by L Neal · Cited by 3 — Most residential central air conditioners and heat pumps are split systems where one heat exchanger (or coil) and the compressor are located outdoors and one
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Air Conditioner Efficiency in the Real World by Leon Neal Tighten up the ducts and what do you find? Central air conditioning systems ofJerating at much lower than rated efficiencies. Field research shows that the price of neglected air conditioner maintenance can be high bills and less comfort. f A. n d vice will last longer, perform better, and vide more owner satisfaction if it is properly tained. Som of the devices we depend on, however, are so reliable and dependable that most of us seldom sider routine maintenance. We see the results only indirectly in high utility bills or in reduced ervi e life. Meanwhile, a crippled machine may continue to operate without ny other noticeable handicaps for eight, ten, or more year . In short, all mechanical and electronic devices need routine maintenance. This is no truer than for the larger refrigeration equipment found in many homes-a central air conditioner or a heat pump which provides cenb·al air conditioning. The e appliances are large complicated, expensive to replace, and can have a large impact on tric costs. The installation and service parameters discussed in this article for central air conditioners apply “doubly” to heat pumps because the refrigeration cycle equipment is used to provide both cooling and heating . .J Where To Find ‘Lost Efficiency’ The North Carolina Alternative Energy Corp. (AEC) has become very interested in the “lost” energy efficiency of cenu·al air conditioners. This lost energy efficiency is the difference becween the “manufactured energy ciency,” which is found through government ratings and testing by Air-conditioning and Refrigeration Institute Leon Neal is a Senior Product Engi,neer with the North Carolina Alternative Energy Corp. in Research Triang/,e Park. “‘) Don’t Split Replacements Homeowners purchasing high-efficiency cenlnll air ditioners as replacemenLS for old units will not get the energy efficiency and lower electric bills they expect if the indoor coil is not replaced at the same time as the outdoor unit. Most residential central air conditioners and heat pumps are split systems where one heat exchanger (or coil) and the compressor are located outdoors and one heat exchanger is locared indoors. fost of the existing indoor coil units are not suitable for matching with a new efficiency outdoor compressor unit. The result of chis match is ofcen a combination that perform little or no better than the old unit. The efficiency of a central air conditioner is rated by its SEER The average SEER for all units shipped by facturers in the United States in 1990 was 9.31. The higher the rating, the more efficient the unit. A homeowner who purchases a unit with a 9.3 SEER, for example, may end up with a unit whose SEER turns out to be an 8 or less if the indoor coil is not replaced with a new coil that is properly matched with the outdoor unit. Some homeowners may choose to replace their old uni LS with those carrying a 10 SEER or higher. New DOE dards require that manufacturers produce split-system air conditioners and beat pumps with a minimum SEER ofl 0. Those who opt for purchasing even higher efficiency units should ask their installing contractors to: Ł Replace the indoor coil with a high-efficiency indoor coil. Ł Match the new indoor coil with the manufacturer’s ification for the installation of the unit. Ł Verify the efficiency of the combination to be installed by showing the SEER rating in a listing such as the conditioning and Refrigeration Institute certification directory. From lO Keep Your Cool and Save Cold ing and Refrigeration Institute, Dept. U-171, P.O. Box 37700, Washington, DC 20013. Tel: (703)524-8800; Fax: (703)528-3816. (ARI) and what owners of systems actually experience in their houses. 1 Ł2 In one field study, AEC measured the taneous capacity (in Btu per hour) and the power (in watts) required by 10 units. We translated these ments into a form compatible to ARI standard empirical test conditions and compared the results (see Table 1). The causes oflost efficiency ranged from dirty compressor coils May/June 1992 Home Energy
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Table 1. Rated versus Measured Performances of Air Conditioners Manufacturer’s Measured Performance Llfe, Efficiency-Rated Performance Related Problems Unit Capacity EER Airllow Capacity EER Btu/ Nominal (Energy Cubic Feet Btu/ Percentage Measured Percentage hour Tons’ Efficiency per Minute hour of Rated of Rated Ratio) Ton” Capacity EER I 35,660 3 7.2 390 36,266 102% 9.1 126% Overfused. lightning problem 2 36,225 3 6.9 290′ 42,2824 117%’ 9.84 142%’ Inadequate airflow 3 35,400 3 7.1 460; 34,222 97% 7.0 99% Comfort complaint 4 24,150 2 6.2 505′ 31,3294 130%’ 8.3′ 134%’ DANGER! Serious overcharge problem 5 50,193 4 6.7 330′ 40,3314 80%’ 6.l’ 91%’ Inadequate airflow 6 42,607 3.5 7.0 354 31,755 75% 6.45 92% Cndercharged 7 33,000 2.75 7.5 395 10,555′ 32%’ 2.0Ł 27%’ Compressor bad, very serious 8 33,000 2.75 7.5 432 22,453 68% 5.23 70% Probably overcharged 9 38,200 3 8.0 420 37,179 97% 8.83 110% Slightly overcharged 10 39,960 3 6.0 438 29,052 73% 6.5 108% Very undercharged, dirty coils 1 Airflow too low ‘Airflow too high ‘Ton= 12,000 Btu 4 Calculated figure doesn’t reflect useful value because air flow was outside the limits specified by the manufacturer. to lightning surge damage, all compromising the ciencies of the units. These measurements represent only the performance across the indoor coil, not how well air conditioning is delivered to the space. The losses in the delivery and distribution system ously combine with the equipment performance losses. However, no simple statement can be made that exactly describes how these losses interact (see “A Million Miles of Ducts: Duct Sealing Update,” HE, Mar/ Apr ’92, p.14). For example, an air conditioner system may move 400 cubic feet per minute (cfm) per ton of air flow over the indoor coil, the capacity across the indoor coil may be exactly the ARI rating, the system may be properly charged, but when the leaks in the return duct are sealed, it may be impossible to move the 400 cfm through the now “tight” ductwork. The resulting capacity across the indoor coil would be severely reduced and this would simply mean that the air return duct was inadequately sized. The solution, of course, is to enlarge the return duct and achieve the proper air flow for the entire system ment plus distribution). Perhaps 30% or more of the potential energy efficiency of the cooling equipment in the United States may fall into the “lost” category. A study by Trinity University for Austin Electric Utility supports this figure. It documented a case where the air conditioner was rated at an Energy ciency Ratio (E’ER) of6.7, but found it actually had an EER of 4.7, a 30% difference.3 More Cooling Studies Interest in measuring, documenting, and improving the actual, in-house efficiency of central air tioners is a fairly recent development. This interest will obviously accelerate as customers have to pay higher prices for systems with higher rated efficiencies. Conse-Home Energy May/June 1992 Source: North Carolina Alternative Energy Corp. field test. quently it’s almost certain that researchers will collect much more and better data on this subject over the next few years. A field study conducted over an 18-month period by Air Conditioning Training and Consulting (ACT) and phy Engineering of Phoenix, Ariz., included low-tonnage air conditioners seven to 25 years old.’ The results showed the culprits contributing to lost energy efficiency: Ł 75% of the condenser coils were dirty. Ł 70% of the units had improper refrigerant charge. Ł 55% of the evaporator coils were dirty. Ł 45% had dirty blower wheels. Ł 10% had a wrong motor or fan installed. Ł 35% had significant duct leakage This study was completed prior to current blower door techniques devised to test duct leakage, so 35% for duct leakage is an obsolete figure. Most recent studies of dential duct systems indicate that almost 100% have nificant duct leakage.” Central air conditioners don’t simply provide cold air to a home but provide comfort for the occupants as well. Several factors in the final assembly of a home that can have a large impact on the ability of the device to deliver fort stand quite apart from its ability to operate efficiently. What are some of these critical final assembly parameters? What should a final assembly quality control inspector look for? Cooling Design Equipment sizing It is extremely important to maximize efficiency by erly sizing a central air conditioner to the actual load of a 33
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house. Here are a number of real, practical, wrong reasons why a heating, ventilation, and air conditioning (HVAC) con tractor may be inclined to oversize an air conditioner: Ł just “to be sure” that it will keep the house cool, Ł to “cool the house” even if all work is not necessarily done perfectly, Ł to avoid service calls on a new installation, and Ł to avoid placing trust in his or her heat loss and heat gain calculations-if any were actually done. For specific houses climate, and equipment, seasonal co ling energy calculations show that if an air conditioner varies from the absolutely corr ct ize, it is more efficient to be lightly und rsized than lO be oversized. Al o, although n one wants the nuisance of ervice calls, it is better to have a way to know that the air conditioner has a problem than to keep operating it with a potentially damaging condition. Oversizing a residential central coo Ii ng unit nOl only can directly affect the energy effi ienc..-y, but it can hav a matic impac on th cooling comfort of the re idence. An oversized unit can reduce the t mperature insid the house, but not run long enough to remove enough ture to keep the humidity down. At relative humidities above 70%, mildew will grow and comfort is unlikely. Sizing Dealers, contractors, or architects sizing central air ditioners should do it properly-by using the method scribed in Air Conditioning Contractors of America (ACCA) Manual J Many compmer programs are available that use this method and make the calculations much easier. Many dealers feel that such calculations are “too much trouble” and “always give the same answer anyway.” They are known to rely on some old rule of thumb or worse, an old joke sizing sheet chat someone published with holes cut out for the house size when viewed through the sheet from the curb in front of the house. A “moldy, oldy” rule of thumb used for houses built prior to our current energy a.,vareness was 400 ft¥ of house per ton of cooling (12,000 Btu). 34 The City of Austin, Texas-in a pretty bot climate-now requires calculations for all new central air conditioning installations and they find an average of about 650 fl2 per ton of cooling. If the calculation shows a need for more than a ton for 600 ft\ the in taller must provide special proof of the accuracy of the calculations. The ACCA Manual] calculations use ASHRAE 97.5% design temperatures-which means that the conditions will be exceeded about 2.5% of the year. Very few air ditioning contractors will agree to use the Manual]’ s ified temperarures for sizing air conditioners because they say. “I know that it gets hotter than that around here, so I will use a higher temperarure.” They like to use the mum temperature anyone can remember plus a degree or rwo. The indoor design tern perature is also a bone of tention. Dealers may use indoor temperatures as low as 70°F under the reasoning that “this client likes it cold, even at extremely high temperatures out.side.” Both extremes point toward lowered efficiency, and possibly less comfort. Field surveys find most air conditioners are oversized. For example, in the same study performed for the Austin Electric Utility Department, researchers found that all of the units in the area were oversized by a consistent 60%. The City of Austin concluded that proper sizing of central air conditioners could provide major peak reductions. Field examination of new and existing houses turns up a variety of ductwork problems, which have a profound effect on overall cooling system performance. Ductwork design-supply and return grille locations The best equipment manufactured cannot provide fort and efficiency with a bad duct system. A major factor in shortening the life of central air conditioners is quate volume of return air back to the indoor coil. Too tle air across the indoor coil can potentially lower the coil temperature to the point of ice formation. An indoor coil covered with ice puts a central air conditioner into tion mode.” Shutting the dampers on supply registers or ing unused rooms is not a good strategy with central air. Field examination of ductwork in new and in existing houses provides an abundance of “horror” stories: Ł supply grilles from which no air is supplied, Ł ducts detached from the boots of grilles, supplying only the crawlspace or attic with conditioned air, Ł rooms with supply grilles but no access to an air return, Ł air noise so great that the occupants have difficulty sleeping or talking, Ł supply ducts with holes large enough to stick a human head through, and Ł flex duct in a crawl space that a dog has chewed through. The residential conservation field wants to make work actually move air from one point to another without leaking. Accomplishing this will bring forth the next formance-related problem-duct systems not properly sized and unable to move the amount of air required for the equipment to work at its rated efficiency. Sensible/latent cooling ratio Often in residential air conditioning, the dealer and the homeowner never think of their choices in selecting the sensible cooling ratio of the equipment purchased. This May/June 1992 Home Energy
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ratio tells how much of the cooling capacity in tons (12, 000 Btu = l ton) at the rating condition is in the form of sensible cooling and how much capacity is in the form of latent cooling. Sensible cooling reduces the room’s dry bulb temperature. Latent cooling removes the moisture in the room (dehumidifies), and thus removes the heat in that moisture (see box “Human Thermal Comfort”). The sensible heat ratio (SHR) is the percentage of total ing that is sensible. Until the rather modern marketing emphasis on a gle ratings number (Seasonal Energy Efficiency Ratio, SEER), essentially all residential equipment used an indoor coil temperature of 42°F as the design condition (see box “Seasonal Energy Efficiency Ratio”). This design constraint meant that the sensible/latent ratio of all cooling ment fell in a fairly narrow band. Relaxing the 42°F design condition to achieve higher SEER has meant that some equipment no longer removes as much latent heat. This can be very critical in humid, hot climates found across the United States. (See “Efficiency versus Comfort with the New Air Conditioners,” HE, July/ Aug ’89, p.28-31.) Graduate students under Dennis O’Neal of Texas culture and Mining University have calculated how often a simulated house will not be comfortable for various sible/latent ratios.5 Using TR..l\fSYS computer simulation, the ASHRAE comfort zone definition, and climate ditions for Houston, Texas, the results showed: Human Thermal Comfort Although human beings differ widely, scientists have defined and tested a thennal “comfort zone” where 80% of the tion indicate that they are “comfortable.” According to 1989 ASHRAE Fundarnental.s, six factors detennine thennal comfort: Łclothing, Ł activity, Łdry bulb temperature (ambient air temperature), Łwet-bulb temperature (relative humidity), Łmean radiant temperature, and Łair movement. Wet-bulb temperature is the thermometer reading with the sensing bulb covered with a wet wick and located in the air. Relative humidity (rh) is the amount of moisture in the air, given as a percentage of the amount of moisture the air can bly hold at the same dry-bulb temperature. Thus wet-bulb perature equals dry bulb temperature at 100% rh. Mean radiant temperature is temperature recorded by a special device that accounts for the radiant energy at the location. An example of the contribution of mean thermal temperature to thermal comfort is that one feels hotter in the sun than in the shade. The standard conditions for the thermal comfort zone used by researchers and equipment designers include lightly clothed, sedate activity such as sitting at a desk, air movement of less than 40 ft per min (less than V2 mph), and a mean radiant perature the same as the dry bulb temperature. The “comfort zone” concept was first advanced by P.O. Fanger prior to 1970. He produced a “Fanger Chart” for fort. 1 ASHRAE Fundamentals discusses thermal comfort in ter 8, and has represented thermal comfort graphically as a comfort chart where a region of acceptable relative ties and ambient (dry-bulb) temperatures define the thennal comfort zone (see Figure 1). Home Energy May/June 1992 Ł The percentage of time outside the comfort zone sistently decreased as sizing decreased. Ł Sightly undersized units posted the minimum energy use. Ł Both percent of time outside the comfort zone and power consumed increased as the SHR varied from 66% to 90%. Ł At an SHR of 90%, the time outside the comfort zone reached 40% or more. Inability of a unit to dehumidify air adequately becomes apparent when an occupant wakes up sweating, usually ing the 3 am-6 am time period. A humidity meter can help regulate cooling in a home. Properly done, cooling load calculations utilizing Air Conditioning Contractors of ica’s (ACCA) Manual] provide the latent cooling ment. However, many who attempt these calculations purposely err on the conservative side by using a higher door dry bulb temperature. This higher temperature, out comparable changes in the rest of the calculations, results in a smaller latent/sensible ratio than the real, rect value and in comfort problems for the occupants. Unit Installation Location outdoors Some very practical considerations in locating the door unit of a central air conditioner can have important Thermal Comfort Zone 15 ‘iii “‘ a 0 0 10 o_ >:::: 3: “‘ a 0 a: 5 ‘6 .E :J :r: 23%rh .. 0 60 70 80 90 Ambient Temperature °F ASHRAE Standard 55-1981 Figure 1. The “comfort zone,” defined by relative ity (rh) and ambient, dry-bulb temperature. Note: Relative humidity coordinates are interpolated approximations. 1 Fanger, P. 0., Thermal Comfurt, Robert E. Krieger Publishing Co., 1982. 35
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consequences for efficiency and equipment life. Most ers and homeowners know that they simply do not want the noise of the outdoor unit near a patio, a den, or a bedroom. But other considerations can loom large. One apartment complex located the outdoor units near the exhausL from t.he clolhes dryers and the chlorine residue from the water and laundry products in theventairsimpl at away the door coil . Lint from a clothe dryer v nL an completely t p lhe air now through Lhe outdoor coil and has res.ulted in proven case of failed com pre ors. Homeowners like lO hide outdoor coils and tend LO plant shrubs around r near them, but the uni are designed to operate correctly nly if surrounded by a clear area of at l a t 2 ft. California builders are noc01-ious for locating the outdoor coil under ad ck. The deck Aoor do ·a greacjob f recir ulating th air through the coil, resulting in lower efficiency. Ductwork air flow All residential central air conditioners are designed for a specific volume of air flow across the indoor coil inside Seasonal Energy Efficient Ratio A new round of standards from the National Energy Efficient Appliances Act went into effect at the beginning of tral air conditioner manufacturers can no longer bmld spht central air conditioners with a Seasonal Energy Efficiency Ratio (SEER) of less than 10. The majority of air conditioning ers have never even heard of SEER. The ones who know a tle about SEER believe that “higher is more efficient” and that annual cooling bills will decrease in direct proportion to the higher SEER. Are these correct thoughts? What really? No, these are not totally correct thoughts. Despite claims that SEER provides a better measure than che old workhorse Energy Efficiency Ratio (EER). it “does not predict actual energy StUTiption, but serves as a comparative rating between various air conditioning units.” 1 ln fact, SEER is really just che steady-state perfonnance of the unit at 82°F outdoors, SO°F indoor temperature, and 67°F indoor wet-bulb tempera lure, mulophed by a “cycling factor. “2 The test that renders a SEER for a given unit assumes the unit cycles of 24 min on and 6 min off. Thus SEER is simply a test devised by the Department of Energy (DOE) to compare units, and has certainly not been proven to be an absolute antee ofwbat cooling costs will be. P1ior to SEER, the try used EER, the ratio between the cooling output (in Blu per hour) and the electrical power input (wattS). The EER rating of an air conditioner is simply the steady state performance at a specified “high temperature condition”-95°F outdoors. 80°F indoor dry-bulb temperature, and 67°F indoor wet-bulb temperature. EER may be a beuer indicator for electric ties interested in reducing summer peak demand. 36 Current techniques for calculating seasonal cooling energy are_a long way from the accuracy w would Like to have. ever, if we were to compare the EER of one unit and the SEER of another, anyone who is familiar with these calculations can easily see that it’s impossible for SEER to indicate seasonal cool· ing energy unless both sizing and lhe sen ible/latent ratio of the two air conditioners are Lhe same and that the two the ductwork in the house. Almost universally this volume of required air flow is ·l:OO fr’ of air per per nal ton of cooling. U nle s t.he duClwork design and the blower speed provide this volume of air, there is no way that the device can provide th rat d capacity and energy efficiency. Causes of low duct air flow can be dirtv filters, a dirtv coil, r closed regist rs, but perhaps the’ mo l frequen’c cau is inadequate r turn duct izing. Again, be aware that the indoor coil may receive the corr ct volume of air ply b cause the air i · h ing pulled dHougb return “leaks.” Properly sealing a leaky return duct, thus redu ing a_ir flow, wiU riou ·ly deurade t.he performance of Ll1 coil. Install rs don ‘tseem to realize that blockage on lhe ren1m (low-pressure) side of a fan has a much larger impact on the air flow volume than a restriction on the supply side (high pressure). The result i · that Lhey ” heat” on the return du<.:t by using hous chas · panning a joist, or ing to save cl et pace. Also who use duct do .not take into account th fncuon loses for this gated air surface, which are about three times as large as for a smooth wall duct. Buddy Wolfe of Klassic Air Conditioning in Houston reports, "Going from lower seasonally adjusted energy ings (SEERs) to higher SEERs, we were ducting in a thermostats act identically and, on average, che summer ing cycles of both run 24 min on, 6 min off. Anyone who is imerested enough to dig into the technical litcramre will be surpri ed to find that both SEER and EER have definitions different than the current "primary" definitions given above. At least lwo studies measured the total cooling produced over a s ason and divided that by tl1e total ity con.summed in watrs lO aITive al the true SEER. Several reports by Oak Ridge National Laboracory have u ed measured teady-statc performance of air condiLioners in a DOE-2 simulation to calculate the seasonal cooling and sonal electricity used. ln chese reports, these calculated values are divided to yield a number designated as "SEER." To be fair, EER also must be examined carefully in any report where it appears. EER as a general term is the state cooling divided by the power being consummed when the cooling is measured. The "tommon" assumption is lhat these measurements are made at the ARI Standard Rating tions given above. But an EERfor a unil may be measured under any steady-state indoor and outdoor conditions. This means that EER is a much more useful engineering concept and graphs of EER for various "off-design" conditions-indoor temperatures (both wet-bulb and dr)'-bulb), outdoor atues (both wet-bulb and dry-bulb), refrigerant charge levels, and coil air flows--are very useful to engineers who wish to understand cooling energy performance. The fact that ARI no longer publishes EER in lheir directory is a handicap to lhose technicians who have been trained to measure air conditioner performance in the field. I. Kuenzi. Cynthia A. and Byard D. Wood, "Evaluation of Energy and Cost Savings from Replacement and Maintenance of Residential Air Conditioning Equipment." Center for Energy S stems zona State University, Oct '87, p. 3 (Contract for Salt River Projec:1, Phoenix, Ariz.). 2. The official definition of SEER is given in Code of Federal tions, January I, 1988, Vol. IO, Paris 400 to 499-Pt. 430, Subpl. B, App.M. May/June 1992 Home Energy
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return air. That wasn't enough, so we started doubling our return air size. In some cases we tripled them and enlarged our copper (refrigerant lines). The result: Our systems work a hundred percent better. Complaints are down thirty-five to forty percent."" Enlarging the ducts also allows a lower fan speed and much lower fan noise as well. Technicians use a charging cylinder to "weigh in" the charge for a new air conditioner. Charging by "feel" is always wrong. Proper refrigerant charge People tend to believe that ifa little is good, then more is even better. Nothing could be further from the truth when adding refrigerant-"charge"-to a central air ditioner. Overcharging has serious consequences on ciency, capacity, and especially the life of the compressor. A large percentage of the air conditioners in service today are likely overcharged. In the small ( 10-unit) field study by AEC, we found three units to be overcharged, with one of these so seriously overcharged that failure seemed imminent. A recent overcharge problem was solved when 10 lbs of refrigerant were removed leaving the correct charge of just 3 lbs 8 oz. In a 1990 California study, 27% of the central air conditioners were found to be charged and 27% undercharged (see "An Ounce of vention: Residential Cooling Repairs," HE, May/Jun '91, p. 23). Over half of all the central air conditioners were not correctly charged! (This result agreed with results found earlier for heat pumps. See "Heat Pumps: Tricks that Can Pump Up Efficiency," HE, Mar/Apr '91, p. 29). In every case investigated (located through high bill plaints) the problem originally attributed to the equipment was actually caused by: Ł house construction defects, Ł duct leakage, or Ł poor quality of service. Improper charge impacts capacity, power draw, EER, and SEER (see "Charging by 'Feel' versus by Spec"). Note that overcharge is doubly bad because not only does ity diminish but the power draw goes up, which also tends to "stress" the compressor. Home Energy May/June 1992 () w < Charging by 'Feel' versus by Spec Table 2. Relative Benefits of Correct Refrigerant Charge EER/ Equipment Capacity Power Efficiency COP' Life Correct Charge Max Normal High High Longest Undercharge Down Down' Low Low Short Overcharge Down Up Low Low Shortest 1 Cooling Energy Efficiency Ratio (EER) = Btu Output Watt Input Heating Coefficient of Performance(COP) = Btu Output Btu Input 2 Lower power not in proportion with lower c apacity. Figure 2. Effects of Refrigerant Charge on Capacity and Power Input (Simulated) IOI GU !UH WlD ?:-110 Qi 105 a. I I/ I J__ a. "' (,) 100 iii ! I I I "O 100 2 ii-. "' er. er. 95 Qi .. I P -. ..1'-' I 95 Qi . I 'k I c a c a 90 . cJ ,,.-I \ I 90 ::a '6 § 85 () < 80 ,I / I ' / I \l I I j.'\ 751; 80 85 90 95 100 105 llO 115 120 125 . % Refrigerant Charge Figure 3. Seasonal Energy Efficiency Ratio Cyclic Test (Measured) for a TXV Air Conditioner w w 9-a I a: >. B u c Q) ·o it: w 7· >. Q) c w co 6 c a (/) co Q) (/) 5 80 85 90 95 100 105 110 115 120 % Refrigerant Charge Note: Full charge= 140 oz. ofrefrigerant. Also, both graphs show about ±20% correct charge while field ments frequently show a much greater swing. Controls c a () Proper controls (thermostats) and location of these trols for central air conditioners can dramatically improve the efficiency of the device and the comfort of the 37
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The Right Stuff If one fact stands out about central air conditioning tems, it is that a trained eye can find a significant cr pancy between th manufactur r’s rated energy efficiency and th actual performance. That’ why proper in tallation and maintenance of any air conditioner system are the only way to achieve the sy tern efficiency and the equipment endurance that the homeowner has lhe right to expect The instruments, techniques, and knowledge to do these jobs properly are simply beyond the capabtie of almost anyone except highly trained service nicians. They almost all agree that !.hey can perform a much more profe sionaljob for an annual service contra t customer than they can for someone whose system has failed under the strain of hot weather usage. A dealer or technician for whom an annual service fee can be justified should offer several services and cations: Ł membership in Refrigeration Service Engineers ety (RSES), Ł a written report with each maintenance visit, Ł an outdoor coil cleaning with each visit and an indoor coil cleaning at least once each year, Ł a report on measured air flow through the duct system, Ł air conditioner refrigerant charge checked by the “superheat method,” preferably when the weather is above 80°F, Ł “meggering” the compressor, Ł a measure of the air conditioner capacity, and Ł an explanation to the occupant about latent and sensible cooling. Ł Endnotes l. Neal, C. Leon, “Efficiency In Real-Life Residential Air ditioners,” AEC-R-87-3, North Carolina Alternative Energy Corp. Staff Report, Oct 3, ’86. 2. “Real-Life Residential Air Conditioning,” Refrigeration Service Contractor, Oct ’87, pp 24-26. 3. Giolma,J., Loxsom, F., Dieck-Assad, G., Meister, D., “Effects of Downsizing Residential Air Conditioners on Aggregate Peak Demand, Final Report-Vol I: Technical Report,” ity University Report for Austin Electric Utility, Jul ’85, p. 24, and “Vol II-Summary Report,” Dec ’85, Table I. 4. “Government Meets Industry to Solve Common Air tioning Problems,” Air Conditioning, Heating & Refrigeration News, Sept 26, ’88. 5. Katipamula, Srinivas, Dennis O’Neal, and Sriram daram, “Determination of the Transient Dehumidification Characteristics of High-Efficiency Central Air Final Report,” ESL/87-04, Energy Systems Laboratory, Texas A & M University, Jul ’87. 6. The Air Conditioning, Heating, and Refrigeration News, Business News Publishing Co., Nov 19, ’90. 7. Davis, Thomas L., Carolina Power and Light Company, Research Department, personal communication. 8. “Electrostatic Air Cleaner Improves Heat Pump Efficiency,” Energy and Housing Report, Apr ’87, p. 8. 9. “Compressor” section, Residential Heat Pump Training and Ref erence Manual, p. 124, The Electrification Council (TEC), 1989. Home Energy May/June 1992 Find Trouble on the Double Introducing the VideoTherm96-Two Cameras in One Looking for trouble? See it both ways -as a visible image, infrared image, or any variable combination of the two. You decide. The new VideoTherm 96 infrared imaging system also has a built-in visible camera. So troubleshooting is faster and easier than ever. You won’t need that 35mm or Polaroid® camera any more. With just your lightweight VideoTherm 96 and a portable video cassette recorder, you’ll have complete video and audio documentation. Like all the portable VideoTherm systems, the VideoTherm 96 was designed specifically for tative maintenance applications. So it has the features you need. There’s high resolution imaging in both infrared and visible display modes. Simple controls and no coolants required. All in an easy-to-use, weight package that’s reasonably priced. It’s easy to find trouble on the double; just get your hands on the VideoTherm 96 today. Contact us for more information. .rff1 LS.LGroup,Inc. MadCl in the USA 211 Conchas SEŁ Albuquerque, NM 87123 (505) 298-7646Ł1·800-821-3642 ŁFAX 505-299-4926 (Circle No. 6 on Reader Request Card) 39
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