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What Is a Ductless Air Conditioner?

CEO Khai Intela
Whether you live in a new home or an older home without ductwork, are adding a room addition, converting an existing space, or if you want more complete year-round climate control over a specific room...

A mini split installed in garage shows what is a ductless air conditioner Whether you live in a new home or an older home without ductwork, are adding a room addition, converting an existing space, or if you want more complete year-round climate control over a specific room or area of your home, ductless systems are an efficient way to expand your comfort, no matter the challenges your space presents. Discover what a ductless system is, learn more about mini split SEER ratings, explore how mini splits can help you save on installation costs, and more.

What Is a Mini Split Air Conditioner?

What is a mini split air conditioner and how do they work? A ductless mini split system includes one outdoor unit and one indoor unit, connected by refrigerant tubing and electrical wiring. The indoor unit is often wall-mounted and delivers heated or cooled air directly into the living space - no ductwork needed. This is called a single-zone system, designed to provide heating and cooling comfort to one specific area. A Carrier ductless multi-zone system combines one outdoor unit with up to five indoor units to provide comfort for an entire home.

Because there are several styles of indoor units available, and installation only requires a hole in the wall for the wiring and refrigerant line, ductless HVAC systems are among the easiest and most versatile systems to install.

A boy in space themed bedroom knows what is a ductless mini split

How Do Ductless Air Conditioners Work?

Pretty darn well, if we do say so ourselves. So, how do ductless air conditioners work?

Ductless air conditioner systems use the same cooling process as a typical central air conditioning system. However, instead of using one centrally located indoor unit that delivers cool air through a series of ducts and vents, a ductless indoor unit blows cooled air directly into one living space.

A complete ductless system includes an indoor unit with an evaporator coil and blower fan, and an outdoor unit with a compressor, condenser coil, and fan. The two units are connected with copper refrigerant tubing and electrical wiring. Ductless AC units are effective for any space in the home:

  • High wall units can be mounted directly to an interior wall, regardless of ceiling height.
  • Console units work for rooms where wall mounting isn't possible or desirable.
  • In-ceiling units are hidden from view if ceiling space allows, offering a ducted unit option.
  • Cassette units can be mounted directly to the ceiling surface.
  • Different sizes of ductless AC units allow for customized heating and cooling depending on the room's square footage.

Outdoor units can be strategically placed to minimize noise heard in living spaces or outdoor gathering spaces. The ability to install narrow cabinets allows for installation in small outdoor spaces or on small lots.

The outdoor compressor unit pumps refrigerant through the refrigerant tubing to the indoor unit's coil. As the liquid refrigerant turns to gas, heat and humidity are removed from indoor air blowing across the coil, sending cooler, less humid air back into the living space. The refrigerant, in gas form, cycles back to the outdoor coil where it is converted back to a liquid as heat energy is released. Ductless heat pump systems operate the same way for cooling, with the additional ability to reverse the process for heating the indoor space.

A living room shows the context of how do ductless air conditioners work

What Is Mini Split AC's Zone? Single- and Multi-Zone Systems

What is a mini split AC's zone, and what's the difference between single- and multi-zone systems when it comes to choosing the perfect ductless AC? Ductless systems can be configured with either one or multiple indoor units powered by a single exterior compressor. The versatility of ductless systems makes them perfect for many applications, including room additions, sunrooms, garages, and they are an ideal air conditioning option for older homes.

A graphic showing what is a ductless mini split system


Ductless air conditioners and ductless heat pumps can be installed so that one indoor unit corresponds to one outdoor compressor. The compressor carries refrigerant and power to the interior unit via a small pipe, running through a small opening, with minimal impact on your home.


One outdoor compressor can power up to five indoor units, each separately controlled by a wireless remote control, offering flexible options for configuring your comfort solutions. You can even choose to add units to your compressor in the future after installing just two indoor units, allowing for more streamlined expansion or renovation of your home as time and budget allow.

Rules Of Thumb For Ductless Mini Splits

Ductless and heat pump systems are like the Swiss Army knife of HVAC. They both heat and cool and can provide comfort in areas where traditional ducted systems can't. Adding a room to an existing home? Converting a basement, attic, or garage into a living space? Providing a boost to a room that's always too hot or too cold?

A Carrier ductless system has a solution for all of the above. With virtually endless configurations and a variety of indoor units to choose from, ductless systems provide the ultimate customizable comfort solution. They are quick and easy to install with no ductwork required.

Ductless systems can work alongside your existing air conditioner or heat pump system and can help you save on your utility bills with ENERGY STAR® qualified systems. By actively heating and cooling only the areas that are occupied, you can minimize your energy use. A mini split SEER rating lets you know how much energy your system will use over the course of the year. Plus, there's no risk of energy losses from leaky ductwork.

Still in the consideration stage? Check out the pros and cons of a ductless air conditioner below.

Pros of a Ductless Air Conditioner

  • Highly energy-efficient cooling system.
  • Easy installation without the need for patching, painting, or indoor wiring.
  • Efficiently cools a room added to an existing home.
  • Effectively cools a space converted into living space, like a basement, attic, or garage.
  • Preserves the integrity of an older home without space for ductwork or vents.
  • Preserves the décor of indoor spaces with low-profile units.
  • Adds cooling power to a room with existing air conditioners and/or uneven temperatures.

Cons of a Ductless Air Conditioner

  • Cost of installation of a mini-split system can be higher than a traditional ducted system (but you may save on utility costs over time).
  • Mini-split units are wall-mounted and can be seen within a room, unlike a traditional HVAC system. However, most designs are sleek and unoffending to the eye.

What Is Ductless AC's Benefit?

Minimal Installation With Ductless

One of the significant benefits of ductless air conditioning is the absence of ducts. No ductwork means no patching, no painting, and no hassle. Configuring your ductless air conditioner system is simple, with virtually invisible installation that requires only a small hole in the wall to connect the pipe from the indoor unit to the compressor unit outside. The outdoor compressor unit also provides power to the indoor unit, eliminating the need for additional indoor wiring.

Check out our Ductless heat pump solutions.

Efficient Heating and Cooling

Carrier ductless heat pump systems perform efficiently in even the most extreme conditions, providing year-round comfort control, regardless of the weather outside. Even at -22°F, select systems can heat at 80% capacity. They can also cool at 100% capacity when the outdoor temperature is 130°F.

Precise Heating and Cooling

Carrier ductless systems deliver pinpointed comfort, no matter where indoor units are placed. With room-based temperature control, you can have a cooler home office and a warmer bedroom. Each room can be set to a different temperature, depending on your comfort needs. Inverter compressor technology makes heating and cooling temperatures more precise. Instead of the constant temperature swings supplied by typical single-stage systems, a variable-speed, inverter-controlled compressor operates like cruise control for your comfort. It efficiently maintains indoor temperatures with minimal fluctuation.

Quiet Operation

Quiet operation is essential for your overall comfort. Carrier ductless outdoor units with inverter-controlled variable-speed compressors operate on longer, lower-speed, and quieter comfort cycles. Long refrigerant lines to the outdoor unit allow flexibility in installing it farther away from decks, patios, or other outdoor living spaces.

Allergy Control

Ductless mini-split systems provide cleaner air in the rooms where they are installed, thanks to filters in each indoor unit. Ductless heating and cooling aren't just about controlling air temperature; they're about controlling air quality. With no cross-contamination of air between rooms, circulation is contained within a confined space.

Frequently Asked Questions About Ductless Mini Splits

Do Ductless Air Conditioners Pull Air From Outside?

No, ductless air conditioners recycle the air already within your home, similar to an HVAC ducted system.

Does Ductless AC Need To Be Vented?

No, a ductless AC system does not create harmful gases and therefore does not need to be vented out of your home.

Does a Ductless AC Purify Air?

Yes, ductless air conditioners can help purify your indoor air because the indoor units include an air filter. The air filter helps trap unwanted particles from being recirculated back into your home.

Do Mini Splits Produce Carbon Monoxide?

No, it is not possible for a mini-split system to produce carbon monoxide.

The benefits of ductless air conditioning shine on their own. To find out if a ductless air conditioner is right for your home and get a quote, contact a Carrier ductless expert near you.

What Is the Difference Between a Mini Split and an Air Conditioner?

The main difference between a mini-split system and a central air conditioner is the way they deliver cool air into your home.

An air conditioner uses a network of ducts to distribute cool air throughout your home. The ducts are typically installed in the walls, ceilings, or floors, and the cool air is delivered through registers or vents. In contrast, a mini-split system does not use ducts to deliver cool air. Instead, it consists of one or more indoor units that are mounted on the wall or ceiling of each room or zone in your home. These indoor units are connected to an outdoor unit via a conduit that houses the power cable, refrigerant tubing, and condensate drain. Each indoor unit has its thermostat, allowing for individual temperature control in each room.

Another difference is that a mini-split system is typically more energy-efficient. Since ductwork can be a source of energy loss, a mini-split can avoid this issue and deliver cool air directly to the room where it is needed. Additionally, mini-splits often have inverter-driven compressors, which can adjust the cooling output to match the needs of each room, resulting in less energy waste.

Overall, the decision between a central air conditioner and a mini-split depends on various factors, including the size of your home, your cooling needs, and your budget. If you have a larger home or need to cool multiple rooms or zones, a central air conditioner may be more practical. However, if your home doesn't have existing ductwork, a mini-split system could be a good option. Additionally, if you want personalized temperature control and energy efficiency, a ductless system may be the better option.

What Is a Mini Split System?

A mini-split system, also known as a ductless mini-split system, is a type of heating and cooling system that consists of an outdoor unit and one or more indoor units. The indoor units are typically wall-mounted and are connected to the outdoor unit via a small conduit that houses the power cable, refrigerant tubing, and condensate drain. Each indoor unit has its thermostat, allowing for individual temperature control in each room.

The main advantage of a mini-split system is its flexibility in providing zoned heating and cooling. With a mini-split system, you can choose which rooms or areas to cool and adjust the temperature in each zone independently. This means you can save energy by only cooling the rooms you use, rather than cooling the entire home.

Mini-split systems are also easy to install as they do not require ductwork, which can be a source of energy loss. Additionally, mini-split systems are often more energy-efficient than central air conditioning systems, as they can avoid the energy losses associated with ductwork.