What Is an HVAC Split System and How Does It Work?

worker standing on a ladder fixing outdoor systems

You know those days when the weather’s just not on your side? Too hot, too cold, or just plain erratic. That’s when a good indoor climate becomes a lifesaver. Many opt for the HVAC split system because of its energy efficiency and optimal temperature control. But, like any home improvement project, it’s essential to understand it fully before diving in. So, what exactly is an HVAC split system, and how does it work? 

In a nutshell, the HVAC split system is like a dynamic duo for your home’s comfort.

Inside, you have the evaporator, which is like a refreshing breeze on a hot day. It pulls in indoor air, cools it down, and sends it back out. Outside, there’s the condenser, chilling in your yard but always on the job. It pumps out heat from the inside and cycles in fresh air for reconditioning. Together, they’re a split system. 

But you might be asking, “What about the heating component?” As the temperatures drop, the HVAC split system steps up to keep you warm. How? It simply reverses its cooling process. Amazing, isn’t it? Now, let’s dive a tad deeper into the specifics.

What Is an HVAC Split System?

HVAC stands for Heating, Ventilation, and Air Conditioning, and as its name suggests, it’s all about creating that perfect atmosphere in your living or workspace. More than just setting the right temperature, it’s about balancing humidity, ensuring clean air, and circulating it seamlessly throughout the room. 

Among the variety of HVAC configurations out there, the HVAC split system truly shines for homeowners.

So, what’s unique about the split system? Well, it’s essentially divided into two main parts, including its connections:

  • Indoor Unit: This unit is installed inside the building or home. It houses the evaporator coil responsible for cooling the air, a filter to purify incoming air, and fans that circulate conditioned air throughout the space.
  • Outdoor Unit: Positioned outside the home, typically in a discrete spot in your yard, this unit holds the compressor, condenser coils, and an expansion valve. The compressor and condenser coils work together to expel heat and humidity from the indoor space.

    Meanwhile, the expansion valve regulates the flow of refrigerant, ensuring efficient cooling. It’s also connected to an open airflow network that could include other areas of your home, like attics and basements.
  • Connections: The indoor and outdoor units are interconnected through refrigerant lines and electrical wiring, enabling them to function cohesively and maintain a comfortable environment indoors.

An HVAC split system can do a lot to keep your home at just the right temperature. Simply put, in the summer, it can kick out all the hot air and refresh what’s inside, and in the winter, you’re looking at basically the opposite. 

But it’s essential to choose the right system for your climate and building size since there are so many varieties out there, like:

  • Heat pumps,
  • Air conditioning systems (multiple for larger homes),
  • Natural gas furnaces,
  • Fan coils (for electric heating),
  • Ductless mini-split systems,
  • Ducted split systems.

A standout benefit of the split HVAC system is its flexibility. Unlike its counterpart, the packaged system, a split setup doesn’t require the installation of ductwork. This makes it an excellent choice for older homes or apartments lacking an established air conditioning infrastructure.

Plus, with most components stationed outside, homeowners enjoy a notably quieter operation.

So that’s the basics of what HVAC split systems are and their main units! Next, let’s take a closer look at how it works. 

How Does an HVAC Split System Work?

worker performing heat pump and air condition units seasona
Photo Credit: welcomia / Canva Pro / License

An HVAC split system is your go-to solution for both cooling during sweltering summers and providing warmth during chilly winters. At first glance, its intricacies might appear complex, but they’re based on the simple principle of heat transfer.

In the summer months, the air conditioner cools your home by drawing heat from inside, using the evaporator, and releasing it outside through the condenser. A bonus is the reduction in indoor humidity, giving you a dry and comfortable atmosphere ideal for summer.

During the colder months, the system flips its operation. It absorbs heat from the external environment and releases it inside. The evaporator then heats this incoming cold air, ensuring your indoor space remains warm and cozy. Let’s delve into the main components that make this possible:

The Thermostat

The home thermostat is like the conductor of an orchestra or, should we say, a cooling and heating system. It actively regulates and monitors the HVAC system’s performance. When you set a desired temperature, the thermostat turns the heater or air conditioner on or off to match that preference.

Electromechanical thermostats rely on physical components for this job, while electronic ones utilize sensors to detect and respond to temperature changes. Many models also offer advanced features that allow you to set varying temperatures for different times of the day, enhancing your home’s energy efficiency and comfort.

Blower Motor

Situated inside the indoor unit, the blower motor plays a pivotal role in circulating air throughout your home. Once the thermostat detects a need for heating or cooling, it sends a signal to the blower motor. This motor then springs into action, spinning the fan that pumps hot or cold air through the air duct system and back out into your living space. 

The two types of motors you’ll find in most HVAC systems are single-speed and variable-speed models. Single-speed motors operate at a steady rate, kicking in when the thermostat reaches its set temperature. On the other hand, variable-speed motors provide varying speed options depending on conditions like airflow and heat demand.


Acting as a medium, the refrigerant in the system absorbs and releases heat to adjust the temperature. It continuously moves between the indoor and outdoor units, transitioning between liquid and gaseous states. The refrigerant absorbs heat from the indoor air when it’s in a low-pressure gaseous state. When it gets compressed and changes to a high-pressure liquid, it releases the absorbed heat outside.

Evaporator Coil

The evaporator coil, located in the indoor unit, plays a vital role in cooling the air. As the refrigerant absorbs heat from the indoor air, it evaporates, turning from a cold liquid to a gas. Consequently, the air surrounding the coil cools down and is then blown into the home.

Outdoor Compressor

Think of the compressor as the heart of the HVAC split system, pumping the refrigerant between the evaporator and condenser coils. It compresses the gaseous refrigerant from the evaporator coil, increasing its temperature and pressure. This high-temperature gas then moves to the condenser coil, where it loses heat and returns to its liquid state.

Condenser Coils

The condenser coil, situated in the outdoor unit, works in tandem with the evaporator coil. As the refrigerant releases the heat it absorbed from inside, it condenses back into a liquid form. This process expels heat out of the refrigerant, which the outdoor unit’s fan then dissipates into the external environment.

Expansion Valve

The expansion valve regulates the flow of liquid refrigerant into the evaporator coil. It acts as a gatekeeper, ensuring that the refrigerant enters the evaporator coil at the correct rate for optimal cooling.

Heat Exchanger

Outside Air Conditioner with Heat Exchanger
Outside Air Conditioner with Heat Exchanger
Photo Credit: TRMK / Canva Pro / License

The heat exchanger is an essential component, especially during colder months when the system is in heating mode. Its primary function is to transfer heat from one medium to another without allowing them to mix. 

For different types of HVAC split systems, heat exchangers work with various heat sources:

  • Heat Pump: A heat pump works a bit differently than traditional heating systems. Instead of generating heat, it transfers it from one place to another. In winter, it extracts heat from the outside air or ground (depending on the type of heat pump) and moves it indoors. 

    The process is reversed in summer when the heat pump pulls heat from the inside of your home and releases it outside. This dual functionality makes it a versatile choice for many homeowners.

    The heat pump system involves a cycle of evaporation and condensation, much like the cooling process in AC systems. However, the difference lies in the direction of heat flow. The refrigerant in the heat pump’s coils absorbs heat from the source (air or ground) and then releases it inside the home. In summer, it does the opposite: absorbing indoor heat and releasing it outside.
  • Furnace:  When the furnace burns fuel (typically natural gas or oil), it produces hot combustion gasses. These gasses pass through the heat exchanger, which has a network of metal tubes or plates.

     As the cold indoor air moves over these hot surfaces, it heats up. Meanwhile, the combustion gasses cool down and are safely vented out of the system.

*Word of Caution:

The heat exchanger needs to function correctly because any crack or leakage can release harmful combustion gasses like carbon monoxide into your home. Regular inspections and maintenance are critical to ensure safety and efficiency.

  • Fan Coil or Electric Heating Systems: These systems do not rely on combustion for heating. Instead, electric elements heat the air directly. The heat exchanger in this scenario is more straightforward – it simply ensures the warmed air from the heating elements is distributed evenly and efficiently into the home.


It’s not just about regulating temperature. An HVAC system also prioritizes the quality of the air you breathe. The filters in an HVAC split system are crucial in trapping and removing contaminants like dust and other pollutants. Regularly checking and replacing these filters is vital for maintaining indoor air quality and ensuring the system runs efficiently.

Air Ducts (depending on your HVAC split system)

These pathways allow cooled or heated air to travel throughout your home. Properly insulated and sealed ducts are vital for energy efficiency and optimal functioning. Over time, ducts might get clogged or damaged, so periodic inspection and maintenance are crucial.

Drainage System

The process of cooling the air can result in condensation. The HVAC split system has a drainage system in place to handle the moisture. It’s typically a pan and a series of pipes that direct the condensed water outside, preventing any potential water damage or mold growth inside the home.

HVAC Split System Units

AC unit central split system hanging outside
Photo Credit: TRMK / Canva Pro / License

There are various HVAC split systems out there, each boasting its own special features. Depending on your local climate and specific requirements, you can select and tailor an HVAC system that fits just right for you. Here is a breakdown of some popular HVAC units of a split system:

Heat Pump Split System

Heat pumps are versatile HVAC split systems that utilize electric power to extract heat from the outdoor air and transfer it indoors. This capability makes them perfect for providing both heating and cooling throughout the year. For optimal performance, it’s essential to position the outdoor unit of a heat pump in a shaded area, away from direct sunlight.

Split A/C Unit

If you need an HVAC system solely for cooling purposes, consider a split-system air conditioner. In these systems, the outdoor unit houses the compressor and condenser, while the indoor unit features an expansion valve, evaporator coil, thermostat, capacitor, and air filter. 

An integrated fan blower (air handler) efficiently distributes the cool air in your home, ensuring a comfortable environment. Split A/C units are efficient and reliable, making them a top choice for homeowners seeking effective cooling solutions.


In regions with chilly winters, furnaces play a vital role in keeping homes cozy. Powered by gas, these units draw in the home’s air, heat it efficiently, and then circulate the warmed air throughout the house via the ductwork. Furnaces are a tried-and-true solution for combatting the cold and creating a comfortable indoor environment.

Fan Coils 

Similar to heat pump systems, fan coils draw heat or cool air from the outdoors, depending on the season. Then, it applies a fan to distribute this air throughout your residence. Be sure to clean and inspect fan coils regularly for optimal performance. It doesn’t require ductwork but might come with additional installation costs.

Ductless Systems 

For households lacking in ductwork or homes undergoing remodeling, consider this so-called “mini split system.” Suitable for keeping energy costs low while still providing efficient cooling throughout your home, ductless systems are designed with individual indoor air handlers for each room. 

Ductless models are a great alternative to full air conditioning units, smaller than traditional split systems and perfect for zoned cooling.

Pro tip: If you’re looking for an even more energy-efficient ductless heating and cooling system, opt for one labeled ENERGY STAR. For instance, ductless heat pumps slash your energy spending by up to 60% compared to traditional systems and help reduce greenhouse gas emissions significantly over their lifetime. 

Duct Systems

Duct systems are like the veins of your home, discreetly connecting the indoor and outdoor units through a web of channels hidden in your walls, floors, ceilings, and crawl spaces. These systems offer precise climate control, delivering warm air from your heating system, such as furnaces, and circulating cool air from air conditioners. 

Though their advanced design can come at a higher cost, they ensure a consistently comfortable indoor environment.

Ductless Mini-Splits vs. Central Air vs. Floor-Standing Split Systems

Ductless Mini Splits AC in a room
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For homeowners pondering about the right HVAC split system for their homes, three primary options often emerge: ductless mini-splits, central air systems, and floor-standing split units. All three are effective, but they serve different needs and come with their own set of pros and cons. Here’s a concise breakdown to help you make an informed decision.

Mini-Split Air Conditioners

Ductless mini-split AC systems are rising stars in the HVAC world, especially for homes without ducted heating systems or where adding ductwork is not viable. These systems consist of an outdoor compressor or condenser paired with indoor air-handling units.

Therefore, they have several energy-saving advantages over central air systems when it comes to reducing cooling costs. Energy.gov estimates that you could save more than 30% in air conditioning costs due to the lack of ducts.

They’re connected through a conduit that carries the power cable, suction tubing, refrigerant tubing, along with a condensate drain. One outdoor unit can often support multiple (up to four air handlers) indoor units, each with its thermostat, allowing for flexible zoning.


  • Zoning Perfection: Tailor your cooling needs room by room, conserving energy in unoccupied spaces.
  • Easy Installation: No massive renovations are needed, just a small wall hole for the air-handling unit.
  • Versatile Placement: The outdoor unit can be placed up to 50 feet away from the indoor units.
  • Duct Loss Absent: Without ducts, energy losses are notably minimized.
  • Design Flexibility: Choose from ceiling-hung or wall-mounted indoor units.


  • Pricey: Expect to pay more upfront compared to traditional systems.
  • Precision Needed: The system’s efficiency relies heavily on accurate sizing and placement.
  • Design Concerns: Not everyone’s a fan of how the indoor units look.
  • Drainage Necessary: You need a spot near the outdoor unit for condensate drainage.

Central Air Conditioners

Central air systems consist of three main parts: an outdoor unit with the compressor and condenser, an indoor unit with the evaporator coil, and a duct system to spread the air all around your home. Usually, the indoor unit is tucked away in a closet, attic, or basement, and the outdoor unit sits on a concrete slab outside.

This system is excellent for bigger homes, giving steady cooling in every room


  • Uniformity: Offers consistent temperature control throughout the house.
  • Aesthetics: All components are hidden, maintaining the home’s interior appearance.
  • Value Addition: It can increase the home’s resale value, especially in hot climates.


  • Duct Maintenance: Requires regular inspection and cleaning of ducts.
  • Energy Loss: Potential for energy loss through ducts, especially if they aren’t sealed or insulated properly.

Floor-Standing Split Unit

Floor Standing air conditioner in a room
Photo Credit: magraphics / Canva Pro / License

Unlike traditional wall-mounted split units that are installed high on the wall, floor-standing units are positioned closer to the ground, usually at the base of a wall or in a corner. 

The outdoor unit houses the compressor and the condenser and is typically located outside the building. The indoor unit stands vertically and can often resemble a portable radiator or a tower fan.


  • Versatility: These units can be installed in almost any room, offering flexibility for rooms with limited wall space or where ceilings are too high or unsuitable for a ceiling-mounted unit.
  • Ease of Access: Being closer to the ground, they are often easier to access for regular maintenance, cleaning, and servicing.
  • Uniform Air Distribution: Ground-level positions sometimes provide more uniform air distribution, particularly in rooms with unusual layouts or furniture arrangements.
  • Efficiency: Many modern floor-standing units boast energy-saving features and inverter technology that adjust power use based on the room’s temperature needs.
  • Easy Installation: As they don’t require wall brackets or ceiling suspensions, installation can sometimes be simpler than wall-mounted units.


  • Space Consumption: While they don’t take up wall space, they do occupy floor space, which might not be ideal for rooms with limited floor area.
  • Aesthetic Concerns: Some people find floor units to be bulkier or less visually pleasing than sleek wall-mounted units.
  • Potential Obstruction: In tight spaces, a floor-standing unit could be an obstruction, particularly if it’s positioned in a pathway or a frequently used part of the room.
  • Cost: Depending on the brand and specific features, floor-standing units can sometimes be more expensive than traditional wall-mounted units.

Comparison Table: Ductless Mini-Splits vs. Central Air vs. Floor-Standing Split Systems

FeaturesDuctless Mini-SplitsCentral AirFloor-Standing Split Systems
DesignNo Ducts (Indoor/Outdoor)Integrated with Ducts (Indoor/Outdoor)Floor-level Split (Indoor/Outdoor)
Placement VersatilityHighLimited to Duct LayoutHigh (primarily floor level)
EfficiencyHigh (no duct losses)Moderate (potential duct losses)Varies by model
Temperature ControlIndividual room controlWhole-house controlIndividual room control
AestheticsVaries (wall-mounted)HiddenFloor-standing
CostGenerally higherModerateVaries based on brand and features
Installation ComplexityModerate (requires wall hole)Complex (requires ductwork)Simple (no wall or ceiling mounts)

Packaged Unit vs. Split System

In the vast realm of HVAC systems, the two predominant types you’ll often encounter are packaged units and split systems. While both serve the primary purpose of heating and cooling your space, their operational approaches, designs, and benefits differ. Here’s a closer look to help you discern the best choice for your home.


The HVAC split-system is a team player. Half of it sits inside (hello, evaporator coil!) while its buddy, the compressor, enjoys the outdoor breeze.


  • Flexibility: Split systems are modular, meaning you can customize the heating and cooling capacities to suit your specific needs.
  • Energy Efficiency: By separating the heating and cooling functions, split systems often deliver more efficient performance, especially in fluctuating weather conditions.
  • Quiet Operation: Since the noisier components (like the compressor) are located outdoors, split systems typically run more quietly indoors.


  • Pricey: Expect to pay more upfront compared to traditional systems.
  • Installation Complexity: Installing a split system can be more complicated, requiring specialized knowledge to connect the indoor and outdoor components correctly.
  • Precision Needed: The system’s efficiency relies heavily on accurate sizing and placement.
  • Maintenance: While the split nature might offer operational advantages, it can also mean that maintenance needs to be conducted in two separate locations, which can be slightly more cumbersome. 

Packaged Unit

All components of a packaged unit, including the compressor, condenser, evaporator coil, and air handler, unite in harmony within a single unit, usually sitting outdoors. 


  • Compact Design: Everything in one place saves space.
  • Simpler Installation: One unit equals fewer installation headaches.
  • Unified Maintenance: A single spot for check-ups and repairs.


  • Roofs: Poor installation of rooftop condensers can cause leaks and problems.
  • Less Customization: Fewer options in terms of capacity and placement.
  • Might be Noisy: The single unit setup could up the decibel levels. 
  • Lifespan: Packaged systems often rust quicker, leading to a shorter life.

Comparison Table: Packaged Unit vs. Split System

FeaturesSplit SystemPackaged Unit
DesignRequires space both indoors & outdoorsSpace-saver, all-in-one
InstallationMore complex due to the separate unitsEasier, less labor-intensive
Maintenance LocationMultiple spotsSingle spot
Noise LevelGenerally quieterPotentially higher
Energy EfficiencyOften more efficientStandard
PriceTypically higherMore affordable

How Do I Choose an HVAC Split System?

split ac hanging on a wall inside a room
Photo Credit: Pixabay

When selecting an HVAC split system, consider the following:

  • Room Size: Measure the area you want to cool. A larger room requires a unit with more cooling capacity. So, always look for BTUs (British Thermal Units). Higher BTUs mean more cooling capacity. (Recommended BTUs HVAC split system: 20 to 30 BTU per square foot of living room.)
  • Energy Efficiency: Look for units with high SEER (Seasonal Energy Efficiency Ratio) ratings. A higher SEER rating means better efficiency and cost savings in the long run. You should consider a minimum SEER rating of about 16 when choosing an HVAC system.


As of January 1st, 2023, SEER2 has become the new HVAC efficiency standard. All AC and heat pump units must comply with the standards set by SEER2 to ensure greater energy efficiency, lower energy bills, and environmental benefits. While this change won’t significantly impact existing homeowners, those in the market for a new HVAC unit should know that AC unit costs are likely to rise as manufacturers update their systems.

  • Features: Modern split air conditioners come with features like smart thermostats, programmable timers, and remote controls. Depending on your needs, select a unit with features that match your lifestyle.
  • Noise Level: A quieter unit can be more comfortable, especially in bedrooms. Check the decibel (dB) rating. A lower dB rating means the unit is quieter. (Recommended dB ratings: outdoor units: 50 – 60 dB/ indoor units: 20 dB)
  • Installation and Maintenance: Opt for a system that’s easy to install and has a reputation for durability. Make sure filters are accessible, as you’ll need to clean or replace them regularly.


A qualified professional should always install and service your HVAC split system. On average, an HVAC split system installation costs around $80 to $150 per hour, depending on the unit size and complexity of the system. The maintenance cost for an HVAC system will depend on your equipment’s type, size, and age. Typically, you can expect to pay anywhere from $100 to $400 for annual maintenance.

  • Cost: Set a budget and look for a unit that provides the best value for your money. While you might be tempted to go for the cheapest option, remember that a more expensive unit might be more energy-efficient and save you money in the long run.
  • Brands and Warranty: Invest in a reputable brand known for its quality and durability. Also, consider the warranty length and coverage.

FAQ About HVAC Split System

Are split HVAC systems worth it?

Split HVAC systems offer several distinct advantages:

  • Energy Efficiency: As mentioned, split systems typically have a SEER rating of 25 or above, ensuring you use less energy and save more on your monthly bills.
  • Flexibility: Split systems provide flexibility in placement, allowing homeowners to install units in preferred locations inside the home.
  • Quiet Operation: The main noisy component, the compressor, is placed outside, ensuring indoor quietness.
  • Value Addition: Due to their energy efficiency, split systems can potentially increase the resale value of your home.
  • Reduced Maintenance: Especially in the case of ductless mini-split systems, maintenance costs can be considerably lower compared to other HVAC systems.

However, like any HVAC system, choosing a split system should be based on individual needs, the size and layout of the home, and any existing HVAC installations.

What are the disadvantages of an HVAC split system?

The disadvantages of split HVAC include:

  • Initial Cost: They’re generally pricier upfront than other types.
  • Complex Installation: They require expert setup, which can be labor-intensive. It needs precise drilling of holes in walls and expert handling to connect the indoor and outdoor units
  • Maintenance: If there are ducts, they need regular checks.
  • Looks: Not everyone loves the indoor unit’s appearance.
  • Function: Some units don’t offer heating, so that you might need another solution for winter.
  • Refrigerant Leaks: These can occasionally happen, affecting both performance and the environment. 
  • Professional Setup: DIY installation isn’t recommended.

What is the difference between an air conditioner and an HVAC?

The terms “air conditioner” and “HVAC” are often used interchangeably, but they refer to different systems. In essence, an air conditioner is a component of a complete HVAC system. While an AC provides cooling, an HVAC system offers comprehensive climate control and improves overall indoor air quality.

How long does an HVAC split system last?

On average, an HVAC split system can last anywhere from 15 to 20 years, given that regular maintenance is undertaken. The lifespan can vary depending on usage, installation quality, and environmental factors. 

Proper care, such as frequent filter changes and annual professional check-ups, can extend the system’s life and maintain its efficiency.

Stay Comfy with an HVAC Split System

An HVAC split system isn’t just about setting the right temperature. It’s about making your home cozy, saving energy, and living better. It has two main parts: one inside your house and one outside. Together, they make sure your home feels just right every day of the year.

The indoor unit extracts warmth from your home during summer and pumps it outside, while in winter, the process reverses. So, whether you’re considering installing a new HVAC split system or upgrading your current one, understanding its operation is key to long-term satisfaction.

Ready to optimize your home’s comfort? Contact a local HVAC specialist for professional advice and assistance. They can recommend the right HVAC split system for your needs and have it installed in no time.

Note: HVAC Gnome may get a referral fee for matching you with contractors in your area.

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Luminita Toma

Luminita Toma is a nature-loving writer who simply adores anything pretty, from colorful flower gardens to chic interior design. After plenty of research on landscaping and home improvement, she’s got a keen eye for what makes a home beautiful. When she’s not sharing what she’s learned, there’s nothing she enjoys more than chilling with her friends, hitting the theatre, or traveling.