Cooling Tower Specifications

SERIES

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Subject Page

Intent ______________________________________________________________ 3Base ______________________________________________________________ 4Thermal Performance _________________________________________________ 5Performance Warranty ________________________________________________ 5Design Loading ______________________________________________________ 5Construction ________________________________________________________ 6Mechanical Equipment ________________________________________________ 7Fill, Louvers and Drift Eliminators ________________________________________ 8Hot Water Distribution System __________________________________________ 9Casing, Fan Deck and Fan Cylinder______________________________________ 9Access ___________________________________________________________ 10Cold Water Collection Basin ___________________________________________ 10

Control OptionsControl System __________________________________________________ 11Vibration Limit Switch _____________________________________________ 11Basin Heater ____________________________________________________ 12

Convenience and Safety OptionsHot Water Basin Access Platform ___________________________________ 13Ladder Extension ________________________________________________ 13Ladder Safety Cage ______________________________________________ 13Mechanical Equipment Access Platform ______________________________ 14

Miscellaneous OptionsFan Cylinder Extensions __________________________________________ 15Equalizer Flume Weir Gate ________________________________________ 15Marley Flow Control Valve _________________________________________ 15Low Noise Tower ________________________________________________ 16

Contents

Base

Options

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AV Series towers are galvanized steel, factory-assembled, general purpose crossflow

cooling towers, designed to serve normal airconditioning and refrigeration systems as well as lightindustrial loads. They evolve from a singleflowconcept of towers pioneered by Marley in the 1950's,and incorporate all of the design advancements thatour customers have found valuable. They representthe current state of the art in this cooling towercategory.

This booklet not only relates the language to use indescribing an appropriate AV Series cooling tower—but also defines why certain items and features areimportant enough to specify with the intention ofinsisting upon compliance by all bidders. The lefthand column of pages 4 thru 16 provides appropriatetext for the various specification paragraphs, whereasthe right hand column comments on the meaning ofthe subject matter and explains its value.

Pages 4 thru 10 indicate those paragraphs which willresult in the purchase of a basic cooling tower—onethat accomplishes the specified thermal performance,but which will lack many operation—andmaintenance-enhancing accessories and features thatare usually desired by those people who areresponsible for the continued and continuingoperation of the system of which the tower is part. Itwill also incorporate those standard materials whichtesting and experience has proven to provideacceptable longevity in normal operating conditions.

Pages 11 thru 16 provide paragraphs intended to addthose features, components, and materials that willcustomize the tower to meet the user's requirements.

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Specification Value

Marley AV Series Cooling TowerSpecifications

1.0 Base:

1.1 Provide an induced draft, crossflowtype, factory assembled, film fill, indus-trial duty, galvanized steel cooling towersituated as shown on the plans. The lim-iting overall dimensions of the tower shallbe _____ wide, _____ long, and _____high to the top of the fan guard. Totaloperating horsepower of all fans shall notexceed ____ hp, consisting of ___ @_____ hp motor(s). Tower shall be similarand equal in all respects to Marley Model_______.

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Your specification base establishes the type, configuration,base material, and physical limitations of the cooling tower to bequoted. During the planning and layout stages of your project,you will have focused your attention on a cooling tower selectionthat fits your space allotment, and whose power usage is accept-able. Limitations on physical size and total operating horsepoweravoid the introduction of unforeseen operational and site-relatedinfluences. Specifying the number of cells, and the maximum fanhp/cell will work to your advantage.

The benefit of crossflow towers is that they are inherently easyto operate, access, and maintain. Unlike counterflow towers, theyhave a spacious, full height plenum for easy access to all of thetower's internal components, and the water distribution system isreadily open to view and cleaning.

If your preference is for a stainless steel tower, or if your wateror air quality suggests that the use of stainless steel is prudent,change “galvanized steel” to “stainless steel” in paragraph 1.1.

Ladder and accessplatform are optionalaccessories. See Page13 for specificationwording.

The ladder can belocated on either end ofthe platform by simplefield rearrangement ofhandrails and posts.

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Marley AV Series Cooling TowerSpecifications Specification Value

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CTI Certification means that thetower has been tested under operat-ing conditions and found to performas rated by the manufacturer underthose circumstances. It assures thebuyer that the tower is not intention-ally or inadvertently undersized by the manufacturer.

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However, CTI certification alone is not sufficient to assure youthat the tower will perform satisfactorily in your situation.Certification is established under relatively controlled conditions,and towers seldom operate under such ideal circumstances. Theyare affected by nearby structures, machinery, enclosures, effluentfrom other towers, etc. Responsible and knowledgeable bidderswill take such site-specific effects into consideration in selectingthe tower—but the specifier must insist by the written specifica-tion that the designer/manufacturer guarantee this “real world”performance. Any reluctance on the part of the bidder shouldcause you some concern.

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The design wind and seismic loads at the left are the minimumallowables for any model in the line under accepted designstandards. Some models can withstand greater loads as listedbelow:

Model Wind SeismicAV61 and AV62 30 psf (1436 Pa) .7gAV63 thru AV65 20 psf (957 Pa) .3gAV66 and AV67 20 psf (957 Pa) .46g

If your applicaton requires higher loads, consult your Marleysales representative. These standards give you assurance that thetower can be shipped, handled, hoisted and ultimately operatedin a normal cooling tower environment.

2.0 Thermal Performance:

2.1 The tower shall be capable of cooling_____ GPM (L/s) of water from ____°F(°C) to _____ °F(°C) at a design enter-ing air wet-bulb temperature of _____°F(°C), and its thermal rating shall beCertified by the Cooling Tower Institute.

3.0 Performance Warranty:

3.1 CTI Certification notwithstanding, thecooling tower manufacturer shall guaran-tee that the tower supplied will meet thespecified performance conditions whenthe tower is installed according to Plans.If, because of a suspected thermal perfor-mance deficiency, the Owner chooses toconduct an on-site thermal performancetest under the supervision of a qualified,disinterested third party in accordancewith CTI or ASME standards during thefirst year of operation; and if the tower failsto perform within the limits of test toler-ance; then the cooling tower manufac-turer will pay for the cost of the test and willmake such corrections as are appropriateand agreeable to the Owner to compen-sate for the performance deficiency.

4.0 Design Loading:

4.1 The tower structure and anchorageshall be designed to withstand a windload of 20 psf (957 Pa), as well as .3gseismic load while operating. The towershall be designed to withstand shippingand hoisting loads of 2g horizontal and 3gvertical. Handrails, where specified, shallbe capable of withstanding a 200 lb. (890N) concentrated live load in any direction,and shall be designed in accordance withOSHA guidelines. Fork lift slots shall beprovided in the basin side supports toallow handling of the tower at grade level.

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Specification Value

Marley AV Series Cooling TowerSpecifications

5.0 Construction:

5.1 Except where otherwise specified, allcomponents of the cooling tower shall befabricated of heavy-gauge steel, protectedagainst corrosion by G-235 galvanizing.The tower shall be capable of withstand-ing water having a pH of 6.5 to 8.0; achloride content (NaCl) up to 500 ppm; asulfate content (SO4 ) up to 250 ppm; acalcium content (CaCO3 ) up to 500 ppm;silica (SiO2 ) up to 150 ppm; and designhot water temperatures up to 125°F(51.7°C). The circulating water shall con-tain no oil, grease, fatty acids, or organicsolvents.

5.2 The specifications, as written, are in-tended to indicate those materials thatwill be capable of withstanding the abovewater quality in continuing service, aswell as the loads described in paragraph4.1. They are to be regarded as minimumrequirements. Where component materi-als peculiar to individual tower designsare not specified, the manufacturers shalltake the above water quality and loadcarrying capabilities into account in theselection of their materials of manufac-ture.

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In the history of cooling towers, no other coating for carbonsteel has exhibited the success and longevity of galvanization inexposure to the normal cooling tower water quality defined atleft. No paints or electrostatically applied coatings, howeverexotic they may be, can approach galvanization's history ofsuccess.

Except for those unusual operating situations where thecirculating water may be so laden with suspended solids, algae,fatty acids, product fibers, active organisms reflected in BOD, andthe like that plugging of the fill is a probability, reasonableattention to the construction materials and/or their coatings is allthat is normally required.

If your preference is for a stainless steel tower, or if your wateror air quality suggests that the use of stainless steel is prudent,change “heavy gauge steel, protected against corrosion by G-235galvanizing” to “heavy gauge stainless steel” in paragraph 5.1.

Factory Assembly

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Specification Value

Marley AV Series Cooling TowerSpecifications

6.0 Mechanical Equipment:

6.1 Fan(s) shall be propeller type, incorpo-rating heavy duty aluminum alloy bladesand electrogalvanized hubs. Blades shallbe attached to hubs with stainless steelhardware, and shall be individually ad-justable. Fan(s) shall be driven throughan industrial grade system of V-belts,pulleys, and tapered roller bearings. Bear-ings shall be rated at 50,000 hours, orgreater.

6.2 Motor(s) shall be ____ hp maximum,Totally Enclosed, 1.15 service factor, vari-able torque, and specially insulated forcooling tower duty. Speed and electricalcharacteristics shall be ______ RPM,single-winding, ___ phase, ____ hertz,____ volts.

6.3 The fan and fan drive assembly foreach cell shall be supported by a rigid,welded, hot dip galvanized steel struc-tural support that resists misalignment.The mechanical equipment assembly shallbe warranted against any failure causedby defects in materials and workmanshipfor no less than five (5) years following thedate of tower shipment. This warranty islimited to the fan, fan shaft, bearings, andmechanical equipment support. The mo-tor, motor components, sheaves andbelt(s) are warranted by their manufac-turer.

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Propeller-type fans require only half the operating hp ofblower-type fans. However, they should be readily adjustable topermit compensation for jobsite conditions that may tend tooverload the motor. The fans of one manufacturer require thepurchase of special positioners for each increment of fan bladepitch.

Unless otherwise specified, motor speed will be 1800 RPM in60 Hertz areas and 1500 RPM in 50 Hertz areas. If you prefer theoperating flexibility of two-speed operation, please specify theRPM to be 1800/900 (1500/750 in 50 Hertz regions). Incidentally,two speed motors are a far better choice than separate “pony”motors which simply double the problems indicated above.

If your preference is for a stainless steel tower, or if your wateror air quality suggests that the use of stainless steel is prudent,change “hot dip galvanized steel” to “stainless steel” in para-graph 6.3.

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Specification Value

Marley AV Series Cooling TowerSpecifications

7.0 Fill, Louvers and Drift Eliminators:

7.1 Fill shall be film-type, thermoformed of15 mil (0.38 mm) thick PVC, with louversformed as part of each fill sheet. Fill shallbe suspended from hot-dip galvanizedstructural tubing supported from the towerstructure, and shall be elevated abovethe floor of the cold water basin to facili-tate cleaning. The air inlet face of thetower shall be free of water splash-out.

7.2 Drift eliminators shall be PVC, triple-pass, and shall limit drift losses to nomore than 0.005% of the design GPMflow rate.

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Louvers integral with the fill keep the flowing water within theconfines of the fill. The separate external louvers used by otherspermit water to escape the fill and form ice or produce an un-sightly situation adjacent to the tower. If you plan to use yourtower in the wintertime, particularly for free cooling, integrallouvers will put your operating concerns to rest.

Drift rate varies with designwater loading and air rate, as wellas drift eliminator depth andnumber of directional changes. Theindicated rate of 0.005% is easilyachievable without premium cost.If a lower rate is required, pleasediscuss with your Marley office orrepresentative.

Louvers

Drift Eliminators

Fill sheets

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Specification ValueSpecifications

8.0 Hot Water Distribution System:

8.1 An open basin above the bank of fillshall receive hot water piped to each cellof the tower. These distribution basinsshall be installed and sealed at the fac-tory, and shall be equipped with remov-able, galvanized steel covers to keep outleaves and debris, and to retard the growthof algae.

8.2 Each basin shall include an inlet holeand bolt circle to accept a 125# flangeconnection per ANSI B16.1. Removable,interchangeable polypropylene nozzlesinstalled in the floor of these basins shallprovide full coverage of the fill by gravityflow.

9.0 Casing, Fan Deck, andFan Cylinder:

9.1 The casing and fan deck shall be heavy-gauge galvanized steel, and shall be ca-pable of withstanding the loads describedin paragraph 4.1. The fan cylinder shall bemolded FRP, and shall be through-boltedto the fan deck to provide a consistentlystable operating shroud for the fan. Thetop of the fan cylinder shall be equippedwith a conical, non-sagging, removablefan guard, fabricated of welded 5/16"and 7 gauge rods, and hot-dip galvanizedafter fabrication.

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Gravity-flow distribution basins are a feature of crossflow typetowers, resulting in operating pump heads of from 10 to 20 feetless than that encountered in counterflow towers with pressur-ized spray systems. Also, these basins are out where they can beeasily inspected—even maintained—while the tower is in opera-tion. Spray systems of counterflow towers, sandwiched betweenthe top of the fill and the drift eliminators, are extremely awk-ward to access and maintain.

If your preference is for a stainless steel tower, or if your wateror air quality suggests that the use of stainless steel is prudent,change “galvanized steel” to “stainless steel” in paragraph 8.1.

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If your preference is for a stainless steel tower, or if your wateror air quality suggests that the use of stainless steel is prudent,change “galvanized steel” to “stainless steel” in the first sentenceof paragraph 9.1. The heavy gauge fan guard remains galvanizedsteel.

Marley AV Series Cooling Tower

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Specifications Specification Value

10.0 Access:

10.1 Large galvanized steel access doors30" (762 mm) wide and a minimum of 42"(1067 mm) high shall be located in bothendwalls for entry into the cold waterbasin and fan plenum area. Access doorsshall be operable from inside as well asoutside the tower.

11.0 Cold Water Collection Basin:

11.1 The cold water basin shall be heavy-gauge galvanized steel, and shall includethe number and type of suction connec-tions required to accommodate the out-flow piping system shown on the Plans.Suction connections shall be equippedwith galvanized debris screens. A fac-tory-installed, float-operated, mechanicalmakeup valve shall be included. A 3"(76.2 mm) diameter drain and a 4" (101.7mm) diameter overflow shall be providedin each cell of the tower. The basin shallinclude a depressed section into whichaccumulated silt can be flushed to permitcleaning. The basin floor adjacent to thedepressed section shall slope toward thedepressed section to prevent buildup ofsilt under the fill area. Towers of morethan one cell shall include flumes for flowand equalization between cells.

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The access doors on competitive towersmay be 18″ (457 mm) wide or smaller, whichis unreasonably small for a human being.Specifying the size of the door will causethose bidders to take exception, alerting youto a potential maintenance headache. Twodoors are standard on all towers so thataccess between cells of multicell towers isassured.

If your preference is for a stainless steeltower, or if your water or air quality sug-gests that the use of stainless steel is prudent, change “galvanizedsteel” to “stainless steel” in paragraph 10.1.

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Marley offers your choice of side suctions and bottom outletsto accommodate a significant variety of piping schemes. Unlessso specified, the tower you may be asked to approve may only beavailable with one type of suction connection, requiring you toredesign your piping layout.

If your preference is for a stainless steel tower, or if your wateror air quality suggests that the use of stainless steel is prudent,change “galvanized” to “stainless” in paragraph 11.1.

Marley AV Series Cooling Tower

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Specification Value

OptionsSpecifications

Control Options

Control System:

Para. 6.4: Add the following paragraph inthe Mechanical Equipment section:Each cell of the cooling tower shall beequipped with a UL listed control systemin a NEMA 3R or 4X outdoor enclosurecapable of controlling single-speed or two-speed motors as required, and designedspecifically for cooling tower applications.The panel shall include a main fuseddisconnect with an external operatinghandle, lockable in the off position forsafety. Across-the-line magnetic startersor solid state soft-start starters as re-quired shall be controlled with a thermo-static or solid state temperature control-ler. Door mounted selector switches shallbe provided to enable automatic or manualcontrol and wired for 120VAC control.Control circuit to be wired out to terminalblocks for field connection to a remotevibration switch and for access to extra120VAC 50VA control power, overloadtrip alarms and remote temperature con-trol devices. The temperature controllershall be adjustable for the required coldwater temperature. If a thermostatic con-troller is used it shall be mounted on theside of the tower with the temperaturesensing bulb installed in the cold waterbasin using a suspension mountingbracket. If a solid state temperature con-troller is used the controller will be doormounted on the control panel. The tem-perature controller will display two tem-peratures, one for outgoing water and theother for set point. Water temperatureinput shall be obtained using a three-wireRTD with dry well in the outlet water pipingand wired back to the solid state tempera-ture controller in the control panel.

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If it is your opinion that the control system for the coolingtower should be part of the tower manufacturer’s responsibility,we are in wholehearted agreement with you. Who better todetermine the most efficient mode and manner of a tower’soperation—and to apply a system most compatible with it—thanthe designer and manufacturer of the cooling tower?

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Specification Value

OptionsSpecifications

Vibration Limit Switch:

Para. 6.5: Add the following paragraph inthe Mechanical Equipment section: Asingle-pole, double-throw vibration limitswitch in a NEMA 4 housing shall beinstalled on the mechanical equipmentsupport for wiring into the owner’s controlpanel. The purpose of this switch will be tointerrupt power to the motor in the eventof excessive vibration. It shall be adjust-able for sensitivity, and shall requiremanual reset.

Control Options

Basin Heaters:

Para. 11.2: Add the following paragraphin the Cold Water Basin section: Pro-vide a system of electric immersion heattoprevent freezing of water in the collectionbasin during periods of shutdown. Thesystem shall consist of one or more stain-less steel electric immersion heaters in-stalled in threaded couplings provided inthe side of the basin. A NEMA 4 enclosureshall house a magnetic contactor to ener-gize heaters; a transformer to provide 24volt control circuit power; and a solid statecircuit board for temperature and low watercutoff. A control probe shall be located inthe basin to monitor water level and tem-perature. The system shall be capable ofmaintaining 40°F (4.4°C) water tempera-ture at an ambient air temperature of __°F (__ °C).

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Unless specified otherwise, a Metrixswitch will be provided. A double-pole,double-throw model is also available. Ifpurchased in conjunction with theControl System, it is also factory-wired.The requirement for manual resetassures that the tower will be visited todetermine the cause of excess vibration.

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The basin heater components described at left representMarley's recommendation for a reliable automatic system for theprevention of basin freezing. They are normally shipped sepa-rately for installation at the jobsite by the installing contractor.When purchased in conjunction with the enhanced ControlSystem option, however, they are customarily factory-mountedand tested.

Submerged in basin water, in which zinc ions are present,copper immersion heaters must not be used. Insist upon stainlesssteel.

The ambient air temperature that you fill in should be thelowest 1% level of winter temperature prevalent at site.

Ask for appropriate Marley drawing.

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OptionsSpecifications Specification Value

Convenience and Safety Options

Hot Water Basin Access Platform:

Para. 10.2: Add the following paragraphin the Access section: Provide an exter-nal platform near the top of the louver facefor access to the hot water distributionsystem. The platform shall be galvanizedsteel bar grating, supported by galva-nized steel framework attached to thetower. The platform shall be surroundedby a handrail, kneerail, and toeboard. Apermanently attached 1'-6" (457.2 mm)wide aluminum ladder with 3" (76.2 mm) I-beam side rails and 1.25" (31.8 mm) di-ameter serrated rungs shall extend fromthe base of the tower to the top of thehandrail.

Ladder Extension:

Para. 10.2: Add the following to the end ofthe Hot Water Basin Access Platformparagraph: Provide a ladder extensionfor connection to the foot of the externalladder. This extension shall be longenough to rise from the roof (grade) level.The installing contractor shall be respon-sible for cutting the ladder to length; at-taching it to the foot of the tower ladder;and anchoring it at its base.

Ladder Safety Cage:

Para. 10.2: Add the following to the end ofthe Hot Water Basin Access Platformparagraph: A heavy gauge galvanizedsteel safety cage shall surround the lad-der, extending from a point 7'-0" (2134mm) to 8'-0" (2439mm) above the foot ofthe ladder to the top of the distributionbasin access platform handrail.

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Periodic inspection and maintenance of acooling tower distribution system is fundamen-tal to preserving maximum cooling systemefficiency. All cooling towers—crossflowor counterflow—are subject to clogging tovarying degrees by waterborne contami-nants such as pipe scale and sediment.Therefore, safe and easy access to these compo-nents is of significant value to the operator.

Access can be provided in a number of ways, includingportable ladders or scaffolding, but for maximum safety andconvenience, Marley offers a factory installed access platformwith guardrails to make this task as safe and user-friendly aspossible. Further, its location on the side of the tower does notadd to the height of the unit, preserving architectural integrity.See graphic, Page 4. It also saves the owner time and money, inthat maintenance personnel may devote their time to inspectionrather than searching for ladders or erection of portable scaffold-ing.

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Many towers are installed such that the base of the tower is2′-0″ (609.6 mm) or more above the roof or grade level. Thismakes it difficult to get up to the foot of the attached ladder. Theladder extension alleviates this problem. Marley ladder exten-sions are available in standard 5′-0″ (1.524 m) and 11'-0" (3.353 m)lengths.

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To meet OSHA guidelines, towers whose distribution basinaccess platforms are 20′-0″ (6.096 m) or more above roof or grade,and which are equipped with external ladders, should havesafety cages surrounding the ladders.

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Specification Value

OptionsSpecifications

Mechanical Equipment AccessPlatform:

available only on AV63000 modelsand larger

Para. 10.3: Add the following paragraphin the Access section: Provide an inter-nal platform approximately 7' (2134 mm)below the level of the fan for access to themechanical equipment. The platform shallbe galvanized steel bar grating, supportedby galvanized steel framework attachedto the tower. The platform shall be sur-rounded by a handrail and kneerail. Apermanently attached 1'-6" (457.2 mm)wide aluminum ladder with 3" (76.2 mm)I-beam side rails and 1.25" (31.8 mm)diameter serrated rungs shall extend fromthe cold water basin to the top of thehandrail.

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Periodic inspection and maintenance of cooling tower fans,motors and other rotating equipment is fundamental to preserv-ing maximum cooling system efficiency. All mechanical draftcooling towers—forced or induced draft—are subject to vibrationand wear. Therefore, safe and easy access to these components forinspection and maintenance is of significant value to the operator.

Access can be provided in a number of ways, includingportable ladders or scaffolding, but for maximum safety andconvenience, Marley offers a factory installed access platformwith guardrails to make this task as safe and user-friendly aspossible. See graphic below. It also saves the owner time andmoney, in that maintenance personnel may devote their time toinspection rather than searching for ladders or erection of por-table scaffolding.

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Extensions are available in 11 ³⁄₄″ (298.5 mm) increments to amaximum extension height of 6′-10 ¹⁄₄″. Such extensions may beconsidered necessary in order to elevate the discharge beyond thebounds of an enclosure. Discuss applicability with your localMarley sales representative.

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Where it is your intention to be able to operate other cells ofthe tower while the flume cover plate is installed, separate outletconnections, float valves, and overflows must be provided foreach cell. Likewise, this would require separate sensors andcontrols for basin heater systems, if installed.

Specification Value

OptionsSpecifications

Miscellaneous Options

Fan Cylinder Extensions:

Para. 9.1: Insert the following after thefirst sentence: Fan cylinder extensionsshall be provided to elevate the fan dis-charge to a height of ___ ft. (___ m) abovethe top of the standard fan cylinder.

Equalizer Flume Weir Gates:

Para. 11.2: Add the following paragraphunder Cold Water Collection Basin:The interconnecting flume between cellsshall be equipped with a removable coverplate to permit the shutdown of one cellfor maintenance purposes, or to permitindependent cell operation.

Marley Flow Control Valve:

Para. 8.3: Add the following paragraphunder Hot Water Distribution System:A heavy-duty, industrial grade flow-con-trol valve shall be provided at the inlet tothe hot water basin. The valve shall per-mit both flow balancing on multicell tow-ers and temporary shut-off for mainte-nance of selected cells. Valve shall havea machined cast iron body, with stainlesssteel operating stem, and heavy-duty lock-ing handle.

Specification Value

OptionsSpecifications

Low Noise Tower:

Para. 1.2: Add the following paragraphunder Base: The cooling tower shall bequiet operating, and shall produce anoverall level of sound no higher than ____dBA, measured at the critical locationindicated on the Plans.

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Sound produced by a AV Series tower operating in an unob-structed environment will meet all but the most restrictive noiselimitations—and will react favorably to natural attenuation.Where the tower has been sized to operate within an enclosure,the enclosure itself will have a damping effect on sound. Soundalso declines with distance—by about 5 or 6 dBA each time thedistance doubles. Where noise at a critical point is likely to exceedan acceptable limit, you have several options—listed below inascending order of cost impact:

• Where only a slight reduction in noise will satisfy—and thesource of concern is in a particular direction—merely turningthe tower may be the answer. Less sound emanates from thecased face of the tower than does from the air intake face.

• In many cases, noise concerns are limited to nighttime, whenambient noise levels are lower and neighbors are trying tosleep. You can usually resolve these situations by using two-speed motors in 1800/900 configuration; and operating thefans at half-speed without cycling “after hours”. (The naturalnighttime reduction in wet-bulb temperature makes this a veryfeasible solution in most areas of the world, but the need toavoid cycling may cause the cold water temperature to varysignificantly.)

• Where noise is a concern at all times (for example, near ahospital), the best solution is to oversize the tower so it canoperate continuously at half (900 RPM) motor speed even atthe highest design wet-bulb temperature. A typical soundreduction is 10 dBA at 1/2 fan speed, but larger reductions areoften possible.

• Extreme cases may require special fans or inlet and dischargesound attenuator sections; however, the static pressure lossimposed by attenuators may necessitate an increase in towersize. This is the least desirable approach because of the signifi-cant cost impact—and because of the obstruction to normalmaintenance procedures.

Your Marley office or representative can help you meet yoursound requirements.

SPEC AV-03

7401 W 129 Street • Overland Park, KS 66213 • 800 462 7539www.marleyct.com • email: info@marleyct.spx.comIn the interest of technological progress, all products aresubject to design and/or material change without notice.©2003 Marley Cooling Technologies, Inc Printed in USA