The High-Head PerformanceSolution

MaxE™ CYK CENTRIFUGaL CHILLERS

Handling applications whenthepressure ison

Performancewherestandardchillerscan’tcompete TheMaxE™CYKcentrifugalchillerincorporatesadesign usingtwocentrifugalcompressorsarrangedinseriesto

handle air-cooled, brine-chilling, and heat-pump applications at conditions outside the range of typical centrifugal chillers.

Theseunitsusethesametechnologyemployedintherenowned lineofMaxEsingle-stagecentrifugalchillers.UsingHFC-134a, MaxECYKchillersareavailableinawiderangeofcapacities:

•    For air-cooled applications (air-cooled radiators): 700 to 2,300TRat44°FLWT(2,500to8,100kWRat7°CLWT)

•    Forbrinechilling:700to1,600TRat20°FLBT(2,500to 5,600kWR at-7°CLBT)

•    Forheatpumpapplications:11,000to38,000MBHat155°F (maximumoutputtemperature)3,200to11,000kWRat68°C (maximum  outputtemperature)

Leaving chilled and condenser water temperatures— compound chillers operate beyond the range of standard  chillers.

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The combination of standard components and unique performancecharacteristicsmakeMaxECYKchillersthe

technologyofchoiceforjobswherestandardchillerdesigns can’t compete. Compound-system technology provides energyandperformanceadvantagesforutilities,institutions, and commercialfacilities.

Understanding  high-head  applications

Certainjob-siteconditionsrequirechillerstooperatebeyond thelimitsfoundintypicalair-conditioningapplications.These extreme conditions are characterized by leaving chilled fluid temperatures below 36°F (2°C), leaving condensing fluid temperaturesabove105°F(41°C),oracombinationofboth.

When the leaving chilled fluid or leaving condenser fluid temperature exceeds standard limits, the lift on the compressor increases dramatically. The compressor must develophigherdifferentialpressureontherefrigerantgasin thecompressionphase,whichresultsinhigherheadpressure.

High-headconditionsarefoundinthreetypical coolingapplications:

1)   Air-cooledradiatorsforwaterchillinginlocationsthat lackwaterforcondensing.

2)   Brinechillingforice-thermal-storageapplicationsand forlightindustrial-refrigerationjobs.

3)   Heat pumps for producing hot waterwith simultaneouschilling.

Highcompressorheadinbrineapplicationsisduetolower evaporator temperature and pressure conditions. In heat- pumpandair-cooled-radiatorprojects,it’sduetoveryhigh condenserrefrigeranttemperatureandpressureconditions.

The chiller designed for high-head conditions

Typicalair-conditioningchillersaredesignedwithinthelimits of the available compression ratio of the compressor. These limits are quickly exceeded by the unique differential pressures encountered in high-headapplications.

The MaxE CYK chiller overcomes these compressor-design challengesbyusingtheprincipleofcompounding.Acompound design arranges two individual compressors in series. By flowing therefrigerantgasthroughtwocompressors,thepressureratio becomesthesumofthetwoindividualcentrifugalcompression ratios.Theresultisamuchhighertotalliftpressureavailable to the system, which is able to handle the high head demandedbyextremeconditions.

Benefits of compressor compounding

Standard components: Each MaxE CYK chiller employs common partsinsteadofa one-of-a-kinddesign.The compressors and heat exchangers use standard technology proven in the successful MaxE packaged chiller line. Each compressorisdrivenbyastandard,open-drive,electricmotor.

Compactfootprint:Compressorsandmotorsaremountedabove theshellstoassurethesmallestfootprintforthistypeofchiller.

Greater adaptability: With the MaxE CYK chiller, the impeller diameter, width and speed can be optimized for each stage of compression based on operating conditions.

The principal of compounding— two compressors operate in series with a common refrigerant  circuit.

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Superior part-load performance: Using a compound arrangement allows the use of pre-rotation-vane (PRV) capacity control for the centrifugal impellers of both compressors.

Pre-rotationvanesactlikeathrottleonthesuctionsideofthe compressortocontrolcompressorload.WithPRVcontrolon bothcompressors,theresultisbetteroff-designperformance than for typical multistagecompressors.

Handles varying condensing conditions: Since chillers spend mostoftheirtimeoperatingatoff-designconditions,off-design performanceisamajorfactorintheenergy-savingequation. A compound chiller can operate with a wider range of condensing-water temperatures than typical chillers. The MaxE CYK chiller unit allows one compressor to be shut off, sothechillercanrunonjustonecompressorduringlow-head conditions.Thispracticenotonlyensuressystemstability,it allowsthechillertorunmoreefficientlyandtakesadvantage ofcooling-watertemperatureswellbelowdesign.

Lowerinrushcurrent:Insteadofstartingasingle,largemotor, the MaxE CYK chiller stagger-starts the motors in sequence. Consequently,peakinrushcurrentisreducedtoabout58% comparedtostartingamotorforasingle,largecompressor.

Lowersoundlevels:Acoustically,withcompoundcompressors sharingtheworkload,compressorRPMsarelowerthanin standard centrifugal designs — and lower RPMs help lower soundlevels.

Economizer option: An optional economizer is available to further improve cycle efficiency for lower energy consumption.

Built-in reliability

An on-boardcontrol panelsimplifies operationbymanaging thestaggered-startsequenceofthecompressors.Thecolored graphical operator interface clearly displays operating parameters, setpoints and alarms for quickresponse.

MaxE CYK chillers operate with environmentally responsible HFC-134a refrigerant with zero ozone-depletion potential, which eliminates chiller downtime for retrofit or replacement.

Tofurtherassurereliableperformance,eachMaxEchiller isassembledatthefactory.Asanoption,theunitcanbe run-testedatdesignconditionspriortoshipment.

For more information on innovative products designed specificallyforapplicationsthatarebeyondtheoperating parametersofstandardchillers,contactyourlocalJohnson Controlsrepresentative.

PRVs on each impeller provide better off-design  performance.

Inrush reduction— sequenced starting of two smaller motors reduces inrush.