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Thread: A/C in the shop

  1. #1
    Join Date
    Dec 2010
    Location
    Southeast Michigan
    Posts
    358

    Default A/C in the shop

    Didn't see much on the subject after searching the forum, so I'll post something.

    My well insulated 28ft x 30ft detached garage/shop is in southeast Michigan where the heat and humidity is frequently quite high in the summer months (90deg, 90 humidity) making it too uncomfortable to work in the shop, not to mention condensation on the machines and tools.

    The shop is heated with an overhead furnace so I got that already covered in winter.

    I've been debating with myself about purchasing one of those DIY mini-split HVAC systems. They're significantly cheaper than a professionally installed mini-split (got a quote for nearly $4000 recently)

    We recently joined Costco where the Mr Cool 18,000btu unit was just a shade over $1300 tax and shipping included. All the reviews all over the web are positive, so I bit.

    I got on Youtube and watched a lot of videos of the installation. The hardest part is drilling a 3-1/2 hole through the wall for the line set between the condenser and the air exchanger. There was a even a video of a girl installing one, fer crying out loud! If a girl can do it, I can do it!

    It'll be here in a week. I'll post progress and pics.
    Last edited by jmarkwolf; 05-24-2019 at 08:17 AM.

  2. #2
    Join Date
    Oct 2014
    Posts
    469

    Default

    For a "well insulated 28'x30'" shop I would think a simple window AC would be just fine. Even if you make a special "port" in the side of the building for it.

  3. #3
    Join Date
    Aug 2009
    Posts
    6,568

    Default

    Quote Originally Posted by wdtom44 View Post
    For a "well insulated 28'x30'" shop I would think a simple window AC would be just fine. Even if you make a special "port" in the side of the building for it.
    Yes, but how many BTU's ?
    My shop is about that size, slightly bigger. I tried a 5000 BTU window unit one year and it didn't make a bit of difference. I run a dehumidifier during the summer and that takes care of the humidity. I can deal with mid to upper 80's for a couple months.


    JL...............

  4. #4
    Join Date
    Jul 2011
    Location
    Medford MA
    Posts
    637

    Default

    Quote Originally Posted by wdtom44 View Post
    For a "well insulated 28'x30'" shop I would think a simple window AC would be just fine. Even if you make a special "port" in the side of the building for it.
    It looks like the unit is a heat pump, which means he’ll be able to heat with it in the winter as well.
    That can be a lot cheaper than some other heat source such as oil or gas.

    Frank

  5. #5
    Join Date
    Mar 2015
    Posts
    3,912

    Default

    I had a Mitsubishi split AC unit installed for $2400. Wish I did it much sooner.

  6. #6
    Join Date
    Sep 2008
    Location
    WI/IL border
    Posts
    2,318

    Default

    My shop occupies a former insulated 2.5-car garage in WI. While we cannot live without AC in the house, there is no need for cooling in the shop. It always feels cool enough for comfortable work (maybe except for a couple of days per season when the temperature is above 105F). Our climate is the same as yours, of course. The shop is in the woods, but still open to the direct sun most of the day.

    What contributes to the comfort the most is my dehumidifier. It's used in there 24/7 during warm season to keep Rh at about 50%.
    As you understand, 85F at rH=50% feels much more comfortable than even 75F at rH=80.

    Of course, an AC will dry the air too, but consume more power, so running it 24/7 to keep your shop dry will be hard to afford.
    Last edited by MichaelP; 05-24-2019 at 08:58 PM.

  7. #7
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
    Posts
    5,574

    Default

    I just put in AC for the house late last summer so I'm ready for our few weeks to two months worth of peak heat... which sounds roughly like what you get on a typical day at your location.

    Your shop is 840 sq ft. And running an AC calculator for that area based on an 8ft ceiling for "average" temperature and "average" house grade insulation came back with a suggested 19,800 BTU. So that Costco unit at 18,000 BTU sounds like a good solution.

    Doing a quick check I did see some "window" style units that run up to around 15K BTU. But these higher output units are up there in price and weight. And likely you'd want to run a port in the wall as suggested above if you had gone that way.

  8. #8
    Join Date
    Jul 2014
    Location
    Southern Indiana
    Posts
    496

    Default

    I am down in southern Indiana, in the Ohio river valley, where it can be in the high 90's or sometimes 100 degree with 95 percent or more humidity. My shop is an insulated (2" fiberglass) that is 24' x 36' x 12' metal building. I cool it with a 29,000 BTU window unit. It cools the shop quite nicely, sometimes in the high 90's makes it run a lot. Mine is a Whirlpool unit that I don't think they make anymore. It was new when I started the shop. Not sure what to replaces it with when it shoots craps.

    Sarge41

  9. #9
    Join Date
    May 2002
    Location
    SE Texas
    Posts
    12,473

    Default

    I am in south Texas so this may not be directly applicable.

    Those AC calculators are OK for a den or a bedroom or even a whole house, but they can fall short in any area where a lot of electricity is used. Any electricity used in an enclosed area ultimately becomes HEAT in that area. So, it may not be as bad as some of the places that I have had to keep cool (note below), but in an area like a shop at least some allowance must be made for the electrical usage. You can add up the typical electrical loads or use a clamp-on Amp meter to get the current draw. Current X Voltage = Power. And power can be converted to BTUs.

    https://www.bing.com/search?q=power+...ZI&form=MOZLBR

    I would use an average power usage number and add it to the AC calculator you are using.

    My shop is in a two car + garage. I started with a 8000 BTU window unit and it was totally inadequate. I moved up to one around 15K or 16K BTUs and it also did not cut the mustard. I finally got a 22K BTU unit and it worked. I got one with heat so I could also work in the winter months. It is a window unit and it required the installation of a 230 Volt circuit. The 15K unit that I had in that window was straining the limits of the aluminum window so I built a wood support for the 22K unit. That support is bolted to the foundation so that takes the entire weight and the window is now doing just fine.

    That unit lasted about 5 or 6 years but now needs to be replaced. Probably my fault due to some questionable cleaning practices. I will be purchasing a new 22K unit in a few days, before summer gets here. My wife is getting a bit testy about the fan in the laundry room door.

    Note: In one instance I had to keep an interior area of the building where I worked COOL in Iowa winters where I have seen the outside temperature drop below -20 F. That was a challenge because AC units are not designed for winter use. This need was totally due to the amount of electricity used inside that area on a constant basis.



    Quote Originally Posted by BCRider View Post
    I just put in AC for the house late last summer so I'm ready for our few weeks to two months worth of peak heat... which sounds roughly like what you get on a typical day at your location.

    Your shop is 840 sq ft. And running an AC calculator for that area based on an 8ft ceiling for "average" temperature and "average" house grade insulation came back with a suggested 19,800 BTU. So that Costco unit at 18,000 BTU sounds like a good solution.

    Doing a quick check I did see some "window" style units that run up to around 15K BTU. But these higher output units are up there in price and weight. And likely you'd want to run a port in the wall as suggested above if you had gone that way.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  10. #10
    Join Date
    Oct 2006
    Location
    Ivins, Ut
    Posts
    1,456

    Default

    Good luck with 18,000BTU. My shop is the same size, the temps here are hotter but the humidity lower and my 24,000BTU unit barely keeps it in the high 70's. Good enough, but no room to spare.

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