_ An "over-sized" air conditioner will cool your house quicker, but it will use more electricity and will not remove humidity adequately. Contrary to popular belief, long run cycles are far more desirable and energy efficient than short run cycles. You can think of this in terms of a car, where you would prefer to buy a car that has mostly highway miles rather than city miles. The greatest amount of energy usage and wear and tear on your equipment occurs at system start up (it takes tremendous torque and, hence, amperage to get your compressor turning). Once started, it takes 10 to 15 minutes before your system is operating at peak efficiency and performance. Because an over-sized system will often bring the temperature down to the thermostat setting in just a few minutes, your over sized system will never get to operate at peak performance and will end up "short-cycling"; starting and stopping over and over again, a fact which will cost you in terms of comfort, utility bills and added repairs.
Another factor to consider with regard to system size is that comfort is a function of temperature and humidity. That is, you can have low humidity (relatively dry air) and be comfortable when the temperature is 77 degrees or be absolutely miserable when you have high humidity and a temperature of 70 degrees. One of the most important jobs your air conditioning system performs is removing moisture from the air in your home or office. Removing moisture requires long run times so that enough moisture-laden air has a chance to blow across the cold indoor coil and condense into water, which then drains from your system. Today's high-efficiency central air conditioners may remove as much as two gallons of water from the air in your home every hour, which makes you far more comfortable. If your system is over-sized, it will cool the temperature down to the thermostat setting too rapidly and the system will shut off before proper dehumidification of the air can occur.
Duct system sizing must be considered too. If your duct system is not big enough to handle the increased airflow required by an "oversized" air conditioner, the evaporator coil may freeze and the system will not work at all. Even if the coil doesn't freeze, reduced airflow will impact operating efficiency and effectiveness and cause premature failure of expensive components such as the compressor.
Obviously, the air conditioner must be sized large enough to cool your home, but too big is just as bad. We can measure the heating and cooling load on your particular home and then recommend a system that is properly sized to cool your home to 77 degrees when it is 100 degrees outside.
However, a correctly sized system is not only based on the size of the structure. Many factors go into determining the size of the system, including type of house and walls, type and size of windows, insulation, basement, attic conditions, house orientation, and so on. A Salesman must visit your home and take detailed measurements and notes while conducting the survey.
At Jones Air Conditioning, we use a computer-aided heat load calculation to properly determine the correct system size needed for your home. We even do a room-by-room load calculation. This heat loss/heat gain analysis is the best indicator of the correct system size and provides optimum results for efficiency and comfort.