General Questions On Central Air-Conditioning
Why Does Central Cost More in 2007?
As of January 2006 manufactures all over the world have had to change from making the less efficient 10, 11 & 12 seer (see "seer rating" below) air conditioners and start manufacturing a minimum of 13 seer. Most dealers had stocked up on the less expensive 10 seer units & sold them until they ran out indefinitely around the middle to late summer of 2006.
There are many reasons why 13 seer air conditioners cost more, one reason is that in order to get the higher efficiency levels central air conditioners have to be made larger with more precious metals, they are not as easy to install and they have to be built with much better quality parts to achieve the higher efficiency levels. the benefits are that you get better & longer warranties due to the fact that they will last longer. they are much quieter (depending on the brand) and they cost allot less to run.
Generally you can expect to pay $500.00 to $700.00 dollars more for a 13 seer depending on the brand and quality level however the benefits are worth every penny!
Air Conditioning Basics
Are you considering buying a new air conditioner? Or, are you dissatisfied with
the operation of your current air conditioner? Are you unsure whether to fix or
replace it? Are you concerned about high summer utility bills? If you answered
yes to any of these questions, this publication can help. With it, you can learn
about various types of air conditioning systems and how to maintain your air
conditioner, hire professional air conditioning services, select a new air
conditioner, and ensure that your new air conditioner is properly installed.
Understanding Air Conditioners
Many people buy or use air conditioners without
understanding their designs, components, and operating principles. Proper
sizing, selection, installation, maintenance, and correct use are keys to
cost-effective operation and lower overall costs.
How Air Conditioners Work
Air conditioners employ the same operating principles and basic components as your home refrigerator. An air conditioner cools your home with a cold indoor coil called the evaporator. The condenser, a hot outdoor coil, releases the collected heat outside. The evaporator and condenser coils are serpentine tubing surrounded by aluminium fins. This tubing is usually made of copper. A pump, called the compressor, moves a heat transfer fluid (or refrigerant) between the evaporator and the condenser. The pump forces the refrigerant through the circuit of tubing and fins in the coils. The liquid refrigerant evaporates in the indoor evaporator coil, pulling heat out of indoor air and thereby cooling the home. The hot refrigerant gas is pumped outdoors into the condenser where it reverts back to a liquid giving up its heat to the air flowing over the condenser's metal tubing and fins.
Types of Air Conditioners
The basic types of air conditioners are room air
conditioners, split-system central air conditioners, and packaged central air
conditioners.
Room Air Conditioners
Room air conditioners cool rooms rather than the entire
home. If they provide cooling only where they're needed, room air conditioners
are less expensive to operate than central units, even though their efficiency
is generally lower than that of central air conditioners.
Smaller room air conditioners (i.e., those drawing less than 7.5 amps of
electricity) can be plugged into any 15- or 20-amp, 115-volt household circuit
that is not shared with any other major appliances. Larger room air conditioners
(i.e., those drawing more than 7.5 amps) need their own dedicated 115-volt
circuit. The largest models require a dedicated 230-volt circuit.
Central Air Conditioners
Central air conditioners circulate cool air through a
system of supply and return ducts. Supply ducts and registers (i.e., openings in
the walls, floors, or ceilings covered by grills) carry cooled air from the air
conditioner to the home. This cooled air becomes warmer as it circulates through
the home; then it flows back to the central air conditioner through return ducts
and registers. A central air conditioner is either a split-system unit or a
packaged unit.
In a split-system central air conditioner, an outdoor metal cabinet contains the
condenser and compressor, and an indoor cabinet contains the evaporator. In many
split-system air conditioners, this indoor cabinet also contains a furnace or
the indoor part of a heat pump. The air conditioner's evaporator coil is
installed in the cabinet or main supply duct of this furnace or heat pump. If
your home already has a furnace but no air conditioner, a split-system is the
most economical central air conditioner to install.
In a packaged central air conditioner, the evaporator, condenser, and compressor
are all located in one cabinet, which usually is placed on a roof or on a
concrete slab next to the house's foundation. This type of air conditioner also
is used in small commercial buildings. Air supply and return ducts come from
indoors through the home's exterior wall or roof to connect with the packaged
air conditioner, which is usually located outdoors. Packaged air conditioners
often include electric heating coils or a natural gas furnace. This combination
of air conditioner and central heater eliminates the need for a separate furnace
indoors.
Maintaining Existing Air Conditioners
Older air conditioners may still be able to offer years of relatively efficient use. However, making your older air conditioner last requires you to perform proper operation and maintenance.
Air Conditioning Problems
One of the most common air conditioning problems is
improper operation. If your air conditioner is on, be sure to close your home's
windows and outside doors.
Other common problems with existing air conditioners result from faulty
installation, poor service procedures, and inadequate maintenance. Improper
installation of your air conditioner can result in leaky ducts and low air flow.
Many times, the refrigerant charge (the amount of refrigerant in the system)
does not match the manufacturer's specifications. If proper refrigerant charging
is not performed during installation, the performance and efficiency of the unit
is impaired. Service technicians often fail to find refrigerant charging
problems or even worsen existing problems by adding refrigerant to a system that
is already full. Air conditioner manufacturers generally make rugged, high
quality products. If your air conditioner fails, it is usually for one of the
common reasons listed below:
· refrigerant leaks. If your air conditioner is low on refrigerant, either it was undercharged at installation, or it leaks. If it leaks, simply adding refrigerant is not a solution. A trained technician should fix any leak, test the repair, and then charge the system with the correct amount of refrigerant. Remember that the performance and efficiency of your air conditioner is greatest when the refrigerant charge exactly matches the manufacturer's specification, and is neither undercharged nor overcharged.
· inadequate maintenance. If you allow filters and air conditioning coils to become dirty, the air conditioner will not work properly, and the compressor or fans are likely to fail prematurely.
· electric control failure. The compressor and fan controls can wear out, especially when the air conditioner turns on and off frequently, as is common when a system is oversized. Because corrosion of wire and terminals is also a problem in many systems, electrical connections and contacts should be checked during a professional service call.
Regular Maintenance
An air conditioner's filters, coils, and fins require
regular maintenance for the unit to function effectively and efficiently
throughout its years of service. Neglecting necessary maintenance ensures a
steady decline in air conditioning performance while energy use steadily
increases.
Air Conditioner Filters
The most important maintenance task that will ensure the
efficiency of your air conditioner is to routinely replace or clean its filters.
Clogged, dirty filters block normal air flow and reduce a system's efficiency
significantly. With normal air flow obstructed, air that bypasses the filter may
carry dirt directly into the evaporator coil and impair the coil's
heat-absorbing capacity. Filters are located somewhere along the return duct's
length. Common filter locations are in walls, ceilings, furnaces, or in the air
conditioner itself.
Some types of filters are reusable; others must be replaced. They are available
in a variety of types and efficiencies. Clean or replace your air conditioning
system's filter or filters every month or two during the cooling season. Filters
may need more frequent attention if the air conditioner is in constant use, is
subjected to dusty conditions, or you have fur-bearing pets in the house.
Air Conditioner Coils
The air conditioner's evaporator coil and condenser coil
collect dirt over their months and years of service. A clean filter prevents the
evaporator coil from soiling quickly. In time, however, the evaporator coil will
still collect dirt. This dirt reduces air flow and insulates the coil which
reduces its ability to absorb heat. Therefore, your evaporator coil should be
checked every year and cleaned as necessary.
Outdoor condenser coils can also become very dirty if the outdoor environment is
dusty or if there is foliage nearby. You can easily see the condenser coil and
notice if dirt is collecting on its fins.
You should minimize dirt and debris near the condenser unit. Your dryer vents,
falling leaves, and lawn mower are all potential sources of dirt and debris.
Cleaning the area around the coil, removing any debris, and trimming foliage
back at least 2 feet (0.6 meters) allow for adequate air flow around the
condenser.
Coil Fins
The aluminium fins on evaporator and condenser coils are easily bent and can block air flow through the coil. Air conditioning wholesalers sell a tool called a "fin comb" that will comb these fins back into nearly original condition.
Sealing and Insulating Air Ducts
An enormous waste of energy occurs when cooled air escapes
from supply ducts or when hot attic air leaks into return ducts. Recent studies
indicate that 10% to 30% of the conditioned air in an average central air
conditioning system escapes from the ducts.
For central air conditioning to be efficient, ducts must be airtight. Hiring a
competent professional service technician to detect and correct duct leaks is a
good investment, since leaky ducts may be difficult to find without experience
and test equipment. Ducts must be sealed with duct "mastic." The old standby of
duct tape is ineffective for sealing ducts.
Obstructions can impair the efficiency of a duct system almost as much as leaks.
You should be careful not to obstruct the flow of air from supply or return
registers with furniture, drapes, or tightly fitted interior doors. Dirty
filters and clogged evaporator coils can also be major obstructions to air flow.
The large temperature difference between attics and ducts makes heat conduction
through ducts almost as big a problem as air leakage and obstructions. Ducts in
attics should be insulated heavily in addition to being made airtight.
Buying New Air Conditioners
Today's best air conditioners use 30% to 50% less energy to produce the same amount of cooling as air conditioners made in the mid 1970s. Even if your air conditioner is only 10 years old, you may save 20% to 40% of your cooling energy costs by replacing it with a newer, more efficient model.
Sizing Air Conditioners
Air conditioners are rated by the number of British Thermal
Units (Btu) of heat they can remove per hour. Another common rating term for air
conditioning size is the "ton," which is 12,000 Btu per hour.
How big should your air conditioner be? The size of an
air conditioner depends on:
· how large your home is and how many windows it has;
· how much shade is on your home's windows, walls, and roof;
· how much insulation is in your home's ceiling and walls;
· how much air leaks into your home from the outside; and
· how much heat the occupants and appliances in your home generate.
An air conditioner's efficiency, performance, durability,
and initial cost depend on matching its size to the above factors.
Make sure you buy the correct size of air conditioner. Two groups—the Air
Conditioning Contractors of America (ACCA) and the American Society of Heating,
Refrigerating, and Air Conditioning Engineers (ASHRAE)—publish calculation
procedures for sizing central air conditioners. Reputable air conditioning
contractors will use one of these procedures, often performed with the aid of a
computer, to size your new central air conditioner.
Be aware that a large air conditioner will not
provide the best cooling. Buying an oversized air conditioner penalizes you in
the following ways.
· It costs more to buy a larger air conditioner than you need.
· The larger-than-necessary air conditioner cycles on and off more frequently, reducing its efficiency. Frequent cycling makes indoor temperatures fluctuate more and results in a less comfortable environment. Frequent cycling also inhibits moisture removal. In humid climates, removing moisture is essential for acceptable comfort. In addition, this cycling wears out the compressor and electrical parts more rapidly.
· A larger air conditioner uses more electricity and creates added demands on electrical generation and delivery systems.
Air Conditioner Efficiency
Each air conditioner has an energy-efficiency rating that
lists how many Btu per hour are removed for each watt of power it draws. For
room air conditioners, this efficiency rating is the Energy Efficiency Ratio, or
EER. For central air conditioners, it is the Seasonal Energy Efficiency Ratio,
or SEER. These ratings are posted on an Energy Guide Label, which must be
conspicuously attached to all new air conditioners. Many air conditioner
manufacturers are participants in the voluntary EnergyStar® labelling program
(see Source List in this publication). EnergyStar-labeled appliances mean that
they have high EER and SEER ratings.
In general, new air conditioners with higher EERs or SEERs sport higher price
tags. However, the higher initial cost of an energy-efficient model will be
repaid to you several times during its life span. Your utility company may
encourage the purchase of a more efficient air conditioner by rebating some or
all of the price difference. Buy the most efficient air conditioner you can
afford, especially if you use (or think you will use) an air conditioner
frequently and/or if your electricity rates are high.
Room Air Conditioners—EER
Room air conditioners generally range from 5,500 Btu per
hour to 14,000 Btu per hour. National appliance standards require room air
conditioners built after January 1, 1990, to have an EER of 8.0 or greater.
Select a room air conditioner with an EER of at least 9.0 if you live in a mild
climate. If you live in a hot climate, select one with an EER over 10.
The Association of Home Appliance Manufacturers reports that the average EER of
room air conditioners rose 47% from 1972 to 1991. If you own a 1970s-vintage
room air conditioner with an EER of 5 and you replace it with a new one with an
EER of 10, you will cut your air conditioning energy costs in half.
Central Air Conditioners—SEER
National minimum standards for central air conditioners
require a SEER of 9.7 and 10.0, for single-package and split-systems,
respectively. But you do not need to settle for the minimum standard—there is a
wide selection of units with SEERs reaching nearly 20.
Before 1979, the SEERs of central air conditioners ranged from 4.5 to 8.0.
Replacing a 1970s-era central air conditioner with a SEER of 6 with a new unit
having a SEER of 13 will cut your air conditioning costs in half.
Hiring Professional Service
When your air conditioner needs more than the regular
maintenance described previously, hire a professional service technician. A
well-trained technician will find and fix problems in your air conditioning
system. However, not all service technicians are competent. Incompetent service
technicians forsake proper diagnosis and perform only minimal stop-gap measures.
Insist that the technician:
· check for correct amount of refrigerant;
· test for refrigerant leaks using a leak detector;
· capture any refrigerant that must be evacuated from the system, instead of illegally releasing it to the atmosphere;
· check for and seal duct leakage in central systems;
· measure air flow through the evaporator coil;
· verify the correct electric control sequence and make sure that the heating system and cooling system cannot operate simultaneously;
· inspect electric terminals, clean and tighten connections, and apply a non-conductive coating if necessary;
· oil motors and check belts for tightness and wear; and
· check the accuracy of the thermostat.