What is Central Air?

Presidential Heating & Air Conditioning

Gaithersburg HVAC Contractors


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central air unit in backyardBefore you decide to install a central air conditioning system in your home, you should understand what it is and how it works. Central air conditioning is a system in which air is cooled at a central location.

Understanding What a Central Air Conditioning System Is

In some central air conditioning systems, the system uses fans to circulate the cooled air through ductwork into the rooms of your home. Warm air from the inside of your house is pulled into ductwork by a fan and released to the outside. A thermostat installed inside your home controls the interior temperature and allows you to set it to your personal comfort level. In some systems, no ductwork is required.

Central air conditioners use two different coils to cool your home. One coil, called the condensing coil, is located in a unit placed outside of your home. This outdoor unit consists of a compressor, the condensing coil, the condenser fan, and a grill cabinet to protect against contact with the fan blade, controls, and two refrigerant lines that run into the home to the evaporator coil. The compressor compresses the refrigerant gas which enables it to discharge heat out of the house, creating cool air.

The other coil, called the evaporator coil, is located indoors. Compressed refrigerant is pumped from the exterior condensing coil to the interior evaporator coil, where it absorbs the heat from the air. The cooled air is then pushed through the ductwork through room vents throughout your home to lower the interior temperature. Meanwhile, the refrigerant circulates through the system back outside to the condenser coil, where the heat that was absorbed is released to the outside. At this point, the refrigerant is returned to a liquid form, continuing the cycle of the refrigerant compression and flow.

Different types of central air systems are available: (1) split system, (2) ductless mini-split, or (3) packaged unit.

Split System

HVAC contractor working with evaporator coilA split-system central air conditioner consists of an outdoor metal cabinet that holds the condenser and compressor. An indoor cabinet houses the evaporator and in some cases a furnace or an air handler. The air conditioner’s evaporator coil is located in the indoor cabinet or the main supply duct of the furnace or heat pump. If your home already has a furnace but no air conditioner, a split system is the most economical central air conditioner to install.

Another type of split system includes a heat pump system. Instead of a furnace and air conditioner, the heat pump supplies cooling in the summer and heating in the winter. It also has an air handler indoors, and the heat pump cabinet sits outdoors.

Ductless mini-split

Ductless mini-split air conditioning systems do not require ductwork. These systems are a great choice if your home cannot accommodate ductwork, such as is sometimes the case when retrofitting an older home or building a home with limited square footage. Ductless mini-split systems have an outdoor air conditioner or heat pump connected to air handling units placed in one or more rooms of the home. Each unit allows temperature control and is controlled separately of the other air handlers. These systems can offer customized room-by-room control over energy use and temperature.

Packaged Unit

A packaged central air conditioner encloses the evaporator, condenser, and compressor in a single cabinet. The unit can be placed outdoors on the roof or on a concrete slab next to the home’s foundation. The air supply and air return ducts connect with the outdoor unit through the home’s exterior wall or roof. Packaged air conditioners often include electric heating coils or a natural gas furnace. The packaged unit combines an air conditioner and a central heater, which eliminates the need for a separate furnace indoors.

Benefits of a Central Air Conditioning System

Regardless of which type of central air conditioning system you choose, central air offers many benefits to homeowners. Some of the most popular reasons to install a central air system are highlighted:

family sitting inside enjoying their new central air systemBetter indoor comfort during hot weather – Central air conditioning helps keep your home cool during those hot summer days.

Dehumidification – One significant benefit to a central air system is that it reduces the humidity levels inside your home. Dehumidifying the air improves the indoor air quality and helps create a healthier environment by deterring the growth of mold and reducing contaminants in the air. Depending on your location, however, your central air conditioning system may need a whole-home dehumidifier to work with it for optimal indoor air quality.

Cleaner air – Your central air conditioning system circulates air by pulling it out of the rooms in your house through the return air ducts. During this process, the air is pulled through an air filter. Depending on the density of the filter, the filter removes airborne particles such as dust, lint, pet dander, and allergens. Some filters are designed to remove microscopic allergens and other pollutants. The filtered air is then routed to air supply ductwork that carries it back to the rooms. Especially for people with impaired or sensitive respiratory systems, a central air conditioning system can contribute to better health.

Quiet operation – Installing the compressor component outside results in less noise inside your home compared to a standard window unit.

Energy efficiency – Newer technology has led to more energy efficient central air systems than in years past. Some are available with multi-stage and single-stage motors, and smart systems that learn your patterns of usage. All of this allows you to precisely control cooling and humidity levels when you want it and not when you don’t, resulting in a high degree of efficiency.


A central air conditioning system does not require a significant amount of maintenance. A simple, annual preventive maintenance agreement with a reputable HVAC contractor will keep your system operating at optimal performance levels. Your HVAC contractor will make sure your filters are clean and all system components are functioning properly.

Contact Presidential Heat and Air for More Information

The expert HVAC technicians at Presidential Heat and Air can answer any of your questions about a central air conditioning system and which system would work best for your home. Contact Presidential Heat and Air to schedule an appointment.

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