Articles - High-Tech Air Conditioning: Costs and Benefits

		HomePro Systems, Inc.

HomePro
Systems, Inc.
2841 Hartland Rd
Suite 201
Falls Church, VA 22043
(703) 560-4663
(800) HOMEPRO (800) 966-4555

Home Pro Inspection
Systems Inc.
969 Eldon Road
Oakwood, Ontario
K0M-2M0
800-832-0519

High-Tech Air Conditioning: Costs and Benefits:

When considering the purchase of a new air conditioning system or even the renovation of an old one few consumers are able to determine what is best for their home. The number of manufacturers, the variety of components of a system, the quality range of contractors and the wide spread of cost estimates for installations make for well founded consumer confusion.

Of primary importance is the separation of fact from fiction about the "as installed" efficiencies of the new equipment. The efficiency of an air conditioning system is rated on a scale called the Seasonal Energy Efficiency Ratio. The SEER is a relative measure of how much cooling you get from the electricity the unit uses. The fact is that SEERs range from a low of about six (typical for equipment manufactured in the 1970s) to a high of around 14. The fiction is that you can expect to achieve very high efficiencies when you retrofit new equipment to older existing duct systems. Before you buy a new compressor or condensing unit for an older ducted system, investigate to be sure they are compatible: too often a combination of the two results in little or no savings.

CONDENSING UNIT:

The expensive mechanical part of central air conditioners is the outside condensing unit. It generally lasts 8 to 14 years and tends to fail when working hard in hot and humid worst weather. When your air conditioner fails, you can usually get it operating again by simply replacing the condensing unit, or even just the compressor in the condensing unit. Replacing a compressor is usually the lowest cost expenditure that will "fix "your unit but it won't improve the efficiency.

At some point, consideration should be given to spending extra money to buy high efficiency gear to lessen your utility bills. Unfortunately, however, the decision is complicated by the fact that some gear will not work at its normal high efficiency when installed as a single outside piece or as part of a restrictive duct system.

You can often estimate your air conditioning costs by subtracting your monthly winter electric bills, provided you don't have electric heat, from the monthly summer bills. If other activities have been roughly the same, the difference can probably be attributed to the electric air conditioning, although you have to make allowances for seasonal price variations.

Once you figure how much it costs to run your air conditioning, you can determine your total savings using more efficient gear by comparing the Seasonal Energy Efficiency Ratios of the existing gear with that of the planned replacement gear. Your local dealer should have a book which lists the SEER and date of manufacture of most existing air conditioners by serial number.

The SEER, as noted earlier, measures the amount of cooling against the amount of electricity consumed. A unit with a SEER of ten will use half of the electricity of a unit with a SEER of five. The wider the difference between the SEER ratings of old and potential replacement equipment the greater the savings.

SAVINGS EXAMPLE:

For example, if your old unit has a SEER rating of five and you replace it with one rated at ten, and you figure your AC usage at $500, your new bill would be $250 ($500 X 5/10).

If your original AC figure was $1,000 and you upgraded from a SEER of six to one of nine, then your new bill would be $667 ($1,000 x 6/9).
Electric central air conditioners consist of an outside unit, generally a compressor, a coil and a fan all housed together and an inside coil mounted within the ductwork of the forced air heating system. A refrigerant continuously circulates between the coils alternately compressing to high pressure (and high temperature) outside, and evaporating to low pressure (and low temperature) inside.

The house duct system recirculates household air over the inside coil where the air loses some heat and humidity. As the circulating refrigerant picks up the household heat energy, it is moved to the outside coil and gets compressed to high temperature where the resulting heat is blown off to the outside air.

Newer equipment is more efficient primarily because it utilizes better compressors, a larger outside coil and a stronger fan to lower the condenser temperature. This allows the system to "move" heat efficiently with the same amount of electricity.

REPLACEMENT GEAR:

As a practical matter, most old duct systems will accommodate higherefficiency AC gear only up to a SEER of about nine. Since the duct modifications required to attain higher efficiencies can easily cost upwards of $1,000, the ultra high efficiency air conditioning systems are most appropriate for new construction where the duct systems can be designed accordingly.

It is important that the flow of refrigerant between the coils of air conditioning systems be regulated and balanced properly. A thermostatic expansion valve is critical on a highefficiency system. Installing a highefficiency outside unit without converting an inside coil with capillary tubes to a coil with a thermostatic expansion valve will most likely prevent the overall system from achieving its optimum SEER rating.

Some older inside coils have thermostatic expansion valves and will work well with a new highefficiency outside unit, but it takes careful measurement by a qualified contractor to determine this.

The average upgrade in efficiency is from a SEER rating of about six to one of about nine or more. The net resulting reduction in air conditioning utility consumption is about 35 to 40 percent. This computes to an average savings of approximately $100 to $175 per season for a 1,200 to 1,500 sq. ft. house that is reasonably tight and adequately insulated.

The available choices of replacement gear are:

1. Replace the compressor.
2. Replace the entire outside package with a similar efficiency unit.
3. Replace the outside package with a high efficiency unit.
4. Replace both the inside and outside units as a balanced package.

In general, alternative 4 is the best way to save money in the long run, although alternative 3 will bring the quickest payback if the existing inside coil is well suited to a high efficiency outside replacement unit; a relative rarity.

INSTALLATION:

Following are some top of the scale estimates for installing a balanced high quality system (SEER of approximately nine) with the best technicians. A ton of air conditioning is equivalent to 12,000 British Thermal Units (BTUs) and will cool approximately 500 sq. ft. of living space if the house is reasonably tight and insulated:

1. Two ton system $3,000 and up.
2. Three ton system $3,400 and up.
3. Four ton system $3,600 and up.
4. Five ton system $3,800 and up.

Keep in mind that a good job of installation could very well depend on the time spent by the mechanic doing the work. Cleanliness and moisture control are important to the equipment's duration, and shortcuts in the area of cleaning, soldering and evacuation procedures could leave you with a vulnerable system. Always ask how long the installation will take and remember: a good mechanic will take two days to install a typical, well balanced air conditioning system.

Have a quality contractor, who won't want the hassles of installing and serving lower quality equipment, choose the brand of equipment for you. It is virtually impossible for the layman to determine the quality of the gear offered.

The actual equipment of a high efficiency system costs far less than the installation. The installation cost tends to stay the same whether the unit is small or large or even if a furnace is installed at the same time. Since the installation cost is the major expense that must be paid back by the savings in utilities, it makes good sense to amortize the installation cost against a larger package installation.

The installation cost of a small, high efficiency air conditioning package can be 50 percent of the total cost, while it might drop to 20 to 25 percent of an air conditioning/furnace package.

UNREALISTIC EXPECTATIONS:

Replacing an operating central air conditioner with a high-efficiency unit would be difficult to justify on utility savings alone, but it is well considered once a unit quits. Get at least three bids beforehand and try to lock in the prices for a reasonable period of time. Don't have unrealistic expectations about the most powerful high efficiency units as these seem to be in the province of new construction only.

WORTHWHILE INVESTMENTS:

In the event that repair of your air conditioning system is being considered, here are some extra cost items well worth the investment:
Copper coils instead of aluminum ones. Repairing pinholes or joints is practically impossible with aluminum coils but relatively easy with copper. The extra $100 or so in cost is easily worth the increased life expectancy and enhanced repair ability.

A thermostatic expansion valve vs. capillary tubes. It takes a top quality technician to service a unit properly with capillary tubes and in the crush of demand for service during the dog days, you won't be able to be so choosey.

A sight glass or "liquid eye." Mounted on the liquid hose, the "eye" costs about $15 and makes it easy to check for refrigerant deficiencies.
A "dryer." Also mounted on the liquid hose, this part keeps the system protected from moisture and promotes longer life. For around $20, it is well worth it.

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