Informational Guide

How To Install & Wire A Ductless Mini Split AC

Learn how to install & wire a ductless mini split ac system, as well as the mistakes to avoid during installation.

by jtanner

Ductless mini split systems are growing in popularity for many reasons. One of those reasons is the simple DIY installation. However, if you have never installed one of these systems, it can be a daunting task.

In this article, we will show you, step by step, how to install a mini split air conditioner system. From mounting to wiring, we cover it all.

Ductless mini splits are one of the rare air conditioner systems that offer a DIY install option. However, it isn’t your only choice. You can always contact an HVAC technician to install the unit for you.

With professional installation, you know that the installation will be done correctly. You can also get a labor warranty with most contractors that you won’t get with a DIY install. With proper measurements, testing, and experience, professional installs are also completed faster.

Unlike a DIY install, the professional installers will have the proper HVAC tools, equipment, and past experience to get the job done right. This doesn’t mean you can’t get a perfect install doing it yourself.

The biggest issue with a DIY install is the difficulty level. You need to know how to perform minor construction, electrical wiring, and understand refrigerant handling. Not all ductless systems can be installed as a DIY project, though, so you need to ensure the chosen model is rated for DIY installation.

If you have the knowledge and time, a DIY install will save you money. However, you also have to budget for the tools, equipment, and desire it takes to install these systems yourself.

DIY Vs Professional HVAC Installation

Important Things To Consider Before Installing A Mini Split AC

Before you set out on your installation project, there are several things you should know and consider. The most important of which is about the refrigerant lines.

Any type of refrigerant can only be handled by a trained professional. Adding, removing, disposal, and transporting refrigerants is regulated by law, and you must hold an EPA 608 certification. If your system is not pre-charged with cut and ready refrigerant lines, you will need to contact an HVAC technician to help or finish the installation.

You also need to ensure that your wiring and refrigerant lines have clear access to the outside of the home where the condenser unit or heat pump is located. DIY mini split systems will come with a set length of refrigerant lines that must reach from the exterior unit to the interior air handlers. Outside walls are generally chosen for their ease of access to both sides of the wall.

You also need to ensure you choose the right type of mini split for your home and needs. There are three main types to consider.

  • Single-zone mini split system. These are systems that work to heat or cool a single room. They are comprised of a single heat pump and a single air handler.
  • Dual-zone mini splits. These systems work to cool two rooms, using a single heat pump or condenser unit and two air handlers.
  • Multi-zone mini splits. These are the largest units and have condensers or heat pumps that can handle multiple air handlers (4 – 8 typically). They also have the most challenging installation.

Finally, you want to ensure you have the right size unit for your home and space. This is measured in BTUs. Mini Splits come in many sizes or capacities, ranging from 900 BTU to over 60,000 BTU.

Each manufacturer will have sizing guides based on the square foot size of the room or rooms you need to control. On average, though, you should plan for at least 20 BTU per square foot of space. The typical single room unit is about 9000 BTU.

How To Install A Mini Split? (DIY Installation)

Now that you have your mini split system picked out and purchased, it is time to perform the install. We will cover the materials and tools you typically need as well as take you on a step-by-step process of a DIY ductless mini split installation.

Tools & Materials Needed

While you should have most of the tools needed for the installation already, your mini split instruction manual will cover all necessary tools, including any specialty tools. However, at a minimum, you will need the following items.

  • Ductless mini split system.
  • Line set and wiring kit.
  • Condenser, line, and wire covers.
  • Wall brackets.
  • Mounting location, flat and level.
  • Adjustable wrench.
  • Screwdriver set.
  • Torque wrench.
  • Drill with hole saw attachment.
  • Bubble level.
  • Tape measure.
  • Pencil or marker.

Step by Step Guide

Before you begin your installation, you should have your mini split system open, unboxed, and laid out so all pieces can be identified and easily accessed. You should also read through the entire installation process in the owner’s manual at least twice.

If you skip a step or do something out of order, it can cause major issues, repairs, or cost you a lot of time and effort. Below, we outline the most basic steps for a typical single-zone ductless mini split. Of course, your exact steps may differ, depending on size, home layout, or even model and brand.

  1. Measure and decide on installation location. For the inside unit, which should be mounted first, you want the bottom of the air handler to be at least 6 feet off the ground. Make sure you measure a few times to ensure you meet the manufacturer’s specifications for clearance. Once you have your measurements and know where the unit will be placed, mark the location with your pencil using the bracket as a guide.
  2. Level and mount the bracket. Once you have the holes marked for drilling, you will want to install the air handler mounting bracket. Reminder, there should be clearance on all sides, and the wall should be free of obstacles on both sides.
  3. Drill hole for refrigerant and power lines. The condensation drain and refrigerant lines need to be mounted at a slight down angle (towards the outside). When you drill your hole, make sure it is at a downward angle of at least 15 degrees.
  4. Feed the line set through the hole. Use care when unrolling your line set so you don’t break or kink any wires or tubes. Feed the line set from the inside to the outside. Once outside, bend and angle the line set towards the condenser mounting area.
  5. Hang the air handler. Once the line set is mounted and flush, hang the air handler on the bracket.
  6. Mount the condenser unit outside. The best method is to install the unit on a concrete slab. However, plastic mounting pads or wall hanging brackets work, too. Whatever method you use, make sure the condenser unit is mounted properly, level, and secure.
  7. Connect refrigerant lines. If the lines do not need to be cut and are pre-charged, now is when you connect them. Make sure you follow all manufacturer’s instructions carefully for this step. If you are unsure, or the lines need to be cut, now is when you call an HVAC tech to finish the installation.
  8. Ensure the drain line and power wires are through the wall hole, too. Connect the refrigerant and power wires (see below).
  9. Cover the line set and drain line and ensure everything is secure.

How To Wire A Mini Split? (DIY Safety Guidelines)

Wiring a mini split system is a little more involved than just connecting wires. If at any time you are unsure or uncomfortable, you need to contact an electrician or your HVAC technician to help you with the installation.

Tools & Materials Needed

Aside from the tools and materials needed for installing your mini split ac, you will also need the following to complete the wiring installation.

  • Power disconnect switch.
  • Open circuit breaker in panel.
  • Circuit breaker (proper rating).
  • Wire cutter.
  • Wire crimping tool.
  • Power wire whip.

Step by Step Guide

As before, you will want to read through your owner’s manual to ensure you know the steps and ratings required for the wiring. For example, some models will require a 20 amp breaker, and others may require a 30 amp or even two 20 amp circuits.

For direct wiring, an electrician or your HVAC technician should be called. However, if you are comfortable with the installation as a DIY project, here are the basic steps you will follow.

  1. Mount the power disconnect box on the outside wall near the condenser unit. It needs to be high enough to be easily reached and close to the condenser unit/heat pump for easy access.
  2. Install the wire whip from the cut-off box to the condenser unit. Ensure the wiring is correct on both ends and remove the pull pin from the disconnect box.
  3. Run your power wiring from the circuit breaker panel to the disconnect box. Once again, ensure your wiring is correct on both ends.
  4. Install the circuit breaker in the breaker panel and turn the breaker on.
  5. Plug the disconnect pull pin in the disconnect box (make sure it goes in the right way). Your system will now have power and can be tested and enabled at the air handler thermostat.

Installing Popular Ductless Mini-Split AC Models

When it comes to a DIY mini split AC installation, there haven’t been a lot of options. Even when mini split systems first made an impact and started growing in popularity, their installation was left to the professionals.

Then came a brand called MrCool. A true pioneer, MrCool mini split systems came directly to the homeowner as a kit with everything they needed to install them, without the need for EPA certifications and extensive training.

The high efficiency of a mini split system and the money saved from a DIY install (while still having a warranty) soon brought other major brands into the fold. You can now install a Mitsubishi mini split system as a DIY project as well as Pioneer.

It won’t be long until other brands begin offering these kits as a DIY service, too. But for now, you should probably stick to the brands that have the reputation and knowledge for creating these home climate control systems.

Installing Popular Ductless Mini-Split AC Models

People Also Ask (FAQ)

Below is a list of frequently asked ductless mini split AC wiring & installation questions.

How long does it take to install and wire a ductless mini-split AC?

For a professional HVAC team with the knowledge and experience installing systems every day, a ductless mini split should only take a few hours to install. For the DIYer, though, assuming it is your first time and following step-by-step instructions, you should count on at least a day, possibly a long weekend, to have everything completed and functioning properly.

How much does it cost to install and wire a ductless mini-split?

On a US average, the base installation will cost about $3,000. On top of that, you can plan for about $2,000 to $4,000 for each air handler/zone installation. A single-zone system will average about $5,500 to install, and a three-zone system ranges from $3,500 to $10,000 for professional installation.

How far can a mini split be from the condenser?

The distance between the air handler system inside and the heat pump or condenser unit outside can be pretty far. Most DIY packages will come with refrigerant lines pre-charged that are 15 to 25 feet in length. However, the maximum distance is up to 200 feet for refrigerant lines, including a maximum of 60 feet liquid lift (vertical travel distance).

Do mini splits have to be on an outside wall?

No, there is no requirement that a mini split must be on an outside wall. However, it is usually recommended because it makes access for the wiring and line kits to be routed from inside to outside, and the exterior walls are usually reinforced, so you don’t have to worry about the added weight on your walls.

Can you run mini split lines in the attic?

Yes, refrigerant lines can run horizontal, vertical, or diagonal. You want to avoid loops in the lines, and it will need to be secured to a support beam about every 3 to 4 feet to prevent drooping or sagging, but you can run the lines anywhere. Be cautious, though, that any vertical climb or descent will require a significant bend in the line, which may cause problems.

Conclusion

Even as a DIY unit, the installation of a mini split system isn’t the easiest thing to do. If you do want to install the system completely by yourself, MrCool, Mitsubishi, and Pioneer are the brands to go with.

You also have the option of a DIY-assisted installation where you install the unit and hire a technician to install the refrigerant lines and wiring. Either way you go, you are sure to save money and have a cooler home in the process.

Last Updated on July 5, 2022

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