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Air Conditioning Tutorial: See How It Works and Why Today's A/Cs Are So Efficient

If you are in the market for a new air conditioning system, it is important to know the different types of systems, how they function and the benefits of each so that you can make a decision that will enhance your home's overall comfort and energy efficiency for many years to come.

How Air Conditioners Cool Your Home

You might think that air conditioning systems create cool air, but that is not the case. Instead, they incorporate the basic physics principle of phase conversion, which is that when a gas converts to a liquid, it absorbs heat. To facilitate that, central air conditioning systems are made up of a compressor, condenser and evaporator, along with tubing/coils that carry a refrigerant throughout the system. As the refrigerant circulates through the coils, it is compressed into a hot, high-pressured gas. The condenser removes the heat from the refrigerant, changing it to a cooled, high-pressure liquid that moves on to the evaporator coils. A blower pushes air over the evaporator coils, the liquid refrigerant absorbs the heat from the air, and the now-cooled air travels through ducts into the home. The refrigerant changes back to a low-pressure gas, returns to the compressor and begins the heating and cooling cycle again. The compressor turns on or off based on the desired thermostat settings.

Types of Air Conditioning Systems

There are basically two types of central air conditioning systems - a packaged unit or a split system. With the help of an HVAC professional, you can determine which system works best for you, taking into consideration the layout of your home, the presence of adequate ductwork and load calculation results.

  • A packaged unit is generally located outdoors, on a roof or near the residence. It contains an evaporator, condenser and compressor all in one cabinet and connects, via an outside wall or the roof, to existing supply and return ducts throughout your home. Packaged heat pump units often include heating coils or a natural gas furnace to facilitate heating without an additional indoor unit. This is particularly convenient for a home where space is limited, although as a singular heat source it is more suited to homes located in more moderate climates. 
  • A split air conditioning system consists of an outdoor cabinet housing the condenser and compressor, and an indoor unit that contains the evaporator. It, too, connects to the duct system already in place for your furnace. For homes without sufficient ductwork, where space is a factor or when only several rooms need cooled, a ductless mini-split system is sometimes an option. Performing similarly to the split air system, up to four small indoor air handling components can be attached to walls, ceilings or floors, connected by conduit to the outside condenser/compressor unit. Each indoor component has its own thermostat and can be turned on or off as needed.

Long-Term Efficiency vs. Up-Front Costs

Installing a new, efficient central air conditioning system can be costly, especially if repairs to ductwork or other airflow considerations are necessary. The choices you make in the size of the system, its energy efficient qualities and the various enhancements you consider will not only make your home more comfortable and cost-efficient now, but they will ensure a valuable long-term investment for your property.

  • Size of your system - The size of the air conditioning system you need is calculated based on a number of factors, including your home's dimensions, sun exposure, the amount of insulation in your home and the number of occupants. If the system is too small for your home, it will need to work harder to produce satisfactory results and that will reduce the life of the system. With a system larger than your needs, it will shut on and off more often, reducing efficiency levels and wearing out parts. It may not properly control indoor humidity levels, which affects overall comfort as well as raising the potential for the growth of mold. 
  • Energy efficient qualities - Air conditioners are given a SEER rating (seasonal energy efficiency ratio) taking into consideration the amount of energy used (in BTUs) during the cooling season compared to the amount of wattage used. The higher the SEER rating, the more energy efficient the unit. All new systems have a SEER rating of 13 or better. An air conditioner that is 10 or more years old was not made with today's energy efficient technology and will perform at a rating of six or lower. While systems with higher SEER ratings are more costly to purchase, the cost savings in energy efficiency can save you much more than the additional cost of the system, over time.
  • Additions and enhancements - There are a number of enhancements that can be added to your air conditioning system that will provide either better comfort, energy efficiency or both. Air filtering systems can reduce in-home contaminants such as pollen, bacteria and mold spores. A thermal expansion valve will regulate the amount of refrigerant flowing through the system. Variable speed fans and fan-only options give you just the right amount of air, when you need it. Your system can even remind you when to change the air filter.

All of these choices will change the cost of the system but will also give you more in return. It is crucial, however, that you work with a factory authorized dealer to ensure that the system you are purchasing meets the needs of your home and is installed in a way that will provide optimum performance. If any adjustments to your existing components are necessary, a good installer should advise you of the potential problems, the measures to take to bring them to compliance and the costs involved.

  • Existing ductwork should be inspected to be sure it is correctly sized and provides adequate supply and return registers. It should be free of leaks and well insulated, especially if ducts are located in attic or crawl space locations where temperatures are more extreme.
  • The blower should produce the right amount of airflow for the system. If air does not flow over the evaporator coils at the manufacturer's recommended rate, the system will need to work harder to achieve the home's comfort level, thereby lowering its ability to achieve the stated SEER rating.
  • The system should be installed with adequate space for maintenance and repair, including replacement of air filters and cleaning evaporator coils. Outdoor units must have adequate airflow and should be placed where the noise from the condenser unit will not disturb you or your neighbors.
  • The system's refrigerant charge must meet the manufacturer's exact specifications.
  • The thermostat should be installed in a location without a direct heat source, such as sunlight or near a stove. Placing a thermostat too near an air conditioning supply duct would give an inaccurate assessment of room temperature.

Maintaining Your New Air Conditioning System

Once your air conditioning system is installed, there are only a few routine maintenance procedures to do, but those few procedures are very important. The air filter must be replaced regularly (every one to three months) as recommended by the manufacturer. Don't block or close supply and return registers so that airflow to and from the system is not compromised. Keep debris and weeds away from the outside unit. Since it is a closed system, for all other maintenance you should schedule pre-season tune-ups with your HVAC professional who will check the refrigerant charge, clean the condensing and evaporator coils and inspect the overall system to make sure it is in good running condition.

If you would like to discuss the advantages of today's air conditioning systems with an HVAC professional, contact We provide dependable and affordable heating and air conditioning services to the Chicagoland area, northwest Indiana and southwest Michigan.


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