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Air Conditioners, HVAC Education, Ductless Systems

What Is Ductless AC, and How Does It Work?

A ductless air conditioning system, sometimes called a mini-split system, is an easy and versatile way to cool when you need cooling only in individual rooms, and for homes with limited space. They’re different from traditional air conditioning systems because in most cases they don’t require ducts inside your wall. In some cases, a ductless unit can be installed with a ducted unit but that is less common. Therefore, because they typically don’t require ducts, this makes them flexible enough to work wherever you need them, including room additions, sunrooms, and garages; they’re an ideal solution for older homes without space to add ductwork.


What is a Ductless AC System?

At the most basic level, ductless AC is one outdoor unit (a compressor, condenser coil, and fan) and one indoor unit (evaporator coil and fan) connected with copper tubing and electrical wiring.

With one outdoor unit you can also install multiple indoor units in rooms throughout your home. There are several styles of indoor units available, and installation only requires a hole in the wall for the wiring and refrigerant line, making ductless AC systems among the easiest and most versatile systems to install.

  • High wall units mount directly to an interior wall quickly
  • 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.

How Does a Ductless AC System Work?

Ductless air conditioner systems use the same process for cooling as a typical central air-conditioning system. The difference is that instead of delivering cool air to the entire home through ducts and vents, a ductless indoor unit blows cooled air directly into one room.

The outdoor compressor unit pumps chemical coolant through tubing to the indoor unit’s coil. As the liquid coolant 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 coolant gas then flows back to the outdoor coil where it is converted back to a liquid and releases heat energy through the outdoor coil.

A single-zone ductless air conditioner has only one outdoor unit and one indoor unit.

A multi-zone ductless AC has multiple indoor units—up to five for each outdoor unit.

Reasons to Choose Ductless AC

  • Cool a room added to an existing home
  • Cool a space converted into living space, like a basement, attic, or garage
  • Preserve integrity of an older home without space for ductwork or vents
  • Preserve décor of indoor spaces with low-profile unit
  • Add cooling power to a room with existing air conditioner and/or uneven temperatures

Easy Installation

  • No ductwork means no hassle, like patching or painting
  • No need for indoor wiring
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