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Central air conditioners provide excellent cooling at a reasonable cost. When choosing a new central air system, keep in mind that there are several elements that can affect the equipment’s efficiency and performance. The following information provides a basic introduction to central air conditioners and some suggestions on features to look for in a central A/C for your Westminster, MD-area home.

Central Air Conditioner Function

Central air conditioners work on a common principle of refrigeration and cooling. They consist of an indoor unit that contains components such as the evaporator and air distribution fans, and an outdoor unit holding a compressor and condenser. The two units are connected to each other by power cables and tubes containing a refrigerant, the substance that makes it possible for heat removal and cooling generation as it circulates between the indoor and outdoor units.

At the beginning of the cooling process, the liquid refrigerant in the indoor unit evaporates into a gas. During this change of state, the refrigerant absorbs heat, cooling the evaporator coil. The air handling equipment blows air over this cooled coil, producing the conditioned air that lowers the temperature inside your home. The air is directed into the supply ductwork and out at vents at the terminal points of the ducts. Stale, expended air is brought back to the system where it’s filtered to remove particulates and other airborne contaminants. The air is then cooled and redistributed throughout your house.

After the gaseous refrigerant does its job indoors, it’s moved through the system by the compressor. The gaseous refrigerant enters the outside unit where it returns to its liquid form in the condenser, with additional pressurization provided by the compressor. As the refrigerant changes state from gas to liquid, it releases the heat it contains, dispersing the heat into the air around the outdoor unit. If you look carefully at the outdoor cabinet, you can often see waves of heat emanating from the equipment. When the refrigerant has fully returned to its liquid state, it circulates back inside and the cooling cycle starts again.

Features to Look for in a Central A/C

Central air conditioners produce excellent levels of cooling at a relatively high level of efficiency and a low operating cost. Certain characteristics of the system can influence the efficiency and performance and should be taken into consideration when selecting a new system. Here are some of the features to look for in a central A/C.

Proper sizing is extremely important to A/C function. When referring to air conditioners and HVAC systems, size does not indicate the equipment’s physical dimensions. Instead, it refers to the air conditioner’s functional capacity, or its ability to produce the amount of cooling you need to meet your indoor temperature preferences. If you buy an A/C that’s too small, it won’t be able to generate enough cooling for your home. It will also work harder to keep up with temperature demands, which will wear out the equipment faster, increasing the chance of breakdowns and reducing the system’s expected life span.

Before sizing a central air conditioner, your HVAC professional should perform a cooling load calculation on your home. The cooling load is the amount of cooling needed to account for the structural and thermal characteristics of the home and for your individual requirements for indoor comfort. The load calculation will require a careful inspection and assessment of your home and the elements that will influence cooling needs. When the process is finished, your HVAC advisor will have the data needed to choose a central air conditioner that will work best for your particular situation. Make sure the load calculation is performed using industry-accepted standards, such as the Air Conditioning Contractors of America’s Manual J, “Residential Load Calculation.”

Another of the important features to look for in a central A/C is efficiency. The efficiency of a central air conditioner indicates how well it will produce cooling and, as a result, how much it will cost each month for that cooling. High-efficiency systems will use less electrical power to operate, which ensures both a lower energy bill for you and a beneficial effect on the local environment.

Air conditioner efficiency is indicated by the system’s seasonal energy efficiency ratio, or SEER. This is the standard indicator of cooling equipment efficiency. Higher SEER numbers indicate higher levels of air conditioner efficiency.

You’ll find that older air conditioning systems often have low SEER ratings. Residential air conditioners manufactured in the United States after January 26, 2006, must carry a SEER rating of at least 13. High-efficiency systems are considered those with a SEER of 14 or higher. The average high  efficiency air conditioning system will have a SEER around 18. For those who want the most efficient systems possible, there are air conditioners available with SEER ratings in the middle 20s.

A high-efficiency central air conditioner will almost always cost more than a comparable lower efficiency model. Higher efficiency ratings usually correspond to higher initial costs. However, keep one very important factor in mind: high-efficiency systems will cost less to operate on a month-to-month basis, and they can slash your cooling costs by a significant percentage. Over time, this will add up to significant savings. In most cases, a homeowner can recover the initial cost of the high-efficiency system within a few years through these monthly savings alone. A standard break-even point is at about the halfway point of the system’s expected lifespan.

A central air conditioner should be installed by a knowledgeable professional with the expertise and experience to ensure the equipment will work at its best. Proper installation also helps ensure that the system works safely and without any added stresses or errors that could damage the equipment and lead to malfunctions or early breakdowns. In many cases, installation is included in the cost of the equipment. Ask your HVAC supplier about installation costs before the equipment is put in.

An air conditioning system also provides dehumidification of your indoor spaces. Proper sizing will ensure that the A/C will perform well at removing excess humidity from your home. Check with your HVAC professional to get more information on how well the central A/C you’ve chosen will work at dehumidification.

Efficiency Features to Look for in a Central A/C

Among the most common features to look for in a central A/C are components that will improve the system’s efficiency. These parts may add to the initial cost of the equipment, but their positive influence on system performance will make them well worth the additional investment.

In older systems, the air handlers that move air through the ductwork operated at only one speed. Newer variable-speed models have a lower speed that can be used when less cooling or airflow is needed. This lower speed saves energy and money while also reducing overall wear on the fan.

A thermal expansion valve improves the flow of refrigerant through the central A/C system, which will help boost both performance and efficiency.

The air filters in your air conditioner are important to both system function and indoor air quality. They help maintain the airflow the equipment needs to work properly while removing particulates from the air circulating through the system. Dirty, clogged filters can cause significant problems, including A/C malfunctions and breakdowns. A filter change light gives a visual indicator of when it’s time to put fresh new filters in the air conditioner.

A fan-only switch allows you set the system to operate using the fan only without the compressor and other components that consume large amounts of energy. Fan-only function is useful when outdoor temperatures are lower, and you only need some air circulation for ventilation or minimal indoor cooling.

Programmable thermostats provide pre-programmed settings that automatically increase or decrease cooling, depending on when it’s needed. It can turn cooling in your home down during the day and automatically increase it in time for you to have a cool, comfortable home when you get home from work or school.

For more information on features to look for in a central A/C, check out Griffith Energy Service’s air conditioning solutions, or call 888-474-3391.

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