Ductless Mini Split Electrical Requirements

Ductless mini splits have become very popular recently. Although more expensive than window and wall air conditioners, they are typically cheaper than installing a central air system (including the ductwork) and more energy-efficient than nearly all other AC types.

Mini-split systems are also compact, attractive, and fitted with modern controls. The latest designs are even Wi-Fi capable, allowing smartphone control via mobile apps and voice control via smart home devices such as Amazon Alexa and Google Assistant.

Unfortunately, ductless mini splits can be challenging to install, especially compared to window and through-the-wall AC systems. Wiring a mini-split can be particularly confusing, which is why most manufacturers advise that you hire an HVAC professional for the job. Failure to work with an HVAC professional can void the product warranty.

This guide explains the main points to know about ductless mini-split electrical components. We also touch on the general wiring process towards the end.  

Mini Split Electrical Wiring Components

Before we discuss the main wiring components of a mini-split, it’s important to mention that electricity enters the home via what’s known as the main service panel.

When electricity enters your home, you’ll usually find an electric meter and the main service panel. The main panel comes in a range of sizes. It’s typically installed outside the house adjacent to the meter, though some people prefer to have it inside the house directly behind the meter.

This panel receives three incoming electrical service wires from the electric post outside your home and routes smaller cables and wires to subpanels and circuits throughout the property. For safety reasons, the panel is grounded.

The main panel features a circuit breaker and fuses to disconnect the home’s electrical circuit from incoming power. This is critical in case of a power surge. Circuit breakers can be shut off manually to disconnect a section of the home from the power grid. For instance, you can manually shut it to disconnect the mini-split during maintenance.

However, it can also trip automatically during power surges to protect the home and your systems and appliances during a power surge.  

Some electrical panels also use levers and fuses in place of the circuit breaker. You can easily pull down on a lever or pull out a fuse to disconnect the mini-split from the electrical supply.

The maximum amperage the main panel can handle is marked on the main breaker. For the majority of homes, the limit is 100 amperes. However, newer homes have 150 amp to 200 amp breakers. Smaller circuit breakers on the mainboard are rated depending on the type of wire and load requirements.

Now, let’s focus on the five main electrical components needed to run a ductless mini-split air conditioner.

A subpanel

Subpanels are special electrical supply centers that directly connect to the main panel and serve specific purposes in the home. An excellent example is a subpanel that serves an air conditioner.

Subpanels are typically located in a different area of the home. AC subpanels, for instance, are located near the air conditioner.

Each subpanel has its own set of circuit breakers and fuses. Your mini-split panel must have the correct power ratings. For instance, whereas most mini-split systems are rated 220 volts, a few low-capacity units draw 110 volts. You need to pick the right panel with properly sized breakers to deliver on your electricity needs.

You may not need to worry too much if you’re working with a licensed, professional electrician. The electrician will ensure that your AC subpanel is the proper size and your wiring is up to code.

Electrical wires

You’ll need many wires to connect the mini-split subpanel to the primary service panel and the AC to the subpanel. However, you can’t just pick any wire for the job. Thickness (gauge) and quality are critical.

  • Wire gauge 

Gauge refers to the diameter of an electrical wire and directly impacts the amount of current the wire can safely carry. It also determines the wire’s electrical resistance and weight. Therefore, you need the proper wire gauge for your mini-split. Otherwise, the risk of fire is high.

Standard wire sizes are 2, 6, 8, 10, 14, and 16-gauges. Lower gauge wires are thicker and can handle more electric current. Meanwhile, higher-gauge wires are thinner and can handle the limited electrical current. For example, whereas a #14-gauge wire can carry a maximum of 15 amps, #6-gauge wires can handle up to 60 amps.

  • Ampacity 

Aside from the diameter measurement, the right mini-split wire is also of the right ampacity. Ampacity is a term for the maximum current the wire can carry in amperes. It’s defined as the amount of current the wire can carry withstand before heating beyond the maximum operating temperature.

Each cable and its jacketing and insulation is rated for specific temperatures. If the heat (resulting from current resistance in the wire) exceeds the cable rating, the cable could fail or possibly catch fire.

Connecting cable

The connecting cable connects the indoor handler to the outdoor compressor. It’s also popularly known as the four-conductor cable. This name comes from the fact that this cable requires a set of four wires to function.

The connecting cable carries information and supplies power between the outdoor compressor and indoor air handlers. You need one for each air handler if dealing with a multi-zone mini split air conditioner.

For typical installations, you need a 14 AWG 4-conductor stranded cable that runs through a conduit. It’s important to verify that the cable meets local codes.

An electrical whip

The electrical whip, also known as a base power infeed or base feed module, is a type of cable that converts a fixed-in-place device into a modular asset. Specifically, air conditioner whips are used to connect the compressor unit to the disconnect box.

The whip is made of high-voltage electrical wires and located outdoors, tucked away in a case to protect it from adverse weather elements, including direct sunshine and rain.

A disconnect box

Also known as a fuse box or switch box, the disconnect box contains a switch that allows HVAC technicians to turn off the power to the mini-split during repairs and general maintenance. The box is typically connected near the outdoor condenser unit.

These boxes are mandatory. If your AC doesn’t have a disconnect box, you’re liable to legal penalties. Professional technicians know this and will never leave without installing a disconnect switch.

Remember also that the disconnect box isn’t designed for regular switching of the AC. It purposely exists to make the HVAC technician’s job easier during repairs and maintenance.

Disconnect boxes can be fused or non-fused. Most homeowners prefer non-fused boxes because the breaker in the service panel protects the fuse. Additionally, it’s easy to reset a circuit breaker on your own than replacing a fuse.

The Actual Wiring Process

We strongly advise that you let a licensed, professional electrician wire your mini-split air conditioner. However, it doesn’t hurt to know how the wiring is done, right?

Step 1: Install the mini-split disconnect box

The first step here is to mark the area where the disconnect box is to be installed. We’ve already mentioned that it should be ideally located next to the outdoor condenser. Once you’ve identified a location, run a 230V or 110V line from the home’s primary breaker box to the location. It’s important to run the right voltage line. If it’s a 230V mini-split, you need a 230V line. If it’s a 110-Volt mini-split, run a 110-Volt line.

Wire two hot leads to fused connections inside the box and the ground to the provided connection. Later on, you’ll need to install a faceplate before inserting the on/off switch. 

Step 2: Connect the electrical whip

This should be a straightforward process. The electrical whip runs from the disconnect box to the mini-split condenser unit. The whip comes pre-packaged and helps ensure that the installation meets local codes. It also keeps the process simple.

You can also run your wire from the fuse box to the condenser unit. However, open rarely meet code. A good trick is to run the wire through an outdoor grade conduit to protect the wires from weather elements if you choose this option.

Step 3: Connect the mini split to base

This process can be a little more challenging because you’ll be dealing with more wires. However, it’s easy once you get going. The only thing you need to remember is that colors must match. Red wires connect to red inputs, black wires connect to black, and green wires connect to green.  

Something else to remember is that the specific details may vary depending on your mini-split. For instance, the wire colors might be different. Electricians know all the combinations, thus can handle the difference without breaking a sweat. If you’re doing the installation yourself, it’s best to refer to the owner’s manual.

Step 4: Connect wires that will eventually connect to the indoor air handlers

With the outdoor unit wired, it’s time to connect the wires that will eventually connect to the indoor air handler. The most important thing here is how many air handler units you have.

The greater the number of air handlers, the more complex the process can be. It’s best to number the indoor units for easy cross-referencing. This way, you can connect the wires to one air handler before moving to the next air handler.

Also important to note is that you need to use 14-gauge stranded wires for air handler installation. You can also use 14-gauge solid wire if you can’t readily access stranded wire. However, stranded wires work best.

Step 5: Wire the indoor air handler(s)

Begin by running the wire inside to reach the indoor air handler. The length of wire required will depend on the distance between the condenser outside the house and the air handlers inside.

Ceiling hanging air handlers typically require the most wire. Since you don’t want to connect wires midway, make sure your wires are sufficiently long. 

Typically, you’ll be dealing with four wires, including a ground wire. Make sure each wire is connected to the correct port. Also, some manufacturers recommend unique crimping methods to ensure a more secure connection. While it’s not mandatory to follow the crimping advice, it can help in the long run.

Congratulations, You’re Done!

You’ve wired your mini-split correctly and are ready to use the air conditioner. The only other thing we must mention is that mini split air conditioners are expensive investments that need appropriate care.

Although manufacturers offer warranties, manufacturer warranties are limited to mechanical failures. The manufacturer warranty won’t cover your AC in case of a power surge caused by lightning.

Installing a surge protector can help. Also, consider getting home insurance. Most providers charge about $500/year, but it’s worth it.