A common misperception on the part of many homeowners is that a bigger air conditioner cools better. The truth is oversized air conditioners cool worse. Comfort is reduced. Utility costs are increased. Repairs are more frequent. Equipment life is shortened. Noise increases. The price is higher. So, why do so many contractors oversize air conditioners?
They oversize on purpose to cover up problems and provide a “safety margin” (e.g., duct leaks, improper airflow across the indoor coil, systems with improper refrigerant charge).
The Result: You feel “cold and clammy.”
Air conditioners dehumidify indoor air. As the indoor coil temperature drops, moisture condenses on the coil. The moisture runs off the coil and is collected in the drain pan and removed. When oversized, air conditioners short cycle. They run for a few minutes, stop, and start again. During the first few minutes of a cycle, the coil temperature drops to the point where moisture condenses on the coil. If the cycle is prematurely halted, the moisture does not run off the coil; it evaporates, returning to the air stream.
The Result: You pay more in utilities than you should.
It takes more energy to start an air conditioner than to keep it running. Air conditioners are least efficient at the start of a cooling cycle. Because oversized air conditioners short cycle, the overall efficiency of your air conditioner drops.
The Result: More repairs over time and reduced equipment life.
Constant starting and stopping taxes your system’s compressor and fan motors, reducing component life.
The Result: Increased noise levels and “blasts” of frigid air
Larger air conditioners move more air, potentially making grille openings “undersized” for the volume of air. Forced through smaller openings, the velocity of the air increases.
The Result: You pay more than necessary.
If reduced comfort, higher utilities, more repairs, and increased noise were not enough, larger air conditioners are more expensive to buy.
© 2005 Service Roundtable