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  1. #1
    Join Date
    Jan 2008
    Location
    Outside The Motor City
    Posts
    666

    How can I make it work?????

    I have a DX system for an surgical room to maintain a room temp of 60 degrees, with an air cooled condenser in Michigan. upon my first visit I found heat tape on the suction line. My first reaction is "RUN FOREST RUN", BUT besides frost control on coils to shut down comp. or a creative hot gas by-pass what else could I do?? (I know I can not achieve this in late July or August.)

  2. #2
    Join Date
    May 2007
    Location
    San Francisco
    Posts
    258
    dude, just put an ice sensor on that evap and run it as low as you want, then reversing mode for a few seconds when it frosts up. no sweat. put a regular heat pump condensing unit on there and get creative with ur controls

    don't forget to kill the evap fan during defrost. don't want to put that warmer air back into the space
    Last edited by little john; 04-29-2008 at 09:16 PM.

  3. #3
    Join Date
    Nov 2006
    Location
    New Hampsha'!!!
    Posts
    274
    maybe you want to think of converting to another refrigerant...or indoor water cooled condenser
    dont worry what people think, they dont do it often

  4. #4
    Join Date
    Sep 2004
    Location
    Kansas City, Kansas, United States
    Posts
    13,832

    Confused

    Quote Originally Posted by hvac248 View Post
    I have a DX system for an surgical room to maintain a room temp of 60 degrees, with an air cooled condenser in Michigan. upon my first visit I found heat tape on the suction line. My first reaction is "RUN FOREST RUN", BUT besides frost control on coils to shut down comp. or a creative hot gas by-pass what else could I do?? (I know I can not achieve this in late July or August.)
    usually op rooms run about 60% humidity.
    how are you doing that?
    I WILL SELL WORK,GENERATE BUSINESS, GO GET NEW CUSTOMERS!
    YOU SHUT THE HELL UP AND QUIT RUNNING YOUR MOUTH!

  5. #5
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,457
    At one hospital we had a cold deck that supplied 55 degree air. The room temp wasnt low enough in the room. The doctors wanted it about 40 degrees for the type of operation they did. We installed a evap coil 12 inches thick in the cold deck. I had condenser bypass for head pressure control and hot gas for the evap. I placed a sensor in the coil and set it at 33 degrees for freeze protection. We were able to get the room to 38 degrees with out any problem. That is with 55 degrees feeding the coil.
    Hot gas set up right on your unit should do it.

  6. #6
    Join Date
    Mar 2008
    Location
    Mid-Michigan
    Posts
    42
    Did you find any reheat in the returns?

    It would seem as though your dew point would be low enough that any moisture collected would be frost, and eventualy freeze the coil over. Controling the humidity is the trick.

  7. #7
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,457
    frost was not a problem, the coil would stay at 34 degrees with the hot gas. If it did drop down it would shut off until the coil reached 45 degrees. These were in operating rooms. They would only run these temperature for certain operation. The rest of the time the room was kept in the low 60's. The nurses hated it. The doctors loved it.

  8. #8
    Join Date
    Jan 2005
    Location
    Area 51
    Posts
    984
    http://www.rawal.com/install_pages/specifications.html

    Try one of these to control capacity at low return air temperature


    http://www.stanref.com/cbk/cbk.htm

    Or a small chiller system, solution being circulated could be any temperture you need to create the right coil temperature.
    Last edited by jayhawker; 05-01-2008 at 07:25 PM.
    "Paddle faster, I hear banjo music"

  9. #9
    Join Date
    Mar 2003
    Posts
    7,321
    That is the trend today. The way to do it is to add recool coils utilizing a process air cooled chiller and glycol. You cannot really be as accurate as they want with one coil.

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