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Choosing the Right System For Your Home

Your home may be trying to tell you something.

Trane understands the sense of frustration that surrounds the purchase of an air conditioner, furnace, or other part of your heating and cooling comfort system. It's not like buying any other appliance, is it? And while it may not be necessary to learn how to completely program your VCR, learning to get the most out of your home comfort system may be one of the most important things you'll do as a homeowner.

Take a look around your home. Are any of these situations familiar:
bulletCooking odors that linger in the kitchen for days on end.
bulletOne room in your home that is always warmer or colder than others.
bulletA bathroom that's humid and damp.

If any of these remind you of your home -- it is trying to tell you something. Your house is not just a floor plan; it's an environmental system. And that system can gradually slip out of balance. In other words, maybe it's time to take a long, hard look at your home.

How an air conditioner conditions air
Heat pump: the mysterious machine that heats and cools
The truth behind those efficiency ratings

How an air conditioner conditions air

A little chemistry, a little physics, and a whole bunch of tubes and wires. Here are the basics of keeping cool.

An air conditioner makes your home cooler, true. But in terms of how the system actually works, it's more accurate so say that an air conditioner makes your home less warm. What it's really doing is drawing heat energy out of the house and transferring that heat to the outdoors (where it's already so blasted hot that nobody notices the difference).

1. A gas (the refrigerant) flows into the compressor, where high pressure turns the refrigerant into a liquid. The compressor pumps this chilly liquid through tubes to . . .

2. The evaporator coil. Here the cold, liquid refrigerant absorbs heat energy from the surrounding air and turns back into a gas. Also, humidity from warm indoor air condenses on the evaporator and drains away. Meanwhile . . .

3. A blower draws warm air from the house, moves it through the evaporator where heat energy is removed and blows this air on through the ductwork into your house -- cooler, dryer and altogether more pleasant. As for the heat energy removed from that air . . .

4. The once-gaseous, then-liquid, now-once-again-gaseous refrigerant carries that heat energy back to the outdoor unit. Here the refrigerant passes through the condenser (sometimes called the condensing coil) where metal fins around the tubing transfer heat to the surrounding air, which is moved over the condenser by . . .

5. An exhaust fan. So you see, that air blowing out the top of your outdoor unit is so hot because it contains heat energy that was inside your house just a couple of minutes before. Whew!

Heat pump: the mysterious machine that heats and cools.

It's really pretty simple. Just think of a heat pump as an air conditioner with a "Reverse" gear.

A heat pump does two jobs, but it uses the same principles for both. On warm days, it works exactly like a regular air conditioner. It extracts heat from inside your home and transfers it to the outdoors. On cold days, it does just the opposite, pumping heat energy from the outdoors into your home.

"Huh?" you may be asking, and that's a very astute question. How can the machine pump heat out of cold air? Because the system's refrigerant evaporates at such low temperatures, drawing heat from the surrounding air. Strange as it may seem, even if it's freezing outside there's still enough heat energy in the chilly air for a heat pump to warm your home. 

Of course, the colder the weather, the more difficult all this heat-transferring business becomes. So Trane air handlers (the indoor part of a heat pump system) have supplemental electric heating that kicks in when the temperature is extremely low. This makes a Trane heat pump a more-than-adequate heating system for homes in all areas of the country. In the colder parts of the country, some heat pump owners prefer to have a gas furnace to run on the most frigid days.


The truth behind those efficiency ratings

How much efficiency is enough? Depends on how fast you want your system to pay for itself.

12 SEER, 14 SEER, 80% AFUE, 90% AFUE - don't get too bumfuzzled by trying to figure out where all the numbers come from. All you really need to know is that these are relative measures of fuel economy -- SEER (Seasonal Energy Efficiency Rating) numbers for air conditioners, or AFUE (Annual Fuel Utilization Efficiency) for gas furnaces. In simplest terms, the higher the number, the more heating or cooling you'll get for your energy dollar.

As you shop around, use the numbers, not vague terms like "high efficiency" or "super high efficiency," to really compare systems. Any air conditioner or furnace on the market today can be called "high efficiency" compared to the equipment of just a few years ago. What was called high efficiency then -- say 9 SEER for an air conditioner or 70% for a gas furnace -- wouldn't even be permitted on the market today!

Air conditioners
bullet10 SEER -- the minimum efficiency allowed by law for new central air conditioning systems
bullet11 or 12 SEER -- trade up to this level from your old system and you'll probably be delighted at how much lower your electric bills are
bullet14 SEER plus -- pushing the upper limits of what's possible with today's technology
Gas furnaces
bullet78% -- the legal minimum for new furnaces on the market today
bullet80% -- another once-impossible degree of efficiency that means drastically lower gas bills than you probably have with an old furnace
bullet90-plus % -- currently the highest efficiency you'll find (but we're working on it)

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Last modified: March 29, 2015