efficient pump selec/on & control - pumps & systems...design tdh: 90 feet pumps: 1 x 15hp bhp at...
TRANSCRIPT
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EfficientPumpSelec/on&Control
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PointsonaPumpPerformanceCurveShut-Off Head/Dead Head
Shut-OffHeadNoflowperformance,don’trunhereformorethanafewminutes(Damagefromheatbuildupcanoccur)
Duty Point DutyPointThedesignflowandhead,thisiswhatisrequired,usuallybasedoncalcula2ons
Run-Out/End of Curve
RunOut/EndofCurveThisisthemaximumallowableflowrateforthepump.Flowsexceedingthisshouldbeavoided(Damagecanoccur) Pump Efficiency
PumpEfficiencyThisisthepumphydraulicefficiency,doesnottypicallyincludemotorefficiency
Brake Horsepower
BrakeHorsepowerThisisthehorsepowerrequiredbythepump.Anypointonthiscurveshouldbelowerthanthemotornameplatehorsepower
NPSHR
NPSHNetPosi2veSuc2onHead,theactualsuc2onheadofthesystemmustbehigherthanthisvalue.Veryimportantinboilerfeedsystemsandsystemswithfloodedsuc2on.Notsoimportantforcoldwaterfromapressurizedsourceorhydronichea2ng/coolsystems
Operating Point Opera/ngPointThisiswherethepumpisactuallyrunning,wherethesystemcurveintersectstheperformancecurve
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Twocommonvariableflowpumpapplica2ons
HVACCircula2on–Hotand/orChilledWaterWaterSupply–PressureBoos2ng
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dP
SUPPLY
RETURN
HVACCircula2onDifferen2alPressuremeasuredremotely
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dP
SUPPLY
RETURN
HVACCircula2onDifferen2alPressuremeasuredacrosspumps
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Suc2onPiping–CityWaterConnec2on
Control
DischargePiping
PressureBoos2ng
PackageMountedSensor
RemoteMountedSensor
WaterSupplyRisers
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PumpHead/CapacityCurve
H
Q
Q
HP
Eff
BEP
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PumpHead/CapacityCurve
H
Q
DesignCondi2on
Headrequiredincreases
withflow
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PumpHead/CapacityCurve
H
Q
DesignCondi2on
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TheAffinityLawsforcentrifugalpumps
1
212 TDHTDHRPMRPM =
When TDH1, RPM1 and TDH2 are known:
2
1
2
1RPMRPM
GPMGPM
= ⎟⎟⎠
⎞⎜⎜⎝
⎛=
1
212 RPMRPMGPMGPM> > Flow varies linearly with pump speed
2
2
1
2
1RPMRPM
TDHTDH
⎟⎟⎠
⎞⎜⎜⎝
⎛=
2
1
212 RPMRPMTDHTDH ⎟⎟
⎠
⎞⎜⎜⎝
⎛=> > Head varies with the square of the pump
speed
3
2
1
2
1RPMRPM
BHPBHP
⎟⎟⎠
⎞⎜⎜⎝
⎛=
3
1
212 RPMRPMBHPBHP ⎟⎟
⎠
⎞⎜⎜⎝
⎛=> >
Brake Horsepower varies with the cube of the pump speed
1=Originalcondi2on(fullspeed)2=Newcondi2on(reducedspeed)
Whataboutefficiency?
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H
Q
60Hz 55Hz
50Hz 45Hz
40Hz 35Hz
30Hz
35% 42% 55%
62%
67%
65%
60%
54%
Curvesofconstantefficiencywithspeedreduc2onsRemember…..theaffinitylawsassumeconstantpumpefficiency.Thepumpcanonlyruncon2nuouslyatitsBestEfficiencyPointalongasystemorcontrolcurvethatfollowsacurveofconstantefficiency
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H
Q
60Hz 55Hz
50Hz 45Hz
40Hz 35Hz
30Hz
35% 42% 55%
62%
67%
65%
60%
54%
ConstantPressure:Asflowreducessodoespumpefficiency!
Curvesofconstantefficiencywithspeedreduc2ons
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H
Q
60Hz 55Hz
50Hz 45Hz
40Hz 35Hz
30Hz
35% 42% 55%
62%
67%
65%
60%
54%
SimilarlywithHVACCircula2onEfficiencyalsoreduceswithreducingflow
Curvesofconstantefficiencywithspeedreduc2ons
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H
Q
60Hz 55Hz
50Hz 45Hz
40Hz 35Hz
30Hz
35% 42% 55%
62%
67%
65%
60%
54%
Whenselec2ngpumpsforvariableflowSelectpumpsbasedonadesignflowthatistotheRIGHTofthepumpsbestefficiencypoint.
Curvesofconstantefficiencywithspeedreduc2ons
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DesignFlow:1000gpmDesignHead:75feet
PumpSelec2onExample
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Option 1 1750 83.16 9.25 26.7 97.60 6 x 5Option 2 1750 82.94 8.39 25.5 81.24 6 x 5Option 3 1750 80.03 12.7 24.7 81.24 5 x 4Option 4 1750 78.09 27.2 24.2 92.69 5 x 4Option 5 1750 83.71 10.1 24.8 89.80 6 x 5
Pump Speed [rpm]Pump
Size [Suc/Dis]
% Max. Diameter
Max. Power [bhp]NPSHr
Pump Efficiency
[%]
DesignFlow:1000gpmDesignHead:75feet
Selec2onToolResults:
PumpSelec2onExample
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Option 1 1750 83.16 9.25 26.7 97.60 6 x 5Option 2 1750 82.94 8.39 25.5 81.24 6 x 5Option 3 1750 80.03 12.7 24.7 81.24 5 x 4Option 4 1750 78.09 27.2 24.2 92.69 5 x 4Option 5 1750 83.71 10.1 24.8 89.80 6 x 5
Pump Speed [rpm]Pump
Size [Suc/Dis]
% Max. Diameter
Max. Power [bhp]NPSHr
Pump Efficiency
[%]
DesignFlow:1000gpmDesignHead:75feet
Selec2onToolResults:
Op2on5=Highestefficiency,butisitthebestchoiceforvariableflow?Youmustlookatthepumpcurvesaswellasthecontrolcurve!
PumpSelec2onExample
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100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 0 0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Head (ft.)
Flow (gpm)
1000 gpm / 75 feet
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100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 0 0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Head (ft.)
Flow (gpm)
65% 75%
80% 84.5% 85%
83.5% 78%
70%
Option 5
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100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 0 0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Head (ft.)
Flow (gpm)
65% 75%
80%
83% 83.5%
82%
78%
70%
65% 75%
80% 84.5% 85%
83.5% 78%
70%
Option 4
Option 5
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100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 0 0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
Head (ft.)
Flow (gpm)
Op/on4Hydraulic(Pump)efficiencyrangesbetween75-83%alongcontrolcurve
65% 75%
80%
83% 83.5%
82%
78%
70%
65% 75%
80% 84.5% 85%
83.5% 78%
70%
Option 4
Option 5
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Option 1 1750 83.16 9.25 26.7 97.60 6 x 5Option 2 1750 82.94 8.39 25.5 81.24 6 x 5Option 3 1750 80.03 12.7 24.7 81.24 5 x 4Option 4 1750 78.09 27.2 24.2 92.69 5 x 4Option 5 1750 83.71 10.1 24.8 89.80 6 x 5
Pump Speed [rpm]Pump
Size [Suc/Dis]
% Max. Diameter
Max. Power [bhp]NPSHr
Pump Efficiency
[%]
Op2on4hasthelowestenergyconsump2on,yetthelowestefficiencyatthedesignflow.Howmanyhoursdoyoureallyrunatdesignflow,ifever…..
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Example:BasicRequirementsDesignFlow:350gpmDesignTDH:90feet
Mul2plePumpOpera2on-Parallel
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Ques2on:Dowejustselecta350gpmpumpwithaheadcapacityof90feetandbedonewithit?
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LoadProfile
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Two50%pumps:
DesignFlow:350gpm
DesignTDH:90feet
Pumps:2x7.5HP
BHPatDesign:11.9
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One100%Pump:
DesignFlow:350gpm
DesignTDH:90feet
Pumps:1x15HP
BHPatDesign:10.5
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(1)CR64-115HP
(2)CR32-2-17.5HP
EnergyConsump2on
Total=20,877kWh/Year
Total=24,856kWh/Year
At75-100%flowthesinglepumphasalowerkWrequirement(higherpump/motorefficiency).Butpumpsgenerallyhavehigherrunninghoursatlowerflowratesthereforethetwopumpsolu/onisabeberchoiceoverallduetothehigherpumpefficiencyatflowslessthan50%.
1x15HPPump
2x7.5HPPumps
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Methods:>Flow>Current[Amps]>Speed>Demand[set-pointnotbeingreached]>Efficiency
ParallelConnectedPumps-PumpSequencing
Whichisbest?Itdepends……..……onalotoffactors
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ParallelConnectedPumps-FlowSequencing
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ParallelConnectedPumps-FlowSequencing
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ParallelConnectedPumps-FlowSequencing
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ParallelConnectedPumps-FlowSequencing
Flowsequencing,needtostartbefore400gpm
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ParallelConnectedPumps-FlowSequencing
Flowsequencing,needtostartbefore400gpm
Flowsequencing,approx.820-830gpm
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ParallelConnectedPumps-FlowSequencing
Flowsequencing,needtostartbefore400gpm
Flowsequencing,approx.820-840gpm
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ParallelConnectedPumps–SpeedSequencing
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ParallelConnectedPumps–SpeedSequencing
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ParallelConnectedPumps–SpeedSequencing
SpeedSequencing,needtostartbefore91%speed.Cavita2oncanhappenif2ndpumpisnotstarted.
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ParallelConnectedPumps–SpeedSequencing
SpeedSequencing,canstartbetween95-99%
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ParallelConnectedPumps–SpeedSequencing
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ParallelConnectedPumps–DemandSequencing
DemandSequencing,headwilldropoffatapprox.91%speed.2ndpumpwillbestartedwhenthisoccursasset-pointisnotbeingmaintained.
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ParallelConnectedPumps–DemandSequencing
DemandSequencing,headwilldropoffwhenbothpumpsreachfullspeed,3rdpumpwillneedtobestarted.
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ParallelConnectedPumps–DemandSequencing
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ParallelConnectedPumps-EfficiencySequencing
Eff.%
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ParallelConnectedPumps-EfficiencySequencing
Eff.%
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ParallelConnectedPumps-EfficiencySequencing
Eff.sequencing,approx.340gpm
Eff.%
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ParallelConnectedPumps-EfficiencySequencing
Eff.sequencing,approx.340gpm
Eff.sequencing,approx.700gpm
Eff.%
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ParallelConnectedPumps-EfficiencySequencing
Eff.sequencing,approx.340gpm
Eff.sequencing,approx.700gpm
Eff.%
Ifflowandheadarecon2nuouslymeasuredand/orcalculated,pumpefficiencyisknownduringopera2on.Thethirdpumpstartedatapproximately700gpmeventhoughtwopumpscoulddothejobupto840gpm.
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Onepump–400gpmat62feet
2.90.683 x 3960
1.0 x 62 x 400 x 3960
SG x H x Qbhppump
===η
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Onepump–200gpmat62feet
4.82x2.40.742 x 3960
1.0 x 62 x 200 x 3960
SG x H x Qbhppump
====η
Savingsof8.7%
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Whatiftherequiredheadchanges?Doesthateffectpumpsequencing?
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ParallelConnectedPumps-FlowSequencing
Changesinpumpheadwillrequirereseqngofflow,speedanddemandbasedsequencing.
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Mostefficient:Stageonefficiency>TotalEfficiency(Electrical+Hydraulic)>HydraulicEfficiency
ParallelConnectedPumps-PumpSequencing
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Mostefficient:Stageonefficiency>TotalEfficiency(Electrical+Hydraulic)>HydraulicEfficiency
Excep2on
>Limitedsuc2onhead,muststartaddi2onalpumpsbeforeflowgetstoohigh Examples:BoilerFeed,CoolingTower,water supplyfrombreaktank
ParallelConnectedPumps-PumpSequencing
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Thankyouforyouraben/on!
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NOTE:
ThefollowingslidesarenotpartofmainslidedeckbutarelesherejustincasetheycanbeusedtohelptheQ&Asession.Ifthepresenta2onismadeavailabletotheviewers,theseslidearetobeLEFTOUT.
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Misconcep2on
Sincevariableheadlossesaresuchasmallpercentageofthetotalheadinhighrisebuildingapplica2ons,variablefrequencydrivesresultinliuleornoenergysavings.
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0
50
100
150
200
250
300
0 25 50 75 100 125 150 175
Flow (gpm)
Hea
d (ft
.)
Shaded areas represent amount of savings potential with vfd driven multi-stage pump+
Shaded area represents amount of savings potential with vfd driven single stage pump
SampleMul/-StageA=25gpmat180feetTDH,2882rpm,bhp=2.3B=25gpmat266feetTDH,3500rpm,bhp=3.9C=Lineofconstantefficiency,49%
SampleSingleStageA=25gpmat180feetTDH,3319rpm,bhp=3.7D=25gpmat200feetTDH,3500rpm,bhp=4.2C=Lineofconstantefficiency,31%
B
C
A
DAt25gpmtheVFDcontrolledMul2-Stagewillconsume45%lessenergy(2.3bhpvs.4.2bhp)thanthefixedspeedsinglestagepump
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Typical VFD Efficiency Curve
84
86
88
90
92
94
96
98
10 20 30 40 50 60Frequency (Hz)
Effic
ienc
y (%
)
100% Torque
75% Torque
50% Torque
25% Torque
Source: Hydraulic Institute/Europump Guide to Life Cycle Costs
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10
20
30
40
50
60
70
80
9.5”
100
0 0 100 200 300 400 500 600 700 800
TOTAL HEAD
IN FEET
10
20
30
40
0
US GALLONS PER MINUTE
9”
8.5”
8”
7.5”
7”
50%
60%
65
%
70%
90 1750 RPM
NPSHR IN
FEET
TypicalSingleStagePumpCurve
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10
20
30
40
50
60
70
80
9.5”
100
0 0 100 200 300 400 500 600 700 800
TOTAL HEAD
IN FEET
10
20
30
40
0
US GALLONS PER MINUTE
9”
8.5”
8”
7.5”
7”
50%
60%
65
%
70%
90 1750 RPM
NPSHR IN
FEET
TypicalEndSuc2onPumpCurve
480 gpm at 65 feet required
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RemembertheBasics…..
SG x H x Qwhp P3 3960==
Waterhorsepower(a.k.a.hydraulichorsepower)
Brake horsepower (Pump Shaft)
x
SG x H x Qbhp Ppump
2 η3960==
Electrichorsepower(InputPower)
bhpehp P
driver1 η
==
x
0.746 x bhpehp [kW] Pdrivemotor
1 ηη==
efficiency driver driverη =
)eta"" symbol(Greek Efficiency Pump liquid ofGravity SpecificSG
feet in Head Hgpm in Flow Q
η ==
=
=