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Thread: hvac rezoning

  1. #1
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    hvac rezoning

    ongoing forum:
    trying to figure out the best way to redo the HVAC system in a commercial building with a lot of open space, old units and not a lot of zones. I will post as much information as I can, and if you need/want additional info let me know and I will try and provide that.
    these plans are for the 5th floor of a multi-story building. this is a typical office building with large atrium-type spaces at the entrances.
    there are two main units and It looks like each unit is in the 10,000-15,000 cfm range.

    On the top floor you will encounter unit 5-1, and that unit is responsible for cooling the 5th and 4th floor along with a unit that was added in the kitchen, see picture. Also pictured is the ductwork that is cooling the 5th floor.

    I have attached the picture of the unit 5-2, that is cooling the 3rd floor, and that's about all the unit cools.
    Then on the 2nd floor, you will notice, see picture, a room with a window ac. Besides that, the whole 2nd and 1st floor are basically open and have no cooling whatsoever. I would like to perhaps add another unit just to cool the 1st and 2nd floor. Perhaps replace unit 1 and 2, and keep the ductwork?

    Please advise. thank you so much for all your help in advance.




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  2. #2
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    Thread Starter
    picture # 1 is unit 2 in the fifth floor. Not that the supply air comes from the roof. picture #2 is the connections going into that unit. I didn't find a thermostat and I think it always runs with the same volume of air regardless if its night or day.
    picture #3 is the supply air in the 5th floor ceiling. picture #4 is unit 1 and that supplies the conference room behind it. it has its own thermostat. Next picture is the unit that was added to the kitchen. The kitchen is open to the 4th floor, thus sharing the air form the unit in the 5th floor. Also, there is no exhaust in the kitchen, I don't know how but there is not one.
    Next picture is the room with its own ac. The 1st and 2nd floor are open to each other and there is no units supplying cold air to those areas.

    I have not done a load test on the building or checked the pressure so I don't know what is the pressure difference. I also don't know if there is any fans in the system.

    If you guys could tell me how to rezone this building. If I could reuse the existing ductwork, and how to ideally add another unit to cool the downstairs. Any comments, suggestions would be very much appreciated.

    I didn't notice any flow rate controller or a control damper.

  3. #3
    Join Date
    Jul 2002
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    What problems are you facing? Why change anything?
    The design of cooling the top floors and ignoring floors 1 and 2 might have some merit if there is never any need for heating.
    There are structural (weight) issues as well.
    This is a job for an engineer, not a contractor. Too many unknowns.
    "I have never let my schooling interfere with my education."
    Mark Twain
    NEVER STOP LEARNING.

  4. #4
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    With all due respect, you're trying to get thousands of dollars' worth of design services and advice for your project. The way that I'm reading your posts, it appears that you may be in over your head and need the help of a more senior engineer or a sub-consultant to the project who can help you out. You are handing out bits and pieces of the puzzle, trying to pique our curiosity and natural desire to want to fix what is broken. The only problem with that approach is that you are wasting everyone's time trying to guess what is actually happening with the building and HVAC systems as a whole. Good luck with your project.

  5. #5
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    Thread Starter
    thank you for this productive post. I understand that I am trying to get advice for free, but you don't have to provide it if you don't want. But instead make a critical comment is just not productive and uncalled for. You could point me in the right direction instead. Thanks anyway

  6. #6
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    I apologize for the rudeness of my previous comment. I have a tendency to be too blunt sometimes in my remarks.

    The issue that I have with your initial post and request for help is that it's partial information. To ask for help with a project of this nature without providing all of the information is, frankly, wasting your time. I enjoy solving puzzles, such as the one you are asking about, but without all of the available information, there's nothing I can constructively offer.

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