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Home , Evaporative cooler, Humidity

Modern Evaporative Coolers Not all evaporative coolers are created equal. Modern machines operate more efficiently and with much less fuss than the old swamp coolers did. ADOBE ADOBE

Here is an inside view (left) and an outside view (right) of a modern by Adobe.

by Larry Kinney dampers, also known as up ducts, in the fer the better comfort and fresh, clean ceilings of rooms on the top story. The air our systems give them. The $300 we ave Emmitt owns Direct Drive process is controlled by a multifunction save them on their utility bill each sum- Service, a company in Colorado that has the smarts to throttle mer just pays for a barbeque with 50 of Dthat specializes in efficient low- back the speed when the setpoint their closest friends.” mass —and high-efficiency evap- is about to be met, rinses Emmitt’s retrofit business is also doing orative coolers. We’re not talking swamp out the reservoir to keep and air quite well. Colorado homeowners who coolers on the roof of a mobile home; clean, and partially automates much of have never had cooling systems generally Emmitt’s staff install coolers in the attics the end-of-season maintenance. tend to install conventional A/C of large, site-built homes. The coolers “We install modern evaporative systems—as do those who are pull in air from large gable vents, cool it cooler systems in new homes that cost disenchanted with their old swamp cool- by 30°F or so, and distribute it via several $2 million,”reports Emmitt. “These ers. But if Emmitt gets to them first, they large ducts, typically to a hallway below. people can afford conventional are more likely to upgrade to one of the Cool air is directed by the patterns of -based cooling and the high-quality evaporative coolers he window openings or by backdraft higher bills that go with it, but they pre- installs, which deliver two or three ACH

24 www.homeenergy.org SEPTEMBER/OCTOBER 2004 • HOME ENERGY HVAC and wash the pollen out of that air before tage of evaporative cooling effects, but tures an indirect/direct evaporative it gets inside. Emmitt is enjoying a grow- use an air-to-air to cool cooler, called the OASys, that was devel- ing customer base, fueled largely by word without raising the of the oped by the Davis Energy Group in of mouth from happy customers. cooled airstream. Indirect/direct coolers Davis, California (see Figure 1). cool in two stages. In the first stage, the The OASys system uses a single Evaporative Cooling air passes through an indirect cooler, blower that pulls in outside air and directs Innovations which lowers the temperature without most of it—about 70%—through the dry adding humidity.The air that enters the side of a heat exchanger that uses 14- Emmitt wouldn’t be getting the same second, direct cooling stage is already inch-thick media to efficiently and indi- good word of mouth if he were rectly cool the airstream without selling old-fashioned swamp adding moisture. This partially coolers, but modern evaporative OASys Air Flow cooled air then passes through a coolers are several technological direct-cooling module before leaps ahead of those old being directed into the home. machines.All evaporative cool- About 30% of the outside ers—old and new—rely on the airstream is used in the other, same design principle:Water can wet side of the counterflow heat be used to cool air.Air blowing exchanger, where it is cooled, through a wet medium—a tee gathers moisture, and is then dis- shirt, aspen fibers (excelsior) or charged to the outdoors. Water treated cellulose, fiberglass, or from both the indirect- and the plastic—evaporates some of the direct-cooling processes gathers water and its dry bulb tempera- in a single reservoir, which is ture is lowered (see “Wet’s the purged with a frequency that is Difference: Dry Bulb and Wet tied to the amount of scale-caus- Bulb ”). The cool- ing in local tap water ing effect of an evaporative and the rate of water use by the cooler depends on two factors. system. The rate of water use in The first is the local difference GROUP ENERGY DAVIS turn depends on the blower between the air’s dry bulb and speed, which is controlled by a wet bulb temperatures; the sec- multifunction thermostat. ond is the cooler’s efficiency This machine incorporates a (see Table 1, p. 27). Exactly how Figure 1. The OASys system employs a single cabinet that houses all its parts. number of improvements over an evaporative cooler takes This simplifies the overall design, helps maintain tolerances, shortens assembly earlier indirect/direct evapora- advantage of water’s chilling time, and ensures a long lifetime. tive coolers designed for effect—the pathway and the residential use. It employs a sin- velocity of the air as it passes gle polyethylene cabinet that over the media combined with the con- substantially cooler than the outside houses all parts of the system. This sub- dition of the media—determines how air, and it can be cooled a good deal stantially simplifies the overall design, efficient it is as a cooling device. more because it’s still largely dry.Com- helps maintain tolerances, shortens Today’s evaporative coolers come in bining these two techniques enables assembly time, and ensures a long one of three general designs: direct, indi- efficient indirect/direct units to deliver lifetime. The OASys also uses an rect, and indirect/direct. Modern direct air that is cooler than the outside wet electronically commutated motor evaporative coolers couple high-perfor- bulb temperature. (ECM) controlled by a smart mance media—generally plastic-coated After losing a good deal of market thermostat, so blower speed can be cellulose—with low-velocity air flow. share to conventional cooling, there’s changed while maintaining high motor This combination maximizes moisture optimism in the evaporative cooling efficiency. This is important, because transfer from the wet media to the hot, industry that higher-quality units will overall system efficiency of the OASys is dry air.The effectiveness with which an lead the way to recovery (see “Copious best at low fan speeds and low air flow appliance makes this transfer—known in Refinements,”p. 28). One particularly rates (see Figure 2). the trade as its direct saturation effective- promising new design is being manufac- Engineers at the Davis Energy Group ness—is a key measurement of the appli- tured by Speakman CRS—short for took these plots of efficiency at different ance’s cooling efficiency. Clean, Renewable, Sustainable—a branch flow rates and other test results—such as Direct evaporative coolers humidify of the Speakman Company,a firm that temperatures delivered under different the incoming air, making them inappro- has been producing showerheads and conditions of wet and dry bulb tempera- priate for use in humid . other water-related products for more tures—and performed simulations of a Indirect evaporative coolers take advan- than 130 years. The company manufac- very efficient 1,600 ft2 home in eight of

HOME ENERGY • SEPTEMBER/OCTOBER 2004 www.homeenergy.org 25 HVAC

California’s zones.The results for Fresno are most pertinent for the OASys Measured Performance at Southwest, as Fresno has a hot, arid cli- Three Supply Air Flow Rates mate not unlike many locations in the 160 Southwest (1% dry bulb 101ºF,mean 140 coincident wet bulb 70ºF).The base case home with a conventional DX air con- 120 ditioning system rated at 12-SEER uses 100 1,890 kWh per year with a peak of 3 kW,while the OASys uses 135 kWh per 80 year with a peak of 0.52 kW. This 60 amounts to an annual energy savings of 93% and a peak demand savings of 83%. 40 In another evaporative cooling devel- 20 opment,AdobeAir has recently Btus Delivered/Watt Primary Btus Delivered/Watt Power introduced its own series of efficient 0 evaporative coolers that fit in a sidewall 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 KINNEY LARRY (see Figure 3).These units are easy to Supply Air Flow (CFM) install either in new dwellings or as retrofits and have clear aesthetic and Figure 2. The data gathered was at entering dry bulb temperatures of 104ºF, with the unit supplying dry bulb tem- mechanical advantages over rooftop or peratures of 68ºF. Power plotted is the sum of fan and power. The vertical axis shows overall efficiency in that concrete-pad-mounted coolers. it expresses the ratio of cooling Btu’s out versus the combined power use of the pump motor (20 watts or so) and that of the power consumed by the fan motor. The point of the graph is that spectacular efficiencies are achieved at lower flows, both because of the overall design of the device and the fact that its motor is quite efficient at low Water and Energy Use speeds—unlike most motors used in the evaporative cooling industry. (Source: Davis Energy Group.) There’s no getting away from the fact that an evaporative cooler relies on, and gallon of water would yield roughly needed to flush out the residue of air pol- so consumes, a significant amount of 8,800 Btu of evaporative cooling. If the lutants and scale in the water. In water, but the newer units use up much flow of water and the flow of air are well inefficient units, water that is not evapo- less than the old-fashioned coolers do. matched in a carefully designed evapora- rated by the cooler is continuously Evaporating 1 lb of water yields about tive cooler, the air is cooled efficiently diluted by makeup water in the reservoir 1,060 Btu of cooling. Accordingly,if an and most of the water in the media is or sump, with the residue going down an evaporative cooler were 100% effective, 1 evaporated. However, some extra water is overflow drain. This bleed system contin-

Wet’s the Difference: Dry Bulb and Wet Bulb Temperatures

Direct Evaporative Cooler Modern Evaporative Cooling Media The temperature of air measured with Wetted pad or other direct a whose sensing element is evaporative media dry is known as dry bulb temperature. If a Outdoor Conditioned air thermometer’s sensing element is air surrounded by a wick wetted with pure water over which air is blown, the sensor Supply fan is evaporatively cooled to its wet bulb MUNTERS PLATTS temperature. When the relative humidity Reservoir Pump (to keep pad wet) is at 100%, there is no difference between Figure A. Direct evaporative coolers use a fan to pull outside air through pads that are wet (left), filtering the dry bulb temperature and wet bulb and cooling the air (right). temperature. But as the relative humidity of the air drops, so does wet bulb temper- ature with respect to dry bulb temperature. In climates such as those in a dry bulb temperature of 90ºF, the wet Direct evaporative coolers use a fan to the Southwest, where humidity is routinely bulb temperature is 58ºF—a difference of pull outside air through media (pads) that quite low, the differences are substantial. 32ºF. This difference is often called the are kept thoroughly wet by water that is For example, at 10% relative humidity and depression of wet bulb below dry bulb. sprayed or dripped on them (see Figure

26 www.homeenergy.org SEPTEMBER/OCTOBER 2004 • HOME ENERGY HVAC

Table 1. Delivery Temperatures for Selected Cities in the Southwest uously dilutes the water and reduces the Temp Temp of scale and impurities, but Dry Bulb Wet Bulb Delivered Delivered this method of cleaning wastes water. Ambient Ambient @ 85% @ 105% Higher-quality units use a more effec- Temp Temp Depression Effectiveness Effectiveness tive and less wasteful batch process to City (ºF) (ºF) (ºF) (ºF) (ºF) deal with impurities. The sump is Albuquerque 193 60 33 65 58 typically sloped so that heavier pollutants Cheyenne 185 57 28 61 56 and scale tend to collect at the bottom. 190 59 31 64 57 There is no continuous ; instead, 106 66 40 72 64 after the cooler has run for several hours, Phoenix 108 70 38 76 68 the reservoir is drained and flushed auto- 194 62 32 67 60 matically.Well-designed machines key Tucson 102 65 37 71 63 the need for dumping to the elapsed run Note: Table shows delivery temperatures under severe conditions. During 99% of the typical cooling season, ambient time of the pump so as to keep the sump temperatures and delivery temperatures are lower than those shown in the table. full, but not overflowing.The residue of several gallons from this sump dump may be piped to a nearby garden. With this system of periodic purging, almost all of the water—over 95% in most places—is used to provide cooling.And the amount of water that is discharged is well matched to the needs of a garden; more water is delivered on hot days when the evaporative cooler works the most and plants are especially thirsty. The trade-off for this water use at a home is that evaporative coolers reduce a power plant’s use of water to generate electricity,because they use substantially less energy for cooling than conventional

ADOBE direct expansion (DX) systems would. Generating 1 kWh of Figure 3. A new evaporative cooler by Adobe installs in the wall at the side of a home (photo and schematic). electricity with a thermoelectric plant in

Indirect Evaporative Cooling means that they must allow for as much ature can drop by 93% of the difference Secondary as temperature conditions allow, between the dry bulb and wet bulb Wetted pad or other indirect evaporative media temperatures. Older-style systems that OutdoorSeconday air airfan fan while minimizing drop, which saves fan power. Well-designed media filter typically use 2 inches of excelsior may Heat Conditioned exchanger air the airstream, but are also self-cleaning, in achieve effectiveness ratings of 50% to at Outdoor air that water dripping across them to the most 80%. I do not recommend the use of these less efficient units, although they are Supply fan sump below performs a cleaning function.

PLATTS The water is typically delivered via tubes less expensive, because they also tend to Pump Reservoir from a small pump that draws from a reser- waste water. Figure B. Indirect evaporative cooling adds a sec- voir below. The reservoir is replenished Indirect coolers commonly make use ond stage of evaporative cooling before the condi- with tap water whose level is controlled by of an air-to-air heat exchanger (see Figure tioned air enters the home. a float valve. The resulting fresh, cool, B). The main fan supplies outside air that humidified air is blown into buildings. is cooled by passing through a heat Direct evaporative cooler performance exchanger into the dwelling, while a A). This both filters the air and cools it. is measured relative to the wet bulb secondary fan draws exhaust air from the Lower fan speeds give the air more depression. Well-designed and properly dwelling, or fresh air, or some combination exposure time to the wetted media, which operating systems with media at least 10 of the two through wetted passages that are achieves greater cooling. Media for evapo- inches thick can achieve 93% in thermal contact with the dry passages of rative coolers have to be efficient, which effectiveness; that is, the dry bulb temper- the heat exchanger.

HOME ENERGY • SEPTEMBER/OCTOBER 2004 www.homeenergy.org 27 HVAC

Copious Refinements

The word on innovations in evaporative use a batch flushing process to clean the pressurized by an evaporative cooler cooling technology is anything but wide- sump, rather than a continuous bleeding blower are typically equipped with digital spread, and this lack of awareness trans- process. The result is better cleaning thermostatic controls. These controls turn lates to meager sales—and the and substantially lower water use. Mod- the system on and off; vary the blower installation of conventional central ern coolers in efficient homes in the speed to maximize energy efficiency in compressor-based cooling systems. To line with local conditions, indoor help overcome barriers to embracing temperature, and the thermostat’s high-quality evaporative cooling systems, setpoint; and control sump-flushing func- we present a summary of salient points. tions both during normal operations and Media. Instead of aspen fibers, or at the end of the cooling season. This excelsior, which tend to shrink down reduces end-of-season maintenance to a with use, causing inefficiency and short- simple chore that can be done in only a ening the life of the unit, modern evapo- few minutes. rative cooling media are made of special Comfort. The increased efficiency of plastic-coated cellulose or similar mate- modern evaporative coolers—especially rial. This material is formed into a rigid indirect/direct models; their digital con- rectilinear shape, typically between 4 trols; and their better distribution of and 24 inches thick. Air passageways cooled air make it possible to achieve are fluted to maximize cooling effective- comfortable temperatures in most ness while minimizing pressure drop Southwest climate zones throughout the (and fan power). The thicker the media, SERVICE DRIVE DIRECT cooling season. Many people thrive on the greater the temperature drop of the the more humid air that evaporative air from entry to exit. Efficient units cooling delivers—but, in truth, others have media at least 8 inches thick; 12 aren’t as enchanted. Short-term discom- inches or more is even better. The media fort in very hot regions that occasionally resist scale and algae, are easy to clean, The photo shows an attic installation of a Phoenix experience periods of high humidity— and last for many years, especially in evaporative cooler by Direct Drive Service. The such as the season in the low regions where the water is largely free cooler is installed close to the fresh-air intake and regions of Arizona—cannot be moves air into 24-inch-diameter supply ducts. The of impurities. ducts are well insulated (improving energy perfor- fully avoided. The solution of backup Appearance. Instead of having air mance and reducing noise) and relatively short, as conventional A/C is undesirable from a flow in on all four sides, efficient they typically feed conditioned air into an upstairs policy perspective, since these periods machines that use thick media are hallway. Intake air ducts range from 28 x 42 inches typically correspond to peaks on the designed to have unconditioned air flow down to 24 x 36 inches; the smaller size will electric grid. Our grandparents dealt with accommodate a 3,000 CFM evaporative cooler. The in on one side, while conditioned air cooler is suspended from trusses and uses vibration it philosophically, with the help, flows out the opposite side or out the isolators at top and bottom. In the interests of no doubt, of plenty of cold beverages. bottom. This allows units to be placed in safety, an electric cutoff is installed close to the unit, Our periods of discomfort are much attics, on sidewalls, or on small pads out- so that it can be maintained without risk of shock. shorter and less intense than theirs side the home, instead of on the roof. were, and the quality of beer has been Air quality. Conventional A/C enhanced immeasurably! systems are most effective when the Southwest use about 3.3% of average Energy. An 1,800 ft2 home in the home is tightly sealed and fresh-air annual residential water use. This Southwest that is about 48% more makeup is at the minimum. Typical fresh- amount of water costs $5–$20 per cool- energy efficient than a home built to air rates for these systems are only 0.33 ing season. just meet the year 2000 International ACH, sometimes much less. Modern Security. Systems that rely on Energy Conservation Code for residential evaporative coolers literally wash and backdraft dampers (up ducts and structures will save 3,600 kWh per filter incoming air, leaving it substantially related devices) to control the flow year by using an efficient evaporative free of pollen, dust, and most pollutants. of evaporatively cooled air allow the cooler rather than a 13-SEER central Typically, they provide fresh air at rates windows in a home to be closed air conditioning system. Those who live of 2–3 ACH. and locked. in less efficient or larger homes save Water. Evaporative coolers use Controls. Systems that make use of much more. water, but well-designed modern coolers dampers that open when the home is

28 www.homeenergy.org SEPTEMBER/OCTOBER 2004 • HOME ENERGY HVAC

Table 2. Water and Energy Use in the Southwest DX Annual Cooling Cooling Source Evaporative Water Evaporative Net Increase HH Energy Energy Energy Water Source Saved at Site Evaporative Water Use DX Evaporative Saved Use Water Source Water Water Due to Evap City (kWh/yr) (kWh/yr) (kWh/yr) (Gal) Use (Gal) (Gal) Use (Gal) Use (Gal) Cool (%) Albuquerque 2,487 334 2,153 1,244 167 1,077 3,470 2,394 2.6 Cheyenne 1,773 287 1.485 1,886 144 1,743 2,435 1,692 1.4 Denver 1,935 279 1,656 1,968 140 1,828 2,685 1,857 1.7 Las Vegas 4,722 497 4,225 2,361 249 2,112 6,696 4,583 2.6 Phoenix 6,043 574 5,469 3,022 287 2,735 8,619 5,884 5.1 Salt Lake City 2,839 357 2,483 1,420 178 1,241 3,981 2,739 2.1 SW average 4,063 438 3,625 2,032 219 1,813 5,754 3,941 3.3

end user of using either a DX-based or an evaporative system to cool an 1,800 ft2 new home that slightly exceeds Energy Star standards in five Southwestern cities.When local water rates are higher with increased consumption, the computations shown assume the higher marginal cost per gallon of water used. Water and electricity rates applicable to single- family residences in each city in 2003 were used to estimate costs. First costs of cooling equipment tend to be a function of their efficiency, whether the systems are conventional IETDIESERVICE DRIVE DIRECT or evaporative coolers. In the case of conventional A/C units, split systems have more than 3 times the market share of packaged systems. Average costs weighted for market share are $1,771 for A/C equipment and $3,265 This attic has an evaporative cooler (shown on p. 28) installed less than 1 ft from this fresh-air intake vent. Vents are closed during the heating season. An option under consideration is the addition of outside insulating shutters. for installed costs. Single-stage evaporative cooling sys- tems that have a saturation effectiveness the Southwest uses about 0.5 gallons Southwest use an average of 5,800 gal- of greater than 80% under all operating of water. lons of water per year at the site, rang- conditions, variable-speed (or at least I ran simulations to estimate the ing from 2,400 gallons in Cheyenne to two-speed) motors, and a sump dump energy and water used for cooling in six 8,600 gallons in Phoenix. For single- feature for effective cleaning with mini- cities in the Southwest (see Table 2). family households, this figure represents mal water use, cost from $600 to The homes modeled are efficient 1,800 an average of only 3.3% of annual $1,120, depending on saturation effec- ft2 structures whose overall energy use is water use. However, from the overall tiveness and blower horsepower. 48% lower than that of homes that just environmental point of view,which Blower horsepower is the principal fac- meet the requirements of the year 2000 takes into account water used at the tor that determines air flow rates. International Energy Conservation power station, net water use for evapo- Equipment for indirect/direct evapora- Code for the weather conditions associ- rative cooling averages 3,900 gallons of tive coolers whose saturation effective- ated with each city. I assumed that the water per year, ranging from 1,700 ness is in the 105%–110% range cost DX systems have an energy efficiency gallons in Cheyenne to 5,900 gallons from $1,700 to slightly less than $3,000. rating (EER) of 11.1—roughly in Phoenix. Installation costs are lower than they are corresponding to a seasonal energy effi- Most important by far is the savings for central A/C systems, largely because ciency rating (SEER) of 12.9—and a in electricity use—and cost to the con- ductwork is substantially simplified. thermostat setpoint of 76°F. sumer—achieved by using evaporative Installations on a concrete pad next to a According to this analysis, modern instead of DX-based cooling (see Table home cost from $600 to $1,000, while residential evaporative coolers in the 3). I compared the annual cost to the attic installations run from $800 to

HOME ENERGY • SEPTEMBER/OCTOBER 2004 www.homeenergy.org 29 HVAC

$1,400, depending on the number of Table 3. Cooling Cost Comparisons upducts that must be installed, and on such factors as access to plumbing Cooling Cooling Cooling Total Net and electricity. Energy Energy Energy Evap Evap Savings Considering these cost ranges, the DX Evap Saved Evap vs total installed cost for an efficient Cost Cost with Evap Cost Cost DX City ($/Yr) ($/Yr) ($/Yr) ($/Yr) ($/Yr) ($/Yr) single-stage evaporative cooling system is typically between $1,600 and $2,200. Albuquerque 214 29 185 15 33 181 The total installed cost for an efficient Cheyenne 151 24 126 16 30 121 indirect/direct evaporative cooler is on Denver 141 20 121 15 25 116 the order of $2,500 to $3,500. In gen- Las Vegas 444 47 397 13 60 384 eral, installed costs for efficient evapora- Phoenix 502 48 454 20 68 434 tive equipment are lower than installed Salt Lake City 185 23 161 15 28 157 costs for comparable compressor-based SW average 335 36 299 12 48 287 central cooling systems. Lifetime (20- year) costs—including first costs, main- tenance costs, and energy costs over 20 attic, and then through attic vents to the optimized to ensure good distribution years—are on the order of $5,500 in outdoors. SCE requires a variable-speed of cooling air. Further, controls need to the Southwest. For a comparable com- fan and a dedicated thermostat remote be developed that not only vary fan pressor-based cooling system, lifetime from the cooler. Both utilities offer an speeds and control water-cleaning costs would be roughly double, additional rebate of $100 for the instal- cycles, but also monitor efficiency per- depending on the local climate. lation of up ducts in the attic. formance to signal the need for main- In Colorado, Utah Power and Xcel tenance. Finally,there is room for Utility Incentive Programs Energy are expanding their programs improvement in the heat exchanger that support evaporative cooling instal- technology used in indirect cooling Meeting demand for electric power lations. Both utilities are experimenting systems. Several companies are working during peak periods in the summer is a with ways to steer consumers toward to develop more efficient systems that major—and burgeoning—problem for buying highly efficient units while still require less pressure drop across most utilities in the fast-growing South- providing some incentives for lower-end indirect media while achieving more west. Indeed, peak demand is rising evaporative coolers. Other utilities in effective cooling. faster than total electricity sales the Southwest either have small-scale HE throughout the region. Most new programs in operation or are in the Larry Kinney is a senior researcher at the homes in the Southwest include air planning stages. Southwest Energy Efficiency Project conditioners whose demands are at least I am hopeful that these types of pro- (SWEEP). 3 kW—sometimes much more—and gram, as well as partnerships between existing housing is increasingly being programs like DOE’s Building America retrofitted with conventional air condi- and those conducted by local utility For more information: tioning. Given these considerations, a companies, will persuade production number of utility companies have initi- builders to construct model homes that “New Evaporative Cooling Systems: An ated demand-side management (DSM) illustrate the advantages of excellent Emerging Solution for Homes in Hot Dry programs that provide incentives to evaporative cooling.These examples Climates with Modest Cooling Loads” owners of both existing and new homes could help to establish the credibility of and “Evaporative Cooling Policy and to install energy-efficient evaporative modern evaporative cooler systems that Program Options: Promising Peak Shav- cooling equipment. are appropriately integrated into well- ing in a Growing Southwest” can be In California, both the Pacific Gas designed homes. downloaded at www.swenergy.org. and Electric Company (PG&E) and To bring the technology to full Torcellini, P.,N. Long, and R. Judkoff. Con- Southern California Edison (SCE) have fruition, designers and builders need to sumptive Water Use for Power programs that provide incentive think of evaporative cooler systems as Production. NREL/CP-550-35190. payments of $300 to $500 for the systems thoroughly integrated into Golden, Colorado: National Renewable purchase of energy-efficient evaporative energy-efficient structures. Techniques Energy Laboratory. November 2003. coolers. To qualify,units must have a for sealing them carefully and simply AdobeAir, Incorporated saturation efficiency of 85% or better; during shoulder and winter seasons, 550 S 15th St. must have sump water removal systems and to eliminate the risk of freezing, Phoenix, AZ 85034 (no water-wasting continuous bleeding need to be developed. Up ducts need Tel: (602)257-0060 systems); and must be configured to to be redesigned to be thoroughly Web site: www.adobeair.com automatically exhaust air through pres- insulated and positively sealed during sure relief dampers (up ducts) into the times when cooling is not needed, and

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