the outside air but can't remember the calculation for determining the latent load on the equipment.   Does anyone have the proper formula?

Thanks, James

Comments

  • Robert O'Brien
    Robert O'Brien Member Posts: 3,541
    Help?

    http://www.engineeringtoolbox.com/cooling-heating-equations-d_747.html
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  • Techman
    Techman Member Posts: 2,144
    edited July 2012
    Latent load

    Where is 4000cfm going once it has entered the bldg? Exhaust fans? Bringing in all of that unconditioned air puts this more  into a "make-up air" application ,than an AC application.I doubt there will be very much latent heat removal because  the "make-up air" AC evap will be operating above the dew point most of the time. Check w/ the smart folks @ CaptiveAir Co.  (exhaust/make-up air) and hear what they have to say. 
  • meplumber
    meplumber Member Posts: 678
    Ditto to Techman

    This is moving from AC into the realm of Make-Up Air Units. The numbers for MUA are crunched differently that for regular AC. As he said, the evap coil will be working its butt off to dehumidify the fresh air.



    Captive Air is a good source, as is PowrMatic. They do makeup air/exhaust fan setups all day every day. They can probably lead you down the right path.



    Let us know how you make out.
  • James Day_2
    James Day_2 Member Posts: 191
    make up air

    customer wants to pump fresh air into space to pressurize space so that it vents out through roof exhausts.  i will check out those two places.  thanks for the help i will keep you posted on it.
  • James Day_2
    James Day_2 Member Posts: 191
    make up air

    customer wants to pump fresh air into space to pressurize space so that it vents out through roof exhausts.  i will check out those two places.  thanks for the help i will keep you posted on it.
  • James Day_2
    James Day_2 Member Posts: 191
    make up air

    customer wants to pump fresh air into space to pressurize space so that it vents out through roof exhausts.  i will check out those two places.  thanks for the help i will keep you posted on it.
  • James Day_2
    James Day_2 Member Posts: 191
    make up air

    customer wants to pump fresh air into space to pressurize space so that it vents out through roof exhausts.  i will check out those two places.  thanks for the help i will keep you posted on it.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Q:?

    What is this building being used for?  That's a lot of air to pressurize a structure.  What pos. pressure does he demand?  OR is this one of those dump a ton of air so the doors blow open......Just curious.



    Mike T.
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