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Thread: Mini split question

  1. #1
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    Mini split question

    I have done a lot of research lately on mini split systems, but I have been unable to find an answer, hoping someone has dealt with this. Let's say you have a 24x30 shop, in the shop you have a 8x10 office. Without buying 2 head units (18,000/9,000 btu), how would you go about having the heat/AC into the office space with just the 18,000 btu unit.

  2. #2
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    Open the window and door into the shop. Have a vent fan through the wall between the two. Or install a bathroom vent fan in the office ceiling to draw in the outside cooled air from the shop.
    Bill D

  3. #3
    They have mini split systems that have one distribution box that feeds several remote units to various rooms according to the needs of each individual room.
    Lee Schierer
    Captain USNR(Ret)

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  4. #4
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    Lee, do the mini split systems that have multiple heads also have individual thermostats? Setting only one thermostat would make the office very cold in the time it takes to cool down the shop area.

    I have two mini split systems in my two story shop. One the the upstairs office and one for the shop area. I can see why Bryan needs something a little different.

  5. #5
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    I know 1 outside condensing unit can serve multiple rooms if you buy the remote units. For instance a Mr Slim DIY unit is $1700 for a 18k btu if you bought a second remote unit 9k btu the price would be $2600. This is what I'm looking to avoid, because $900 seems waisted in such a small place, when and 18k unit should be plenty big enough based on calculators I have used, to do the entire space. Maybe if you built a section of the partition wall with small server fans you could get enough airflow to cool the office portion.

  6. #6
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  7. #7
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    I have a 2 story building, about 750 sf per floor: my office / pool table on the second floor, shop on the first. The second floor has a Mitsubishi split system and in the summer I put a box fan at the top of the stairs and blow cooled air down into the shop. If it's 90 degrees out, the shop stays at about 75 or so. (NW Indiana) For the winter, I put a duct at the ceiling of the second floor with a blower that sucks the hot air off the ceiling and dumps it down into the shop. Works well enough that I only need the electric heater in the shop on really cold days.
    If it wasn't for the "last minute", nothing would ever get done.

  8. #8
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    Clearly, the only solution without having a second interior unit for the office is to provide pathways for heated/cooled air to get into the office and vice versa. For noise reduction the pathway(s) cannot be direct, so something that's fan driven to move air into the office with an indirect path as well as an indirect return will be necessary. What this solution lacks is the ability to have full control over the actual temperature within the office when it's closed off from the rest of the shop. It's going to be what it is based on multiple complex factors including where the indoor unit is on the wall relative to the office space and how the air is conditioned near the inlet to the office.

    The bottom line...you can do it with something like I described, but "best" technical environmental results would be with separate indoor units where you can have full control of the temperatures of the office and the shop separately.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #9
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    The system I am looking at has head units that talk to each other and adjust based on their shared zone conditions. I will have a storage / parts area. This area will have 8 foot walls versus 10 foot walls elsewhere. The HVAC guy has offered that a couple of fans, one in and one out, should circulate the cooled air from the main shop enough to make that area usable without the addition of another head. Sub-optimal but, that area will experience limited, targeted use so that is the plan at this point. I have a couple of the 1980's Vornado circulators that have been going strong for decades. I hope they never die despite the lifetime warranty. The newer units are OK but, not really comparable. For your size space you wouldn't need that kind of air movement. A decent 20" or two on low speed should circulate things nicely.
    Last edited by glenn bradley; 05-31-2020 at 10:10 AM.
    "The Danish government believes that if we train 5,000 designers, and produce
    one Hans Wegner, the money is very well spent." - Ole Gjerlov-Knudsen

  10. #10
    Check these Airshares out. Tjernlund (pronounced Chern-lund) is an excellent outfit and I have used thousands of these fans successfully on large jobs. For your use I would simply run it on a switched outlet.
    https://www.tjernlund.com/airshare_ventilation.htm

  11. #11
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    Ask yourself how much dust in the office are you willing to put up with?
    That will guide you in what to do

  12. #12
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    https://www.acwholesalers.com/coolin...ni-splits.html

    There appears to be several options

  13. #13
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    Thanks for all the input, really it comes down to dust mitigation and cost.

  14. #14
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    Quote Originally Posted by Bryan Lisowski View Post
    Thanks for all the input, really it comes down to dust mitigation and cost.
    And noise mitigation, say if you have a CNC working that you are watching through a window removed from the noise. But yea, dust counts big time!
    --

    The most expensive tool is the one you buy "cheaply" and often...

  15. #15
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    If I ever got to the point of having a CNC Jim, your right noise could be a factor. I still think I would struggle with the learning curve.

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