How Do Ductless Air Conditioners Work?

Ductless air conditioners use an indoor and outdoor unit connected by refrigerant lines, providing efficient, flexible, and zone-specific cooling without ductwork.

Ductless air conditioners, also known as mini-split systems, have become a popular choice for homeowners and businesses seeking efficient, flexible, and cost-effective cooling solutions. These systems offer several advantages over traditional central air conditioning systems, especially in homes without existing ductwork. But how exactly do ductless air conditioners work?


The Basics of Ductless Air Conditioners

A ductless air conditioner consists of two main components: an indoor unit and an outdoor unit. These units are connected by a conduit that houses the power cable, refrigerant tubing, suction tubing, and a condensate drain. Here’s a breakdown of each component:

Indoor Unit

The indoor unit, also known as the air handler, is usually mounted high on a wall or ceiling. It contains an evaporator coil, a fan, and an air filter. The indoor unit blows the cooled air directly into the room. It operates quietly and can be controlled via a remote or a wall-mounted thermostat.

Outdoor Unit

The outdoor unit contains the compressor, condenser coil, and expansion valve and is typically placed outside on a concrete pad. The compressor is the heart of the system, responsible for circulating refrigerant between the indoor and outdoor units. The outdoor unit dissipates the heat absorbed from inside the building, releasing it into the outside air.

How Ductless Air Conditioners Operate

Refrigerant Cycle

Ductless air conditioners operate using a refrigeration cycle, similar to traditional air conditioning systems. Here’s a step-by-step look at how they work:

  1. Refrigerant Absorption: The indoor unit absorbs the warm air from the room. The refrigerant in the evaporator coil absorbs the heat from this air, causing the refrigerant to evaporate into a gas.
  2. Compression: The refrigerant gas travels through the conduit to the outdoor unit. The compressor compresses the gas, raising its temperature and pressure.
  3. Heat Release: The high-pressure refrigerant gas moves to the condenser coil in the outdoor unit. Here, it releases the absorbed heat to the outside air, causing the refrigerant to condense back into a liquid.
  4. Expansion: The high-pressure liquid refrigerant then passes through the expansion valve, reducing its pressure and temperature.
  5. Cooling Cycle: The cooled refrigerant returns to the indoor unit, ready to absorb more heat from the room. This cycle repeats, maintaining a cool and comfortable indoor environment.

Zoning Capabilities

One of the standout features of ductless air conditioners is their zoning capability. Each indoor unit operates independently, allowing for customized temperature control in different rooms or zones. This flexibility enhances comfort and improves energy efficiency, as you can cool only the occupied areas rather than the entire building.

Advantages of Ductless Air Conditioners

Energy Efficiency

Ductless systems are known for their high energy efficiency. Since there are no ducts, there is no energy loss associated with duct leakage, which can account for up to 30% of energy consumption in traditional systems. Additionally, the ability to cool specific zones reduces unnecessary energy use.

Easy Installation

Installing a ductless system is less invasive than installing a central air conditioning system. The absence of ductwork means less construction work, making it a great option for older homes or buildings without existing ducts.

Improved Indoor Air Quality

Ductless air conditioners often come with advanced filtration systems that reduce dust, allergens, and other pollutants. This leads to better indoor air quality, which is especially beneficial for those with allergies or respiratory issues.

Quiet Operation

Both the indoor and outdoor units of ductless systems are designed for quiet operation. The indoor unit often operates at a whisper-quiet level, making it ideal for bedrooms, living rooms, and other quiet spaces.


Ductless systems are versatile and can be used in various applications, from single-room additions to entire homes and commercial spaces such as offices and retail stores.

St. Louis Air Conditioning

Ductless air conditioners are excellent for efficient, flexible, and cost-effective cooling. Their unique design and operation offer significant advantages, particularly in energy efficiency, ease of installation, and personalized comfort. A ductless air conditioner might be the perfect choice if you’re considering a new cooling system for your home or business in the St. Louis area. Contact Thomas Hoffmann Air Conditioning & Heating today for professional advice and installation services!

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At Thomas Hoffmann Air Conditioning & Heating, we pride ourselves in being a locally owned and operated HVAC company. With more than 30 years of experience and a master technician and mechanical engineer as our owner, we can replace, repair, and provide maintenance for your business or home’s HVAC system.

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