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Slippery GRM+ Memberand UberDork
4/15/21 9:05 a.m.

I have been on the fence about installing a mini split in the garage for a few years. I spend a lot of time there and it can get extremely hot 9 months out of the year. Opening the door doesn't work here as there is no breeze and the bugs will eat you alive at night. 

I have a three car garage, 660 sqft with insulated doors. I usually open the door to the house and let it cool down with the house AC for a while before I go in, a fan is still a must. I also thought about a ceiling fan, like my brother, but seemed too much work for not much roi. 

Browsing through the Costco website, I finally gave in and took the plunge. 18k BTU Mr. Cool DIY Mini Split. It just happened to be that there is a $300 federal rebate, so that was an added bonus. 

captdownshift (Forum Supporter)
captdownshift (Forum Supporter) GRM+ Memberand UltimaDork
4/15/21 9:12 a.m.

10/10 would do.

mtn MegaDork
4/15/21 9:17 a.m.

Let me know how the install is. We're considering one for my parents lake house. We have portables now, which work fine, but are annoying. What I'd really like is for us to just replace 2 windows in the place and use some window units, but that is not happening.

frenchyd GRM+ Memberand UltimaDork
4/15/21 9:29 a.m.

In reply to mtn :

I used 3 mini splits in my 5500 sq ft house.  Went in very easy.  

Slippery GRM+ Memberand UberDork
4/15/21 10:23 a.m.

Two days later Jim, my UPS driver delivered the two biggest boxes I have ever seen UPS carry. 


Luckily my wife was home and she had him help her put them inside. Jim is great. 

jwagner (Forum Supporter)
jwagner (Forum Supporter) GRM+ Memberand Reader
4/15/21 4:36 p.m.

I'm in Wisconsin and installed one of those about a year and a half ago.  It was installed to heat the garage, and it does make it a lot more usable when it's cold out, although it doesn't work all that well below about 20 degrees.  I was surprised at how much nicer it is to work on the cars when it's hot and muggy.  Makes a huge difference to get the temp down but even more so the humidity.  No more being soaked in sweat while wrenching.  Also works well to keep the garage at the right temp in March and early April to make Kolsch.  BTW, my garage is not insulated.

Still need to find a line cover that fits for the outside of the garage, maybe this summer...

Slippery GRM+ Memberand UberDork
4/15/21 9:14 p.m.

In all honesty, once I got it I just opened the boxes and did not even read the instructions. I think by then I had watched about 20 different youtube videos of people installing this brand Mini Split. 

In retrospec, I should have read them. I have the gen 3 unit and it seems that its a pretty new unit so some of the videos differed a bit. Not a huge deal. 

First thing was to figure out where to mount the inside unit. My garage is basically a rectangle offset from the house, red below. That meant that to simplify my life I could use either walls A or B for the inside unit, and A for the outside unit. I would need to drill a 3.5" hole through block wall on either of the blue parts. 

Slippery GRM+ Memberand UberDork
4/15/21 9:16 p.m.

There was ready a 3.5" drilled through the wall at one point, so that's where the inside unit went. 

It's not centered, but it will have to do. 

At that point the wall transitions from CBS to drywall, and therefore there is about a 1" step. So I had to find a way to make the two surfaces match.

The unit comes with a cardboard template to drill the wall and show you where to mount the wall bracket. I used a piece of plywood I had and cut it to match the cardboard template on the CBS side of the wall. 

Once the wall was leveled, the bracket went on and then the inside unit while fishing the hoses through the hole. 

The system comes with a liner for the hole, its angled slightly towards the outside, so I had to chip off some of the block. I the filled the extra space between the liner and block with expanding foam. And caulked around the outside cover. I will later paint the wall.  


Slippery GRM+ Memberand UberDork
4/15/21 9:41 p.m.

At this point I realized I did not want to deal with making a base for the outside unit so I ordered the wall bracket along with the line set cover. The bracket was $50 and the cover $80, got them both from Ingrams online. 

Bracket mounted to the wall right on the other side of where the wall unit went. 

Unit on the bracket:

Had to make a quick run to Home Depot and buy some bolts to mount the unit to the bracket as those where not included. 5/16 bolts, washer, nuts did the trick. 

From here you connect the lines between the outside and inside unit. The lines have rubber o-rings and are quite simple to connect, they are full of freon. Once connected and the pressure in the system released, I took a sprayer bottle with soap and water and checked for leaks. Once you determine that its all good, you cover the connections with some sound deadening material and line it all up with some vinyl tape they send you. The vinyl tape is a royal pain as it does not have glue on it. 

I then installed the line set cover and that left me with the electrical connection. For the electrical wide, I run conduit from my outside main box as there where a few slots left. That made it easier as the power goes to the outside unit, which in turn powers the inside unit with a provided wire attached to the inside unit. 

Slippery GRM+ Memberand UberDork
4/15/21 10:24 p.m.

The inside unit mounted. 

It's slightly offset to the right, but that is OK given that I did not have to drill a hole in the brick and I usually work on that side of the garage. 

Slippery GRM+ Memberand UberDork
4/16/21 10:33 a.m.

The unit has only been up and running for about a week, and it has not been really hot here. I can still tell that it was money well spent. 

I will probably get to test it tomorrow as it looks like it will be in the 90s. 

Its WIFI so you can turn it on and off remotely and monitor all the functions. I downloaded the Mr. Cool DIY app but found that it was very basic. 

Luckily there is a different app from a third party, MrCool SmartHVAC, that has many more features, from geofencing to being able to track its usage. I am sticking to that app. 


Slippery GRM+ Memberand UberDork
4/18/21 7:44 p.m.

So far my thoughts after a hot weekend. 

- I should have done this 5 years ago, maybe 10. 
- Its extremely quiet. 
- Makes a huge difference when it comes to humidity. 

Install was quite straight forward and easily doable in one day if you have all the parts lined up. 

Below is the settings I kept it at all weekend. I plan on leaving it like this for the time being and check how much electricity it consumes. I doubt the electric bill will increase significantly.

rob_lewis UltraDork
4/18/21 8:23 p.m.

TIL what I mini split was.  I've kicked around adding A/C to my garage but didn't want to reduct my home A/C and since the garage doesn't have windows, figured I've have to cut a hole in the wall somewhere.  This seems like a much better solution.


MazdaFace (Forum Supporter)
MazdaFace (Forum Supporter) Dork
4/18/21 10:06 p.m.

Nice! Man my dad did this in his shop with 3 units and in texas its an absolute game changer

Toyman01 + Sized and
Toyman01 + Sized and GRM+ Memberand MegaDork
5/17/21 8:12 a.m.

Nicely done. I've installed 5 mini-splits over the years. I've been happy with all of them. 


grover GRM+ Memberand Dork
5/17/21 2:46 p.m.

I put one of these in our garage apartment also in wpb. It was pretty amazing and only used a 20amp breaker as I recall. I bought mine off of Craigslist from a guy in Miami who had a warehouse full- a little sketchy but I was doing a home reno and trying to save money. I'm glad this is working for you!!

Lof8 - Andy
Lof8 - Andy GRM+ Memberand SuperDork
5/19/21 12:29 p.m.

Wow, perfect timing.  I'm looking to do the same thing here soon.  Glad to hear you're happy with the results!

Jesse Ransom
Jesse Ransom GRM+ Memberand UltimaDork
5/19/21 12:46 p.m.

Congrats! Nice to hear another success story! I'm already pretty well decided that this is the ticket for the new shop, but every bit of confirmation helps...

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
5/19/21 12:48 p.m.

VERY nice. 

I had a electrical conduit line installed in my wall when I had the shop built so that I could put in a mini-split one day. I'm hoping for a unit that heats and cools (even in Chicago winters).

I got a little scared off of the 'precharged' units because they seem to good to be true - honestly why are the DIY units 1k when the professional units are more like 5k?   

Toyman01 + Sized and
Toyman01 + Sized and GRM+ Memberand MegaDork
5/19/21 1:27 p.m.

In reply to Robbie (Forum Supporter) :

Mark up.

The Chinese company makes them for $1000. Sells them to an importer who sells them for $2500 to a distributor. The distributor sells them for $4000 to your installer and he sells it to you for $5000. 

Or, the Chinese company sends a family member over to set up a US importer. They sell directly to the public for $1500 or to someone like mrcool.com for $1000 and he sells it to you for $1500. 

malibuguy GRM+ Memberand HalfDork
5/20/21 7:03 a.m.

that is great.  My parents had one (mitsubishi iirc) added to their remodeled attic space and it works well.

I have thought about trying to find an old hotel hvac to retrofit into my garage but I rarely do anything in there these days, I just do all my work at my shop.  Plus my garage needs a whole lot of work 

jimbob_racing SuperDork
5/20/21 7:21 a.m.

In reply to malibuguy :

Sounds like you're talking about a ptac unit. They're fairly inexpensive and usually have a heater function. I've been leaning towards one of them to make a sunroom more comfortable year round here in Western Pennsylvania.  

I've wondered alot about the difference between a name brand mini split at $5k versus a do it myself system for $1k to $1.5k. 

Slippery GRM+ Memberand UberDork
5/20/21 10:37 a.m.

In reply to Robbie (Forum Supporter) :

I am not sure what the difference is, but I asked my AC guy for a ballpark number on a mini split installed and  he said I was probably looking at $4k for a Mitsu unit. I figured if this one is sold by Costco, then it has to be good. As soon as I received it I opened and looked at all the fittings and they looked to be of high quality, so I decided to keep it. 

So far it has been working great and its so quiet you do not even notice it. I have been keeping unit set to turn on at 81 and off at 77, but last Friday I set it to 74 as I was going to be working in the garage that weekend. It cooled it down with no problems, it was actually cooler than the house. 

This one has both heat and cool functions, I don't think I will have to use the heater here. 

I would definitely do this again. 

Slippery GRM+ Memberand UberDork
5/20/21 10:40 a.m.

The one thing I did not like was the length of the pre-charged lines. I wish they had a couple of different options. 

I read a bunch of installs and everyone says not to coil up the excess vertically like I did, it should be left parallel to the ground. I did not like how it looked on the ground so I just went for it, if anything happens I will get my AC guy to cut them to length and resolder them and charge it again. 

thealbatross New Reader
5/20/21 10:44 a.m.

I've been thinking about this lately too, also in Florida and wondering how effective it would be. I have a few questions about insulation: you mentioned garage door insulation, do you just have the kind you buy at home improvement store and DIY install? Do you have insulation in the ceiling/attic above the whole garage? Do you have any added insulation on the inside of your concrete block walls?

Trying to gauge how much insulation I'd need for something like this to be effective in the Florida heat! Thanks.

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