SEASONAL ENERGY EFFICIENCY RATIOOn January 1, 1979, Carrier Corporation started expressing its residential cooling unit and heat pump efficiencies in Seasonal Energy Efficiency Ratios (SEER).EER - By way of background: ARI introduced the Energy Efficiency Ratio (EER) in 1975. This was an HVAC industry instituted and policed way to determine the relative efficiencies of one unit to another in the cooling mode. EER was determined by dividing the published steady state capacity by the published steady sate power input at 80°F dB/ 67°F Wb indoor and 95°F dB outdoor. This was quite objective yet unrealistic with respect to system "real world"operating conditions.1) Congress passed public Law No. 94-163 whereby labeling of certain appliances(including 1-phase air conditioners through 65,000 Btuh capacity) was mandated.2) The National Bureau of Standards (among others) was commissioned to develop testingstandards for air conditioners that would fairly and accurately determine the values thatwould show on such a label. Such information would include the unit's capacity, theseasonal energy efficiency ratio (SEER), and the estimated yearly cost of operation underspecific stated conditions.3) The Federal Trade Commission was given the task of coming up with the specific formatfor the label.4) Testing on the product is required such that there is 90% (or better) statistical confidencethat the product's energy usage is within 5% of the advertised values, including that shownon the label.5) These new laws affect only units with an ARI capacity of 65,000 Btuh or less, includingYAC's, PAC's, Heat Pumps, and Split Systems. There are laws governing RAC's, butthey are not covered in this write-up.SEER - The new concept of Seasonal Energy Efficiency Ratio (SEER) is an improvement over the old EER concept in two very important ways and is intended to better approximate what happens in the actual end use application for the product. Instead of a single test as is used in determining EER in the old concept, the new SEER concept requires four tests to take into consideration a variation in outdoor temperature as well as the effect of cycling the unit on and off.The SEER of a system is determined by multiplying the steady state energy efficiency ratio (EER) measured at conditions of 82°F outdoor temperature, 80°F dB/ 67°F wb indoor entering air temperature by the Part Load Factor (PLF) of the system.(PLF is supplied by the government.)Heating Seasonal Performance Factor (HSPF)HSPF =The total watt-hours input during the entire heating season are used to calculate the HSPF.By definition - For electric resistance heaters:HSPF = 1.0If heat pump HSPF is greater than 1.0, then heat pump is more efficient than resistance heat.For example:If HSPF = 1.83Heat Pump is 83% more efficient than resistance heat on a seasonal basis.COEFFICIENT OF PERFORMANCE (COP)COP is the ratio of work output divided by work input. The output is the amount of heat absorbed by the system. The input is the amount of energy required to produce this output. However, in a heat pump system, the output is the heat of rejection of the total system. The energy input is inclusive of compressor, indoor, and outdoor fan motor watts.COP =Btuh Input = Total watts input (compressor, indoor, andoutdoor fan motor) x 3.4141 Watt/Hr = 3.414 Btuh1 kw/hr = 3414 BtuhBtuh Output = Rated output from product sheetEFFICIENCY RATINGS -- WHAT SEER MEANS TO YOUThe purpose of rating the efficiency of an air conditioner is to indicate the relative amount of energy needed to provide a specific cooling output. The more efficient the equipment, the less energy will be used to do the same job.It's a lot like the miles per gallon ratings for automobiles. However, instead of "MPG", central residential air conditioners now use the designation "SEER" which stands for Seasonal Energy Efficiency Ratio.Previously, the air conditioning industry used the term "EER", which stood for Energy Efficiency Ratio. This was a simple mathematical ratio of cooling output measured in British Thermal Units per Hour (BTUH) versus electrical power input (watts). Recently, the U.S. Department of Energy (DOE) developed a more complicated test method, which rates the performance of a unit over a wide range of operating conditions. The result (SEER) in indicative of the unit's operation throughout the cooling season.Assume a home requires a unit with a cooling capacity of 36,000 BTUH and is located where the cooling system necessitates running the unit a total of 1,500 hours. Assume electricity costs residential customers 5 cents per kilowatt-hour.FORMULA -- APPROXIMATE YEARLY COST OF OPERATIONCAPACITY (BTUH) X COOLING LOAD HOURS X ELECTRIC RATE = COST OF OPERATION SEER 1,000In the case of our hypothetical house, the formula would go like this:SEER 6.0: 36,000 X1,500 X .05 = $450.6.0 1,000SEER 8.0: 36,000 X1,500 X .05 = $290.9.3 1,000From this, you can see that the higher efficiency unit would save $160. each cooling season. Obviously, this amount will vary in real-life situations depending on:1. Whether the unit operates more or less than the 1,500 hours used in the example,2. Family size and living habits, and3. The electric rates.(Your local electric utility should be able to provide information on cooling load hours for yourarea as well as electricity rates.)Nevertheless, the example does illustrate that higher efficiency results in lower energy costs. However, since the higher efficiency model is often more expensive, you may want to calculate the payback period in which it will "pay for itself" in terms of lower utility bills.The SEER of a system is determined by multiplying the steady state Energy Efficiency Ratio (EER) measured at conditions of 82°F outdoor temperature, 80°F dB/ 67°F Wb indoor entering air temperature by the Part Load Factor (PLF) of the system. That is:SEER = PLF X EER82FThe PLF is a measure of the cyclic performance (CD) of a system and is calculated as follows:PLF = 1 - (CD X 0.5)The CD value in the above equation has been determined by the government to be 0.25. Hence, the government contends that the PLF should equal:[1 - (.25 x .5)] which yields:PLF = 0.875A number of major HVAC manufacturers have argued that the "CD = 0.25" criterion is too severe and not representative of modern cooling units. As a consequence, the government has established a procedure by which each manufacture may calculate their actual CD factor. This calculation involves making two additional tests on a cooling system with an outdoor entering air condition of 80°F dB/ 57°F Wb (dry coil test). One test (Test A) requires the system to be cycled on for 6 minutes and off for 24 minutes to measure the cyclic response of the system. The second test (Test B) requires the unit to be run at a steady state (on all the time) and provides a basis for comparison with the cycling test. Data taken from the two tests is used to compute the CD factors as follows:1 -CD =Where: EER = capacity / wattsX 2.0CLF is an approximate of equipment run time.A CLF of .2, for instance, is equivalent to saying the unit will be running 20% of the time.。
