Installing Summer Garage AC – MRCOOL Split System

Working in the garage had sweat dripping off of my face after a few minutes of starting a project. The heat had to go! I learned about ductless mini split systems and how easy they were to install without hiring anyone. I found a few kits on amazon that were sold specifically as DIY versions, but costed a bit more than the non-DIY versions. I found a scratch/dent MRCOOL Advantage 24k BTU unit on ebay. The previous owner left behind a spare concrete pad outside the garage utility door which I commandeered for my own purposes:

Installing ductless systems like this one was pretty simple. Drill a hole in the wall where the A/C lines will go, mount the indoor unit to the wall, then run the A/C lines to the outside unit!

The indoor unit, attached on its mount, with coolant lines running through the wall

I ran new electrical to the unit. I only needed 120V for this heat pump, but I ran enough to run a 240V unit just in case the need arises in the future. I quickly learned how hard it is to run THWN wire through conduit, especially when I didn’t use 90 degree sweeping connectors.

Electrical box and lines roughed in. I learned after installation I could have used a sweeping 90 degree bend.Make sure you have your favorite beverage available while working!

The DIY versions of the MRCOOL units come with a copper lineset that is already evacuated, which saves the installer from needing an vacuum pump to do it during installation. I decided to save some money and purchase a vacuum pump kit and do it myself. I watched a handful of youtube videos and did a few trial runs. The copper lineset ends had to be flared so they could mate correctly on the heat pump. I tried the flaring tool at my local hardware store but couldn’t get it to work correctly. Probably a little operator error, probably a little $5 Chinese tool couldn’t cut it. I purchased a better flaring tool and practiced a few dozen times to get comfortable. From what I read online the leaks are most likely to happen at the connectors, so I tried to make sure I got them correct the first time.

Pulling a vacuum and waiting a few hours to see if the vacuum holds.

Admittedly using a gauge like this isn’t ideal to test for a vacuum, but I let it sit for several hours to make sure it wasn’t leaking. I also didn’t have a tank of nitrogen on hand to purge the lines before either.

After the vacuum held for several hours I let coolant into the system by unscrewing the stopper on the outside of the heat pump. Pressure built inside the lines, which I also monitored for a few hours to make sure they weren’t dropping. I put soapy water on all of the connectors to check for bubbles but didn’t find any!

Coolant released into the lineset, time to test!

Now what I had been waiting for since I moved into this house:

54°F air blowing down on me!

One minor downside of this system, the thermostat that controls the system is not wired, it uses IR to set the temperature, turn on/off. Very annoying!

MRCOOL thermostat above the gas fired garage heater thermostat

Every time a change to the system needs to be made the thermostat has to be removed from the wall and pointed at the unit first. This damn thing has wifi, but not a wireless controller??

Back outside I finished up the lineset by covering it with a hide-a-line kit and getting the electrical pvc conduit attached to the siding. I might have taken the amount of drop the condensate drainage pipe needed, but it certainly won’t get clogged up with that amount of fall!

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