Should You Splice A Mini Split Communication Wire?


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 yes you can splice your mini splits communication wire (but don’t). You can do most anything once you put your mind to it. But, will it be worth the savings between splicing the wire and creating a problem or running a new cable from end to end? If it’s just not available like a lot of materials in these covid days, then I’d probably splice it and hope it works.

So to clear up 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.

Splicing power and ground wires, if done correctly, is generally not a problem. I would do that in a heart beat. Digital signals are temperamental or sensitive to disruption (like 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. If the splice is not near perfect then the indoor and the outdoor unit may not communicate well.

Not communicating well means that when you push buttons on your remote and the unit doesn’t respond as you would expect. 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 not good.

There are several methods of creating wire joints and splices that you may want to consider. It could compare to Bubba telling Forest Gump how many ways there are to serve shrimp. You may not like all of Bubba’s recipes and your for sure not gonna like a bad splice in a communication cable.

  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 some unseen frequencies floating around in some unexpected areas. You can actually see some of these things floating around by using an augmented reality app. 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 actual wireless signals that would bombard a communication cable connecting your mini split head to the outdoor unit but it’s just a simulation of why you should consider a shielded cable.

But, and it’s a big but, I haven’t used shielded cable for a very long time I have experience absolutely zero interferences from any type of outside frequencies. If for some reason your installation is near a lot of wiring or motors that emit some 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 25 ft coil on Amazon. It’s available in many different lengths depending on your need. Just search for 14/4 stranded communication cable either in Google or Amazon and you’ll find more choices.

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

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

You are going to find the wire size information on the label of your unit. 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 ground for the communication/power cable to the indoor unit.

Starting from left to right above the yellow line is 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 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 ends of the cable. 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 either 120 Volts 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 a communication wire. The 240 Volt units have a ground, 2 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.

Below is an image that will send you to Amazon and check out prices and information on shielded cable. The difference shielded and regular cable is noticeable as you examine it.

You can splice power wires all day long if it’s done correctly without interference of power. It’s done repeatedly in your home. But digital signals are a different animal.

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

Inspectors always seem to have blinders on when it comes to me and other HVAC contractors running this power cable. I have heard that electrician just don’t want to bother with a small job of running one cable. They are so busy doing other and in my area anyway 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 if you are talking about the main power or the control cable. If your mini splits maximum fuse size or circuit breaker is 20 amps then 12 gauge solid wire for the power cable would work fine.

This is where you and I need to read the installation instructions. Information about wire size is even listed on the equipment label. Is it worth using the wrong materials and leaving a loop hole for our warranties to be voided or equipment to malfunction? Chances are the manufacture won’t even know the wire size, but why temp 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 insert into those tiny screw on connections inside the units 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 out when you know the maximum breaker size. Standard wire sizes for amp draws are 30 amps use 10 gauge wire, 20 amps use 12 gauge wire and 15 amps use 14 gauge wire.

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

Since you’ve read this far, why not travel just a bit further and scope out a couple of my favorite heating and cooling products and tools.

Thank you for reading my article. I hope the information has led to your ability to make good decisions in either working on or discovering how to solve problems in your home HVAC equipment. These are affiliate links, so if you do decide to use any of them I do earn a commission. In all honesty they are products that I would use in my own home or the homes of my friends and family.

Fireplace remotes by Skytech Remote Control Products . My wife loves this and it probably took all of 30 minutes to install. Replace that wall switch or thermostat for your gas fireplace. Easy installation and instructions. In fact I wrote an article that covers the job pretty thoroughly I think.

Honeywell Thermostats. My favorite two Honeywell stats are the T6 Pro and the 8000 Pro series but their is a bunch to select from besides those two models. You can select WiFi that has the capability of operating your system from your smart phone no mater where you are. Honeywell tech support for homeowners is the best out there. Call them if you need at 800-468-1502 or comment below if you have questions.

Fieldpiece HS33 Expandable Manual Ranging Stick Multimeter for HVAC/R. I carry two of these in my service truck. Just like a spare tire, when I get out away from everything, it’s no time for a break down. The Fieldpiece HS33 gives me the ability to do any aspect of my trade. I can measure motor or element amps, check capacitors, and AC or DC voltages. Even different scales of OHMS for finding shorted windings or grounded conductors in motors or compressors.

Chad Peterson

Chad Peterson is near 40 year veteran of the HVAC industry. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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