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Mini Split Wiring: Electrical Requirements and Wiring Diagram

Mini Split Wiring

Ductless mini splits are one of the most popular AC choices for homeowners and businesses alike. Mini split air conditioners are a leading seller on  our website, and, on our blog, have previously written about all the benefits of and features to consider when purchasing a mini-split AC of your own.

Installing ductless mini splits requires a high level of electrical knowledge for the job to be done safely and without harm to yourself or the unit. As such, we don’t recommend homeowners try to install the unit themselves. Unless you are an advanced DIYer with extensive experience in electrical work, we strongly advise you to hire a professional to get the job done.

But even professionals have to learn the ropes, and so if you are an electrician who simply has not undertaken a mini split installation project before, this post is for you. Here, we offer a step-by-step guide to everything you need to know about the electrical specifications for installing ductless mini splits.

NOTE: These instructions are in regards to electrical specifications only, and do not include line set installation or refrigerant set-up. Always check the installation manual for the specific system you are installing as requirements can vary from item to item.

Mini Split Electrical Requirements


The first thing to note is the voltage of your mini split. Ductless mini split systems generally require 208/240v, but some smaller mini split models only require 110v. Many single-zone mini splits come in 110v or 208/240v versions, while larger systems with a capacity over 12,000 BTUs typically operate on 208/240v.

Dedicated circuits

Mini splits must also have their own dedicated circuit to prevent overloading and repeated tripping of the breaker. According to the National Electrical Code, major appliances including ductless mini splits should have their own dedicated circuit. A dedicated circuit is one that has its own circuit breaker. This prevents it from overloading and tripping other circuit breakers in the electrical box.

Disconnect Switch

A disconnect switch or service disconnect must be installed at the location of the unit outside. This device allows you to cut off power to the unit which can be useful when servicing the unit or in the event of an emergency. Disconnects are housed in a weatherproof enclosure so that they are safe to be outside. A disconnect switch is required by code in most places for all mini split installations. 

Featured disconnect switch for mini splits:

Quick Disconnect Switch Kit for Mini Split Air Conditioner Systems

The Diversitech DDS-30 is designed to be easy to install and use. The included fuses install into the pull out handle. The terminals are arranged for simple hookup with heavy duty wiring, and the door is reversible to make it easy to fit into any area. 

It also features easy to read indicator lights for blown fuses. The knockouts are located on the side, back, and bottom and allow for 1/2″, 3/4″, or 1″ connections. The package comes with two fuses of your choice. Select the fuse based on the maximum overcurrent protection amp rating of your system.

Quick Disconnect Switch Kit for Mini Split Air Conditioner Systems
Price: $69.00 Quick Disconnect Switch Kit for Mini Split Air Conditioner Systems

Disconnect boxes are required by code for the installation of a mini split system. The disconnect switch is located next to the mini split outdoor unit. Power...

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Electrical whip

The outdoor portion of the wiring must also be encased in an electrical whip. This is a weatherproof casing that protects the wires from the elements. The whip connects the power line from the disconnect box to the condenser unit.

Mini Split Wiring Considerations

Before wiring a mini split system, let’s go over critical factors you need to consider when wiring a mini split wiring.

  1. How many wires are needed for a mini split?

There are two kinds of wires used by mini split systems:

The first is the wire from the circuit breaker to the disconnect. The second type of wire is the one that goes from the outdoor unit to the indoor unit.

  1. What wire size do I need from the circuit breaker to the disconnect? 

The wire size is determined by the power draw of the mini split, the distance, and local electrical codes. See our full guide to Wire Sizes to determine the gauge for your unit.

  1. What wire size do I need to connect the outdoor and indoor units?

Mini-split wires are used to connect the outdoor compressor unit with the indoor evaporator unit, delivering electricity and control signals. For most ductless mini-splits, the right wire is a 14/4 stranded conductor cable, however check the specs of your mini split to ensure the proper size. 

A 14/4 stranded cable provides two 14-gauge conductor wires for power, one communication wire and one ground wire. The ground wire is essential for safe operation, preventing damage to the air conditioner and protecting your family, which is why going with 14/4 is always better than 14/3.

Featured mini split wire:

Honeywell Genesis Cable 10703908 50 Foot Roll 14 AWG 4 Conductor THHN Mini Split Cable

This mini split cable is specifically designed for use with any mini split system. The 14/4 cable wire will work with most major brands and allows for easy wiring from the indoor unit to the outdoor unit. With a 600v capacity, it is PVC coated, sunlight resistant and rated for direct burial.

Honeywell Genesis Cable 10703908 50 Foot Roll 14 AWG 4 Conductor THHN Mini Split Cable
Price: $59.00 Honeywell Genesis Cable 10703908 50 Foot Roll 14 AWG 4 Conductor THHN Mini Split Cable

Why gamble with other cables when you can get the right one?Honeywell mini split cable is specifically designed for use with any mini split system. The 14/4 cab...

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Some areas also require the wire to be armored by code. We carry armored cables to ensure your wiring is compliant.

Featured armored cable for mini splits:

Honeywell Genesis Cable 10753908 50 Foot Coil 14 AWG 4 Conductor Metal Clad Mini Split Cable

The Honeywell Genesis metal-clad 14 AWG / 4 conductor cable is specifically designed for use with any mini split system. With this cable, there is no need for additional conduit as this wire is already metal-clad and can be installed right into the wall as is.

Each conductor is 7 stranded bare copper wires. It is sunlight and oil resistant and rated for direct burial, and can handle up to 600V. 

Honeywell Genesis Cable 10753908 50 Foot Coil 14 AWG 4 Conductor Metal Clad Mini Split Cable
Price: $119.00 Honeywell Genesis Cable 10753908 50 Foot Coil 14 AWG 4 Conductor Metal Clad Mini Split Cable

Why gamble with other cables when you can get the right one? Honeywell Genesis metal clad 14 AWG / 4 conductor cable is specifically designed for use with any m...

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  1. When do I use a 10/2 or 10/3 for mini splits?

When installing a mini-split air conditioner, it’s vital to choose cable that’s large enough to handle the current your system requires. For ample spaces and significant heating/cooling, some homeowners choose a mini-split with 36,000 BTU capacity. This type of system can require a 30-amp circuit, so you would need 10-gauge wire to handle the current. Every unit will list its amp draw and the wire choice will vary based on that.

What do 10/2 and 10/3 wire numbers mean? The first number is the thickness in AWG (American wire gauge). Don’t forget that in AWG, smaller numbers mean thicker wires. So a 14-gauge wire is medium sized, 12-gauge would be a little bigger, and 10-gauge is the biggest wire you’re probably going to need for a mini-split.

The second number is the amount of connectors the wire has. A 10/2 wire has two connectors, the black and white, both hot/lead wires as well as a ground wire. On the other hand, 10/3 wires have three connectors, black, white and red plus a ground wire. 

For additional guidance on wire sizing, check out: Wire Size Guide: What Size Wire Do I Need?

With any electrical project, be sure to check with a licensed electrician and verify the requirements of your local codes.

How to Wire a Mini Split System

Now that we have that clarified, follow these steps to wire up your ductless mini split system:

Step 1 – Mini-Split Shut-Off Box:

Run a 230/208 volt or 115 volts* dedicated line from the main break box to the area where the shut-off box will be installed next to the unit.

* Voltage depends on the system. The vast majority of mini-split units are 230/208V, but some are 115V.

Step 2 – Mini-Split Wiring:

Mount the shut-off box on the outside wall and connect the wires from the breaker box.

Electrical Shut off box
electrical shutoff box detail
208/230 Volt Shut Off Box

To meet the code, you must have a shut-off box at the location of the unit. This makes system repairs safer and easier. Wire the two hot leads to the fused connections in the box and the ground to the provided connection. Then, reattach the faceplate and insert the on/off switch. It should be kept in the off position while you continue to work on the unit.

Step 3 – Electrical Wire Whip:

Electrical Whip
Attach an electrical whip to the shut-off box and run it to the unit.

An electrical whip is a premade, outdoor grade wire set that is intended to run from a shutoff box to the unit being installed. Using this ensures that you will have no issues with meeting code and keeps the process simple for you. The whip must be wired into the shutoff box and then to the unit as we will talk about next.

Alternatively, run your own wire through an outdoor grade conduit so that it is protected from the elements. (an electrical whip is simply a pre-done version of this.)

Step 4 – Mini-Split Wire Connection to Base:

Connect the wires to the unit based on the instruction manual.

While it might be difficult to see through the other wiring in the unit, here we have included a picture of the main power connections to a Friedrich Mini Split Unit. You can see the green, black, and red wires connect the terminal blocks on the bottom right. The exact details of a connection like this are specific to your unit. Always reference the instruction manual before attempting any electrical connections.

Mini Split Wiring Diagram:

LG Wiring Diagram

Step 5 – Mini-Split Wiring Connecting Inside to Outside Unit:

Mini Split Wiring
Connect the wire for the indoor unit to the outdoor unit.

Depending on whether you are installing a single zone or a multi-zone unit, you will have a different number of connections. This Friedrich multi-zone unit has connections for 4 units, all of which are numbered for easy cross-referencing to the indoor unit. Make sure to write down which wire color is connected to which number. It is also critical to make sure that each indoor unit on a multi-zone system is wired to the same input that its line set is connected to. Otherwise, the system will not operate correctly.

It is recommended to use 14 gauge stranded wire for most installations. Pictured is a 14 gauge solid wire which will work but should only be used if the stranded wire is unavailable. Total Home Supply offers Honeywell 14/4 Mini Split wire in 50 ft and 250 ft rolls.

Step 6 – Secure the Mini Split Wiring

Just like the outdoor unit, the indoor connections must be made in the correct order. Connect the 3 main wires along with the ground to their respective terminals. Some manufacturers recommend using round crimp style terminals for a more secure connection.

Indoor Mini Split Electrical
Run the wire inside.

After this, the electrical portion of the installation is done! Congratulations!

From figuring out the difference between 10/2 or 10/3 wires to the nitty-gritty of the wiring and installation of your mini split, we hope to have resolved your electrical wiring concerns.

Do I Need a Surge Protector?

A surge protector is a device that protects appliances from voltage spikes that can be caused by lightning or other surges in the AC circuit. A voltage surge can degrade wiring insulation and severely damage the components of electrical appliances that are plugged in all the time.

A mini split surge protector safeguards the system from voltage spikes and lightning surges. Because mini splits represent a considerable investment and are plugged in all the time, it’s recommended to have a surge protector.

Recommended mini split surge protectors:

ICM493 Advanced Single Phase Surge Protector and Live Voltage Monitor for Mini Splits

The Single Phase Advanced Surge Protector features a bank of 5 surge arrestors, fully encased in a metal NEMA Type 3R Rated enclosure. This surge protector is perfect for use with mini splits, air conditioners, refrigeration systems and other electronics and appliances. It is water sealed for outdoor use.

It offers single phase protection against over and under voltage from 180 – 264 VAC for a more balanced distribution of power. The ICM493 also includes a built-in 40A contactor. Its dimensions are 4″H x 8″W x 8″L.

The unit installs between the disconnect switch and the condensing unit.

ICM493 Advanced Single Phase Surge Protector and Line Voltage Monitor for Mini Splits
Price: $259.00 ICM493 Advanced Single Phase Surge Protector and Line Voltage Monitor for Mini Splits

The Single Phase Advanced Surge Protector features a bank of 5 surge arrestors. This offers added protection against voltage spikes and lightning strikes. It is...

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ICM517 Wet Location Surge Protector for Mini Splits

The Single Phase Wet Location Surge Protector will protect your mini split against voltage spikes as well as lightning power surges. It is fully encased in a metal NEMA Type 3R Rated enclosure and is installed on your electrical panel. 

It can protect your item against a surge current of up to 100,000 Amps. Your equipment must be protected by a circuit breaker rated 20 – 60 amps. It is for use with 120/240 Volt, Single Phase service.

This model is UL listed in the US and Canada, and has dimensions of 2.16″H x 2.78″W x 5″L.

ICM517 Wet Location Surge Protector for Mini Splits

If you have any further questions regarding the electrical specifications of installing ductless mini splits, please do not hesitate to contact us at 1-877-847-0050 and speak to one of our qualified representatives.

Ready for the next step? Check out our multi zone mini split buying guide!

Learn More About Mini Splits:

Ductless Mini Split AC Installation

Mini Split Placement Guide

Ductless Mini Split Sizing Guide: Heat Load & BTU Calculator 

Mini Split Failures, Problems & Troubleshooting Guide

Kristen Turner

Featured blogger for Total Home Supply.

55 thoughts on “Mini Split Wiring: Electrical Requirements and Wiring Diagram”

  1. Great information but I have a question. I’m installing 2 multi split system in my house. The condenser requires a 30 amp breaker. It also calls for 12-3 cables from the outdoor condenser to each unit. But my question is, what wire do I need to run from the main panel to the outdoor box since I’m installing 2 multi split systems?

          1. Tim Maddison says:

            If the units are co-located and serviced by the same disconnect, can’t you run a single 40A , 10 AWG circuit to the disconnect?

          2. Mickey Luongo says:

            It is not advisable and probably against code to have two units running on the same disconnect.

  2. Maria Flores says:

    Our electrician says he will install 220v for our 230v/208v mini split. He says 220 and 230 are the same. Is this accurate?

  3. If my split system is 220 v how do I connect it to my 110 V supply?

    is there a transformer in the unit?
    Do I need to buy a transformer?

  4. Please help anyone who might know. I need a dual zone mini split unit the is only 115 volts. This is for a disaster relief trailer we are building for Tyson foods. We are limited to 115 volt power supply. Any suggestions are welcome.

    1. Mickey Luongo says:

      Unfortunately, none of the major manufacturers make a multi-zone unit that is 115 volts. You could use two single zones instead.

  5. Jason Smith says:

    I am planning on using dedicated 6-3 UF wire w/ 50amp breaker to exterior 30amp-rated condenser a a 4-zone system with disconnect then 12-2 from condenser to each indoor handler.

    Question is, would i have to pass all 4 12-2 wires through conduit into soffit and then unto rest of the house?

    1. Mickey Luongo says:

      Unless your unit calls for it, 12/2 it is overkill for going from the outdoor unit to the indoor units. Most brands require 14/4. Depending on code in your area, you should not need to run the wire through conduit unless this is a commercial installation.

      1. Hello

        I has Air conditioner Panasonic 208/230V. My house has 120V how to do 230V Please help me. Thank you

        1. Mickey Luongo says:

          Every home has the option of using 208/230 volt. Contact an electrician for more details.

  6. Bob Powell says:

    The out side unit specifies , max breaker size at 20 amps. My questions is that 20 amp circuit gtoing to power both inside and outside unit or do I have to have two different circuits, one for inside unit and one for outside unit? The system i have is 18000 btu heat and AC.

    1. Mickey Luongo says:

      It depends on your specific unit. Most mini splits only require power to the outdoor unit. Then, wiring is run from the outdoor unit to the indoor unit.

          1. This is what I got to install my system from LG. I got 1 20 amp circuit in the main panel. I got a a romex 10-3 wire between the main panel and a outside fuseless break box. I got a a whip between the outside box and the compressor unit. From the compressor to each of the airhandlers I installed a 14-4 soft cable (make sure it’s not solid wire). It was difficult to find and get the required 14-3 cable.

  7. Great electric advice, THANKS! Planning a system into a ‘50s house, with 4 indoor air handlers and one condenser. Questions: 1. Recommend / must use a GFCI at the main breaker? 2. Do most installs of 4 indoor units draw their power off the outside unit (vs. making a separate electric run to the main breaker box. )? 3. Are the indoor units just basically low current devices – small fans & condensate pumps (no electrical heating elements, etc.), OK to run 4 on a single run of 14/2 wire ? 4. Most indoor units, if wired separate from the outside unit, call for a 15 amp breaker. If the external unit calls for 40 amps and you run 14/2 wire from that outdoor unit to power the 4 indoor units, does the outdoor unit have its own internal breaker or current limiter built in, so in the event any of the 4 internal units start to fail, power to them is rapidly cut off as the draw on that line approaches 15 amps (vs the much more beefy 40 fed to outdoor unit)? 5. Can the typical indoor cassette mount flush within a 16” (and/or 20”) OC joist hard ceiling? 6. When mounting into a hard ceiling do you typically mount to the joists or suspend from the roof rafters? 7. Are cassettes sufficiently sealed / fire rated such that you can pile 32” of blown in fiberglass insulation directly on top of them without heat or fire issues? Thanks!

    1. Mickey Luongo says:

      I would recommend contacting our sales department at 877-847-0050 for help with your questions.

  8. Marty Wright says:

    How far can you run the condensing lines from the outside unit to the inside unit ? Is 20′ to much ?

  9. Rob Walter says:

    Is it ok to run 12/3 solid core wire with a double pole 15 amp from the breaker box to the disconnect, then run 14/3 stranded from the disconnect to outside and inside unit. 14/3 stranded is hard to fine and expensive. I have a 75 ft run from breaker to disconnect and only 30 ft from outside to inside unit.

    1. Mickey Luongo says:

      Exact wire specifications depends on your units needs. I would not recommend using 14/3 from the disconnect to the unit. You should use an electrical whip designed to go from the disconnect to the unit. These are usually a heavier gauge and weather sealed. For the outside unit to the inside unit you should use 14/4 mini split wire.

  10. Hi, I’m not an electrician so what to make sure I don’t cause an issue

    We have two Mitsubishi Mr. Slim units; one upstairs apartment and one downstairs. My unit upstairs has been working fine and then the next day it wouldn’t turn on. I noticed at the shut off/disconnect box, the downstairs unit on/off switch setting was different from my unit. Although, not sure what signifies on or off.

    In any case, I pulled my switch out and turned it upside down and my unit works now and my switch now looks like the downstairs switch. Since I’m not an electrician, if my unit didn’t work when the switch was in and by turning it upside down and now it works, would this cause an electrical issue? Meaning, even though my unit was working before I flipped the switch (turned it 180 degrees) is it possible the switch had nothing to do with it failing? The reason I’m confused is the neighbors nor I changed (flip) the switch.
    Its possible someone snuck in the backyard and flipped the switch. So would that be the only way the unit didn’t turn on…someone had to have flipped the breaker? Or can the unit work no matter if the switch is flipped on or off? Or it can only work if its on and never works when off? Just want to make sure I don’t cause an issue by flipping the switch

    1. Mickey Luongo says:

      It sounds like someone flipped the switch on you. It may be worth investing in a lock for your disconnect switch.

      1. Thanks Mickey! Since it was not working and by flipping the switch and it works now, only way for it to not work someone had to have flipped it?

  11. Hi, I am installing a Split Duct unit in my house can I install the outdoor unit on the exterior wall “above” the height of the indoor unit ?

  12. I want to install a mini-split system for cooling in my house to supplement the existing central AC which doesn’t work well on the top floor due to a lot of glass and a lot of sunshine. Getting 240V to the location is not easy and looks like it is going to be expensive due to the existing wiring. The area I need to cool is around 500 sqft and I’m wondering if I should just go with a low voltage system given the small area. Thoughts? Any negatives of going this route vs 240? Thanks

  13. Very good information, I have one question: I am planning to install an 18,000 BTU Mitsubishi ductless air condition. The distance from the panel to the outside disconnect box is approximately 70 ft the specs for the unit says 20 Amps max , 220 Volts. Should I use a 12/3 or 12/2 romex wire from the panel to the disconnect box? (If understood correctly 12/2 is the one because you do not use the neutral wire) -thanks

  14. Dale in upstate NY says:

    I have 10-2 w/gnd wired to outdoor disconnect box, which means I would wire the whip’s ground and neutral to the supply ground wire in the disconnect box.

    Is this code-acceptable, or will I need to have 10-3 w/gnd from house breaker box to outdoor disconnect?

  15. Mini Split Accessories & Components - A Guide on Which You Need says:

    […] is crucial to select the right size for your system, as ones that are too large or small will cause your system to […]

  16. My upstairs unit cannot he a straight run back to the compressor/controller. I had an electrician come in and make the run to code which required the wiring to be spliced because of the run. Now the unit will power on and shut down in under a minute. Is there a specific type of splice that needs to be done or does the splice need to be soldered? Thanks

  17. Barefoot Lover says:

    Is it okay to use a mini-split ceiling cassette with a 115V condenser? If not can the blower motor be switched with a 115V blower motor?

  18. Larry Duwa says:

    Can you run the wires from the outdoor unit to the indoor unit in the same conduit on a commercial job without causing any problems as long as all the wires are rated the same voltage

  19. Hello. My Mini Split calls for 20 amps, 220 volts. If I run one line to my mini split that is 12-3 gauge from a 20 amp double pole breaker, is there room for me to add an identical mini split to a separate disconnect box in the future? Everything would be identical, same unit, same location, separate disconnect.

  20. Lino Somarriba says:

    I am installing a 30k btu lg air mini split with an 18k cieling cassette and a 12k wall unit. I am going to wire a 10/2 from panel to disconnect to outside unit, do I need another wire to supply power to the indoor units or will it recieve all the power from the outside? So all the power I need for these units is whay goes to outside unit?

    1. Mickey Luongo says:

      The indoor units receive power from the outdoor unit. You need to run 14/4 from each indoor unit back to the outdoor unit.

  21. Clay Fisher says:

    I am installing an 18000 BTU Mitsubishi mini split in the room above my garage. I asked the builder of the house to prewire for the minisplit. Now that the house and the bonus room are complete I checked and the builder only ran a 12-2 wire (2 insulated wires and a bare ground). Can I use this wire to run the required 230V circuit with a 20 Amp breaker. I thought that I needed 3 insulated wires and a ground??? Many thanks for your answer.

  22. Hi, is there a max distance the indoor unit can be away from the outdoor unit
    For the 14/4 stranded control wiring to work properly?
    Thank you

    1. Mickey Luongo says:

      The concern with distance between indoor and outdoor unit isn’t the electrical, it’s the refrigerant. Every system will have a maximum distance it can run.

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