Chiller Selection Made Easier with myPLV™

8/18/2019 Chiller Selection Made Easier with myPLV™

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2 Trane Engineers Newsletter volume 44–4 providing insights for today’s HVAC system designer

myPLV Overview

The intent of the myPLV program is toprovide HVAC system designers with aneasy-to-use, spreadsheet-drivenapplication to accurately analyze chillerperformance to determine the bestreturn on investment.

The key to the tool’s simplicity is that ituses bin energy analysis. The key to thetool’s accuracy is that it creates binconditions that are customized to theactual operation of the building and

chiller, specifically, operating temperatures and time in each bin.

The myPLV tool provides no advantageto any one chiller type or manufacturer.It simply provides a bin analysis for theload profile and chiller performanceentered by the program user.

Calculations use the specific chillerperformance data provided by theindividual manufacturers. It assumesthe user will request and themanufacturers will provide accurateand verifiable chiller performance dataat each user-specified chiller load point

and associated condenser watertemperature. Figure 1 illustrates theflow of the myPLV analysis method.

The goal of the myPLV tool is toevaluate chiller energy (assumingproper plant operation) based onperformance in a specific building typeand climate zone. The tool does notaccount for pump or fan energy.

User input(SI or IP units)

Program computation myPLV output

Building:

• location

• type

• peak cooling load

Plant

• number and size of chillers

• tower cell design performance(assuming one tower cell perchiller)

• the cooling tower controlmethod

• maps the location to a weather zone

• selects the PNNL building load data

• scales its 8,760 load data to the peak cooling loadspecified

• saves the weather and plant load data

• determines how many chillers and tower cells areneeded to satisfy each plant load point (hour)

• applies the tower cell performance and tower controlagainst the outdoor load and wet-bulb temperature

• stores the 8,760 leaving tower water temperature(entering condenser) along with the individual chiller loadresults

• creates the Plant Loading chart shown

• segments the chiller loads into four operating zones(bins) based on 8,760 load points

• computes a weighted entering condenser watertemperature and a fractional weighting for each bin

• records the maximum load for each month for electricaldemand computations

• Creates the Chiller Loading chart andPeak and Bin Loading tables

Plant loading chart(viewable in the myPLV Charts tab)

Chiller loading chart(viewable in myPLV Charts tab)

High level data is copied to themyPLV Bid Form tab

User saves the file. (Files can be saved separately foranalysis of alternative chillerselections.)

Peak and Bin Loading tables

scaled building load scatter plot(not viewable—displayed here to illustrate initial

data set for plant and chiller load profiles)

Figure 1. Graphical depiction of the calculation process

Every AHRI certified chillermanufacturer must have the ability toprovide any random operating pointduring certification so to provide theselected bin conditions is a reasonablerequest to any vendor.


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providing insights for today’s HVAC system designer Trane Engineers Newsletter volume 44–4 3

Building Load Profile. Establishing aload profile is often the most difficult partof an energy and economic analysis.Fortunately, ASHRAE and PacificNorthwest National Labs (PNNL) provide asolution. As a result of various ASHRAEstandards efforts, PNNL has created a

library of annualized load profiles (8,760hours of data) for various building types inall weather zones of interest. The myPLVtool incorporates 200 of these loadprofiles within its database. Each of thebuilding types listed in Table 1 has beensimulated within 20 climatic zonesincluded in the myPLV database (Table 2)resulting in the 200 pre-defined data sets.

Users simply select location informationand building type and enter a peaktonnage for their particular building. Theprogram scales the PNNL load profile to

the peak cooling tons entered. Theresulting load profile can be viewed oncharts generated by the tool.

Most of the building types listed in Table 1have profiles both with and without anairside economizer. Those profilesrepresenting systems without an airsideeconomizer will contain loads duringcooler outside conditions. Load profilesincorporating an airside economizer willeliminate most low temperature loadssince the economizer will satisfy theneeded cooling. For those chilled-water

systems that incorporate watersideeconomizing (free cooling), users maywish to select load profiles with an airsideeconomizer since the chillers will not beoperating to satisfy loads during thecooler weather conditions.

A custom load profile can be entered forchiller plants with load profiles muchdifferent than the available buildings (i.e.,process loads or data centers). Customload profiles can be entered via theCustom Load Input worksheet. Usersmust enter 8,760 hours (one year) of data,

including chiller plant load (tons), as wellas the outdoor dry bulb and wet bulbtemperatures. The program calculates theappropriate chiller submittal points.

Local Weather. Having representativeweather data is key to overcoming theIPLV problem of oversimplified analysistechniques which assume the same chilleroperating conditions from Jeddah, SaudiArabia to Fairbanks, Alaska andeverywhere in between.

The myPLV tool uses the 8,760 hourweather data set (TMY) contained within

the PNNL load profile for a wide range ofweather zones. Users may either enter aglobal location that maps to a standardweather zone according to the datasetcontained in ASHRAE Standard 169, orenter the weather zone explicitly byselecting By Climate Zone in the Region dropdown. The selected weatherconditions (ambient wet bulb and dry bulb)for each operating hour of the year areused to establish the operating conditionsfor the cooling tower or air-cooledcondenser.

Chiller Plant Information. The numberof chillers in the system and the capacityof the chillers are needed for myPLV toassess the operating conditions and timefor the chiller-specific operating zones orbins.

The program assumes all chillers are equalcapacity. Entering this informationseparate from the building peak loadallows the program to account foroversizing of the plant capacity. Theprogram outputs the plant oversizing

factor per ASHRAE Standard 90.1,Appendix G for reference.

An undersized plant is flagged in redwith a negative oversize factor. In thiscase, the program will produce asolution; however, it will assumeadditional chillers are available beyondthat specified with the input set.

Cooling tower performance and controlimpact the operating conditions of thechiller for water-cooled plants. Usersenter design tower performance dataand selects a cooling tower controlmethod. Based on this information,myPLV calculates the enteringcondenser water temperature for eachhour of the load profile.

Chiller Performance. From theprevious input information, the myPLVdetermines the weighted averageoperating conditions for the chillers in

the plant for bins centered on the 25, 50,75 and 94 percent chiller load points.The program also requires the chiller’sfull load design performance to assessutility demand charges and to ensure anappropriate chiller is selected to satisfythe design requirements of the job.

While the use of 25, 50, and 75 percentload points is similar to IPLVmethodology, the ton-hour values andcondenser water temperatureweightings deviate from IPLV/NPLV toreflect the application. For the last bin,

Table 1. Building load types included in myPLV

Office (with, without econ) 12 hour operation; 5 days a week

Hospital (with, without econ) 24 hour operation; 7 days a week; heavier day occupancy

High rise apts (without econ) 24 hour operation; 7 days a week; lighter day occupancy

Primary school (with, without econ) 12 hour operation; 5 days a week; seasonal

Secondary school (with, without econ) 12 hour operation; 5 days a week; seasonalHotel (without econ) 24 hour operati on; 7 days a week

Table 2. Weather zones included in myPLV

Zone Very cold Humid (A) Dry (B) Marine (C)

0 x x

1 x x

2 x x

3 x x x

4 x x x

5 x x x

6 x x x

7 x

8 x

To access the Custom Load Input worksheet, check the box adjacent tothe Region input or choose the CustomLoad selection in the Region drop downlist on the myPLV Calculator tab.


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87.5 percent to 100 percent chillerloading is represented by a center-weighted point at 94 percent.This better captures the chillerperformance in this region and reduceserror.

Using the 94 percent point instead of100 results in a five-point rating systemwith the fifth point representing thedesign conditions for electricaldemand calculation. While not used forthe myPLV energy calculations, thisfifth point assures that the selectionprocess using myPLV will still result inan appropriate chiller for the load, liftand application duty required, andprovide certified performancenecessary for the system design.

This bin information, along withalternate pricing requested from thequalified chiller manufacturer can beinput to calculate the annual energyusage and investment payback for thevarious chiller alternatives—completelyimpartial in its analysis.

myPLV ExampleMyPLV is built as a Microsoft Excel ® workbook. The two worksheets thatrequire user input to perform the

calculations are the myPLV Calculator and myPLV Bid Form .

myPLV Calculator: Building andplant configuration. Figure 2 showsuser inputs in blue for the building andplant configuration in the myPLVCalculator worksheet. Inputs selectedfor this example include:

• Location: Memphis, Tennesse

• Building type: Office building withairside economizing (standardPNNL profile is used)

• Chiller type: Water-cooled

• Building peak load: 500 tons

• Number of chillers: 2

• Chiller size: 300-ton chillers

Next, the cooling tower design datais input (Figure 3). In this example, twocooling tower cells are selected at adesign wet bulb condition of 80ºF witha 5ºF tower approach.

The towers are operated at a fixedtower approach setpoint of 7ºF with aminimum water temperature of 55ºF.

The final step in this worksheet isgenerating the submittal points.Pressing the Calculate myPLV Conditions button (Figure 4)generates the submittal points for thefour load bins and the full load designoperating conditions shown (Table 3).

Table 3. Submittal points generated

load (%) tons ECWT (ºF)

25 75 64.3

50 150 77.5

75 225 80.1

94 282 79.4

100 300 85 (design)

The submittal points serve threepurposes:

• First, they are used along with thechillers’ performance at those pointsto determine the chiller’s myPLVrating number .

• Secondly, they are used in the myPLVBid Form to calculate the chillerenergy use and cost for a year and asimple payback period for investing inmore efficient chiller technology.

• Finally, they can be specified in thechiller guide specifications as thechiller factory test points to ensurethe customer receives the chillerperformance they purchased at themost important realistic operatingconditions.

Figure 2. myPLV user i nputs for building and plant configuration

Figure 4. Submittal point generation in myPLV

Figure 3. Cooling tower design inputs


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myPLV Bid Form worksheet: Alternatechiller performance and paybackanalysis. The myPLV programautomatically copies the building andplant setup and the weighted submittalpoints to the myPLV Bid Form worksheet. This worksheet allows usersto perform simple payback analysisbetween chillers with varying efficiency

and price.

Figure 5 displays the user-entered chillerdata (blue fields) used to compute thealternate chiller comparisonperformance metrics.

To perform a chiller comparison usersgather myPLV point performance andprice information for each chilleralternate as well as the local utility ratesfor the cost of energy consumption anddemand power (e.g., cost per kWh, costper kW demand, ratchet rate). For this

example, the needed chillerperformance data corresponds to chilleroperating points shown in Figure 5 (A).

An example comparison follows for fivedifferent compressor technology, water-cooled chillers:

• Fixed-speed screw compressor(Base Scrw FS)

• Variable-speed screw compressor(Scrw VS)

• Fixed-speed centrifugal compressor(Cent FS)

• Variable-speed centrifugalcompressor (Cent VS)

• Variable-speed high efficiencycentrifugal compressor (HiE CentVS)

The following electrical cost data isassumed; see Figure 5 (B):

• $0.12/kWh

• $10/kW demand

• 75 percent ratchet

The performance data for the fivechillers is entered into the Water CooledChiller Selection table as a base chillerfollowed by four optional chillers. Asshown in Figure 5 (C), the column labelscan be edited to reflect each alternate.

It’s expected that users will enter datafor the lowest cost chiller into thebaseline column. The more expensivechillers are assumed to be more efficientthan the baseline and therefore maypayback with a lower electrical cost.

The cost for each alternate chillercombination can be entered as the actualfull price or the baseline chiller modelcost can be set to zero, and thedifference between the baseline chillerand the specific alternate combinationentered for the other chillers. Eithermethod results in the same values for thesimple payback computation.

For each chiller considered, the myPLVBid Form computes the following:

• myPLV value —a formulation basedon the weighted bin performance

• Annual kWh energy consumptionfor the chillers —the sum of the bincalculations of ton-hours multiplied bythe kW/ton performance at that bin.

• Annual consumption charge —theproduct of the annual kilowatt-hoursmultiplied by the dollar per kWhspecified by the user.

• Annual demand charge —asummation for 12 months where themonthly demand tons which includesthe ratchet (from the monthly PeakLoading table) is multiplied by thechillers’ 100 percent load kW/ton andfurther multiplied by the dollar per kWdemand specified by the user.

• Total annual energy charge —computed as the sum of theconsumption and demand costs.

• Simple payback in years —thedifference in cost (option x - baseline)divided by the difference in the annualenergy charge (baseline - option x).

Note that electrical rates varyconsiderably with as many different ratestructures as there are utilities. Thecomputations included in the myPLVspreadsheet attempt to capture only thebasic calculation for a single electricalconsumption cost per kWh and a singledemand cost per peak kW.

Also note that actual building electricaldemand is based on the building meter,not just the chiller power draw. The bid

form only computes demand cost on anincremental per alternate chiller basis.

Finally, the electrical demandcalculations use the chiller’s designkW/ton value since it assumes they willbe running at peak conditions when peakdemand points occur. The chillerdemand charges include the impact ofthe ratchet value. The program providesa monthly Peak Loading demand datatable on the myPLV Charts worksheetfor users who wish to better understandthe value and effect of the chiller(s)demand.

The Save and Send button allows theuser to save and/or e-mail the myPLV BidForm with the job appropriate myPLVTest and Submittal Points in a separateworking Excel file.

Figure 5. Data input for alternate chiller performance metrics

A

B

C


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myPLV OutputThe remainder of this EN explainssome of the intracacies of the myPLVengine to help guide users on inputselections. This adds transparency to

the myPLV calculations.

Load charts. A review of the loadcharts is recommended to ensure theload profile looks appropriate for aparticular application. myPLV enablesusers to examine plant operation andthe weather impact via two weatherand load-related charts shown on themyPLV Charts worksheet. The firstchart (see Figure 6) describes theoperation of the plant as a function ofthe outdoor wet bulb, if the chillers arewater-cooled, or as a function of

outdoor dry bulb, if the plant is air-cooled. To build the chart, myPLV sumsthe annual hours (blue line), operatinghours (red line), and cooling ton-hrs foreach outdoor temperature value andplots the trend line (black line).

Consider the following when reviewingthe example chart:

• Does the trend for the number ofannual and operating hours lookappropriate with regard to theoutdoor temperature?

• Does the plant shut down(operating hours goes to zero) at atemperature that makes sense inlight of economizer operation?

• The peak wet bulb temperaturevaries considerably for dry climatesand the default selections may notrepresent local conditions. Thismay only be a problem for the datanear the peak wet bulb conditions.This is important to an accurateanalysis because considerationssuch as design cooling tower anddesign chiller condenser waterconditions need to reflect the plantlocale.

• Is the peak outdoor wet bulb (inthis case, ~82ºF) representative ofthe locale that is being reviewed?

• Is an appropriate design wet bulbspecified for the tower selection?

• Is an appropriate chiller designcondenser water temperaturespecified based on the peak wetbulb encountered?

If the standard building profiles do not

adequately reflect local conditions, then acustom load profile should beconsidered.

The second myPLV chart (Figure 7)displays the load profile’s percentage ofcumulative ton-hr as a function of theoutdoor temperature. One observationfrom the example chart is thatapproximately 12 percent of the coolington-hr occur below a 60ºF wet bulb and100 percent of the ton-hr occur below82ºF wet bulb.

This chart illustrates the opportunity forwaterside economizing (free cooling). Forexample, the best opportunity forwaterside economizing is when outdoorwet-bulb conditions are approximately45ºF and below. However, the data onthis graph indicates the percentage ofannualized cooling load below 45ºF isnear zero—indicating little to nowaterside economizing benefit.

Users need to be especially mindful of

the operation of the building at lowtemperatures when evaluating awaterside economizing opportunity.

Also note that the PNNL load profilesused in myPLV were developed forASHRAE Standard 90.1-2010. Per thisASHRAE Standard, at low temperatureoutdoor conditions, mechanicalventilation is provided to the rooms. Asa result, there is a natural economizingeffect because most of the coolingload for the building is satisfied atthese conditions. However, if the

actual building has less outdoor airventilation or the ventilation is pre-conditioned to room-neutralconditions, then a significant chillerplant cooling load may exist that thePNNL load profile incorporated in themyPLV tool does not include.

70000

60000

50000

40000

30000

20000

10000

0

t o n - h r

b y

i n t e g e r w

e t - b u

l b v a

l u e

350

300

250

200

150

100

50

0

n u m

b e r o

f h o u r s

outdoor wet-bulb temperatures (ºF)

30 40 50 60 70 80 90 100

ton-hr distributionNbr annual hr Nbr operating hr

Figure 6. Summary trends for hours and ton-hrs as a function of outdoor conditions

100

80

60

40

20

0 t o n - h r p r o

b a

b i l i t y f o r o u

t d o o r w e t - b u

l b ( % )

outdoor wet-bulb temperatures (ºF)

30 40 50 60 70 80 90 100

Figure 7. Load profile's percentage of cumulative ton-hrs as a function of the outdoor temperature


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Cooling tower performance andcontrol (water-cooled plants).Cooling tower design performance,operating limits and control method arerequired inputs for myPLV to calculatethe correct 8,760 hour chiller load pointEntering Condenser WaterTemperature (ECWT). With thisinformation the program can generatethe appropriate submittal point ECWTdata.

As illustrated in the earlier example,cooling tower design performance isspecified by the user by enteringDesign Full Load Tower Wet-BulbApproach and the Design Outdoor

Wet-Bulb Temperature (Figure 3).Tower control is specified by selectingone of four control methods along withthe corresponding control setpoint andthe minimum allowed condenser watertemperature.

The program performs two calculationsto determine the correct ECWT foreach operating hour and takes themaximum temperature of the two.

First, myPLV determines the ECWTbased on tower performance at full fan

power as illustrated in Figure 8. Theprogram computes the ECWT as asum of the ambient wet-bulbtemperature plus the tower approach.Since this computation reflects toweroperation at full fan power, the valuecomputed is the lowest ECWTpossible.

The second calculation is based on theuser selected Cooling Tower ControlMethod. The four tower controlselections supported are listed belowand discussed in the next section:

• chiller tower optimization

• fixed tower approach

• fixed temperature

• full tower fan flow

Generally speaking, the operatingECWT provided by the tower for anyhour may be quite different from theentering condenser water temperaturebased on full fan power, since thecooling tower fans are actively

controlled to a setpoint condition. Aslong as the tower control setpoint iscausing the fan speed to operatebelow its maximum speed, the coolingtower provides a water temperaturebased on the method of control. Thelowest ECWT is only used when thecontrol method causes the tower fansto operate at maximum speed.

ECWT Example. Assume the chillerplant is operating at a 50-percent loadpoint and the tower control is asked tosupply 75-degree water (see Figure 8).

If the outdoor wet bulb is 50°F (purpleline), the tower approach would be10°F if the tower fans were running fullspeed. This results in a lowest ECWT of 60ºF (50°F WB + 10°F approach).

Since the control system calls for 75°Fwater, the tower fans are slowed (orcycled) until the operating ECWT is75°F. If, however, the outdoor wet bulbtemperature is 70°F (red line), then thetower approach is 6°F and the lowestleaving tower temperature at full fanflow is 76ºF (70°F WB + 6°F approach).

In the latter case, myPLV programreturns an operating ECWT of 76ºF,even though the setpoint was 75ºF.

So what causes the saw tooth pattern?In order to simplify the myPLVprogram, the chiller and tower cellsequencing is assumed to occur at thechiller design tonnage. Since threechillers were specified for the plant,chillers and tower cells are turned on at33 percent and 67 percent of the plant

capacity. At these steps, the amount ofheat rejection to the tower cells isredistributed to the additional towercells and the active towers’ heatrejection and therefore the towerapproach drops accordingly.

Also note that the tower approachincreases as the ambient wet bulbtemperature decreases. This is due tothe reduced latent heat capacity of theair at lower temperatures.

Tower control methods. The

following provides more detail for eachcontrol method within the myPLV tool.Note that any of the following controlmethods may specify a low ECWT thatcannot be achieved by the coolingtower operating at full fan power. Inthis case the ECWT used by myPLV forthis load point is the ECWT operatingat full fan power (the higher value).

Full tower fan flow. . This selectiondetermines the ECWT that resultsfrom the cooling tower running at fullfan speed (lowest ECWT) for each

hour’s conditions (see Figure 8).However, if the result is a temperatureless than the minimum user-specifiedvalue, the temperature will be set tothe minimum value specified.

Fixed temperature. This controlmethod is typical of many installationsthat run the cooling towers to aconstant temperature setpoint. Thisselection requires a temperature

16

14

12

10

8

6

4 t o w

e r a p p r o a c h ( º F )

% plant capacity0 25 50 75 100

0

2

80ºF WB

70ºF WB

60ºF WB

50ºF WB

Figure 8. Tower approach assumed for full fan power

Cooling towerperformancecurves used for theecwt prediction.The tower cellperformance wasspecified to be a 7°Fapproach at a 78ºFwet bulb.


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setpoint entry by users. This method ofcontrol was described in the previousECWT example.

Fixed tower approach. This selectioncomputes an ECWT equal to theoutdoor wet-bulb temperature value

plus the tower approach setpointentered by the user. If this methodresults in a temperature value less thanthe minimum user-specified value, thetemperature will be set to theminimum value specified.

Chiller-tower optimization. . Thisselection simulates a Trane algorithmfor a dynamic and optimally changingECWT setpoint as a function of chillerloading and ambient wet-bulbtemperature. As with other controlmethods, if this method results in atemperature value less than theminimum condenser watertemperature specified, the minimumtemperature setpoint value will beused.

The tower control strategies for ChillerTower Optimization, Full Tower FanFlow, and Fixed Tower Approach willyield similar looking results forsubmittal point ECWTs since each ofthose control methods’ resultingcondenser water temperatures will bemoving with the outdoor wet bulb. Themain difference is how the particularcontrol mode affects tower fan powerwhich is not part of the myPLVanalysis.

However, the Fixed Temperature selection can dramatically change thechiller selection points since this

control method creates a minimumcondenser water temperature at allwet-bulb temperatures. Depending onthe user-specified fixed setpoint, thesubmittal point ECWTs may be higherthan the other control methods (highfixed setpoint) or close to the Full

Tower Fan Flow ECWT (low fixedsetpoint). In any case, this minimum isreflected in the weighted condenserwater temperatures for the four binnedperformance points.

Chiller Loading Chart. The scatterplot on the myPLV Charts worksheetdetailing the myPLV/IPLV enteringcondenser water temperatures for thechillers deserves some explanation.Figure 9 shows the chart for a three-chiller plant with the chillers sized at750 tons.

The plot shows the load and ECWT foreach hour of chiller operation. Thesmall blue data points detail thoseconditions where only one chiller isoperating. The maroon points detail theoperating conditions when two chillersare operating, and the green datapoints show where all three chillers arerunning.

In other words, the first chiller runs atall conditions detailed by the blue,maroon, and green data points. The

second chiller runs at the conditionsdetailed by the maroon and green datapoints. Finally the third chiller only runsat the conditions shown with greendata points.

The chart is broken up into four binswith three dashed vertical lines asseparators. The first vertical line ispositioned midway between the 25and 50 percent bin points at a 37.5percent chiller load (281 tons). Thesecond is positioned midway between

the 50 and 75 percent bin points at62.5 percent (469 tons). Finally, thethird vertical dashed line is positioned12.5 percent to the right of the 75percent bin point at 87.5 percent (656tons).

For this example, a 55ºF minimumcondenser water temperature wasspecified and therefore, the minimumcondenser water temperature for allthe load points was at 55ºF.

The myPLV and IPLV rating points arealso illustrated on the plot—the bluecircles and the red open circlesrespectively. The blue myPLV circlesrepresent the load in tons at the 25, 50,75 and 94 percent load points, and thecorresponding myPLV submittal pointcondenser water temperatures.

Note that the myPLV point ECWT are aton-hr weighted temperature of all theload points in each bin. The open redIPLV circles are shown for comparisonand represent the condenser watertemperature for the IPLV rating points.This allows users to determine if thereare significant differences betweenIPLV ECWT and actual ECWT.

Figure 9. myPLV/IPLV entering condenser water temperatures for the chiller

Example office buildingwith economizer andthree 750-ton chillersNote: The chiller-tower optimization

control strategy calculation and, in

some cases, the fixed-tower approachsetpoint may assume the chiller can runreliably at a condenser watertemperature that is slightly above thedesign point. This is typically a goodoptimization assumption and may workwell to reduce overall system energy.However, users should review thescatter plot of the computed ECWT todecide if the tower control method orchiller design point should be modified.


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Air-cooled vs water-cooled. ThemyPLV computations become simpler

when an air-cooled device isconsidered. For the case of air-cooledchillers, the entering condensertemperature comes directly from theoutdoor dry-bulb temperature in theweather data.Therefore, the binanalysis used to compute a weightedcondenser condition is processeddirectly on the outdoor dry-bulb value,in contrast to evaluating a coolingtower control method for a water-cooled chiller.

Summary

myPLV is based on bin methodologythat leverages the PNNL Energy Plusmodeling results to create an easy-to-use methodology to guide chillerselection based on specific userconditions.

The accuracy for the condenserconditions is achieved by adjustingECWT for load, outdoor air wet bulb,and tower control and by the use ofton-hr weighting for the myPLVsubmittal points.

These submittal points enable users togather actual certified performancedata from chiller manufacturers atmeaningful weighted conditions andthen convert them to energy usage andcost.

The result is a simple, accurate andtransparent chiller analysis tool that canbe used to analyze any chiller’sperformance to make a more informedchoice for the chiller equipment.

If a complete plant energy analysis is

necessary, a full energy model using atool such as TRACE ® Chiller PlantAnalyzer should be used for analysis.

Visit www.trane.com/myPLV todownload the latest version ofmyPLV™

By Brian Sullivan, systems engineer, and JeanneHarshaw, program manager, Trane. You can findthis and previous issues of the EngineersNewsletter at www.trane.com/engineersnewsletter.To comment, send e-mail to [email protected].

References

[1] ASHRAE/IES 90.1-2010 Energy Standard forBuildings Except Low-Rise ResidentialBuildings.

[2] EnergyPlus files developed by PacificNorthwest National Labs (PNNL) The web sitefor the PNNL files can be found at http:// www.energycodes.gov/development/ commercial/90.1_models.


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Trane believes the facts and suggestions presented here to be accurate. However, final design andapplication decisions are your responsibility. Trane disclaims any responsibility for actions taken onthe material presented.

Trane, A business of Ingersoll Rand

For more information, contact your local Traneoffice or e-mail us at [email protected]

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Chiller Selection Made Easier with myPLV™