One of the most popular air conditioner types available today is a split system AC, also called a split or mini split. Although they fulfill the same purposes as a central AC system, split air conditioner systems work according to different, more efficient operating principles.

Only by knowing how a split AC system works and how it differs from other solutions can you understand why this type of air conditioner is an excellent choice for climate control in your home.

Basic Operation Principles

All air conditioners work according to the same principle: pulling warm air out and releasing cool air inside to lower the indoor temperature. Heat pump systems invert this principle to increase the interior temperature.

Quality AC systems absorb ambient moisture from indoor air, decreasing humidity levels. Their air filtration systems can also remove dust, pollen, and contaminants, improving indoor air quality.

There are two main types of air conditioner configurations: packaged and split. Traditional air conditioners may also be called packaged, central, or all-in-one air conditioning. Traditional AC systems use a single outdoor unit containing heat exchangers, a compressor, a fan, and a blower. The outdoor unit blows hot or cool air through a system of ducts and vents into the various rooms in your home.

Split air conditioners separate these elements into two different unit types: One outdoor unit and an indoor handler unit. Outdoor units contain a fan, a compressor, and an outdoor heat exchanger, whereas indoor units contain a blower and an indoor heat exchanger.

Parts of a Split AC System

A typical split air conditioning system features multiple interconnected parts and elements that constantly work and communicate with each other to control the temperature in your house. 

Although some of these elements may vary slightly between models and manufacturers, a Gree mini split system may look different from a Mitsubishi; all feature an indoor unit, an outdoor unit, and connecting elements, each with its own set of parts. Split ACs also require a refrigerant to function, without which they would be unable to absorb hot air. The type you need depends on your system’s make and model.

Outdoor unit

Although the outdoor unit of a split AC system is often referred to as the compressor, in reality, the compressor is only one of its components. An outdoor unit also contains a condenser, a cooling fan, and an expansion valve.

The condenser coils receive warm refrigerant from the indoor units, circulating it several times around the cooling fan, which pulls in cool exterior air to cool it down again.

The compressor is the most critical element of a split AC outdoor unit. Its purpose is to compress incoming hot gas refrigerant, decreasing temperature and increasing pressure to the point of becoming a cool liquid again. It then passes through an expansion valve, cooling down further before being sent to the indoor units.

Indoor unit

A split system may come with one or multiple indoor units, depending on the square footage of the space you need to heat or cool. Each indoor unit features evaporator coils, a blower, and air filters.

Evaporator coils inside the indoor unit receive cold refrigerant from the outdoor unit via the connecting line set. These coils circulate several times around a blower, pushing cold air into the room and absorbing warm air, turning the refrigerant into a hot gas. The hot refrigerant then returns to the outdoor unit to complete the cycle.

Connecting elements

The elements connecting the indoor and outdoor units are the line set and the cable set.

The line set contains two pipes: a refrigerant line and a water drain line. The refrigerant line circulates the refrigerant compound through the system, and the water drain line captures water condensate generated in the indoor units and redirects it outside.

The cable set includes the electric line powering the system and a few electronic control cables. The control cables allow the system’s units to communicate with each other and your devices like a  remote control or smartphone.

The defining trait of a mini split AC system’s connecting elements is the lack of a traditional ducting network typically used by central AC. Instead of a single unit distributing cool air via ducts, a split system produces cool air directly at the indoor units.

Refrigerant compound

The refrigerant compound is the substance circulating through the system’s refrigerant line, allowing the AC system to distribute cool air inside and push warm air outside. Modern products currently available on the market, such as LG split air conditioner systems, use a hydrofluorocarbon (HFC) refrigerant called R-410A, also known as Puron or Forane.

However, in September 2021, the Environmental Protection Agency (EPA) issued a plan to phase out R-410A and all other HFCs by 2023. Future split AC systems may use newer, more efficient refrigerants such as R-32 or R-454B.

Zones, Sizing, and Capacity

The main advantages of split air conditioning are the zoning options available. A split system may be either single-zone or multi-zone.

The number of zones in a multi-zone system refers to the maximum number of rooms a single split AC system can serve simultaneously. Most multi-zone split systems can support between two and five zones.

In addition to the number of zones, each split system has a specific total capacity, measured in British Thermal Units or BTUs. Air conditioners need approximately 20 BTU to efficiently cool each square foot of living space. The higher the total BTU rating, the larger the total space the unit can heat and cool.

Each indoor unit also features its own BTU capacity rating expressed as a single number. This is critical when deciding which room the unit should serve. Multiply this number by 1,000 to obtain its BTU capacity. For example, a unit with a rating of 9 means it is a 9,000 BTU unit.

Many multi-zone systems feature indoor units with different individual capacities for controlling the climate in rooms of various sizes. For example, a Mitsubishi mini split multi-zone system with a “9-12-18” rating indicates that this product is a tri-zone system. The indoor units have a respective capacity of 9,000 BTU, 12,000 BTU, and 18,000 BTU.

How to Choose the Right Split AC System

The best way to determine your split AC system’s zones and capacity is to determine which rooms of your house need climate control and measure their size.

The most common locations are the main bedroom, guest or children’s bedrooms, the living room, the kitchen, the basement, and the attic. Make sure to select no more than four or five rooms to ensure that a single AC system can support all of them.

Measure the floor area of each zone you wish to cool. The minimum capacity of a single indoor unit is typically 6,000 BTU, which is enough to serve an area of 150-250 ft² (assuming a standard room height of 8 feet). Refer to this chart to choose the right capacity:

• 150-250 ft²: 6,000 BTU
• 250-300 ft²: 7,000 BTU
• 300-350 ft²: 8,000 BTU
• 350-400 ft²: 9,000 BTU
• 400-450 ft²: 10,000 BTU
• 450-550 ft²: 12,000 BTU
• 550-700 ft²: 14,000 BTU
• 700-1,000 ft²: 18,000 BTU
• 1,000-1,200 ft²: 21,000 BTU
• 1,200-1,400 ft²: 23,000 BTU
• 1,400-1,600 ft²: 24,000 BTU

For example, the average living room area in the United States is about 340 ft², which requires a minimum of 8,000 BTU to cool efficiently.

After calculating the base BTU from your room’s area, check its characteristics. Then, add all calculation variations that apply:

• If the room is a kitchen, add 4,000 BTUs.
• If the ceiling height is higher than 8 feet, add 25% for every additional 2 feet of ceiling height.
• If the room is drafty or poorly insulated, like a garage, add 20% to the original BTU calculation.
• If you live in an area with hot and humid summers, routinely exceeding 90°F, add 30%.

Benefits and Advantages of Split Air Conditioners

Split AC systems offer numerous benefits over all-in-one packaged units. Here are the top six reasons you should consider a mini split for your home:

1. Complete climate control

Although their primary function is to serve as air conditioning units, most split air conditioner systems can also function as heat pumps. This allows you to use them during the colder months and gives you complete year-round climate control.

Split AC systems are the ideal solution to keep your home at the most comfortable temperatures, regardless of the season or the exterior conditions. Many split AC systems are also programmable and compatible with mobile applications, allowing you to turn your home’s AC on and off and even configure it remotely.

2. Low noise levels

The indoor units of a split AC system are designed to operate with the lowest amount of noise possible, making them suitable for use anywhere from a busy kitchen to a quiet children’s bedroom. According to data gathered by IAC Acoustics, the average noise of a typical centralized air conditioning unit is 60 dB (at 100 feet) or about as loud as a television.

The noise levels generated by split AC units vary depending on their cooling capacity and whether the element measured is an indoor or outdoor unit. The loudest parts of a split AC system are the outdoor fan and compressor.

However, independent testing has shown that even high-capacity split AC systems maintain noise levels between 37 and 45 dB inside the home, with outdoor units rarely reaching higher than 55 dB. These low noise levels make split AC systems the quietest way to cool your home, ideal for keeping bedroom climates comfortable without disturbing the occupants’ sleep.

3. High efficiency

Most split AC systems are ductless, so they do not require ducts and vents to cool your home. The lack of ductwork makes split AC systems highly energy-efficient because the cool air (or warm air during the colder months) does not leak or dissipate in the ducts before it can reach the inside of a room.

Additionally, a split AC system does not need to run all the time, saving you considerable amounts of money in energy expenditure. A properly sized split AC system can target a specific temperature and start cooling or heating only when its sensors detect a significant difference between the target and current temperatures. If the target temperature has been reached, the only energy expended is the electricity needed for the system’s sensors and electronics.

4. Flexible zoning system

A split AC system works according to a zoning system. Once you know the number and size of the zones requiring climate control, your air conditioner can function as needed in the areas of your home you use the most, with little waste.

For comparison, a traditional AC system can only be entirely on or off, including in the rooms you don’t use. In contrast, a split AC system can independently detect whether a specific zone needs cooling or heating. They are much more flexible because they work in the parts of your house you use the most and only turn on as necessary to control the climate.

5. Improves indoor air quality

Split AC systems do more for your home than simply keeping the temperature at a comfortable level. The air filtration systems in each indoor unit are designed to catch multiple types of air pollutants and contaminants, such as dust, grime, or pollen. This ensures the indoor air  remains of high quality and healthy.

In addition to air filtration systems, split AC systems naturally work as dehumidifiers. When indoor units cycle warm air out of the house, they also capture and separate the condensate from the air.

6. Easy to maintain

Although a split AC system’s functional elements and moving parts are separated between the outdoor and indoor units, maintenance is quick and easy.

Indoor units are the easiest to maintain; all you need to do is to periodically remove and clean the air filters with water and mild detergent at least once every three weeks. Cleaning the filter is crucial to maintain optimal cooling performance and air quality and prevent the spread of bacteria in your home.

Outdoor units are also relatively easy to maintain. Keep it free of leaves, twigs, and other debris, ensuring the outdoor fan is not clogged. You can also clean dirt off the outside shell with a garden hose and a cloth. Cleaning the interior of your outdoor unit is also easy; regularly check the fan, the coils, and the condensate pan. Clean as necessary every so often, and your AC system’s efficiency will remain at optimal levels.

Take Control of Your Home’s Climate with ComfortUp

ComfortUp is a leading online provider of ductless mini split air conditioning systems. Our mission is to equip households with the latest and most efficient HVAC technologies at the most reasonable prices. Browse our inventory today and choose from top-quality mini split systems from leading brands like Gree, LG, Mitsubishi, Rheem, and Boreal.

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