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What Is a Split System Air Conditioner?

CEO Khai Intela
One of the most popular types of air conditioners available today is a split system AC, also known as a split or mini split. While they serve the same purpose as central AC systems, split...

One of the most popular types of air conditioners available today is a split system AC, also known as a split or mini split. While they serve the same purpose as central AC systems, split air conditioner systems operate on different, more efficient principles.

In this article, we will explore how a split AC system works and its advantages over other types of air conditioning solutions. Understanding the functioning and benefits of a split AC will help you make an informed decision when it comes to climate control in your home.

Basic Operation Principles

All air conditioners work on the same principle of removing warm air and replacing it with cool air to lower the indoor temperature. Heat pump systems, on the other hand, can reverse this process to increase indoor temperature.

Quality AC systems not only cool the air but also reduce humidity levels by removing moisture from the indoor air. Additionally, their air filtration systems can eliminate dust, pollen, and other contaminants, thereby improving indoor air quality.

There are two main configurations of air conditioners: packaged and split. Traditional air conditioners, also known as packaged, central, or all-in-one air conditioning systems, consist of a single outdoor unit that contains the necessary components such as 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 different rooms in your home.

Split air conditioners, on the other hand, separate these components into two units: an outdoor unit and an indoor handler unit. The outdoor unit contains a fan, a compressor, and an outdoor heat exchanger, while the indoor unit houses a blower and an indoor heat exchanger.

split ac system parts Fig: Split AC system parts

Parts of a Split AC System

A typical split air conditioning system consists of several interconnected parts and elements that work together to control the temperature in your home. Although these elements may vary slightly between models and manufacturers, they all include an indoor unit, an outdoor unit, and connecting elements, each with its own set of parts. Split AC systems also require a refrigerant to function effectively, and the specific type of refrigerant depends on the system's make and model.

Outdoor unit

The outdoor unit of a split AC system, often referred to as the compressor, contains more than just the compressor itself. It also houses a condenser, a cooling fan, and an expansion valve.

The condenser coils in the outdoor unit receive warm refrigerant from the indoor units and circulate it several times around the cooling fan, which draws in cool exterior air to cool the refrigerant down again.

The compressor is the most critical component of the outdoor unit. Its primary function is to compress the incoming hot gas refrigerant, lowering its temperature and increasing its pressure until it becomes a cool liquid. The refrigerant then passes through an expansion valve, further cooling down before being sent to the indoor units.

Indoor unit

A split system can come with one or multiple indoor units, depending on the size of the space you want to heat or cool. Each indoor unit consists of evaporator coils, a blower, and air filters.

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

Connecting elements

The connecting elements between 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, while the water drain line captures the water condensate generated in the indoor units and directs it outside.

The cable set includes the electric line that powers the system and several electronic control cables. These control cables allow the system's units to communicate with each other and with your devices, such as a remote control or smartphone.

A defining feature of a mini split AC system's connecting elements is the absence of traditional ducting networks commonly used by central AC systems. Instead of a single unit distributing cool air through ducts, a split system produces cool air directly at the indoor units.

Refrigerant compound

The refrigerant compound is the substance that circulates through the system's refrigerant line, allowing the AC system to distribute cool air inside and push warm air outside. Modern split AC systems typically use a hydrofluorocarbon (HFC) refrigerant called R-410A, also known as Puron or Forane.

However, it is important to note that the Environmental Protection Agency (EPA) plans 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

One of the main advantages of split air conditioning is the zoning options it offers. A split system can be either single-zone or multi-zone.

The number of zones in a multi-zone system refers to the maximum number of rooms that 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 (BTUs). Generally, air conditioners require approximately 20 BTUs to efficiently cool each square foot of living space. The higher the total BTU rating, the larger the space the unit can heat and cool.

Each indoor unit also has its own BTU capacity rating, which is expressed as a single number. This rating is essential when deciding which room the unit should serve. To obtain the BTU capacity, multiply this number by 1,000. 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 to control the climate in rooms of various sizes. For instance, a Mitsubishi mini split multi-zone system with a "9-12-18" rating indicates that it is a tri-zone system with indoor units having respective capacities of 9,000 BTU, 12,000 BTU, and 18,000 BTU.

choosing the right capacity Fig: Choosing the right capacity

How to Choose the Right Split AC System

To determine the ideal zones and capacity for your split AC system, you need to identify which rooms in your house require climate control and measure their sizes.

Common areas that may require air conditioning include the main bedroom, guest or children's bedrooms, living room, kitchen, basement, and attic. It is advisable to select no more than four or five rooms to ensure that a single AC system can support them all effectively.

Measure the floor area of each zone you want to cool. The minimum capacity of a single indoor unit is typically 6,000 BTU, which is sufficient for an area of 150-250 square feet (assuming a standard room height of 8 feet). Refer to the following chart to choose the appropriate 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 square feet, which requires a minimum of 8,000 BTU for efficient cooling.

After calculating the base BTU from your room's area, consider its specific characteristics and add any applicable variations to the calculation:

  • 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, such as a garage, add 20% to the original BTU calculation.
  • If you live in an area with hot and humid summers, regularly exceeding 90°F, add 30%.

choosing mini split unit Fig: Choosing the right mini split unit

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

While the primary function of split AC systems is air conditioning, most of them can also function as heat pumps. This allows you to use them for both cooling and heating throughout the year, providing complete climate control for your home. Additionally, many split AC systems are programmable and compatible with mobile applications, allowing you to control and configure your home's AC remotely.

2. Low noise levels

The indoor units of a split AC system are designed to operate with minimal noise, making them suitable for use in various settings, from busy kitchens to quiet bedrooms. According to data gathered by IAC Acoustics, the average noise level of a typical centralized air conditioning unit is 60 dB (at 100 feet), roughly equivalent to the volume of a television.

The noise levels produced by split AC units vary depending on their cooling capacity and whether the measurement is of an indoor or outdoor unit. The loudest components 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 exceeding 55 dB. This makes split AC systems the quietest way to cool your home, ensuring a comfortable bedroom climate without disturbing sleep.

split air conditioner benefits Fig: Benefits of split air conditioners

3. High efficiency

The absence of ducts in most split AC systems makes them highly energy-efficient. Ducts can cause cool air (or warm air in colder months) to leak or dissipate before reaching the intended room. Additionally, split AC systems do not need to run continuously, resulting in significant energy savings.

A properly sized split AC system targets a specific temperature and starts cooling or heating only when sensors detect a significant difference between the target and current temperatures. Once the target temperature is reached, energy consumption is minimal, limited to the power required by the system's sensors and electronics.

4. Flexible zoning system

Split AC systems operate on a zoning system, allowing them to cool specific zones as needed. Once you determine the number and size of zones that require climate control, the air conditioner can independently detect whether a particular zone needs cooling or heating. This flexibility makes split AC systems more efficient since they only activate in the parts of your house that require climate control.

In contrast, traditional AC systems can only be entirely on or off, including in rooms that are not in use.

5. Improves indoor air quality

Split AC systems do more than just regulate temperature; they also improve indoor air quality. The air filtration systems in each indoor unit capture various types of pollutants and contaminants, such as dust, grime, and pollen, ensuring that the indoor air remains clean and healthy.

Moreover, split AC systems work as dehumidifiers by removing excess moisture from the air when cycling warm air out of the house.

sitting beneath mini split air

6. Easy maintenance

Although the functional elements and moving parts of a split AC system are divided between the outdoor and indoor units, maintenance is relatively simple.

Indoor units are easy to maintain; just remove and clean the air filters with water and mild detergent at least once every three weeks. Regularly cleaning the filters is crucial for optimal cooling performance, air quality, and preventing the spread of bacteria in your home.

Outdoor units are also straightforward to maintain. Ensure that they are free of leaves, twigs, and other debris, and check that the outdoor fan is not clogged. You can clean the exterior of the unit with a garden hose and a cloth. Cleaning the interior, such as the fan, coils, and condensate pan, is also easy and should be done occasionally to maintain optimal efficiency.

In conclusion, split AC systems provide efficient and flexible cooling and heating solutions for homes. With features like zoning, low noise levels, high efficiency, improved air quality, and ease of maintenance, split air conditioners are a compelling choice for your home's climate control needs.

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