How to install a 3rd generation MRCOOL ductless mini split AC
Kimberly Sebring / Wednesday March 23, 2022
Looking for an easy way to heat and cool your home? A MRCOOL DIY ductless mini-split AC unit can keep you and your family extra cool this summer with climate control you’ve installed yourself, and you can use it to warm up again once winter rolls around.
Mini split systems have an outdoor compressor unit connected to a slim, wall-mounted indoor unit that you can place high on your wall or ceiling, even if you don’t have any HVAC experience.
The MRCOOL DIY system comes with everything you need to set up, including 25 feet of pre-charged R-410A quick-connect lines so you don’t have to worry about handling refrigerant. You also won’t have to tear down walls or ceilings to install it!
If you need replacement parts for your MRCOOL mini split or other air conditioner, you can use your model number to find what you’re looking for at AppliancePartsPros.com. We also have thousands of free DIY troubleshooting and repair guides to help you fix your AC yourself.
Disclaimer: The information in this article may not apply to your specific appliance model. While we strive to offer helpful advice for all types of appliances, variations in models and configurations can lead to differences in cleaning recommendations. For the most accurate guidance, we strongly recommend consulting the use and care manual for your specific appliance model.
READ MORE: How does a MRCOOL mini split AC work?
Make sure you have the correct 3rd generation MRCOOL unit
There are four combination units to choose from when selecting a MRCOOL DIY mini split: 12 BTU, 18 BTU, 24 BTU and 36 BTU. BTU stands for British Thermal Units, which measures the amount of energy the unit uses to provide air conditioning.
The higher the BTU, the greater the space that can be conditioned. If you need more square feet to be covered by this DIY unit, choose one of the larger options.
It’s important to choose the right-sized unit for your space so it works correctly and remains energy efficient. If you select a unit that’s too small, the unit may overwork itself and break down faster. If you select a unit that’s too large, the temperature may be uncomfortable and it may waste energy, which could cost you in the long run.
- The 12 BTU unit cools and heats 500 square feet
- The 18 BTU unit can cool and heat 750 square feet
- The 24 BTU unit can cool and heat 1000 square feet
- The 36 BTU unit can cool and heat 1500 square feet
READ MORE: What size MRCOOL mini split AC do you need?
Before you install
Remember that mini split AC units must be installed in accordance with any local and national requirements and standards. Depending on the electrical work in your space, you may need to hire a certified and trained electrical technician to install your unit.
While you don’t usually don’t need any specialized tools to install a MRCOOL DIY mini split system, you will need to have some basic technical and electrical skills. If at any point you don’t feel comfortable completing this installation yourself, stop and contact a qualified HVAC professional or an electrician for assistance.
READ MORE: How much power does a MRCOOL mini split unit use?
What you need
Your MRCOOL unit should include almost everything you’ll need to complete the installation. When you unpack everything, double-check what you have against the manual to verify that all the necessary parts are there.
Once you’ve checked the packaged parts, gather up these items:
- Stud finder
- Level
- Drill or Phillips head screwdriver
- Utility knife/knife/saw
- 3 1/2-inch hole saw
- 2 adjustable wrenches
- Electrical tape
- Soapy water (either in a spray bottle or with a bowl and brush)
READ MORE: How long do MRCOOL mini splits last?
How to install a 3rd generation MRCOOL DIY ductless mini-split
Step 1: Measure & mark the installation area for the air handler
The MRCOOL unit should include a cardboard wall template to make measuring and marking easy. The drill points for the mounting screws should be located on wall studs. Don’t forget to use a level while you’re marking so that your bracket is installed evenly!
- Use a stud finder to find the best spot for the mounting bracket.
- Use the wall template to measure and mark both drill points for the mounting hardware.
- Use the wall template to mark the spot where the wall hole will be drilled.
Step 2: Install the mounting bracket
- Find the mounting bracket on the back of the indoor air handler and remove it from the so you can install it on the wall.
- Detach the mounting plate with a drill or screwdriver.
- Line the plate up with the markings you’ve made on the wall.
- As you secure the mounting plate, use a level set on top of it so the bracket doesn’t slope.
- Once the mounting plate is secure, drill a hole through your wall using your 3 1/2-inch hole saw. You want the mark you made for the hole to be the center point for the saw.
Step 3: Install the wall sleeve (included with your purchase)
- Push the wall sleeve through by hand.
- Make a note of how far the sleeve sticks out on the outside. It needs to be as close to flush with the exterior wall of your home as possible.
- If needed, use a saw or knife to cut the wall sleeve to size.
Step 4: Prep and install the air handler
- Slowly unfold the air handler’s piping until it’s sticking straight out from the back.
- Bind the drain hose and refrigerant lines together loosely with electrical tape. The drain pipe MUST be on the bottom of the bundle. DO NOT bind the ends of the piping since you’ll need to access them later.
- Feed the air handler’s communication wire through the wall sleeve to the outside.
- Feed the refrigerant lines and drain hose through the wall sleeve and push all three and the remaining communication wire through all the way.
Step 5: Connect the air handler to the wall bracket
The top of the air handler should hook onto the top of the wall bracket. It will then snap into place at the bottom.
Step 6: Set the condenser unit
Outside, place the condenser unit firmly on the ground or attach it to a secure metal bracket or pad.
It should have a minimum of:
- 24 inches (60 cm) of clearance above the unit
- 12 inches (30 cm) of clearance between the back of the unit and the wall if installed on the ground, or 6 inches (15 cm) if mounted on a bracket
- 12 inches (30 cm) of clearance on the left side
- 24 inches (60 cm) of clearance on the right side of the unit, where the valves are
- 79 in (200 cm) of clearance on the vent side (front) of the unit
You don’t need a drain pipe under the unit unless it’s elevated. Consult your product manual for more information.
Step 7: Install the wall sleeve cover
- Set the wall sleeve cover in place on the outside.
- Feed the wire, refrigerant lines and drain hose through the cover.
- Pressing the cover into place.
- Slowly bend the refrigerant lines so they point downward along the wall.
Step 8: Add protective neoprene
- Add the protective neoprene to the inside of the wall sleeve and around the line set. You can use foam spray instead of the wall sleeve to fill any space not taken up by the piping and lines.
- Double-check that the air handler is secure.
Step 9: Prep and connect the line set (included with condenser)
- Uncoil the lines.
- Pull the insulation up on the refrigerant lines that are connected to the air handler to expose the line ends.
- Unscrew the color-coded caps on each end.
- Thread the line set and the refrigerant line ends together by hand.
- Use two wrenches to tighten the lines down completely.
- Carefully roll up any excess tubing and place it flat on the ground behind the condenser. Leave yourself with enough slack so the line isn’t stressed later on.
Repeat these steps on the refrigerant line at the condenser to unscrew the caps, thread them together by hand, and tighten it all down with two wrenches.
Step 10: Open the valves
- Remove the top valve cover on the condenser.
- Open and shut the valves with the included Allen wrench. Turn the wrench counterclockwise until it stops and don’t force it past that point.
- Reinstall the cap and then tighten it securely.
Repeat this step with the bottom valve.
Step 11: Check the refrigerant lines for leaks
Use a spray bottle with soapy water to spritz water on the condenser connection points and the air handler’s connection points. If there are leaks, you’ll see the water bubble.
If you find leaks, tighten the connectors down and check again. Your product manual will also have additional information about checking for and dealing with leaks.
If the connections near the air handler are leak-free, dry them off and wrap them with the sound-deadening pads. This will protect the connections and reduce vibration.
Final steps
- Replace the white insulation around the lines and wrap it up with electrical tape.
- Connect the condensate drain hose by twisting it into place.
- Turn off all power to the system before performing any electrical work.
- If needed, contact a certified electrician to supply power from a disconnect switch of an appropriate rating. For a detailed explanation of how the electrical work is done for your specific unit, consult the product manual.
Once the electrical work is done and tested, put batteries in your remote control and press power, and your new AC should start working. You can further improve the look of things outside and better protect the cables and piping by installing the optional MRCOOL LineGuard assembly.
READ MORE: How to clean & maintain a MRCOOL mini split AC
More information
Thank you for reading! We hope this guide helped you install your MRCOOL mini split.
If you have any other appliance repair needs or projects, don’t hesitate to explore our other troubleshooting guides and videos.
If you need replacement parts or some extra help with ordering them, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, read our DIY blog and more.
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Kimberly Sebring started reading books and newspapers at a very young age, and her curiosity eventually led her to start a career in journalism. She previously worked as a reporter, editor and digital producer before arriving on the AppliancePartsPros.com blog team. She’s thrilled to be able to help people learn more about their appliances so they can save time and money through DIY repairs. Outside of work, she enjoys spending time outdoors, shopping and hanging out with friends and family.