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  1. #1
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    Jan 2005
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    Houston TX
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    Confused Makes.no sense does it, or am I wrong about this ?

    In the Galveston area I have a commercial application of a building dehumidifaction system that uses 100% outdoor air and no recirculation at all. There are about 25 RTU's with a 10% make up outside air with discharge humidity sensors that control the damper and discharge air temp and humidity. Why would want a 100% outside air in a very high humidity area. Several other commercial applications in the area have recirculation, make up air and exhaust capabilities. As could be expected the units using 100% outside air never shutdown until it goes into unoccupied mode. Does not make any sense to me.

  2. #2
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    Mar 2008
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    kansas
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    I’m no expert bud the only place I’ve seen 100% is labs that is was spec’d due to hoods and air changes .
    Honeywell you can buy better but you cant pay more

    I told my wife when i die to sell my fishing stuff for what its worth not what i told her i paid for it

  3. #3
    Join Date
    Nov 2011
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    Are you saying you have a separate unit that handles dehumidification, along with the 25 RTU’s?

    What kind of building is it? Offices? Warehouse? Sports complex?

  4. #4
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    Aug 2006
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    Mixing oil and fire with a big spoon.
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    I have a senior living facility that used to use 100% outdoor air due state requirements. When I started taking care of them, they had adding controls that monitor air quality and that allowed for recirculating. Chiller was grossly over sized and now we have a nice, new and much smaller Chiller in place.

    Did your building used to be used for something else?
    Don't step on my favorite part of the Constitution just to point out your favorite part.

    Political Correctness is forced on you because you have forgotten decency.

    Technically speaking, they are all heat pumps.

  5. #5
    Join Date
    Feb 2006
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    Float'N Vally, MS
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    We have a building that is high in occupancy.
    This has an OA AHU with cooling/heating coils for C02 control.
    Everything is adjusted through the control system.
    Life is too short, Behappy!
    TFMM

  6. #6
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    Jan 2005
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    Houston TX
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    Thread Starter
    This is a retail store, as built. It has all those RTU's as this is a high square footage with RTU's sized from 5 to 25 ton cooling capacity, most smaller. I went through the manufactures IOM and it clearly recommended a recirculating air for high humidity areas, I would think that would include Galveston. I agree about the 100% outdoor air for labs, one time through and out. All these RTU's have dehumidifaction function along with reheat (if needed). You should see the condensate draining out of this unit, looks like a 3/4" garden hose.

  7. #7
    Join Date
    Oct 2011
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    Chicagoland Area
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    Target?
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  8. #8
    Join Date
    Nov 2011
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    East Side
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    Quote Originally Posted by ga1279 View Post
    This is a retail store, as built. It has all those RTU's as this is a high square footage with RTU's sized from 5 to 25 ton cooling capacity, most smaller. I went through the manufactures IOM and it clearly recommended a recirculating air for high humidity areas, I would think that would include Galveston. I agree about the 100% outdoor air for labs, one time through and out. All these RTU's have dehumidifaction function along with reheat (if needed). You should see the condensate draining out of this unit, looks like a 3/4" garden hose.

    so, all of these units are standard RTU's with dehumidification function, but they have zero return air ductwork, and rely solely on the outside air damper for "return air"?

    the short answer is prolly that some engineer thought it was a great idea.

  9. #9
    Join Date
    Aug 2002
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    Southold, NY
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    Quote Originally Posted by 71CHOPS View Post
    so, all of these units are standard RTU's with dehumidification function, but they have zero return air ductwork, and rely solely on the outside air damper for "return air"?

    the short answer is prolly that some engineer thought it was a great idea.
    That has stock in the local utility!

  10. #10
    Join Date
    Jan 2005
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    Houston TX
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    Thread Starter
    No, all the RTU's do recirculate return air with a minimum of 10% outside air. There are 2- 30 ton Addison outdoor simair units that do no recirculation. They attempt to pull the moisture from 100% outside air, before it pushes it in the store. There is also a 12 ton Munters unit that recurs less air mixed with outdoor air. 2sac yes !

  11. #11
    Join Date
    Sep 2008
    Location
    Grand Rapids, Michigan
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    You indicate a 10% minimum outside air yet say it is at 100%. Does the unit normally run at 10% minimum, then open to 100% outside when it goes into dehumidification or cooling mode? You mention humidity sensors in the DAT are there maybe space and outside humidity also? Are your humidity sensors accurate? Could the building controls system be using an enthalpy calculation to determine whether outdoor air enthalpy verses indoor is more favorable to use during cooling cycle??

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