With the long summer days beginning to heat up, it’s time to make sure your air conditioners are in good working order so you can stay cool and comfortable this season. Whether you have central air as part of your existing HVAC system or rely on a portable or window air conditioning unit, this is the time of year that air conditioning questions and concerns tend to pop up.
Fortunately, we’ve got your answers right here. If you’ve ever wondered how your AC unit works to keep your house full of fresh, cool air, you’ve come to the right place. Read on for the answers to all of your burning — or maybe freezing! — questions about your air conditioning system.
Do Air Conditioners Dehumidify?'
Yes, they do — but it’s not their primary job. The moisture gets sucked out of the air basically as a side effect of the cooling process. To understand how that works, it’s helpful to know a little more about your air conditioner.
Your air conditioner operates by using a chemical refrigerant that flows through it. Cold refrigerant flows through the evaporator coils and cools the air in your home. As it does so, it also absorbs heat from the room — a central air conditioner is actually more like a heat remover than an air chiller, though the end result is the same. The refrigerant flows to the compressor and condenser, which are located outside. As the refrigerant is compressed, it releases all the excess heat into the air outside before flowing back indoors to keep the cycle going.
Because the air around the indoor evaporators is so cold, it allows condensation to form. This is basically the same as when your icy drink starts to "sweat" on a hot summer day: Condensation has formed on the cold surface of the glass. (For science nerds, this happens because relative humidity increases when the temperature decreases. The surface of the glass has such a steep temperature drop that humidity levels on its surface have reached 100 percent and water droplets form.)
Once the condensation forms on a glass, it drips down to a coaster and eventually evaporates back into the air. With your air conditioner, however, the excess moisture is collected in a tray and allowed to drain out the window, or, in the case of a central air conditioner, through a floor or wall drainage system. Because the water is removed from your room, eventually the humid air turns to dry air because the condensation isn’t allowed to evaporate back into the air indoors.
Do Dehumidifiers Cool a Room?
No. Dehumidifiers technically add heat to a room, though they may help you feel cooler. A dehumidifier works the same way an air conditioner does: by creating cold air on the evaporator coils so that condensation can form and be collected. While a whole-house dehumidifier might have a dedicated drainage system, a portable model typically collects water in a removable tank to be poured out every few days as needed.
The major difference is that a split system air conditioner directs all the excess heat outside to be released into the already warm air outdoors. A dehumidifier doesn’t bother with this, so the excess heat released in the condenser system is simply let go back into the room. This actually can raise the indoor temperature by a small amount, especially if the dehumidifier if running nonstop on a humid day.
On the other hand, lower humidity levels in your home will make you feel cooler overall. This is because dry air allows your personal cooling system — perspiration — to work more efficiently. The reason why humid summers often feel so miserable is that the higher humidity means that your sweat can’t evaporate off your skin quickly. This leaves you feeling sticky — and still just as hot, since the process of evaporation is what cools you off. If the air in your home is drier, you’ll feel better even if the temperatures are high since your body will be able to cool itself the natural way. In fact, using a dehumidifier and a ceiling fan may allow you to deal with higher humidity when it’s not actually all that hot out, especially in places like Florida and the rest of the East Coast.
How Does a Portable Air Conditioner Cool a Room?
If you read that bit about split systems taking the hot air directly outside, you might be wondering what this means for portable air conditioners. Don’t they make heat, too? Does this mean they release the excess heat into the house the same way a dehumidifier does?
The answer is all about the venting system. Unlike a central air system or window unit, a portable air conditioner does have its condenser coils right in the same unit, similar to a dehumidifier. However, good portable A/C units allow you to vent hot air through a window, door or other point of egress so that you get all the benefits of the cold air without worrying about your system fighting against itself by dumping hot air back into the room. The closer you’re able to place your portable unit to the window, the shorter your vent hose will be, and that will allow your unit to run as efficiently as possible but directly the heat outdoors.
Is It More Energy Efficient to Use a Dehumidifier Than A/C?
Probably not. Since both systems use a compressor and basically work the same way, they use about the same amount of electricity to operate, so your energy bills aren’t likely to show much of a difference — assuming you would run an air conditioner for the same amount of time each day that you run a dehumidifier. But it’s ultimately up to you to decide what makes you more uncomfortable: excess humidity or high temperatures. Keep in mind that this question is only for people in humid climates. If you live in the desert, a dehumidifier isn’t going to do much for you, since your air is already dry. Your best choice to save on energy costs is to consider an evaporative cooler, which actually cools the air by adding water vapor instead of trying to take it away. In a dry climate with very low humidity, water will evaporate quickly and lower the temperature of the air around it as it does so. Because evaporative coolers don’t use a compressor system, they use far less electricity and are much cheaper to operate.
How Does an Air Conditioner Affect Indoor Air Quality?
A good air conditioner that is well maintained shouldn’t have an adverse affect on your air quality overall. The main trouble with running an air conditioner for long periods of time is that you see the windows closed, which can allow pollutants and allergens to build up inside your home. When you can, consider opening the windows to let in some fresh air, or using the vent/fan function on your air conditioner instead.
It’s also important to either clean or replace the filters on your A/C unit regularly, which will keep it running efficiently and prevent particulates from getting into your system. You may also want to consider duct cleaning every few years, which will remove any debris or allergens so that they aren’t distributed throughout your house when the central air conditioner is running. It’s also a good idea to have your HVAC system serviced at least once a year.
Finally, you can save energy and increase your rest air quotient by running your air conditioner less. Turn up the thermostat so it doesn’t kick on as often, and consider turning it off when you’re not at home — or in rooms that aren’t occupied. Cutting back in these small ways will decrease your usage overall.
Does an Air Conditioner Need a Thermostat?
Your A/C unit doesn’t need a thermostat to operate, but it’s a good idea to have one. Being able to set the temperature will keep your unit from running nonstop while it’s on. That’s about more than just comfort — though preventing meat locker conditions is always a good idea. A thermostat will also help you save money, especially if you turn it up when you’re out for the day. While a central A/C system is connected to the house's main thermostat, a portable unit may have a thermostat directly on its control panel.
In addition to a thermostat, it’s also helpful for portable units to have a timer so that the compressor will shut off after a certain amount of time. This will also keep you from running A/C all day or all night long and keep your energy bills in check. Other features to look for are humidity control, vent systems, eco mode and a sleep mode to turn things down at night. Any feature that helps you run your A/C less often is one that will help you be more environmentally friendly, even during the worst of the summer heat and humidity.