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DIY Mini Split Installation [Mr Cool DIY 18k]

In this DIY mini split installation tutorial, I show you how to install a DIY mini split (Mr Cool DIY 18k) for temperature and humidity control in a workshop or garage.

Tools I Used




DIY Mini Split for Workshop and Home Office

Essentially, my workshop is a separate building from my main house and it has 2 levels.  

The first level is my workshop and the second level is my home office.  In turn, I decided it was best to remove the original HVAC system.  

Ultimately, It was very old and not worth the cost of repair.


Home Office & Workshop

First, I decided to install a DIY mini split in my home office during the fall of 2016.  

After many hours of research of DIY min split installation articles, I installed the Mr Cool DIY 18,000 BTU 1.5 Ton Ductless Mini-Split Air Conditioner and Heat Pump (model:  DIY-18-HP-230A) for my home office.  

At this time, I did not worry about cooling or heating my downstairs workshop because winter was coming.  

Furthermore, I decided to test the performance of the ductless mini split in my home office before deciding on a cooling and heating system for my workshop.

Ultimately, I was pleasantly surprised with the performance of the DIY mini split in my home office.

As a result, I decided to purchase the same unit for my workshop.


MRCOOL DIY Ductless Mini Split Installation

I chose the Mr Cool DIY 18k (model DIY-18-HP-230A) because of the price, features, size, and it is 100% DIY.

Obviously, MRCOOL DIY mini splits are DIY units as the name implies.

In addition, the refrigerant lines are pre-charged with R410A refrigerant.  In turn, this reduces the need to hire a professional for the installation.

DIY Mini Split Price

The total price for the Mr Cool DIY Mini Split Installation was $1,457.00 plus $50.00 for the wall mount bracket.  

In total, the price was $1457.00 before tax as of 2017.

I received multiple quotes from HVAC professionals on installing a similar unit to the Mr Cool DIY-18-HP-230A and the prices ranged from 2.5 to 3 times more than the Mr Cool DIY mini split.  

HVAC Professionals

Keep in mind, there are certainly many reasons and advantages to hiring an HVAC professional to install a mini split or conventional system. 

However, this was my workshop and home office and not a critical conditioned space.

As a result, I decided it was worth the risk to buy the DIY mini split unit and install it myself.  

If I were faced with the same decision for my home, I probably would have chosen to hire an HVAC professional.  

Ultimately, Reputable HVAC professionals guarantee their installation, support manufacturer warranties, and provide service agreements.

In addition, Mini Splits versus traditional central HVAC systems are beyond the scope of this article.

If you are faced with this decision, I encourage you research these topics and decide what is best for your situation and environment.


Mr Cool DIY 18k Mini Split Features

The features of the Mr Cool DIY mini split supported my needs even though it may not have the features of more expensive brands.  

Below are the features I like most:

  • Dual heat pump and AC unit.
  • Refrigerant leakage detection system ensures the system operates efficiently without degradation due to corrosion.
  • WiFi adapter allows it to be connected to the Internet and controlled remotely via an app.
  • Warranty: 7 year compressor and 5 year parts.
  • Low Noise:  57dBA decimal rating.
  • Variable Speeds
  • Louver Position Memory and Swinging capability.


Mr Cool DIY Mini Split Sizing

Obviously, There are different Mr Cool DIY mini split models for different size areas.  

Additionally, the Mr Cool DIY mini split model I purchased and installed covers 850 square feet.  

I was concerned with the 18′  high ceilings in my workshop, so I purchased this unit which covers more square feet than my workshop. 


How to Install a Ductless Mini Split Overview

Keep in mind, this DIY tutorial is not meant to replace the manufacturer’s instructions.

Rather, it is a supplemental video guide to the manufacturers instructions.


Unboxing Mr Cool Ductless Mini Split

First, I ordered the Mr Cool DIY mini split online and it arrived in 2 boxes:  the outside condenser unit and the inside unit.  

Ultimately, both boxes were packaged very well.  

Next, I inspected each part for damage very carefully.  

Then, I carefully inspected the refrigerant hose which was wrapped with a plastic coating and tie wraps.

Mr Cool DIY 18k Unboxing


Assemble Wall Bracket

I purchased the wall mount for the outside condenser unit separate.  

Ultimately, I chose the wall mount option rather than mounting the unit on a slab.  

Moreover, it is easier to assemble the wall mount bracket before installation rather than in the middle of the installation.

DIY Mini Split Wall Bracket Assembly


Mount Inside Unit

First, I used the metal bracket and cardboard template to mount the inside unit.

DIY Mini Split Inside Unit Bracket Assembly


Before proceeding, I attached the drain hose and checked for any links by running water through it.

Essentially, I chose to mount the inside unit at the back wall of my workshop below the staircase.  

Under normal circumstances, the inside unit is mounted directly to a wall, but the back wall in my shop is not ideal for air flow.  

In addition, The back wall provided convenient access to the back of my workshop and the electrical junction box.  

So, I constructed a wooden support frame that matched the cardboard wall template and securely mounted it to the underside of the staircase.

DIY Mini Split custom bracket


Next, I slowly bent the refrigerant lines to match the location where I planned to drill the exit hole – straight back.  

Also, the refrigerant lines can exit the unit to the right, left, or directly back (default is left).

Mr Cool DIY 18k flex refrigerant Pipes


Next, I examined the plastic latches.  The plastic latches were not broken or damaged.

Mini Split Inside Unit


Then, I lifted the unit and set it on the metal bracket.

Mr Cool DIY 18k Mount Inside unit


Drill Hole & Route Refrigerant Bundle

First, I drilled the 3.5″ hole with a hole saw bit and 3/8″ arbor at a downward angle for proper drainage.

Mini Split drill 3.5 inch hole through wall


Next, I installed the round plastic sleeve into the hole.

Mini Split Plastic pipe Sleeve


Then, I fed the refrigerant piping through the hole.  I removed the protective passive wrap after the piping was through the wall.

Mini Split Route Refrigerant Pipes through hole


Next, I mounted 2 garage bike hooks to the bottom of the staircase so the pipe bundle could rest in them and keep them straight.  

Additionally, I put the drain hose through the hole below the refrigerant pipe bundle.

DIY Mini Split Drain hose through wall


There was a trim piece to the plastic pipe, but I didn’t use it.  I plan to build a box to hide the refrigerant pipe at a later date.

In addition, I decided to use spray foam to seal the hole.

DIY Mini Split Foam around Hole


Mount Outside Unit

The outside wall bracket for the condenser unit was easy to mount.  

First, I made sure the cross support piece was level and secured it to the wall with screws.  

Next, I slid the 2 support arms on the cross support piece.

Then, I slid the 2 support arms on the cross support piece.

How to Install a Mini Split - Outside Condenser Unit Arms


While mounting the bracket, I heard a buzzing sound around my thigh.  As I result, I glanced down and noticed a wasp nest about 6 inches away from my leg.  

Thankfully, I didn’t get stung!

Mini Split Wasp Nest


Mini Split Outside Condenser

The outside condenser unit weighs 80 pounds.  It’s not very heavy, but it is definitely awkward.  

First, I placed the unit on the support arms and made sure the rubber feet and bolts were aligned correctly.  

Next, I tightened them with a wrench and socket.

DIY Mini Split Installation Outside Condenser Unit


Then, I used my magnetic I-beam level to make sure the top of the unit was perfectly level.

Mr Cool DIY 18k level outside condensor


Connect Refrigerant Lines

First, I wrapped the excess refrigerant piping around the outside of the bracket in wide, loose loops.  In hindsight, I wish I would have left the excess piping inside.

Then, I removed the top plastic cap to expose the electrical components and the bottom water tray to expose the refrigerant piping.

DIY Mini Split Installation refrigerant lines

DIY Mini Split Installation Electrical


After removing the plastic seals on top of the high and low side, I immediately attached the refrigerant piping.

DIY Mini Split Installation Rubber Cap Remove


Next, I aligned the refrigerant pipes and made sure they were not stressed.

After I tightened each screw connector by hand, I tightened the bottom screw connector and then the top according to the instructions.

In addition, the instructions are very specific, so I made sure to read them carefully.


DIY Mini Split Quick Connect Tapping Rings

Also, the couplings work with tapping rings, so they may leak if the pipes are loosened and reconnected.  

First, I removed the cover on the top valve and opened the valve with a 19mm hex wrench counterclockwise.

Then, I repeated this process on the bottom valve.

DIY Mini Split Installation Loosen Hex cap


Finally, I checked for leaks with a spray bottle that contained dawn soap and water.

DIY Mini Split Installation Check for leaks


Connect Mini Split Electrical Lines

First, I connected the electrical cable from the inside unit to the outside unit.

Next, I made the electrical connections, attached the water box and electrical box, and put pipe installation around the refrigerant pipes.

Also, I’m not including the electrical part of the installation process.  

Ultimately, I’m simply not qualified to provide this advice to you.

I encourage you to call a professional electrician to perform this work because it is not worth the risk.


Mr Cool DIY 18k Remote Mount, Filters, & WiFi Adapter

First, I installed the remote control cradle and the batteries.  

Next, I installed the remote control cradle near the door to my workshop.

DIY Mini Split Remote Install


Then, I climbed up my ladder and installed the air filters.

Mr Cool DIY 18k filter install


The USB WiFi adapter was easy to install in the port on the underside of the door as well.

How to Install a Mini Split WiFi Adapter


DIY Mini Split WiFi and App

Once I connected to the SSID of the unit, I opened up the Mr. Cool app and configured the unit.
Furthermore, the app doesn’t have the exact same features as the remote control.
However, it is still very useful.  
As I mentioned, I have 2 mini split units.  
So, I chose the workshop unit.

DIY Mini Split Installation App home view


Obviously, I can change modes from cool, to dry, to heat, to auto and back to cool by pressing the mode button.

First, I turned the unit off by hitting the power button to the lower left of my screen.

DIY Mini Split Installation Power Off


In addition, I can set a schedule for the unit to turn on and off at a certain time. 

DIY Mini Split Timer


IR Thermometer Test Mr Cool DIY 18k

Keep in mind, there are specific instructions in the installation manual for testing the unit.  

First, I used my IR thermometer to measure the cold air exiting the unit.

Essentially, this unit cooled my 25’x25’ workshop with 18’ ceilings quickly.

I also performed a DIY mini split installation in my spray foam attic to control humidity and moisture levels.

Ultimately, I’m very happy with it.

Mr Cool DIY 18k IR thermometer test



In conclusion, I hope this DIY mini split installation tutorial of the Mr Cool DIY-18-HP-230A provided you with some value.

Also, learn how to repair THIS mini split and how to automate a dust collection system with voice commands.


Wednesday 2nd of June 2021

I’ve installed a few mini splits- I’m a homeowner but I worked in construction part time through college and have above average experience but had not installed a mini spit until last year. I had the tools to pressure test snd evacuate the supply lines, so I didn’t purchase a pre-charged line like the Mr. Cool units. The hardest thing I encountered was bending the 1/2 “copper return line. My bender only went up to 3/8”. Had get another on the internet. No mention of bends in your article.

Congressional HVAC

Thursday 20th of June 2019

Thank you for sharing this ultimate guide for DIY mini split type aircon installation. The images were really a big help to see the actual way of installation. Hats off to you Sir.


Thursday 6th of June 2019

I just received my 24k BTU unit and I noticed the line set is wrapped in some big vinyl sleeve. I assume that stays on? Most of the install vids I've seen don't look like this - they look taped instead. Sorry you had to rip it out. I hope I have better luck....

Richard Allen

Monday 30th of July 2018

Did you buy a Mr. Cool mounting bracket or a generic one? I like the one you used. Where can I get it? Thanks-Richard

Toni hill

Thursday 18th of April 2019

I am thinking about buying a used unit. Will I them have to refill the refridgerant? Is this a 220 electric unit?

Luis Jimenez

Monday 16th of July 2018

Milwaukee 49-56-0193 3-1/2-Inch Ice Hardened Hole Saw this tool can be use to drill on a concrete wall ? if you have any other suggestion or tool can be work on concrete let me know , thank you

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