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  1. #1
    Join Date
    May 2009
    Location
    Superior, WI
    Posts
    25

    Any Mini-Split units that can use "real" thermostats?

    Are there any mini-split units that can use a 'real' thermostat? I want to be able to use a commercial thermostat with temperature lockouts with it so that there's no abuse and no one makes the building's heater fight the mini split unit.

    A little background - the building is in Superior, Wisconsin where the design temperature is 76 F for the summer (and something like -27 F for the winter). State law says that the AC can't be designed for more than the design temperature... the problem is it gets well over 76 F for at least a month every summer, several days in the mid 90's. So the system could barely keep up as it was, and now we've added more users and workstations to one of the rooms that was already marginal at best. And the room faces west, with large windows, brick walls, and a flat black rubber roof.

    The heating system kicks butt, of course. Gas hot water boiler with a gas furnace to back it up, and just in case there are electric strip heaters everywhere.

  2. #2
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,330
    Quote Originally Posted by p38fln View Post
    Are there any mini-split units that can use a 'real' thermostat? I want to be able to use a commercial thermostat with temperature lockouts with it so that there's no abuse and no one makes the building's heater fight the mini split unit.

    A little background - the building is in Superior, Wisconsin where the design temperature is 76 F for the summer (and something like -27 F for the winter). State law says that the AC can't be designed for more than the design temperature... the problem is it gets well over 76 F for at least a month every summer, several days in the mid 90's. So the system could barely keep up as it was, and now we've added more users and workstations to one of the rooms that was already marginal at best. And the room faces west, with large windows, brick walls, and a flat black rubber roof.

    The heating system kicks butt, of course. Gas hot water boiler with a gas furnace to back it up, and just in case there are electric strip heaters everywhere.
    Why not use a mini split that utilizes a control that can be locked. I know Mitsubishi's have them.

  3. #3
    Join Date
    Jul 2003
    Location
    Massachusetts
    Posts
    288
    We service a church that has about 8 mini's controlled by one commercial stat. Once a call is initiated, each mini then energizes from individual relays in an electrical room. Then they react to their individual remotes which are mounted on the opposite wall. The first time I went to this location, I was not aware of the setup. That was fun.

  4. #4
    Join Date
    May 2009
    Location
    Superior, WI
    Posts
    25
    We already have 3 mini-splits - a "real" Carrier, a Bryant/Carrier (It has both stickers on it...), and a Mitsubishi - every one of them seems to have a thermostat that goes with the 'kind of more or less maybe' approach.

    I guess another question - any other ways of cooling off a small area with a lot of people in it? I used a portable unit with two hoses to cool off an auxiliary server room, I just don't have that kind of floor (or wall) space in this room. All I have is ceiling.

  5. #5
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,330
    Quote Originally Posted by p38fln View Post
    every one of them seems to have a thermostat that goes with the 'kind of more or less maybe' approach. What is that? Could you be elaborate.

    I guess another question - any other ways of cooling off a small area with a lot of people in it? I used a portable unit with two hoses to cool off an auxiliary server room, I just don't have that kind of floor (or wall) space in this room. All I have is ceiling.
    You can use any system that is sized for the people load you expect. All those manufactures make ceiling mounted mini splits. What do you have to handle the primary cooling of the building?

  6. #6
    Join Date
    May 2009
    Location
    Superior, WI
    Posts
    25
    Sure - none of them can get the room temperature anywhere near what it says on the display. The Carrier/Bryant unit almost always cools to 10 degrees above the set point - if you set it to 63, it will be 73. if you set it to 73, it will be 83. Sometimes, it actually cools off to the set temperature... we finally told the people in that office to turn the AC off if it was cold and turn it back on when it got hot.

    The Mitsubishi overcools - set it to 74 and it will be 68 in there (sometimes, it decides that 74 means 78 though, just depends on the mood its in)

    The older Carrier also over cools, frequently 5-10 degrees below the setpoint.

    The primary cooling in the building is a 10 ton Trane Voyager rooftop unit that just doesn't have enough oomph - and no one can make it any stronger due to Wisconsin not allowing anything stronger than schedule M/J calculations, which state that the design temperature for the area is 76 degrees, which absolutely sucks when it's 95 outside - usually only for a week every year, but oh that smell...brings back memories of high school gym class.

    At 76 degrees outside, it can maintain 74 inside with both compressors running on the roof - and it's pretty much a 1 for 1 temperature increase inside after that

  7. #7
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    17,921
    As long as you guys are working on living within your means, you might consider repealing any legislation that dictates human suffering as a legal requirement.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  8. #8
    Join Date
    May 2009
    Location
    Superior, WI
    Posts
    25
    Hah well we're a trucking company so we have plenty of other regulations that dictate human suffering - they all seem to start in California and spread like the plague. The one that causes the most aggravation is the anti-idle law for the truck drivers - no matter how hot it is, no idling the engine unless the truck is rolling. No running Auxilliary power units unless the truck is rolling in some cities either - and the drivers sleep in the trucks, so we're not talking about a convenience issue. That's a much bigger concern to me than the office staff having to work in an 80 degree environment - but nothing I can do about it. As far as I can tell, most of the truck drivers just idle the trucks anyway and hope that the police (who are sitting in an idling car watching for the idling trucks) will be too busy to write the $1000 (or more) ticket.

  9. #9
    Join Date
    Sep 2006
    Location
    Laurel, MD
    Posts
    1,472

  10. #10
    Join Date
    May 2009
    Location
    Superior, WI
    Posts
    25
    Thanks that looks like what im after

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