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Home Air Conditioning Components

Want to know the difference between an air handler and an evaporator coil? Now you're speaking our language.

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Air Conditioning Components

Your local ARS®/Rescue Rooter® technician knows central AC systems inside and out, and will always be happy explain things in plain terms. All the same, it's good to familiarize yourself with certain air conditioning components and concepts so you can better explain your situation—and understand the importance of regular air conditioning maintenance. Here are the five main parts you should know:


Looking to install a new thermostat? Depending on the age of your system, there are two basic types of thermostat: electro-mechanical and digital. Their role is the same—controlling your system to deliver the exact room temperature you desire—but their operation is different. Digital thermostats are also now available with Internet connectivity, offering a whole new level of comfort and convenience.

  • Electro-mechanical thermostats are the older types with little metal coils and a mercury tube inside. As the temperature in a room shifts, the coils either contract or expand, pushing the mercury to one end of its tube or the other, which signals the HVAC system to either turn on or off.

  • Digital thermostats are much more accurate at keeping your home comfortable. Most models today are programmable thermostats, which means you can set times for your system to run or shut down. Because you have much more control, you can save on your energy costs by reducing your heating and cooling when you don't need as much.

  • WiFi-enabled thermostats allow you to set your temperature from wherever you are using your computer or mobile device. Many can also detect when your house is occupied or empty, learn your routine and preferences, and adjust the temperature accordingly. The result? Lower utility bills—and a much more predictably comfortable home. The Nest Learning Thermostat® is a great example of this technology.

Air Conditioning Compressor

What is an air conditioner compressor? It's a simple question that sometimes requires a lengthy and detailed explanation, but you can boil it down to this: an air conditioner compressor "squeezes" refrigerant in order to add energy and get the cooling process started. The real question is how to keep it in good working order—and how to tell when a little expert attention is needed.

Your local ARS®/Rescue Rooter® specialist knows everything there is to know about AC compressors, and can explain the part and the process in detail. But before you schedule an appointment, it's a good idea to familiarize yourself with the compressor's role in cooling your home. If you're having air conditioning issues, it may help you understand what's going wrong—and help us address the issue quicker.

  • Refrigerant arrives at the compressor as a cool, low-pressure gas. The compressor adds pressure to increase its energy and temperature, and the working fluid leaves the compressor as a hot, high-pressure gas.
  • This compressed gas then passes to the condenser, the part of your air conditioner that has metal fins all around. The fins help the heat dissipate more quickly.
  • When the working fluid leaves the condenser, its temperature is much cooler and it has changed from a gas to a liquid under high pressure. It then heads inside to complete the cooling process in the evaporator coil.
  • In a central air conditioning system, the compressor (and the condenser) is located in the box outside your home. If your air conditioner runs, but is only blowing warm air and not cooling your home, the problem is often the air conditioner compressor.

Evaporator Coil

The evaporator coil takes a lot of the credit: this is the air conditioning component that absorbs heat energy from the surrounding air, transforming hot, humid air into something cooler, drier and more comfortable.

There's a lot of ingenious science behind air conditioning and HVAC systems, but the process in the end is actually quite straightforward. Here's how your evaporator coils work:

  • The compressor and condenser turn the Freon™ (or similar refrigerant gas) into a cool liquid under intense pressure.
  • Evaporator coils allow the liquid to evaporate back into gas.
  • The evaporation process extracts heat from the surrounding air, lowering the air temperature.
  • Now that you have cool air, it needs to circulate through your home—and that’s where the air handler comes in.

Air Handlers

An air handler is the indoor unit that provides conditioned air circulation through your home.

An air-handling unit includes a blower, heating and/or cooling elements, filter racks or chambers and dampers. Air handlers usually connect to ductwork that distributes the conditioned air through the building and returns it to the air handler.

If you have a forced air furnace, the air handler is the part that blows the hot air out. It probably also circulates cooled air from your air conditioner.

If you don’t have a furnace, you may have a stand-alone air handler to blow cool air from your air conditioner and/or hot air from your heat pump through your home’s ductwork.

Changing your filters regularly is the key maintenance for your air handler, whether it's part of your furnace or a stand-alone unit. You should also have your entire system inspected and maintained by a professional each year to make sure that any potential problems are caught before they become big.

Air Ducts

Your air conditioning is a complex system, but it can only be as effective as the air ducts that circulate the conditioned air. To fully feel the benefits of your air conditioning and heating system, your ductwork must be well- designed, sealed, and maintained.

What most people don’t realize is that their equipment is only part of the solution. To fully feel the benefits of your air conditioning and heating system, your ductwork must be as well thought out—and maintained—as your HVAC unit.

Some new homes these days are being built with ductwork running through the conditioned living space. By constructing an insulated zone between the ceiling joists and a dropped ceiling, or between the walls mainly in the corners of a room, ducts can exist in an area where any lost air would contribute to the overall comfort of the home.

Of course you don’t have to build a new house to improve the efficiency of your ductwork. One thing you can look at is your duct’s configuration. A radial design, where air supplies and returns have direct connections to the unit, or a trunk and branch design, where supplies and returns branch off from a long “trunk” directly connected to the unit, are best for most houses.

Poorly planned or installed ducts can negate energy savings. Joints that aren’t sealed properly can allow a lot of that precious heated or cooled air to escape. The same applies to old ductwork that may be kinked, restricting airflow, or not be up to par with today’s new standards. Even newer ducts, when placed in areas where temperatures can be extreme (like attics), can experience difficulty maintaining temperature of that comfy conditioned air.

Get your system inspected

You should also have your entire system inspected and maintained by a professional each year to make sure that any potential problems are caught before they become more significant (and more expensive to repair!).

Call us today to set up an appointment with your local ARS®/Rescue Rooter® air conditioning specialist—and ask us about our worry-free air conditioning Home Service Plan, which comes complete with our Exceptional Service Guarantee.

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