Should You Splice A Mini Split Communication Wire?

Yes, you can splice a mini split communication wire, but it’s not recommended.

This site contains affiliate links. I make a small commission, but you don’t pay more.

But it may not be worth the savings between splicing the wire and creating a problem or running a new cable from end to end. If new 14-4 stranded wire is unavailable, like many materials during COVID-19, I’d probably splice it and hope it works.

Do you love being tormented? If so, go ahead and splice it and cross your fingers. Chances are it will work just fine, maybe for a while or maybe forever. Have I created enough doubt in your mind?

So, to clarify one little issue, the communication cable is called a communication cable, even though only one of the four wires is a digital or communication wire. The other three wires are power and ground.

Digital Signals Through A Mini Split Communication Wire

If done correctly, splicing power and ground wires is generally not a problem. I would do that in a heartbeat. Digital signals are temperamental or sensitive to disruption (like splices). For some reason, digital signals don’t like flowing through splices.

But if you can put your hands on some 14/4 stranded wire, then I’d say no, don’t splice it, but you’re the boss. The indoor and outdoor units may not communicate well if there is an imperfect splice.

Not communicating well means the unit won’t respond as expected when you push buttons on your remote. My wife and I talked early this morning and had the same idea at the same time. You know what good communication is, right? And you know when it is not good.

There are several methods of creating wire joints and splices that you may want to consider. If you are considering soldering the wire, even the wrong solder can make a poor connection and restrict communication through the wire.

Below are some materials commonly used to connect wires.

Twist on Wire ConnectorAmazon
Heat Shrink Butt Connectors – Insulated Waterproof Amazon
Heat Shrink Butt Connectors KitAmazon
  1. Wire caps that you twist on
  2. Wire caps that you crimp on
  3. Butt connectors

What Kind Of Wire Do You Use For A Mini Split?

When I first started installing mini splits, my suppliers recommended shielded cable. They were convinced that outside influences on the cable would disrupt communications between the circuit boards of the indoor and outdoor units.

mini split 14/4 cable

It’s true that sometimes our atmosphere contains unseen frequencies floating around in unexpected areas. Using an augmented reality app, you can see some of these things floating around. This link will take you to the site that describes the app and has a video showing how this works.

I’m not saying these are the same wireless signals that would bombard a communication cable connecting your mini split head to the outdoor unit; this is just a simulation of why you should consider a shielded cable.

But, and it’s a big one, I haven’t used shielded cable for a long time. I have experienced absolutely zero interference from any type of outside frequencies. If, for some reason, your installation is near a lot of wiring or motors that emit signals, then you might consider the shielded cable just to be safe.

My go-to wire is stranded 14/4 cable. You can view a sample of a (ad) 25-ft coil on Amazon. It’s available in many different lengths depending on your needs. Search for 14/4 stranded communication cable on Google or Amazon, and you’ll find more choices.

Mini Split Signal Wire Indoor Outdoor UV Protected 14 AWG Direct 14/4 (100FT) Amazon

Stranded cable is more flexible than solid wire. The difference in conductivity between stranded and solid wire is minimal. The advantage of stranded cable is its ease of installation and durability. Solid wire can break off when the ends are stripped incorrectly or when some vibration occurs.

10/2 Or 10/3 Wire For A Mini Split?

You will find the wire size information on your unit’s label. But one of the questions here is how many conductors. For either a 120-volt or 240-volt mini split, all you need is 2 conductors and a ground.

The two screws circled in yellow are for equipment grounds. The one on the left is ground for the power, and the one on the right is for the ground wire in the communication/power cable (14/4) to the indoor unit.

Starting from left to right above the yellow line are 1(L1) and 2(L2). These are the power from your panel. This unit is 230 Volts. On a 120 Volt unit, one of these would be power from the breaker, and the other would be a neutral wire.

The next three wires are your cable connecting the indoor and outdoor units. Make double-dang sure you connect them in the same order on both cable ends. I like to think of them as red, white, and blue (black) 1, 2, and 3. Just for me, it keeps it simple.

What Voltage Does A Mini Split Use?

Typically, mini split units are available in 120-volt or 240-volt models. The four conductors or wires in a mini split communication cable each have a specific purpose.

The 120-volt units have a ground, neutral, power, and communication wire. The 240-volt units have a ground, two power wires, and a communication wire. It’s important to note that the communication wire is not a power wire. Communication is digital. Digital signals are easily disrupted, and there lies the trouble when considering splicing this cable.

Go to Amazon and check out what shielded cable looks like. The difference between shielded and regular cable is noticeable as you examine it.

18/4 AWG Shielded CNC Wire (50FT) Amazon

You can splice power wires all day long if you do it correctly without power interference—it’s done repeatedly in your home—but digital signals are a different animal.

On a side note, I have found it quite humorous that the inspector allows me to run the power cable from the outdoor unit to the indoor unit when installing a mini split. I have two electrical licenses for the state of Oregon. One allows me to work inside a piece of HVAC equipment, and the other allows me to run a thermostat wire.

Inspectors always seem to have blinders on regarding me and other HVAC contractors running this power cable. I have heard that electricians don’t want to bother with the small job of running one cable. They are so busy doing other jobs that in my area, you won’t find one to even answer a phone call, let alone come out to run a communication wire.

Can I Use 12 Gauge Wire For A Mini Split?

It depends on whether you are talking about the main power or the control cable. If your mini split’s maximum fuse size or circuit breaker is 20 amps, then 12 gauge solid wire for the power cable would work fine.

We need to read the installation instructions here. Information about wire size is even listed on the equipment label.

Is it worth using the wrong materials and leaving a loophole that could void our warranties or cause equipment to malfunction? Chances are, though, the manufacturer will never know the wire size, but why tempt fate?

I know for a fact that even the 14 gauge stranded wire for the control cable between indoor and outdoor units is a struggle sometimes to get inserted into those tiny screw connections inside the unit’s wiring compartments.

So, if you are wondering what size breaker or wire to use for your mini split, it’s all right there on the label of your equipment. Wire sizes are easy to find when you know the maximum breaker size. Standard wire sizes for amp draws are 30 amps using ten gauge wire, 20 amps using 12 gauge wire, and 15 amps using 14 gauge wire.

Remember that in most industries, bigger is not always better. It can be a useless expense, especially given the price of copper wire.

Chad Peterson

Chad Peterson is a veteran of the HVAC industry since 1977. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

Recent Posts