Back in the days of cheap electricity, correctly sizing residential central air conditioners wasn’t a high priority. Builders simply covered for any shortfalls by installing an AC unit significantly larger than needed. Now, homeowners can not manage to operate an over-sized air conditioner with half of the BTU tonnage than their home actually demands. On the flip side, nobody needs a unit that is too little, either. Sizing involves ascertaining the property’s heat load: The exact capacity in BTUs per hour and also cubic feet per minute of airflow to keep a 78 degree temperature from the home. Several methods are available — in the most exact to a general rule-of-thumb quote — to dimension the right central air conditioner for your needs.
Manual J Calculation
Developed by the Air Conditioning Contractors of America and integrated into applications used by HVAC contractors, Manual J is the gold standard for correctly ascertaining the heat load on your house. The program utilizes information about your climate and the size of your house, together with room-by-room data about the size and type of windows, the more air-tightness of the house, quantity and quality of insulation, the amount of residents and the varieties of appliances and lighting. The software generates BTU tonnage and airflow figures that permit you to correctly match an air conditioner to the particular requirements of the house.
Online Sizing Estimators
Available at many HVAC contractor and air conditioner sales sites, online calculators permit you to input a limited number of data about the size and setup of your house as well as its own Department of Energy climate. The calculator yields a rough estimate in BTUs and airflow to your ac unit that most closely fits your home’s cooling load. Since the precision of sizing calculations decreases as data is reduced, online sizing estimators are not as exact as a home visit by an HVAC contractor with Manual J software.
Compare and Contrast
Nearby homes in the exact same area or house development are often of equal size with similar floor plans. If a neighbor in a residence similar to yours has an air conditioner that produces adequate comfort and acceptable efficiency, request info about his AC unit including the serial and model number. This may give you an overall idea of what is needed to create similar benefits in your home.
Look at Your Existing Unit
If you’re replacing the air conditioner installed on your house due to malfunction, but it produced otherwise acceptable benefits in comfort and efficiency for your family, locate the manufacturer’s model and serial number plate, typically situated on the exterior condenser unit. Access the manufacturer’s customer support online or by phone to get sizing data concerning this unit, like its BTU capacity and airflow. With this information, you’ve got a starting point to make informed sizing decisions about upgrading to a new unit of greater or lesser ability.