Mr cool mini split DIY
I recently had built a 30x60 metal building with 14 ft sidewalls. Had it spray foamed 3” on ceiling and 2” on walls.

Last Friday I put a 36000 btu DIY mini split in.

Not a difficult installation running the line set was the most challenging as they are fairly stiff.

It works great to cool my shop, seems to be keeping it pretty close to 72-74 even with temps up to 91 outside

It did pull between 20 and 30 gallons of water out of the air the first 3 days, so carefully consider condensation tube placement if you put one of these in here in east Texas.

1800 sq feet is on the high side of what they suggest for this unit, but it’s keeping up well I suspect the spray foam is really helping with that.
Just for grins, I plugged your dimensions into an online BTU calculator that I used to estimate the heating needs for my shop.  I guessed at a desired 25 degree temp differential.  It showed that you would need about 31.2K BTUs to cool that size space if the space is well insulated with few leaks.  It sounds like your shop fits the bill.

Sometimes I think I'd like to cool my space (25 x 44 with 12 foot ceilings).  But I have two large overhead doors; they're insulated, but still leak quite a bit.  Plus, I'd have to consider that AC for my shop is a pure "luxury".  Heat a necessity in the upper Midwest, but AC not so much.  The needs are probably reversed in East Texas.
3 tons. Does that really qualify as a "Mini" Split?
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(05-31-2019, 04:47 PM)Snipe Hunter Wrote: 3 tons. Does that really qualify as a "Mini" Split?

             Yes in TX 3 tons is still considered a small unit. My shop it a 20x40 8' eaves metal building. Conventional metal building with pipe posts and 2x2 steel welded in a 5' on center grid and roll fiberglass insulation.
       I have a 2 ton window unit and it works well IF you let it run and keep the shop cool. When summer hits and it's 117* and humid and you want to to work in the shop you will need to start it the night before the afternoon you want to work in the shop. The problem with metal buildings is that the sheet steel is connected directly to the steel framing. This crushes the fiberglass insulation there and creates a really good thermal bridge so the framing acts are radiators heating in the summer and cooling in the winter. 

    If you want a conditioned building and  use a steel building you have to spray foam it and all the framing has to be covered in 2" of foam. This means basically you need to build an internal wood wall to support anything you want to hang on the wall. If I were to build another shop I would probably wood frame it and then cover it in steel. That makes the thermal bridging a comparitive non issue. I do plan on adding to the shop but am on the fence as to if I want to keep it all steel or wood frame the addition which will be a paint booth basically.

        The Mrcool units are pretty nice. I have installed Pridiom, LG and a few off brands. Most even the name brands seem to use some of the same parts and steel and most use the same compressors. The fittings they use on the lines are Marine fittings that require no vacuum pump etc. My dad wants a minisplit in his garage and I may go that way for convienence though it is a little more expensive.
I had not heard of these until now. Looks like an affordable unit,
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
I saw one of these at a pizza joint we went to a few weeks ago.  It was cranking it out.  We were there a couple of hours watching a friend play and it seemed to work well and was very quiet.  I've been seriously considering something to heat/cool my shop.

(06-01-2019, 12:56 PM)Mr Eddie Wrote: I saw one of these at a pizza joint we went to a few weeks ago.  It was cranking it out.  We were there a couple of hours watching a friend play and it seemed to work well and was very quiet.  I've been seriously considering something to heat/cool my shop.


           They work extremely well and most are quiet. The issue with them is the filter. The cheaper brands will only have a filter like a window unit has. It will keep the big dust bunnies out but will not catch the normal crud floating around the house. The better units have larger filters and sometimes two and can be replaced with much better filtering units. This is one area that I see people not check before buying a mini split. 

         We had two in one of our airB&Bs in Greece and it was wonderful having one in the bedroom. I set it at 20c and slept better than I have in years. I want to put one in the kitchen as in TX you don't cook much in the summer cause the AC cant keep up well when cooking. Also thinking one in the new master bedroom so it can stay nice and cold at night for better sleeping.

           Often for a shop the best bet is to go with a package unit. You set the whole thing outside. Run power and gas to it and an intake and return duct. Takes up no room inside, easier to mount than a window unit and easy to add better filtration and ducting and it is much quieter as it's all outside. I would prefer a package unit in our house to a conventional upflow...
I can see the utility of a completely contained outside unit for air filtration reasons, but the cost savings putting in the mini split outweighed wanting better air filtration.

As it is now, the unit does a great job of getting the temp at the floor where I want it so comfort is great.

I do have an old furnace squirrel cage fan set up as an air cleaner that I have placed in front of the mini split to help circulate air while I am in the shop, while this isn’t necessary, it does decrease the time it takes for the unit to get the shop comfortable.

I am finding it really easy to use the phone app to set the temp to 80 or so when I am at work. When I am about to leave work, if I plan to spend time in the shop, I just open the app, reset temp and set it on Turbo. 20-30 min later, it’s comfortable.

Overall, I am happy with the mini split from a cost and function perspective.


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