Why Is It Important To Have A Properly Sized Air Conditioner

Like furnaces, cooling systems have a rated capacity and they are rated in BTU’s (British Thermal Unit); the difference is that furnaces are rated on how much heat they can add to your home where as a cooling system is rated on how much heat it can remove from your home. This makes sizing your cooling system very important, if its heat removal capacity is insufficient, you will never cool your home to the desired temperature. When considering a new air conditioner, just remember, bigger is not always better.



  • Your cooling system not only lowers the temperature of the air, it also removes moisture from the air. The indoor evaporator coil gets cold as the outdoor condensing unit feeds refrigerant to it. As your furnace blower pulls warm air from your home across the evaporator coil, the cold coil takes the heat out of the air. As this happens, moisture is also relieved from the air because cold air cannot carry as much moisture as warm air; so the moisture condenses on the cold evaporator coil. If your cooling system is oversized, it will cool the air in your home rapidly but it will not have sufficient time to remove enough moisture before the thermostat reaches set point. This scenario will leave a lot of humidity in your air and you will find that the relative humidity in your home could exceed the desired level of 50% and could leave your skin feel clammy.


  • Electrical motors are the primary energy expense when cooling; you have the compressor, the condenser fan motor and the blower motor. The larger size horsepower motors will of course consume more energy than the smaller ones and larger capacity cooling systems use larger compressors and condenser motors. So having the smallest sized unit that will properly remove the heat from your home is the best strategy to maximize energy usage. Additionally, oversized cooling systems tend to cycle on and off more frequently then correctly sized units. When a motor starts, it is using the greatest amount of energy, once it gets up to speed; its electric consumption is cut in almost half. Therefore, a longer cycle time uses less energy than a few short cycles.


In closing, a properly sized cooling system will adequately remove the heat from your home as well as run long enough to relieve the humidity from the air. In doing so, you will minimize energy consumption because you will be using the smallest horsepower motors to do the correct job. This will also prevent short cycling which will extend equipment life. The professionals at RJ Kuhn in Oswego, IL. will always calculate the correct sized unit for your home to ensure the highest level of comfort while minimizing your energy consu