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Energy Extension Service SPACE HEATING & COOLING: Air Conditioning Questions:
What does a SEER rating on air conditioners
mean, and how do I compare ratings between 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). Is it cost-effective to buy high-efficiency,
air-conditioning units? 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. When buying a new central air conditioner,
what should I look for to ensure a high-efficiency unit that will last? The higher the SEER, the more efficient the unit will be.
Federal legislation dictates a minimum SEER rating of 10 for central air conditioners
sold in the residential marketplace. Air conditioning units are now available
with SEER ratings as high as 16. Long life and ease of service are two other important considerations
when purchasing an air conditioner. One recent development in compressor design,
the scroll compressor, offers a long, trouble-free life and low noise level.
Scroll compressors are also more efficient than conventional compressors.
Scroll compressors are often used on units with a SEER of 12 or greater. When
receiving bids, be sure to ask if the unit uses a scroll compressor. Contact at least three air-conditioning service companies in the area to obtain bids for comparison of features, warranties, and efficiency. Be sure to carefully evaluate the proposed size of the units. Purchasing a properly sized unit is critical to achieving good performance Why is it important to properly size
an air conditioner? Determining the proper size for a residential air-conditioning
system calls for a cooling load analysis. This procedure takes into account
the size of the home, insulation levels, roof color, orientation of windows,
shading of windows, tightness of construction, and number of occupants. However, on extremely hot days, usually less than three percent
of a normal cooling season, the indoor temperature may rise or swing upward
a few degrees Fahrenheit during the hottest part of the day. This is a small price to pay for improved performance and
comfort during the balance of the cooling season. Furthermore, comfort can be easily maintained during a designed
temperature swing by using a fan to create air movement and delaying activities,
such as cooking, that produce internal heat gain until the air conditioner
has recovered. A cooling load analysis of a home can be performed by most heating and air-conditioning contractors or by an independent energy auditor. What is the status of the refrigerant
used in my home air conditioner? Is it being phased out like the refrigerant
in my car? Some air-conditioner manufacturers are offering equipment
filled with refrigerants that pose no harm to the atmosphere. The operating
efficiency of these air conditioners is no higher than those filled with R22. These products may carry a higher price, but the refrigerants will be available after the scheduled 2020 phase-out of R22. When adding central air conditioning
to an older home, what do I need to watch out for? If a home has an older heating system with no provisions for
central air conditioning, the ductwork may be smaller than what is required
for air conditioning. Increase the fan speed to compensate for the ductwork.
A larger motor often is required to achieve this higher flow rate. The location of the return-air registers also plays a role
in comfort. In older homes, there were often no return-air registers installed
on the second floor of a two-story home. It is difficult to cool the second
story if this is the case. It may be necessary to install return-air ductwork. If a floor drain is not available below the level of the furnace,
it is possible to purchase a small condensate pump set. For approximately
$60, this set will pump the condensate to a convenient disposal site. A final consideration is the arrangement of the ductwork at the furnace outlet. The ductwork around the furnace must leave sufficient room for the installation of the cooling coil. When installing central air, it is an excellent time to check the supply and return air ducts for leaks. Inadequate air flow across the cooling coil is the No. 1 cause for poor air-conditioning system performance. What can I do to reduce summer air-conditioning
costs? (Part I) Weatherstripping and caulking reduce both heating and cooling
costs. Inspect existing weatherstripping for wear and possible replacement. In addition to caulking window and door frames, inspect for
hidden cracks such as those that exist along foundations, or where exterior
wiring or air-conditioning lines may penetrate the wall. It is preferable to block the sunlight before it penetrates
the window. Although a drape will delay the instantaneous solar gain, it's
more effective to stop the sunlight completely by using exterior shading or
reflective blinds. Deciduous trees provide an excellent means for natural shading
in the summer, yet allow exposure of the window in the winter. Removable exterior
awnings can provide a similar advantage. Unventilated attics can reach high temperatures during the
summer, contributing considerably to the cooling load in the home. Attics should be properly ventilated by having sufficient
openings along the low side of the attic, such as in soffits as well as openings
along the high side of the roof for exhaust. For ventilation, have at least one square inch of free opening
for every square foot of attic space. Openings should be distributed equally
between the low and high sides of the attic. Remember that screens and louvers
block up to 50 percent of the ventilation area. Move air in and through the home without relying on an air
conditioner. When the outdoor air is cool, yet the home is warm, a whole-house
fan, which draws air through open windows and discharges into the attic, may
provide all the cooling necessary. Additional attic ventilation is necessary when using a whole-house
fan. Within the home, portable fans or ceiling fans can provide some cooling relief. What can I do to reduce summer air-conditioning
costs? (Part II) Inspect the gasket around the refrigerator door to assure
that it has not worn and needs to be replaced. The cooking range and clothes
dryer should be vented to the outdoors, as should exhaust fans in bathrooms. Heat loss from a water heater adds both to water-heating costs
as well as air-conditioning costs. A water heater that is warm to the touch
should be insulated with a water-heater insulating jacket. Prepare a furnace for summer by replacing or cleaning the
air filter, and lubricating, where possible, any bearings on the blower or
motor. Consider extinguishing the pilot light if the furnace is equipped with
a pilot. Many new furnaces use an electronic device for igniting the flame
whenever the thermostat calls for heat rather than using a standing pilot
light. This will probably not result in a significant reduction in
gas costs; however, the pilot does contribute a small amount of heat to the
home that then must be removed by the air conditioner. Contrary to some earlier
information, extinguishing the pilot light will not shorten the life of the
furnace. Be sure that if the furnace is equipped with a central humidifier
that it is turned off, drained, and cleaned. An air conditioner needs adequate air flow through the condenser
for the unit to operate at maximum efficiency. Plantings and fencing should
be no closer than three feet to the condensing unit. The condensing unit should be cleaned annually by carefully
removing any debris from the fins of the condenser. Consider hiring an air-conditioning service contractor to
clean the condenser thoroughly, particularly if it has not received maintenance
in the last two or three years. Service contractors will use a variety of cleaning solutions
to remove any buildup on the condenser fins as well as straighten any fins
which may have been damaged, lubricate any exposed bearings, and check for
appropriate refrigerant levels in the air conditioner. Taking advantage of these and other opportunities should help to reduce cooling costs this summer. My home has a whole-house fan and central
air conditioner. How can I use them both for the most economical cooling? Use the fan when the outdoor air temperature is at or below
the desired indoor temperature, usually during the late evening and night
hours. Use the fan at night to help create more comfortable sleeping conditions
without air conditioning. Central air conditioning cools by lowering the temperature
and humidity of indoor air. When it is hot and humid outside, the house is
closed up and the indoor air is conditioned. Central air conditioning and
a whole-house fan should never operate at the same time. The best strategy may be to use the whole-house fan extensively
during the late spring and early fall when the demand for cooling is rarely
large and extended heat waves are unlikely. Also, use the fan in the summer
when temperatures and humidity are at or below normal. When outdoor temperatures and humidity rise to uncomfortable
levels, close up the house and switch to air conditioning. In deciding what will be most comfortable, follow the weather
patterns and use one system or the other for a few days. In general, avoid
using both systems every day, especially during very humid weather. The whole-house fan may significantly raise the moisture level
inside a house by bringing in outdoor air. Switching to air conditioning the
next day may drop the temperature, but might be less comfortable. The most economical approach to minimize the effects of the sun's heat on a home is to use fans and the whole house fan as a first choice, and switch to air conditioning when the heat and humidity become oppressive. Can ceiling fans effectively reduce
air-conditioning costs? The cooling effect of moving air can compensate for as much
as a four-degree rise in temperature. Keep in mind, that during the heating season, the air movement caused by the fan will still have the same cooling effect. How can I keep my home cooler
in the summer without air conditioning? Interior shades are inexpensive and easy to install. Use pull-down
or Venetian blinds in addition to regular window coverings. Window coverings
should be light colored (white or beige). Natural shading is another way to block heat gain in summer.
For example, plant broad-leafed trees on the south and west sides of the home.
They shade a home in summer months and will let in sunlight during winter
months when they have shed their leaves. Certain steps will help keep a home warm in winter and will
help cool it during the summer. Insulated walls and roof reduce heat gain,
just as they lower heat loss in winter. As a general rule, ceiling insulation
should have an R-value of 35 to 45, and walls from 19 to 27. A light-colored
roof also decreases heat gain. Use the above suggestions, coupled with circulating fans inside the home, and utility bills will be less than if air conditioning was the only cooling source. Is it better to leave the fan running
continuously with the air conditioner or to place it in the automatic position? This amount can be reduced by cycling the fan only when it's
needed. If air distribution is poor within the home or business and
hot spots or very cold areas result, the fan can be run to even out the temperatures.
However, the fan should be set to the auto position when the building is unoccupied. Even better, shut the air conditioner off or raise the thermostat setting when leaving the building. Will I save energy by turning off my
air conditioner when I leave home, or am I better off just letting it run? During the day, keep windows shut and close curtains or blinds
on any windows that will be exposed to sunlight. The thermal mass of the house will probably keep the indoor
temperature well below the outdoor temperature, and the house should cool
quickly when the air conditioner is restarted. Use a programmable thermostat
or timer to turn on the air conditioner 30 to 45 minutes before the expected
arrival home. If the home is still warm upon arrival, turn on a fan to create
air movement. Moving air can make the air feel about four degrees cooler than it really is. Can I plant bushes to hide the outside
of my air conditioner? Although it is possible to plant bushes near the condenser,
leave room for adequate air circulation. Without good air circulation, the
temperature near the condensing unit will rise. The higher temperature will
reduce the capacity of the air conditioner, causing it to work harder and
provide less cooling. This could also kill the shrubbery. If the shrubs will not form a continuous wall around the unit, plant them so that, when they mature, there will be three feet of clearance. If the shrubs will be continuous, then allow five feet of clearance. Are there any simple checks I can
perform to see if my air conditioner is operating properly? The smaller line -- the high pressure line -- should be warm,
but not hot. It should be 20 to 30 degrees warmer than the outside temperature.
In extreme cases, it will be hot to the touch, so be cautious. If this is
the case, call a service technician. Some air conditioners are equipped with a sight glass in the
high-pressure line (the small line). The glass should be clear, with no bubbles
visible, while the system is running. Cloudy liquid in the sight glass may
indicate contamination of the system. One final check is to measure the temperature of the air as
it leaves the register. It should be 15-20 degrees cooler than the room temperature. If the building is warm, humid, or if the ductwork is not
insulated, then there may be smaller temperature differences. These guides are not intended to eliminate the need for an annual check by a qualified service person. If problems are suspected, call for help from someone familiar with air conditioners. Would I be better off using several
window air conditioners? A central system is more convenient to operate when cooling
the entire home continually, and possibly at a lower cost of operation. If sound level is a consideration in the home, keep in mind
that window units are typically noisier than central air conditioning. In terms of efficiency, top-of-the-line central units are
generally more efficient than window units. Since there are positives and negatives about window units and central systems, consider personal needs and preferences before choosing a system. What is a ton of air conditioning? One ton of air conditioning removes 12,000 British thermal
units (Btu) of heat an hour. The term was derived from the time when ice was
used for refrigeration. One ton of air-conditioner cooling capacity removes
the same amount of heat required to melt 2,000 pounds, or one ton, of ice
in 24 hours. Typically, residential central air conditioners will range in capacity from one and one-half to four tons. Window units will many times be rated in Btu per hour. For example, a 6,000 Btu/hr. window unit would have the capacity of one-half ton. |Engineering Extension | College of Engineering | Kansas State University| Copyright © 2001 - Engineering Extension
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