How-To: Ductless Mini-Split Installation

Ductless mini-split installation is fairly straightforward. We'll go through the basic process along with tips, advice, and where you should leave the work to a professional. For mini-split installation that is as simple as can be, make sure you check out our MRCOOL DIY products.

This short guide is intended to walk you through the basics of mini-split installation to familiarize you with the process. It is not intended as a replacement for a manufacturer-provided installation manual. Nor is it intended to be a replacement for appropriate HVAC training. Should you attempt amateur HVAC product installation, you do so at your own risk!

Ductless Mini-Split Installation Basics

These are the basic steps necessary for proper ductless mini-split installation.

1. Choose Your Mini-Split Installation Site

Properly placing the interior air handler is critical. You need to choose a location that will push maximum air flow into the operable zone while still allowing plenty of clearance around the unit.

You should also:

  1. Never place the air handler in direct sunlight or near a significant heat source.
  2. Always make sure the wall is strong enough to support the weight of the air handler.
  3. Always avoid locations near televisions, radios, phones, and other electronic devices the operation of which might interfere with the unit.

Of course, mini-split installation is more than just worrying about the inside. Make sure that the interior location will allow your lines and wires to reach wherever it is you plan to set up the outside condenser. Ideally, you should attempt to minimize the distance between interior and exterior components whenever feasible. This will help conserve operating energy.

2. Wall Mount or Base Pad Mini-Split Installation

Aside from where you want a unit to go, the main decision to make regarding the condenser in a mini-split installation is the choice between using a wall mounting bracket or a base pad. A base pad is very simple. You buy a base pad or pour some concrete, plunk the unit down, and you're good.

In many cases, a wall mounting bracket can be a better choice. A wall mounting bracket will elevate the condenser, and that helps protect it against yard debris and deep snow. Both of which can do a number on your condenser.

3. Assemble Your Tools for Mini-Split Installation

Before starting mini-split installation or any other sort of HVAC work, it is always a good idea to assemble the tools you will need for the job. Figure out what you have and don't have. At the very least, you might be able to make only one trip to the hardware store for your project.

For most mini-split installation jobs, you'll need the following:

  1. 3.5" hole saw
  2. Drill
  3. Wrenches
  4. Stud Finder
  5. Level
  6. Wall Anchors
  7. Polyurethane Foam

4. Place and Secure the Interior Mounting Plate

Most ductless units come with a mounting plate for the interior air handler.

Roughly fix the plate on the wall where you want to place the air handler. Use your level to make sure the plate is straight and level. Drill holes according to the installation manual and the plate guidelines.

Ideally, use a stud finder to place at least one of the drill holes in a stud for better support. When the holes for the screws cannot be placed in a stud, use wall anchors to make sure the air handler will be adequately supported. Once the holes are drilled and the anchors are in place, secure the plate to the wall with screws. Most mini-splits will include the appropriate screws to use.

5. Drill a Hole in the Wall

Using the plate and the appropriate installation manual as a guide, decide where you're going to cut your hole in the wall. When you make your cut, you will want to do so at a slight downward angle. This will help ensure condensate drains out effectively during unit operation.

As always, be careful when operating power tools at any point of the mini-split installation.

6. Connect the Air Handler to the Wall Bracket

Using electrical tape, bind the refrigerant lines, communicating wire, and condensate drain together. You will need to make certain the drain is on the "bottom" of the bundle and not kinked. This will help ensure water flows freely out of the air handler.

Next, carefully run the taped bundle through the hole in the wall. Attempt to minimize bending the refrigerant line at all points of this process.

Secure the pipe, drain, and communicating wire to the appropriate points on the air handler. Refer to the product installation manual to ensure you are doing this correctly. If you are not capable of connecting electrical wiring or refrigerant lines, hire a professional to help you complete this step.

Now, lift the air handler into place and secure it by pressing firmly against the mounting plate.

7. Mini-Split Installation Condenser Placement

Before placing the condenser during your mini-split installation, make sure that the unit will be able to operate without obstructions within 12". If you're mounting the condenser on a pad, you may want to use rubber cushions under the feet to reduce operating vibration. As with the air handler, ensure any electronic devices will be at least 10 feet away from the condenser.

8. Condenser Connections for Mini-Split Installation

Remove the electrical cover on the condenser. Refer to the wiring diagram in the mini-split installation manual, and make the appropriate connections. Follow all manufacturer instructions regarding proper wiring. When finished, make sure the cover is properly secured.

If you are not a professional electrician, we highly recommend you hire a professional to connect all electrical components. Failure to hire a professional could void your warranty on some products.

Next, connect the refrigerant lines to the appropriate pipes on the condenser. Connecting the refrigerant lines and modifying their length, if necessary, should be performed by a trained HVAC professional. If you are not a professional, we highly recommend you install a unit intended for amateur mini-split installation such as the MRCOOL DIY.

After the lines are connected, specialized HVAC tools will be necessary to properly vacuum and charge the system. Again, we highly recommend you hire an HVAC professional to conduct these steps. Failure to do so will void most HVAC product warranties.

Once the refrigerant lines are secure and connected, wrap the joints with insulation and insulating tape. This will help to reduce energy loss during operation.

Secure any exposed cable between the condenser and the air handler to the wall with clamps. You can also use a protective cover product to further guard against damage or efficiency loss.

Finally, seal the exterior of the hole in the wall with an expanding polyurethane foam or other insulating product.

Comments or Questions About Mini-Split Installation?

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3 comments (view/add)
  • Franklin Taft
    Franklin Taft
    Posted on 7/8/2019

    Highly recommending a HVAC professional is an understatement. Not ensuring your lines are in a perfect vacuum can cause the unit to fail and unit replacement possibly required.

  • Mike McCarthy
    Mike McCarthy
    Posted on 7/19/2019

    my line set is not attached to the air handler, all the instruction videos show them as attached and pre charged? have I missed something?
    is the freon stored inside the outside condenser unit and then fills the lines once connected and unlocked?

  • Kyle
    Kyle from Ingrams
    Posted on 7/19/2019

    Most ductless line sets are NOT attached to the air handler. The main system that features an air handler with a pre-connected line is the MRCOOL DIY.

    I'm not sure if you missed something, Mike, but you may have meant to buy a MRCOOL DIY and you got something else. Regular (i.e. - conventional) mini-splits are going to require you to connect the system, evacuate the lines, and then charge the system with the refrigerant in the condenser. And sometimes you have to add some depending on the line length.


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