June 12, 2024
How Do Ductless Mini-Splits Work?

Ductless mini-splits are among the most popular HVAC systems in the U.S. They’re affordable to purchase and install, and homeowners can often take advantage of rebates and tax credits. They’re also highly efficient and economical to run every month. Let’s explore the main components of a ductless mini-split and how they function.

Outdoor Unit

The term mini-split refers to a split HVAC system. That means that there’s indoor HVAC equipment and outdoor HVAC equipment. Every mini-split will have an outdoor unit, also called a condenser unit. The condenser unit houses the following:

  • Core refrigerant system
  • Condenser pump
  • Condenser coil
  • Condenser fan
  • Electrical system

A condenser unit can support one or multiple indoor units, also called heads. Single-zone mini-splits support one head, and multi-zone mini-splits support two or more heads. The upper limit is usually eight, but installing two or more condenser units in a series is possible to increase that limit.

Refrigerant System

All modern HVAC systems in the U.S. use a refrigerant called R-410A. The purpose of refrigerant in an air conditioner or heat pump is to absorb heat energy. The system can then transfer that heat energy inside or outside depending on whether it’s cooling or heating. HVAC refrigerant systems are closed systems and don’t consume refrigerant. That means you don’t lose refrigerant over time or have to top it off. Systems can lose refrigerant if there’s a leak, however.

Condenser Pump

The role of the condenser pump is to pressurize the refrigerant. The pump pushes the refrigerant into the condenser coil. The pump is subject to extensive wear and tear and requires annual lubrication. Ideally, a technician should disassemble and rebuild it once a year.

Condenser Coil

The refrigerant moves through the condenser coil, which is under great pressure and brims with heat energy. The cooler ambient air passes over the coil, and heat energy is exchanged. This is how an AC “moves” hot air from inside the home to the outside.

Condenser Fan

The condenser fan is a large fan often oriented so that it blows air skyward. Its purpose is to draw air through the system. This runs air over the condenser coil to facilitate the heat exchange. It also exhausts hot air so the condenser pump and fan motor don’t overheat.


Conduits are packaged cables and wires running between the condenser and indoor units. It includes electrical wiring and a refrigerant line. They’re usually about 3 inches. This is one of the few requirements for a mini-split. You need to be able to run the conduit through the exterior wall. That said, manufacturers offer many creative adapters to overcome any challenging scenario.

Indoor Units

The indoor units in a mini-split system are effectively air handlers. Mounting them on walls is typical, but ceiling and floor mounting are options.


Each indoor unit has its thermostat. It reads the temperature in its zone. The thermostat also lets you set a desired temperature and relays that information to the condenser unit, letting it know how much refrigerant to direct to that particular unit.


Each head also has a blower. This variable-speed fan can adjust up and down based on the current cooling or heating needs. It draws room air in and pushes it out through louvers.

Evaporator Coil

An evaporator coil, also called an evaporator core, absorbs heat energy. During cooling mode, air passes over it, and the coil transfers heat energy from the air into the refrigerant inside it. Dehumidification occurs as a byproduct. In other words, the evaporator coil creates condensation.

Condensate Drainage

The condensation from the evaporator coil drips down into a tray. Condensate drain tubing runs from that tray to outside the home to allow for drainage. In a typical scenario, this happens entirely through gravity. When that isn’t possible, the indoor unit will have a pump instead.


As the blower draws air into the unit, it first passes through a filter. The air filter traps particulates, keeping them out of the system and improving air quality. The typical mini-split air filter is washable. Usually, you must wash it every two weeks and replace it annually. Most air filters have a minimum efficiency reporting value rating (MERV). MERV indicates filter effectiveness and airflow restriction. Most modern mini-splits support a MERV as high as 13.

Remote Access and Control

Most mini-split brands include a remote control with each indoor unit so you can operate the unit from the couch. Wi-Fi is a prevalent feature. In Wi-Fi mode, a remote can control every indoor unit in the home. Many brands offer an app that lets you use your smartphone or another device instead.

Heat Pump

Some mini-splits are cooling-only systems. Others provide heat and cooling, which means that they’re heat pumps rather than ACs. The main difference between an AC and a heat pump is a reversing valve.

Reversing Valve

Think of the heat exchange process described earlier as a loop. A reversing valve reverses the flow of refrigerant, allowing the system to transfer heat energy into the living space rather than out of it.

Electric Strip Heat

Air-source heat pumps become less efficient around 35 degrees Fahrenheit. Some manufacturers include an electric strip that radiates heat to deal with this. This helps to heat the zone during freezing nights.

Additional Components

Additional components are common to the modern ductless mini-split. These include programmable thermostats, manual and automatic directional airflow, and dry and self-cleaning modes.

Programmable Thermostat

A programmable thermostat lets you set different temperatures while you’re home, awake, sleeping, or away. This can reduce your heating and cooling costs by as much as 10%. Many units also have smart features like voice control, sleep timers, and monitoring energy usage.

Directional Airflow

Depending on the mounting location, a mini-split can blow air directly on you, which can be uncomfortable. Most systems have a lever that lets you move the louver up and down and left and right.

Automatic Directional Airflow

A more advanced feature of this feature includes a sensor that can detect people. When it does, it will automatically move the louvers to keep the air from blowing directly on them. You can also set this feature to do the opposite. This can be convenient, for instance, when working out in front of the TV.

Dry and Self-Cleaning Modes

Dry mode is a dehumidification mode. It slows the fan speed down so the air stays around the evaporator coil longer. A self-cleaning mode kicks in whenever the mini-split cycles off. It will continue running air over the evaporator coil to dry it, which helps prevent biological growth.

Your Local Ductless Mini-Split Pros in Shawnee

Air Care Heating & Cooling installs, maintains, and repairs ductless AC and heat pump systems in Shawnee and the surrounding areas. Our HVAC technicians also specialize in gas and electric furnaces, gas and electric boilers, air-source and geothermal heat pumps, and air conditioners.

We also install and service whole-house air purifiers, dehumidifiers, and humidifiers. You can also count on us for tank and tankless water heater installation and repair.

Call us today with questions about ductless mini-splits, or book your appointment online.

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