What Is a Ductless Air Conditioner?

by | Mar 10, 2023

happy family enjoying clean purified air

You’ve heard the terms before: ductless, mini split, or mounted cooling systems. So what is a ductless air conditioner? You guessed it – no ductwork. With a ductless mini split, you don’t need it.

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.

What Is a Ductless Mini Split?

A ductless mini split system, in its most basic form, 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 and it’s 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 because 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.

How Do Ductless Air Conditioners Work?

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

At the minimum, a complete ductless system includes an indoor unit with an evaporator coil and blower fan; and it has 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:

  • Have high wall units mounted directly to an interior wall
  • Console units work for rooms where wall mounting isn’t possible or desirable
  • In-ceiling units are an example of a ducted unit which is hidden from view if ceiling space allows
  • Cassette units can be mounted directly to the ceiling surface

Outdoor units can be strategically placed to minimize noise heard in living spaces or from patios or outdoor gathering spaces. Narrow cabinets make installation possible in small outdoor spaces or on small lots.

The outdoor compressor unit pumps chemical refrigerant through the refrigerant tubing to the indoor unit’s coil. As the liquid refrigerant turns to gas, heat and humidity is 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 through the outdoor coil. A ductless heat pump system operates exactly the same way for cooling, with the additional ability to reverse the process for heating the indoor space.

Single and Multi-Zone Systems

Ductless systems can be configured with either one or multiple indoor units powered by a single exterior compressor. The versatility of ductless systems make them perfect for many applications, including room additions, sunrooms, garages, and they are an ideal air conditioning option for older homes.


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, installed with very little impact to your home.


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

Things To Consider About Ductless HVAC Systems

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 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, they can help you save on your utility bills with ENERGY STAR® qualified systems and by actively heating and cooling only the areas that are occupied. 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
  • No ductwork means no hassle, like patching or painting
  • No need for indoor wiring
  • Efficiently cool a room added to an existing home
  • Effectively cool a space converted into living space, like a basement, attic, or garage
  • Preserve the integrity of an older home without space for ductwork or vents
  • Preserve the décor of indoor spaces with low-profile unit
  • Add cooling power to a room with existing air conditioner 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 the utility costs over time)
  • Unlike a traditional HVAC system, mini split units are wall mounted and can be seen within a room. However, most designs are sleek and unoffending to the eye.

The Benefits of Ductless Air Conditioning

Minimal Installation With Ductless

One of the many benefits of ductless air conditioning is no 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 pipe from the indoor unit itself to the compressor unit outside. The outdoor compressor unit also provides power to the indoor unit, so there’s no need for additional indoor wiring.

Efficient Heating and Cooling

Carrier ductless heat pump systems continue to perform as efficient heating and cooling systems in even the most extreme conditions, providing year-round comfort control, no matter what the weather’s like 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. Want a cooler home office, but a warmer bedroom? No problem. Room-based temperature control is one of the many benefits of ductless air conditioning. Because units can be controlled separately, rooms can be set to different temperatures, depending on your comfort needs. Inverter compressor technology makes heating and cooling temperatures more precise as well. Instead of the constant up-and-down 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 only minimal fluctuation.

Quiet Operation

Never underestimate the role quiet operation plays in your overall comfort. That’s why the best heating and cooling systems should be appreciated, but not heard. 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 also allow the flexibility to install the outdoor unit farther away from decks, patios or other outdoor living spaces.

Allergy Control

With filters in each indoor unit, Ductless systems provide cleaner air in the rooms where they are installed. With Ductless, it’s not just about controlling air temperature, it’s about controlling air quality. When circulation is contained within a confined space, there’s no cross-contamination of air between rooms.

Frequently Asked Questions About Ductless Mini Splits

Do Ductless Air Conditioners Pull Air From Outside?

No, ductless air conditioners do not pull air from outside of your space. Ductless systems recycle the air already within your home, like an HVAC ducted system.

Does Ductless AC Need To Be Vented?

Nope! A ductless AC system does not need to be vented out of your home. These systems do not create harmful gasses that 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 ductless 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 shines on its own. To find out if a ductless air conditioner is right for your home, and to get a quote, call us at 262-783-6000 or contact us online.

Love Gross Heating? Tell your friends and family about us and you’ll get $100 cash back when they have a furnace, AC, or boiler installed. Have a lot of friends and family? That’s great because there’s no limit! Ask for details.

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Gross Heating & Air Conditioning
3260 N. 126th Street
Brookfield, WI 53005
Phone: 262-783-6000
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