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AC Installation By a Pro Ensures Maximum SEER Performance

AC installation may seem like a straightforward process, but the reality is a little more complex. If your contractor cuts corners or makes errors at even a single step of the installation process, your new system won't perform as it should. With minor errors, you may not notice much difference in your comfort. Where you will see the difference, however, is in your electric bills.

Although systems with higher SEER (seasonal energy efficiency ratio) numbers are more expensive to purchase than less efficient systems, they'll lower your energy bills and save you money in the long run. High-efficiency air conditioners are particularly good investments in areas with long cooling seasons, such as Chicago, Northwest Indiana and Southwest Michigan.

If not installed correctly, though, an air conditioner won't run as efficiently as it could. To reach its maximum SEER, your air conditioner must be sized correctly, receive the optimal amount of airflow and contain the right amount of refrigerant.

What's more, your ducts also need to be primed for efficiency. All of these are things an experienced professional HVAC contractor will address as part of the AC installation process.

Duct Efficiency Affects System Efficiency

No matter how efficient your air conditioner is at cooling air, its efficiency at distributing cool air throughout your home depends on your ductwork. Unfortunately, ductwork is often installed in a way that allows air leaks or heat transfer. Duct joints may be simply pushed together instead of sealed or the ducts left without insulation.

Studies suggest that the average home's ductwork causes the cooling system to lose around 35 percent of its cooling capacity. When you've invested good money for a high-SEER system, that's no small loss.

Inefficient ducts reduce your comfort, too. You may notice that your rooms never seem to be the right temperature no matter how your thermostat is set. Stuffy rooms and an excessive amount of dust on the furniture also occur with inefficient ductwork.

A knowledgeable professional will inspect your ductwork and address any problems before your AC installation and before your new air conditioner is sized. The more efficient your ducts, the smaller, less expensive cooling system you can install without sacrificing comfort. It makes good financial sense to optimize your ductwork before you buy a new system.

Your contractor will address three main areas:

  • Correcting problems: Before installing your new AC installation, your contractor will inspect for punctured or kinked ducts. This is a common problem with flex-duct and fiberglass duct board. The contractor will also check the air balance between the supply and return ducts. Many homes lack a sufficient return air supply, which hinders the cooling and heating system's efficiency.
  • Air leak sealing: Sealing should be done at joints where one section of duct meets another, where ducts meet registers and grilles, and where the ductwork meets the air handler. Mastic and metal tape are the appropriate sealing materials. Although you can do the job yourself, there are reasons to let a professional take care of it. An HVAC pro can choose the ideal sealant from among the dozens available and will know how to apply that sealant for effective, long-lasting results.
  • Insulating: Ducts in unconditioned areas, such as the attic, crawl spaces or the basement should be insulated to reduce heat transfer through the duct walls. If the ducts aren't insulated, cool air passing through will pick up heat from the hot attic or other areas and will arrive to your rooms warmer than it should. To minimize this, ducts can be wrapped in sheet insulation or specially designed duct wrap.

Once the ducts are repaired, sealed and insulated, your installation expert will perform an airflow test to ensure minimal air leakage.

Accurate Sizing

Incorrect sizing is one of the most common AC installation issues that prevents systems from reaching their potential SEER. An undersized system won't have the capacity to keep you cool on the summer's hottest days. An oversized system will waste energy and tend to short cycle. Short cycling occurs when the system kicks on and then quickly shuts off again. This causes a number of problems, including:

  • Reduced efficiency -- An oversized system will turn on and off before the motor reaches the speed at which it runs most efficiently. That means the system will always be running in a less-than-optimal state. A system oversized by 50 percent will use around 9 percent more energy than a correctly-sized system.
  • Reduced comfort -- Quick bursts of cool air cause uncomfortable temperature fluctuations. Because an oversized AC doesn't run long enough to mix cool air with warm room air, you'll have hot and cool spots in your rooms. To make matters worse, an oversized system's short cycles won't remove humidity sufficiently.
  • Equipment costs -- The larger the system, the more it costs. There's no sense paying more for an unnecessarily large system. Maintenance will cost more for oversized systems because short cycling places excess wear on the components.

Despite these issues, some inexperienced HVAC contractors try to err on the safe side by oversizing equipment to make sure it has the capacity to perform well in high temperatures. Some contractors may estimate the system size based on the size of the home or the size of the old AC system. Both of these methods usually result in inaccurate sizing.

Studies indicate it's not uncommon to find systems oversized by 24 percent and even more than 100 percent. This kind of oversizing is unnecessary and ultimately detrimental to your comfort and energy savings. Experts from the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) recommend AC systems be sized to run full-time for just 2.5 percent of the cooling season.

To determine the ideal AC size for your home, your contractor will use software to run the calculations found in ASHRAE's Manual J. This set of calculations accounts for factors like your home's cubic footage, floor plan, air infiltration rates, insulation levels, number and type of windows, orientation toward the sun, and landscaping. The result is far more accurate than any estimation.

Proper Airflow

Air conditioners are designed to have a specific amount of airflow over the coils. If the outdoor (condenser) coil receives too little airflow, it can't efficiently release heat outdoors. This reduces its cooling capacity. In humid climates like Illinois, Indiana and Michigan, precise airflow is even more important. Excess airflow reduces the system's ability to dehumidify. With too little airflow, however, there's a risk that the evaporator coil will freeze. Other potential problems include hot and cold spots in your home, reduced output from your registers, and a system that runs almost constantly.

As with other installation-related issues, airflow also affects your system's ability to achieve its SEER potential. Incorrect airflow could reduce a cooling system's efficiency by around 10 percent. During AC installation, your contractor should take steps to ensure that the airflow through the system is neither too high nor too low.

Causes of airflow issues include:

  • Wrong indoor unit -- If the indoor air handler isn't matched to the rest of the equipment, the system may not get sufficient airflow.
  • Undersized outdoor unit -- An outdoor unit that's too small for your home may be unable to create the necessary airflow.
  • Poorly located outdoor unit -- Installing the unit too close to plants or structures blocks airflow. It also increases the chance that the unit will become clogged with debris.
  • Duct problems -- Undersized ducts can't supply sufficient airflow. A ductwork design with a lot of twists and turns or with very long ducts also impedes airflow. Even the wrong type of register vents and return grilles can cause airflow problems.

In addition to correcting duct problems before AC installation, your contractor should measure the airflow across the coils after installation.

Correct Refrigerant Charge

Without refrigerant your air conditioner can't operate at all, so it should be no surprise that the system's refrigerant level affects its performance and energy efficiency. Split-system air conditioners, the most common type, are charged with refrigerant on site during installation, which means there's always a chance of human error.

Research shows seven out of 10 air conditioners are over- or undercharged with refrigerant. Long line sets make a system especially prone to being undercharged. Undercharging is the most common problem, but it's not uncommon to find systems overcharged by more than 100 percent. In certain situations, a system overcharged by just 20 percent will perform at a full SEER number below its potential.

The manufacturer's guidelines specify the correct refrigerant charge. After your AC installation, your contractor should check the charge to ensure that it's within a few ounces of the specified charge. This should be done after measuring the airflow because if the airflow isn't optimal, the refrigerant charge reading won't be accurate. You can verify these measurements along with your contractor.

AC installation is a tricky process, but an experienced, responsible contractor knows how to avoid common errors and is willing to invest the effort in doing so. To work with a true pro, contact us at We'll ensure that your system reaches its maximum SEER and keeps you in comfort all summer.

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