eﬃcient pump selec/on & control - pumps & systems...design tdh: 90 feet pumps: 1 x 15hp bhp at...

EfficientPumpSelec/on&Control

GrundfosTechnicalIns2tutewww.grundfos.us/training

•  VirtualClassroom–  Self-Paced–  Over50courses–  Cer2ficatesofComple2on

•  Webinars–  LiveandRecorded

•  Face-to-FaceTraining

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

Twocommonvariableflowpumpapplica2ons

HVACCircula2on–Hotand/orChilledWaterWaterSupply–PressureBoos2ng

dP

SUPPLY

RETURN

HVACCircula2onDifferen2alPressuremeasuredremotely

dP

SUPPLY

RETURN

HVACCircula2onDifferen2alPressuremeasuredacrosspumps

Suc2onPiping–CityWaterConnec2on

Control

DischargePiping

PressureBoos2ng

PackageMountedSensor

RemoteMountedSensor

WaterSupplyRisers

PumpHead/CapacityCurve

H

Q

Q

HP

Eff

BEP


H

Q

DesignCondi2on

Headrequiredincreases

withflow


H

Q

DesignCondi2on

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?

H

Q

60Hz 55Hz

50Hz 45Hz

40Hz 35Hz

30Hz

35% 42% 55%

62%

67%

65%

60%

54%

Curvesofconstantefficiencywithspeedreduc2onsRemember…..theaffinitylawsassumeconstantpumpefficiency.Thepumpcanonlyruncon2nuouslyatitsBestEfficiencyPointalongasystemorcontrolcurvethatfollowsacurveofconstantefficiency

H

Q

60Hz 55Hz

50Hz 45Hz

40Hz 35Hz

30Hz

35% 42% 55%

62%

67%

65%

60%

54%

ConstantPressure:Asflowreducessodoespumpefficiency!

Curvesofconstantefficiencywithspeedreduc2ons

H

Q

60Hz 55Hz

50Hz 45Hz

40Hz 35Hz

30Hz

35% 42% 55%

62%

67%

65%

60%

54%

SimilarlywithHVACCircula2onEfficiencyalsoreduceswithreducingflow


H

Q

60Hz 55Hz

50Hz 45Hz

40Hz 35Hz

30Hz

35% 42% 55%

62%

67%

65%

60%

54%

Whenselec2ngpumpsforvariableflowSelectpumpsbasedonadesignflowthatistotheRIGHTofthepumpsbestefficiencypoint.


DesignFlow:1000gpmDesignHead:75feet

PumpSelec2onExample

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

[%]


Selec2onToolResults:

PumpSelec2onExample



Size [Suc/Dis]

% Max. Diameter


Pump Efficiency

[%]


Selec2onToolResults:

Op2on5=Highestefficiency,butisitthebestchoiceforvariableflow?Youmustlookatthepumpcurvesaswellasthecontrolcurve!

PumpSelec2onExample

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

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

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

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



Size [Suc/Dis]

% Max. Diameter


Pump Efficiency

[%]

Op2on4hasthelowestenergyconsump2on,yetthelowestefficiencyatthedesignflow.Howmanyhoursdoyoureallyrunatdesignflow,ifever…..

Example:BasicRequirementsDesignFlow:350gpmDesignTDH:90feet

Mul2plePumpOpera2on-Parallel

Ques2on:Dowejustselecta350gpmpumpwithaheadcapacityof90feetandbedonewithit?

LoadProfile

Two50%pumps:

DesignFlow:350gpm

DesignTDH:90feet

Pumps:2x7.5HP

BHPatDesign:11.9

One100%Pump:

DesignFlow:350gpm

DesignTDH:90feet

Pumps:1x15HP

BHPatDesign:10.5

(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

Methods:>Flow>Current[Amps]>Speed>Demand[set-pointnotbeingreached]>Efficiency

ParallelConnectedPumps-PumpSequencing

Whichisbest?Itdepends……..……onalotoffactors

ParallelConnectedPumps-FlowSequencing


Flowsequencing,needtostartbefore400gpm



Flowsequencing,approx.820-830gpm



Flowsequencing,approx.820-840gpm

ParallelConnectedPumps–SpeedSequencing


SpeedSequencing,needtostartbefore91%speed.Cavita2oncanhappenif2ndpumpisnotstarted.


SpeedSequencing,canstartbetween95-99%

ParallelConnectedPumps–DemandSequencing

DemandSequencing,headwilldropoffatapprox.91%speed.2ndpumpwillbestartedwhenthisoccursasset-pointisnotbeingmaintained.


DemandSequencing,headwilldropoffwhenbothpumpsreachfullspeed,3rdpumpwillneedtobestarted.

ParallelConnectedPumps-EfficiencySequencing

Eff.%


Eff.sequencing,approx.340gpm

Eff.%




Eff.%




Eff.%

Ifflowandheadarecon2nuouslymeasuredand/orcalculated,pumpefficiencyisknownduringopera2on.Thethirdpumpstartedatapproximately700gpmeventhoughtwopumpscoulddothejobupto840gpm.

Onepump–400gpmat62feet

2.90.683 x 3960

1.0 x 62 x 400 x 3960

SG x H x Qbhppump

===η

Onepump–200gpmat62feet

4.82x2.40.742 x 3960

1.0 x 62 x 200 x 3960

SG x H x Qbhppump

====η

Savingsof8.7%

Whatiftherequiredheadchanges?Doesthateffectpumpsequencing?


Changesinpumpheadwillrequirereseqngofflow,speedanddemandbasedsequencing.

Mostefficient:Stageonefficiency>TotalEfficiency(Electrical+Hydraulic)>HydraulicEfficiency


Mostefficient:Stageonefficiency>TotalEfficiency(Electrical+Hydraulic)>HydraulicEfficiency

Excep2on

>Limitedsuc2onhead,muststartaddi2onalpumpsbeforeflowgetstoohigh Examples:BoilerFeed,CoolingTower,water supplyfrombreaktank


Thankyouforyouraben/on!

NOTE:

ThefollowingslidesarenotpartofmainslidedeckbutarelesherejustincasetheycanbeusedtohelptheQ&Asession.Ifthepresenta2onismadeavailabletotheviewers,theseslidearetobeLEFTOUT.

Misconcep2on

Sincevariableheadlossesaresuchasmallpercentageofthetotalheadinhighrisebuildingapplica2ons,variablefrequencydrivesresultinliuleornoenergysavings.

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

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

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

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

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 ==

=

=

eﬃcient pump selec/on & control - pumps & systems...design tdh: 90 feet pumps: 1 x 15hp bhp at...

Documents