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Cooling Systems

Air Conditioners

Oversized Air Conditioners Are Bad

It's important to have a properly sized air conditioner. According to the Environmental Protection Agency (EPA), up to one half of all homes have oversized air conditioners. It's best to use a properly sized air conditioner because it saves energy, costs less, and improves comfort. If your air conditioner is oversized, it will run for short periods of time on hot days and frequently turn itself on and off. This not only wastes energy, but also causes the air conditioner to wear out more quickly.” On a hot day, it is more efficient to have an air conditioner that runs continuously. Oversized air conditioners are less effective at removing humidity from your air and are noisier because the air flows faster.

Properly Sizing an Air Conditioner

Some contractors size the air conditioner by only using the home’s square footage. This is not the proper way to size an air conditioner. Cooling size should by set by using guidelines such as the Air Conditioning Contractors of America’s Manual J.

Some of the factors needed to calculate the air conditioner sizing include measuring floors, ceilings, walls, and windows. Also, the insulation value of attics, walls, and crawlspaces affect the cooling load. The indoor and outdoor temperatures, shading, number of occupants, type of siding, ceiling height and roof color can also affect the cooling load. Ask your cooling contractor for a copy of the cooling load calculations. If the calculations don't include the items mentioned earlier, ask the contractor about it. It can take several hours of time to properly calculate the size of your air conditioner. Avoid working with someone who doesn't take the time to properly size your air conditioner.

Seasonal Energy Ratio

The Seasonal Energy Ratio (SEER, sometimes called EER) measures the efficiency of an air conditioner. The higher the SEER, the more efficient the air conditioner is. It costs more to buy a higher SEER unit, but it will save you money in the long run. Try to get a unit that has a SEER of 12 or higher.

Compressor Type

The compressor of an air conditioner is one of the most expensive parts to replace. There are 2 main types of compressors used in air conditioners. “Reciprocating” compressors have more moving parts and tend need more repairs. A “scroll compressor” has fewer moving parts, and will likely need fewer repairs. Scroll compressors also tend to be more efficient and are usually found on better quality air conditioners.

Location of Central Air Conditioner

Try to place your unit on the north or east side of your home and in the shade. Air conditioners generate noise so you might take that into account. For example avoid having the air conditioner by bedrooms. It should be placed where it can be easily be accessed or removed. To simplify maintenance, position the air conditioner so it is easy to access the coils and air filter. There should be adequate space around the air conditioner to allow air to flow. There should be at least 4 feet of airspace above the air conditioner. You may want to mention your placement preference to your builder early on so that the cooling subcontractor will know about it when installing the air conditioner.

Air Conditioner Maintenance

During the summer, you should check the air filter monthly and clean or replace it when it gets dirty. The coil should be cleaned every 2 years. In the fall and winter cover the external unit to protect it from falling branches and ice.

Air Conditioner Ready

If you are not going to install a central air condition in the home, you may still want to make your home air conditioner ready. Installing the proper wiring, venting, and furnace plenum while you are building the home is less expensive than modifying the home later to add a central air conditioner. Even if you don't plan to install an air conditioner, this feature may make your home more appealing for a future homebuyer. Also, when choosing a furnace, be sure the blower is strong enough to support the size of the future air conditioner. If the furnace blower is not strong enough then you may need to replace your furnace in order to add an air conditioner in the future.

Ductless Air Conditioners (High Velocity Air Conditioners, Mini-Split System)

You can have central air conditioning without needing large air ducts throughout the home. A ductless air system uses small pipes to distribute cold air. These pipes are around 2 inches wide. These systems can be very quiet and they have smaller vents. Typically the vents are put in the ceiling and this can also make it easier to arrange furniture because you can eliminate floor vents. Ductless air conditioning is easier to install in older homes that don't have ducts. Ductless air conditioning is also helpful for homes that use radiant heating.

Window Air Conditioner Units

If you have a window air conditioner, have the unit slightly tilted towards the outdoors. This will help water condensation to run outdoors. Also, be sure to use weather stripping to seal the area around the unit. In the summer, shut your heating ducts to reduce the amount of space you are cooling. Most window units are designed for double hung windows. If you have casement windows then look for units that are designed for casement windows. A unit with a lower profile may still give you some view out of the window and let more light in. The filter will need to be cleaned every few weeks. Look for a unit that has a washable filter that can easily be removed for cleaning. Some units will remind you when you need to clean the filter. One concern of having a window unit is that the window is open and this can make it easier for a thief to break in or steal the air conditioner.

Swamp Coolers (Evaporative Coolers)

Swamp coolers are an alternative to air conditioners. A swamp cooler typically sits on top of a roof and contains a filter pad that is kept moist. A fan brings outside air through the filter pad and the moisture in the pad helps lower the temperature of the air. Then the cooler air is blown into the home. The temperature inside the building is controlled by the speed of the airflow. The breeze also helps the air to feel cooler. To use a swamp cooler, air needs to flow through the home and exit. A window or vent needs to be open when using a swamp cooler. Unlike air conditioners, swamp coolers cannot recirculate air from inside the home because this could cause moisture problems inside the home. Also, you usually need to have a window open when using a swamp cooler and this can create a security risk.

Swamp coolers cost less to install and operate then air conditioners. A swamp cooler may be helpful in areas that have low humidity. In dry climates, air conditioners may remove too much moisture from the air and make the air uncomfortable. However in humid climates swamp coolers are not very effective because the air can become too humid. In general, the eastern half of the USA has too much humidity to use a swamp cooler. Swamp coolers are more common in the western half of the USA. Also, swamp coolers may require more maintenance work. You may need to seal up the cooler when it is not being used and occasionally clean the swamp cooler. Some subdivisions may have covenants that prohibit or restrict the location of roof mounted cooling devices such as swamp coolers.

When buying a swamp cooler, consider getting one with variable speeds. This gives you more control over the temperature in your home. In general, centrifugal (drum shaped) fans are quieter then axial (propeller) shaped fans. Automatic shutoff dampers can be helpful for closing off the unit's vents when the fan is not running (this reduces chance of pollen, dirt, and insects getting in the unit and may eliminate the need to seal the unit after the summer is over). Automatic electronic thermostats can do a better job of maintaining a comfortable temperature in the home (compared to mechanical thermostats). Some units will automatically drain themselves when not in use (to reduce chance of algae or mold growing in the water).

If you have hard water it may be a good idea to use a water treatment system to remove minerals from the water that goes to your swamp cooler (to reduce corrosion). However, if your water softener uses salt then the salt can build up in the swamp cooler and corrode metal parts. If you have salt in the water you may need to bleed water off to prevent salt from becoming concentrated. Some swamp coolers let you adjust the bleed-off rate. If you have excessive salt concentrations and have to waste a lot of water then this can make it more costly to run a swamp cooler. Swamp coolers tend to require more homeowner maintenance the air conditioners.

Dual Air Systems

Some manufactures now provide cooling devices that combine the benefits of air conditioners and swamp coolers. During periods of low humidity the device functions as a swamp cooler and can cool the home and use less energy. During humid periods the air conditioning portion of the device runs to reduce the humidity of the air that is being used to cool the home. In addition both the swamp cooler and air conditioner may run together to help reduce cooling costs (the swamp cooler can pre-cool the air to reduce the work needed by the air conditioner) . These systems can usually run without having to leave a window open.

Misting Fans (Misters)

Misting Fans or misting systems can be used to cool outdoor areas. A fine mist of water is sprayed into the air and this can reduce the heat of nearby areas by up to 20 degrees F. Misters can be an effective way to cool outdoor areas which have low humidity. Using a mister in an area that has high humidity will not have any noticeable affect and may raise the humidity level. Misters cool the air by creating a mist that is quickly evaporated and the evaporation causes the air to be cooled. Mister can also be installed to surround a patio or gazebo to help quickly cool the air in those areas.

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