Circuitry & Wiring Specifications for Installing Ductless Mini-Splits & HVAC Units
Ductless mini splits are one of the most popular AC choices for homeowners and businesses alike. We sell tons of mini split air conditioners each day 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 in order for the job to be done safely and without harm to yourself or the unit. For that reason, we do not recommend homeowners try to install the unit themselves. Unless you are an advanced DIYer with extensive experience in electrical work, we strongly advise you 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.
Step 1 – Mini-Split Shut-off box:
Run a 230/208 volt or 115 volt* 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 there are some that are 115V.
Step 2 – Mini-Split Wiring:
Mount the shut off box on the outside wall and connect the wires from the break box.
In order to meet code, you must have a shutoff 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:
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 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.
Step 5 – Mini-Split Wiring Connecting Inside to Outside Unit:
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 installation. Pictured is 14 gauge solid wire which will work, but should only be used if stranded wire is unavailable. Total Home Supply offer Honeywell 14/4 Mini Split wire in 50 ft and 250 ft rolls.
Step 6 – Mini-Split Installation Complete:
Run the wire inside.
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.
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!