The day will come— or has already arrived— when you need a new air conditioner. So you call your local HVAC company. They send someone over to look at the system and within a day, you have an estimate. Whoa! That was fast.
When you push back a bit, asking how they determined what size system you need and why they recommended this one . . . the guy says he or she is just replacing the unit you had. That’s when it’s time to step back and take a deep breath.
New era in air conditioning
For starters, today’s air conditioners are much more efficient than the old models. You might be able to get by with a smaller-size unit that will cost less to operate. [For a good summary on the subject, see this web page: http://energy.gov/energysaver/articles/central-air-conditioning]
If your contractor doesn’t perform tests such as a Manual J or a Manual D (software to estimate the amount of conditioning capacity you need and software to analyze the ductwork), get a second opinion. [Here’s our service page for finding a qualified contractor in your area: http://www.acdoctor.com/find-contractor/]
It’s important that the HVAC contractor put some thought into ductwork. Back in the day, when cooling technology was far less sophisticated, they just ran a tube from the central AC to each room. Nowadays, you want more AC delivered to a bright, sunny dining area with southern exposure than you do to a north-facing bedroom. Replacing the AC unit without examining the ductwork is like declaring a person healthy whose heart is strong but whose arteries are clogged.
No, bigger isn’t always better
It’s even more complicated when they get around to sizing the AC unit. Contemporary AC’s can be fine-tuned to the climate where you live, your home’s location, exposure, insulation, number and size of the rooms, height of the ceilings, number of windows, number of occupants, and various other factors.
If the unit is too small, it won’t cool the house evenly. If it’s too large, it will be shutting off and on before the humidity can be removed from the air.
You may will hear a contractor tossing around terms such as ‘tons’ and ‘SEER’. A ton in air conditioning lingo is equal to 12,000 BTUs of cooling capacity. Typically, a 2-ton unit will cool 24,000 BTUs per hour.
The other relevant term is SEER, or Seasonal Energy Efficiency Rating. This is a grade given by the government to indicate energy efficiency. SEER 24 is twice as efficient to run as a SEER-12 unit. If your HVAC guy lapses into tech-talk, throwing off phrases about load calculation and R-values, ask him or her to please explain it in layman’s language. How much cooling capacity do you need, in tons? What’s the SEER of the unit he or she is recommending?
They should give you a written analysis, which you can then use to compare several quotes. In fact, before you call anyone, take a look at our service page on sizing. At least the contractor’s talk won’t sound like a foreign language. http://www.acdoctor.com/get-educated/be-efficient/get-a-manual-j/
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