In air conditioning, bigger is not better. It’s just the most common mistake we see in
air conditioning design. Compared to a
correctly sized air conditioner, an oversized air conditioner cools poorly,
costs more to operate, is noisy, and has a shorter lifespan.
Design Occurs In The
Field
Air conditioning systems are not designed in the
factory. They are designed by us and
other contractors like us. Each system
we design is unique. We account for your
home’s design and layout, the type of construction, it’s orientation to the
sun, shade, our local weather, and most important, your lifestyle. How you plan on using your air conditioner
has a big impact on the design.
After we collect the necessary information, we crunch
through a series of engineering calculations.
Sometimes we make the calculations on the spot. Other times, we return to the office to use
special design software. When we perform
the calculations in the field, it’s not unusual for us to double check them in
the office.
We use many factory designed and built components in the
systems we design. We also fabricate
parts of your system in the shop or on-site.
You will be unhappy with an air conditioning system, no
matter how reliable and well made you consider the air conditioner and other
components if the design is wrong, the field fabrication is poor, and the
installation is sloppy.
The Impact on Comfort
When an air conditioner is oversized, it powers on, runs for
a few minutes, lowers the air temperature at the thermostat to the setting, and
stops. A few minutes later, the air
temperature rises and it powers back on.
To you, it feels like the air conditioner is intermittently blasting
frigid air. This is likely an air
conditioner that is short cycling.
An important role of air conditioning is
dehumidification. When an air
conditioner short cycles, it pulls moisture from the air stream and leaves it
on the indoor coil, where it evaporates back into the air stream. An air conditioner’s ability to remove
moisture from the air stream is lowest at the start of the cycle. Inadequate moisture removal results in a
cold, clammy feeling.
When the air conditioner runs for longer cycles, it does a
better job pulling moisture from the air stream and disposing it down the
condensate line. Cold, clammy air
indicates oversizing.
The Impact on
Acoustics
The air conditioner and duct system should be designed
together. If the system is sized larger
than the duct system, the volume of air pushed through the ducts raises air
velocity, creating a windstorm. Noisy
grilles, registers, and diffusers indicate oversizing or too small ducts.
The Impact on
Efficiency
Short cycling is not efficient. It takes a lot more energy to start a motor
than to keep one operating. With your
air conditioner, you start three motors:
the compressor, the outside fan motor, and the indoor fan motor. In addition, you are operating larger, more
expensive motors than you need.
Think of a properly sized air conditioner as a fuel
efficient car rolling down the highway.
The oversized air conditioner, by contrast, is like a 1960’s muscle car
in stop-and-go traffic. The miles per
gallon is pathetic. Oversizing costs
money.
The Impact on
Equipment Longevity
Short cycling causes your equipment to wear out sooner. Just like an old car with lots of highway
miles has more life left than one used for city driving, a correctly sized air
conditioner will out last an oversized one.
Identifying Oversized
Systems
If your air conditioner starts and stops (i.e., cycles)
regularly on very hot days, it’s probably oversized. Have us perform a set of engineering
calculations if you’re unsure.
A continually running air conditioner does not guarantee
that it sized correctly. Oversizing
covers up other problems. For example,
if your system is oversized and has a refrigerant leak, it may not be readily
apparent until the compressor fails.
If you think your system is oversized, don’t make
guesses. Call us at Elite to run the
engineering calculations on your home.
918.610.7300.
