Window units offer zone control whereas central air units provide overall climate control.
The size of a central air conditioner to use for a structure is determined loosely on the square footage. A 1,200 square foot area requires a minimum of 30,000 British Thermal Units (BTUs) for proper operation. A 30,000 BTU central air system would be rated as 2.5 tons. The calculation, however, is inaccurate. You need to incorporate additional elements to properly gauge heating and cooling needs. Does this Spark an idea?
Square Footage Calculation
A realtor will list a structure based upon the total area, or square footage, of the structure. Cooling requirements need to be based upon the internal dimensions of each room. Measure the length and width of each room that would be impacted by the central air unit. Include hallways, laundry rooms and bathrooms in the calculation. Do not calculate rooms or areas that will be blocked off from the unit, such as basements, attics or closets. Square footage is length times width. Keep each room's measurements separate.
Converting Square Footage to BTUs
BTUs are the measurement of how much heat is pulled out of the air by a system with regard to cooling the area. Converting square footage to BTUs requires some basic calculations. For 100 to 150 square feet you'd need 5,000 BTUs; 150 to 250 square feet equals 6,000 BTUs; 250 to 350 square feed need 7,000 BTUs of cooling power. Areas larger than 350 square feet need to have the total area multiplied by 25 to get the estimate for BTUs. Add 4,000 for kitchens and 1,000 for bathrooms, laundry rooms or other humid rooms. Add each room's calculations together to get the total BTUs for the structure.
Selecting a System
Central air conditioners are rated by tonnage. BTUs convert easily to tons by dividing the total BTUs by 12,000. For example, a 1,200 square foot house needs roughly 30,000 BTUs. The tonnage calculates to 2.5 tons by dividing 30,000 by 12,000. Choosing a system starts with identifying the tonnage necessary and choosing a model that is closest to that calculation. Always round up to the nearest 5/10th. For example, 4.1 tons should be rounded to 4.5 tons. The next step in choosing a system is selecting the right size system that meets your needs for noise quality, electrical needs and warranties.
Options
Structures that have minimal needs for cooling may benefit from more cost-effective units. Central air can be highly expensive if electrical and ductwork needs to be installed. Window units provide zone control that can readily cool a small area for the same monthly cost or cheaper than a central unit. Ductless mini-split systems are cheaper to install as they do not require ducts but provide ample zone coverage to equal, if not improve, upon central units. Ductless has the benefit of only operating when and where you need cooling.
Tags: each room, based upon, BTUs square, central unit, central units, feet need
