SEER Ratings & Units;
The SEER is equal to Btus of cooling supplied during the year divided by kilowatt-hours of electricity consumed in a year. The higher the SEER rating, the more efficient the air conditioner will be.

For example, a unit with a cooling capacity of 24,000 BTU that consumes 2,400 kilowatts of electricity would have a SEER of 24,000/2,400, or 10. Units with high SEERs will cost more initially, but the energy savings throughout their lifetime will more than make up for the cost difference.

When comparing SEER ratings of different air conditioners, compare only those with similar capacities (Btu).

Cost effectiveness
It is cost-effective to buy high-efficiency, air-conditioning units because if the unit serves a home or business that air conditions throughout the summer rather than on an intermittent schedule. The additional cost of the higher efficiency units can be justified from the energy savings.

The minimum seasonal energy-efficiency rating (SEER) is 10, but the Department of Energy is considering increasing the minimum to a SEER of 12.

Homeowners and business operators can justify the purchase of air conditioners with a SEER of 13 or 14 in applications where energy costs are high or the cooling season is long. In buildings used less frequently, such as churches and meeting rooms, energy savings usually won’t offset the cost of the highest efficiency units.

Sources:http://www.engext.ksu.edu/ees/henergy/space/air.html#SEER

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• My hunt for air conditioner (jayant7k.blogspot.com)

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An air conditioner is a very tough piece of equipment. It is engineered to withstand all sorts of abuse and keep on running. This is great in most respects, but it can lead to complacency about maintenance. Like a car, air conditioners need regular tune-ups to run properly.

Without regular maintenance an air conditioner looses about 5% of it’s original efficiency for each year of operation. This means that the 12 SEER unit that you bought just a few years ago may be functioning like a 9 SEER unit today! The good news is that you can recover most of that lost efficiency through regular maintenance. Studies show that with regular tune-ups a unit will maintain up to 95% of it’s original efficiency. This means that the cost of an annual tune-up is recovered very quickly in savings on your monthly electric bill and reduced repair costs. A properly serviced air conditioner will also do a better job of dehumidifying your home.

Many local air conditioning firms offer special prices at this time of the year. Some even offer annual service programs that insure that you will be reminded of the need to service the unit at the beginning of the cooling and heating seasons.

The service check should include cleaning the condensing unit coils, checking the amp draw of the compressor, oiling the fan motors, checking that belts are well adjusted, and checking the system operating pressures and temperatures against the manufacturers specifications. One of the most important items to check is the coolant level (commonly know as Freon) in the air conditioner. A system that is only 10% low on coolant will cost about 20% more to operate! The Air Conditioning Contractors of America (ACCA) recommends that coolant levels be checked every year.

If your unit is low on coolant, and more must be added, there are new laws governing its use. Freon is a chlorofluorocarbon (CFC) that will damage the Earths protective ozone layer if released into the atmosphere. The laws governing CFC’s now do not allow your air conditioner contractor to add Freon to a leaky system. They are first required to find and fix the leak in the system. Don’t ask them to violate this law as they may loose their license if they are caught doing this.

There are some things in addition to yearly tune-ups that you can do to help ensure a high level of comfort and proper system operation. First, buy good filters and change them regularly. Next, keep bushes and other materials away from the outside unit of your air conditioner. Another good idea is to avoid closing supply air outlets in your house. In almost all cases, closing supply outlets is harmful to the operation of the overall system.

All equipment, even the most reliable, needs routine maintenance. Complicated equipment like today’s air conditioners benefit in many ways from annual service. They recover much of their lost efficiency, they are less likely to suffer a major break down, they have a longer life span, they increase your comfort, and they operate for less money.

Click to find more information including the Sustainable Building Sourcebook compiled by the City of Austin’s Green Builder Program at the:-> Sustainable Sources website.

Sources:http://www.greenbuilder.com/general/articles/aas.ac.html

To know if your home currently has enough insulation, contact your local contractor to find out the recommended insulation levels for various parts of a home in your area. They will be able to tell you if your home meets the recommended R-Values for ceilings, walls and floors.

In order of cost-effectiveness for an existing home, it generally pays to insulate first your attic or roof, second your foundation or floor, third your windows, and last, your walls. If you are unsure of where to begin, you may want to have an energy audit. To learn more about audits, click here.

Source:Home Energy Library

Besides their relatively low cost, other advantages include being easy to install because they pour to fill irregular spaces, they are also non-corrosive, non-combustible and vermin resistant.

Source:Home Energy Library

It is recommended to get help on a major purchase like this from a professional because simple guidelines and rules of thumb may or may not work. Some contractors joke about the rule-of-thumb that if you can completely cover the house with one finger on your extended hand when standing at the street in front if it, it needs a one ton unit, but if it takes two fingers, that takes a 2 ton unit. That’s not good enough, and if it’s your money and your comfort, you want to be sure it’s properly sized.

Undersized systems will run continuously and never get the house down to the thermostat setting. Over-sized systems will cycle on and off frequently. But they cool the air so quickly, it does not get well dehumidified leaving occupants feeling cold and clammy.

Sizing heat pumps has its own special challenges. In warm climates, where they are being sized for a cooling load, they may be oversized for the heating season, and then the reverse is true. A heat pump in a colder climate sized for heating may be oversized for cooling. These considerations make it all the more important to rely on the expertise of a professional when it comes to sizing a heat pump for your home.

Source:Home Energy Library

The key to understanding how it works is recognizing that at the same pressure, the refrigerant boils at a much lower temperature than water. This is a critical concept to understanding how the refigeration cycle works, so if that went by too fast, read it again and think about it for a minute. For example the refrigerant commonly used in refrigerators boils between 40° and 50°F as compared to water’s boiling point of 212°F.

The cool, liquid refrigerant entering the indoor coil, known as the evaporator. As its name implies, refrigerant in the evaporator “evaporates.” Upon entering the evaporator, the liquid refrigerant’s temperature is between 40° and 50°F; and without changing its temperature; it absorbs heat as it changes state from a liquid to a vapor. The heat comes from the warm, moist room air blown across the evaporator coil. As it passes over the cool coil, it gives up some of its heat and moisture may condense from it. The cooler, drier room air is recirculated by a blower into the space to be cooled.

The vapor refrigerant now moves into the compressor (which is basically a pump that raises the pressure), so it will move through the system.

Once it passes through the compressor, the refrigerant is said to be on the “high” side of the system. Like anything that is put under pressure, the increased pressure from the compressor causes the temperature of the refrigerant to rise. As it leaves the compressor, the refrigerant is a hot vapor, roughly 120° to 140°F.

It now flows into the outdoor coil, (known as the condenser). Again, as the name suggests, the refrigerant condenses here. As it condenses, it gives up heat to the outside air, which is blown across it by a fan. The outside air is able to pick up heat from the coils because even though it may be over 100°F, it is still cooler than the 120-degree coils. This is the hot exhaust air you feel when passing the outdoor unit of an operating air conditioner.

As the refrigerant leaves the condenser, it is cooler, but still under pressure provided by the compressor. It then reaches the expansion valve. The expansion valve allows the high-pressure refrigerant to “flash” through becoming a lower pressure, cooled liquid. When pressure is reduced (as with spraying an aerosol can or a fire extinguisher), it cools. The cycle is complete as the cool, liquid refrigerant re-enters the evaporator to pick up room heat.

In summary, the indoor and outdoor coils (condenser and evaporator) are where the refrigerant changes “phase”, absorbing or releasing heat through boiling and condensing. The compressor and expansion valve facilitate the pressure changes, increased by the compressor and reduced by the expansion valve.

Source:Home Energy Library