Air conditioning units are sized to the job per so many cubic feet of air space. Take tonnage. It has nothing to do with weight, it is the amount of heat an AC unit can remove in an hour. A one-ton AC unit can remove about 12,000 BTU per hour. But why rate cooling in tonnage?
Why is Air Conditioner Cooling Tonnage Calculator
Back in the good old days, those that could afford it used ice to cool the house and refrigerate food. Hence the ice box. Well it takes about 143 BTU to melt one pound of ice. A 2000 pound (a short ton) it takes about 286,000 BTUs to melt that ton completely. If the melt rate is spread over 24 hours it take about 11,917 BTU/hour, we round that up to 12,000 BTU per ton of AC capacity. The rule of thumb used in sizing AC units is one ton for 400-1000 square feet of space, depending on factors like window area and ceiling height. Given an 8-foot ceiling height that is equal to about 8000 cubic feet of air. Why not just throw up a 5-ton unit and be done with it? Water heating, running a clothes dryer and your AC are the energy hogs of the typical all electric house hold.
Causes of Heat Distribution in a House
With modern LED lighting one heat producing factor removed, most of the radiation from incandescent lighting was in the infrared bands, i.e. heat. Computers and electronic entertainment gadgets also produce heat. All those fans in your desktop computer are pushing heat from your computer into your living environment. Your AC must be sized to accommodate this added heat. The AC therefore must be sized to the space for which it is responsible. The bigger your unit you are burning power you don’t need to, too small and you’re very uncomfortable and sweaty.
Every gardener knows about zones. The AC people have zones as well, cooler climates need smaller unit. Just like gardening we live in a red zone, meaning hot, hotter and hottest. The formula therefore changes to 600-900 square feet per 1.5 tons of AC.
Package VS Split System AC
One consideration is split or packaged systems. Packaged AC (think roof top) have all the components inside of one frame. Split are the ones sitting on the ground in the back yard have compressor and condenser coils outside and the expansion coils and house air fan in an air handler on the inside. Packaged AC units are not available with the high efficiency ratings of the split units who are approaching 20 SEERS. So split systems tend to be more efficient given there is room for the air handler.
Seasonal Energy Efficiency Ratio (SEER)
That raises another issue. What is SEER? Seasonal Energy Efficiency Ratio (SEER) and measures the amount of cooling put out for each unit of energy consumed. Higher the SEER the more efficient the unit is. However, the SEER is derived from tests done by the manufacturer under supposedly standard conditions. They are rated in an ambient temperature of 82 0F. You lose an entire ton of cooling if the temperature rises to 95 degrees. Consider the here in the southwest ambient temperatures can climb to 115 degrees for multiple days. Another rating that the industries consider more accurate is the Energy Efficiency Ratio. The SEER rating is somewhat of a misleading factor but is indicative of the unit’s efficiency, so more is better regardless of the standard.
Air Conditioner Inspections, Repairs & More in Purvis, Oak Grove, Dixie, Sunrise, Barrontown, Leeville, Petal & Hattiesburg MS & Pine Belt, Mississippi
Something to consider in new construction. In older housing you replace a unit with a like unit, one that is in most cases will be more efficient. Steve’s Heating and Air can meet all your central air conditioning needs. Contact us to schedule an appointment today!