Variable Flow Pumps – Control Strategies

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Variable Flow Pumps – Control StrategiesBBT Conference – Feb 4/5, 2015Presented by Steve ThompsonVP - Residential Product Management – Taco Inc.Mobile (401) 441-2934E Mail: stetho@taco-hvac.comVariable Flow Pumps – Control StrategiesAgenda: IntroductionGeneral DescriptorsVFD or not VFD – That is the Question (VFD Assessment Tool)System & Pump CurvesSelfsensing PumpsApplicationsBalancing VFD Pumping SystemsDelta TWarning!!!Efficiency––– To trim or not to trimECM Permanent Magnet TechnologyAffinity LawsCommissioning TipsDOE / ASHRAE / ACEEE 1

General Descriptors T Differential Temperature Net temperature differential between two points (typically supply and return)20 Deg F “Normal” differential temperature design for high mass, medium temperature systems10 to 15 Deg F for radiant10 to 12 Deg F for chilled water primariesSetpoint Temperature Temperature sensed at single locationIf sensor built into the pump, the pump must be installed at sensing locationMake-up air coil a good example P Differential Pressure Pressure measured or sensed across two pointsTypical closed loop system pup inlet pressure is relatively constant PC – Differential Pressure Constant (flat pump curve) PV – Proportional Pressure (inclining pump curve)Self Sensing Pump (Circ) adjusts speed without any physical sensorsReacts to changes in impeller loading as a result of system flow changePrimary Circuit Dedicated to moving fluid to/from heating or cooling sourceSecondary Circuit Supplies fluid to building conditioned spaceCirculator vs Pump Pumps boost pressure (Well Pumps, Pressure Booster Pumps, Boiler Feed PumpsCirculators invoke fluid movement by overcoming friction loss (could be any Hp)Residential vs CommercialWhat’s a Variable Flow System ApplicationAnd Why Does This Matter? An HVAC system is like our body Working out - system under load Brain BMS (BAS) systemHeart pumpStomach boiler or chillerArteries piping systemBody - heart rate up, increased blood pressure,consumes more energyBuilding – more BTU’s (flow), more headSleeping - system under low load or setback Body – heart rate and blood pressure down,consumes less energyBuilding – less BTU’s, lower headAt least that’s the way it is supposed to work!What if our heart and blood pressure didn’t change?Conclusion – all HVAC APPS are variable flow! 2

StartVFD Assessment – New SystemsNeed to varydutycontinuouslyNoConsider fixed speed pumps, On-Offcontrol, Multiple sizes, etc.YesVFD potentially usefulMostlyfriction?Check overall benefitsincluding non-energy itemsi.e.: reduced maintenance costNoYesVFD potentially usefulCalculate total annual operating cost withalternative system solutionsDoes the pumprun most of thetime?NoNoIs VFD suitable?Use fixedspeed ViridianYesYesVFD almost certainly beneficialUse VFDVFD Assessment – Retrofit SystemsStartIs dutyvariableNoYesYesVFD potentially usefulMostlyfriction?NoConfirm existing fixedspeed pump iscorrectly sizedConsider modification orreplacement of equipmentRetain existinginstallation if efficientCheck overall benefitsincluding non-energy itemsi.e.: reduced maintenance costNoYesCalculate total annualoperating cost with alternativesystem solutionsVFD potentially usefulYesDoes the pumprun most of thetime?YesVFD almost certainlybeneficialNoIs VFDsuitable?NoAre existing pump andmotor suitable forproposed VFDNoYesVFD 3

System Curves3-Way Control ValveDesign Operating Point300 Gallons Per Minute53 Feet of Head60 GPM each fan coil150 ton system@ 12deg Delta TSystem CurvesSystemCapacityHead (H) in(Q) inFeetGPM0.00100.00200.00300.00400.00500.00Design Operating Point07255390136 4

System CurvesPump CurvesPump Curve70KS Model 4009Test Data at 1760 RPM0.00100.00200.00300.00400.00500.008.00" DiameterHead Efficienc BHP(Ft)y (%) 3.0371.4456.082.863.404.505.476.056.17Head (H) in FeetCapacity(GPM)60504030201000100200300400500Flow (Q) in GPM 5

System Curves3-Way Control ValvePump CurvesThis image cannot currently be display ed.KS Model 4009With an 8.00” impellerTest Data at 1760 RPMPumpEfficiencyCapacityHead .002.8603.40 6.914.50 24.915.47 52.766.05 89.836.17 473.0371.4456.08SystemHead(Ft) 6

SelfSensing PumpsVariable Loads (Zones Closing)3-Way ValveSelfSensing PumpsValves ClosedMinimum Flow100Valves OpenMaximum Flow9080Head (Ft.)706050403020100050100150200250Flow (GPM)300350400450 7

SelfSensing PumpsValves OpenMaximum FlowValves ClosedMinimum Flow100908070Head (Ft.)60504060 Hz3050 Hz40 Hz2030 Hz1020 Hz0050100150200250Flow (GPM)300350400450SelfSensing PumpsValves OpenMaximum FlowValves ClosedMinimum Flow100908070Head (Ft.)605060 HzControl Curve40302020 Hz100050100150200250Flow (GPM)300350400450 8

Integrated VFD with Sensorless ControlConstant Pressure ModeProportional Pressure ModeTrue System Curve ModeApplicationsExample:Chilled water primary / secondary system 9

Constant Flow ModeSelf-sensing CONSTANT flow is self-balancing and automaticallyadjusts flow to maintain user-defined flow set point.Used on constant flow chiller / boiler pumpsBenefits:––––––Balancing through reduced speed – not false headReduced speed increases equipment lifeBalancing done internally and automaticallyAuto adjust over the life and fouling of the systemUsing full trim impellersAllows for design vs. reality differencesVariable Flow ModeSelf-sensing variable flow adapts to system pressure variations andautomatically follows the system performance curve to meet demand.Used on secondary variable speed pumpsBenefits:––––Lower install costsNo error in setpointImproved system efficiency and performanceReduced coordination and construction schedule 10

Variable flow Constant flow Balancing complexity - highDirect Return Piping System(first in / first out)TERMINAL UNITSCONTROLVALVEHYDRONIC VALVEMULTIPURPOSEVALVEBALANCEVALVEHIGH EFFICIENCYAIR & DIRT SEPERATORSUPPLY PIPESUCTIONDIFFUSERTACO VERTICALINLINE PUMPRETURN PIPEEXPANSIONTANKBOILER Variable flow Constant flow Balancing complexity – low Reverse Return Piping System(first in / last out)TERMINAL UNITSSelf BalancingCONTROLVALVEHYDRONIC VALVEMULTIPURPOSEVALVEHIGH EFFICIENCYAIR & DIRT SEPERATORBALANCEVALVESUPPLY PIPERETURN PIPESUCTIONDIFFUSEREXPANSIONTANKTACO VERTICALINLINE PUMPBOILER 11

Variable flow Constant flow Balancing complexity – dependsPrimary Secondary Systems(pumped secondary)TERMINAL UNITSCONTROLVALVEHYDRONIC VALVEMULTIPURPOSEVALVEHIGH EFFICIENCYAIR & DIRT SEPERATORSUPPLY PIPESUCTIONDIFFUSERTACO VERTICALINLINE PUMPBALANCEVALVECROSSOVERBRIDGERETURN PIPEEXPANSIONTANKBOILER Variable flow Constant flow Balancing complexity Injection Pumping SystemTERMINAL UNITSCrossover bridges balance Which circs variable flow?CIRCULATINGPUMPINJECTIONPUMPHIGH EFFICIENCYAIR & DIRT SEPERATORSUCTIONDIFFUSEREXPANSIONTANKSUPPLY PIPEMULTIPURPOSEVALVEBALANCEVALVERETURN PIPETACO VERTICALINLINE PUMPBOILER 12

LoadMatchVariable flow Constant flow Balancing complexity – none req’dCircs variable flow?TMSingle Pipe Pumping SystemTERMINAL UNITSLOADMATCHCIRCULATORTWINTEEHIGH EFFICIENCYAIR & DIRT SEPERATORMULTIPURPOSEVALVEPRIMARY LOOPSUCTIONDIFFUSEREXPANSIONTANKTACO VERTICALINLINE PUMPBOILERBalancing VFD Systems (ASHRAE)The main goal of the secondary chilled water system is to distribute the correctamount of water to satisfy the load. It must first accurately monitor the system forchanges in load dynamics.Secondly, it must respond to these load changes with the “correct” amount of flowRun VFD’s at constant speed – balance then set pumps to AUTO 13

SelfSensing Pumps vs. Sensors Sensors are frequently placed in the wrong locationin the system; this incorrect sensor placementresults in system inefficiency. In a typical system, trial and error must be used(i.e. physically moving the sensor) until theoptimum location is determined. Another strategy is to use multiple sensors toincrease the odds of correct placement. These strategies can become costly. Even if correct placement is achieved, correctsetpoint is rarely used.Determining the Set Point for theDifferential Pressure SensorThe sensor must keep enough pressure differential across the supply and return to “push”the design capacity flow through the coil and control valve.Setpoint Sum of coil pressure drop control valve pressure drop at design conditions (17’) 14

Location of P TransmittersEffeciencies are dramatically affectedTERMINALUNITCONTROLVALVEDIFF. PRESSURETRANSMITTERBYPASSW/VALVEPRIMARYPUMP80’ RYPUMPDIFF. PRESSURETRANSMITTER17’ setpointDifferential TemperatureDelta-T lends itself to even more cost effective variable speed pumping.The issues associate with placement and of Delta-P sensors is replaced with ease and simplicity of thermisters.As the Delta-T falls below setpoint, the pumps would slow down.As the Delta-T rises above setpoint, the pumps speed up.Remember that BTUH GPM x T x 500 15

CautionBoiler Temperature Sensor Location Consideration Be careful with sensor location for boiler plant controlSensors right at plant discharge can cause boiler short cycling because of lack ofthermal massThe short cycling can significantly hurt system efficiency.Newer lower mass high efficiency boilers are very sensitive to low flow rates inthe system (VFDs) and need a thermal flywheel. (Buffer tank)Variable Speeds and Mechanical Seals – CAUTION!Minimum Speeds Effect Mechanical Seals Noise (remember the noise when you turn a pump off during the lastfew revolutions – it’s dry a dry running sealSeal face lubricationRules of Thumb 4 Pole (1,750 RPM) min 15 Hz, preferably 20 Hz6 Pole (1,150 RPM) min 25 Hz 16

Causes of Excess System Flow Poor / excessive balancingPoor control valve selection (oversizing)Improper installation of control sensorsSet point too high on DP transmittersOversized pumps (with/without VFD’s) P transducers in the wrong location is a common mistake (see next slide)Universal Problems The secondary system will try to distribute more chilled water than is needed. Thisis inefficient and used excess horsepowerHigher flow causes low system temperature differentials, excess flow and change inflow direction in the crossover bridgeThe chiller plant must keep more chillers on-line than is required by the load. Thechillers and their chiller pumps are brought on just to keep up with excessivesystem flowSolution: Designing and installing a variable speed pumping system can helpeliminate these problems. A well designed and commissioned system can greatlyimprove an owners chiller plant utilization and life cycle cost.Chiller Plants – Things to Consider The flow rate of the chiller plant should be equal to or greater than the systemflow rateChanges in the direction of flow in the cross over bridge can be used for chillerstagingControl valve problems (or balancing) can result in artificially high flows, lowtemperature differentials, and the need to rerate chillersWatch out for the physical configuration of the cross over bridge, especially 6”and above.Make sure that chiller plant loop has sufficient volume to cover chiller minimumrun times.Boilers – Things to ConsiderThe flow rate of the primary boiler plant does not need to be greater than thesystem flow rateBoiler plants and distribution loops can be designed with different temperaturedifferentials to take advantage of smaller pipe sizes and mixing in the bridgeThe mixing in the bridge can be used to protect non-condensing boilers in awater source heat pump system. 17

Benefits of Variable Speed PumpingEnergy SavingsThe Pump Affinity Laws are a series of relationships relating, Flow (Q), Head (H),Horsepower (BHP), and Speed (N in units of R.P.M.)The Affinity Laws Relating to Speed Change Are:Flow: Q2 Q1 X (N2/N1)Head: H2 H1 X (N2/N1)2Horsepower: BHP2 BHP1 X (N2/N1)3Reducing the speed has a cubed effect on HP 1/2 Speed 1/8 HPMost systems operate at reduced capacity most of their 50%50%25%12.5%25%25%6%1.2%To Trim or Not To TrimDesign Point A - 3,600 USGPM @ 55’ TDH, 12” Dia, ῃ 90.7% - BHP 55.13Actual Operating Point B - 3,900 USGPM @ 52’ TDH (throttle), 12” Dia, ῃ 90.5% - BHP 53.91Actual Operating Point C (57.5 Hz) – 3,600 USGPM @ 44’ TDH, 12” Dia, ῃ 90.7% - BHP 44.10Annual Operating Cost PER PUMP (Hospital @ 8,736 Hrs/Year, 0.11/kWh)Point A - Full Trim, no Balance 52,977.73 (not including chiller efficiency decrease)Point C - Full Trim, Speed Reduction 42,378.34ANNUAL Savings PER PUMP 10,599.39! 18

PC vs Constant SpeedDesign load 1,600,000 BTU’s or 160 USGPM @ 20 deg T25% load (shoulder heating season) 400,000 BTU or 40 USGPM TDH @ constant speed TDH @ constant pressure TDH @ proportional pressureBHP BHP Design BHP 25 % BHP pc BHP pv H (Ft) x Q (Usgpm)Eff (0.?) x 396035 Ft x 160 Usgpm0.6 x 396043 Ft x 40 Usgpm0.4 x 396035 Ft x 40 Usgpm0.6 x 396013 Ft x 40 UsgpmDesign flow – 160 USGPM25% load flow – 40 USGPM0.6 x 3960 2.4 1.2 0.6 0.2Let‘s Talk About EfficiencyFlow(% of BEP)Motor Load(% Full Load)100%75%50%25%15 Hp (100%)7 Hp (42%)2 Hp (13%)0.3 Hp (2%)Motor Eff*93%92.6%85%78%Drive Eff**96.5%93.5%84.5%44%* 15 Hp Premium Efficiency** VFD interpolated from “Energy Tips – Motor (Motor Tip Sheet #11) July 2008Calculating Annual Electrical Cost to Operate a Pump – need to know: Information above on motor (driver) and drive (VFD) – efficiency at various loads# of operating hours at each flow (load) condition (load profile – heating or cooling)Average cost of electricity (USA average is 0.11 per kW)Head, flow and efficiency of the pump (wet end) - assume constant with VFDLine to Water kW 0.745 xH (Ft) x Q (Usgpm) x SGῃP x ῃM x ῃD x 3960500 x 81 x 1.00.74 x 0.93 x 0.96.5 x 3960“Knowns” 500 USGPM @ 81’ (100% load or flow) Pump efficiency @ H/Q “design” 74% Motor efficiency @ design 93% Drive efficiency @ design 96.5% Assume SG 1.0 19

Motor Efficiency – AC Motors Optimum operating range 60% to 80%!EISA, NEMA and ASHRAE only refer to FULL LOAD minimum efficiencyEnergy Efficient Circulator Options European energy efficient circulator technology is becoming availabletoday in U.S. but acceptance has been slow because:–––––U.S. hydronic heating installed base is much smaller than EUA very small portion of new homes in the U.S. use hydronic heat.U.S. hydronic systems typically only run for small portion of yearElectricity in U.S. is less expensiveCost of energy efficient circulators is nearly double traditional wet rotorcirculators. 20

Comparison AC / EC MotorAC-motorNon controlled or VFD controlledAsynchronous-squirrel-cage motorRotor is a sheet steel pack with nail likerods parallel to the rotor shaftThe rotor movement is caused by therotating stator magnetic fieldEC-motor Viridian ECM Technology– Brushless electronically commutatedsynchronous motor using a permanentmagnet rotor– The rotor magnetic field “grabs” therotating stator magnetic field, causingrotor rotation– Rotor (impeller) speed is determined bythe pre-programmed drive software.Benefits of ECM Technology Viridian is 15 to 20% more efficient than pump / VFDPermanent magnet (ECM) motors have flatter torque / efficiency curves than ACmotors (better motor efficiency at low motor loads) PM rotor is driven by magnetic field created by the motor windingsOpposite polarity attracts, similar polarity attracts at the same time!Higher “turn down” ratios (max vs. min speed relationship – Viridian is 6.8 to 1!)PM motors have 300 to 400% higher starting torqueViridian is soft start (no power surge)Doesn’t consume any energy in order to magnetize the rotorCreates continuous thrust 21

-30-10 10 30 50Pressure HPercentage of output(HVAC systems are DYNAMIC – loads / flows continually change)Seasonal load profilePump load profileFlow (USGPM)Outdoor Air Temp6% time at design load (max)15% time at 75% design load35% time at 50% design load44% time at 25% design loadPower PHeating - Pump Operation:Flow (USGPM)-30-10 10 30 50Pressure HPercentage of output(HVAC systems are DYNAMIC – loads / flows continually change)Seasonal load profilePump load profileFlow (USGPM)Outdoor Air Temp% LoadOld % HrsCurrent % Hrs100171753942503345251112Power PAC Part Load Analysis - ARI StandardFlow (USGPM) 22

Energy Savings Calculator – Chilled WaterCW Load Profile and 8000 Hours, 0.11 / kWhChilled Water ‐ Constant Speed Pumps, Throttling Valves (no VFD's)% Load ConditionsARI Standards% LoadGPMHead (ft) Eff Pump Eff Motor Drive NIC(USGPM)Wire to P1 to P4Annual KW Annual Costwater effHp1%100%50080.6574%93%100%69%14.761181 %64%46%13.0112.724371145805 4,808 5,03912%25%12595.9737%62%100%23%13.2112677 1,395Totals103375 11,371.25Chilled Water ‐ Variable Speed PumpsWire to P1 to P4Annual KW Annual Costwater effHp% Load ConditionsARI Standards% %GPMHead (ft) Pump Eff Motor Eff(USGPM)Drive Eff15.346.712.401227225468638 135 2,480 9500.62597 66Totals33008 3,630.88Energy Savings Calculator - HeatingHeating Load Profile and 6000 Hours, 0.11 / kWhHeating ‐ Constant Speed Pumps, Throttling Valves (no VFD's)% Load Conditions EUStandards% LoadGPMHead (ft) Eff Pump Eff Motor(USGPM)Drive NICWire towater effP1 to P4Annual KW Annual CostHp6%100%50080.6574%93%100%69%14.765315 58515%75%37587.5170%91%100%64%13.0111708 1,28835%50%25092.7559%78%100%46%12.7226720 2,93944%25%12595.9737%62%100%23%13.2134863 3,835Totals78606 8,646.67Heating ‐ Variable Speed Pumps% Load Conditions EUStandards% LoadGPMHead (ft) Pump Eff Motor Eff(USGPM)Drive EffWire towater effP1 to P4Annual KW Annual CostHp6%100%50080.774%93%97%66%15.345523 60815%75%37545.474%93%94%64%6.716039 66435%50%25020.274%85%85%53%2.405039 55444%25%125574%78%44%25%0.621641 180Totals18242 2,006.60 23

Payback AnalysisBased on 6,480 annual operating hours, pump costs and 0.11/kWh cost of powerData from LCL Excel file for energy comparison – Viridian vs1900 SeriesECM and Self Sensing TechnologyFAQs: Availability of larger ECM motors ECM motors in Residential markets ECM/Variable Flow in Solar – why/why not? State Incentive Programs – residential and commercial ECM Failure Modes Available Voltages Sensor Lessons Learned ASHRAE and DOE Activities 24

ASHRAE?DOE Regulations?Incentives?Federal regulations mandateall states use ASHRAE 90.1 orIECC as a minimum efficiencystandard 25

ASHRAE 90.1 - 2010All about T. Either control directly with atemperature reactive VFD pump or valvesand a pressure reactive pumpVSD (VFD) pumps are mandated for use onsecondary systems on larger systemsReducing pump flow by 50% 10 Hp onsystems with valves30% wattage at 50% design flow descriptor P sensor locationLoadMatch systems are NOT required tohave variable speed pumping as they haveno more than 3 control valves 26

30% wattage at 50% design flow descriptorHigher velocities (smaller pipes) with VFD!DOE?Regulation Due this fall – 5 years to comply 27

DOE?Full Effect 2019?Extended Product – Pump/Motor/Drive Probable regulation evaluates variable load line to water efficiencyPump/Motor Probable regulation evaluates constant load line to water efficiencyState Incentive Programs 28

Facts and Figures2000 Figures 40 Quads (1 Quad quadrillion Btu’s) of electricity is produced annually in the USA13 Quads (3,800 billion kWh) of electricity is delivered from the source to the pointof use – balance is lost via thermal waste heat to the environment!Approx 40% of the energy consumed in the USA is used in Commercial Buildings25% of the energy consumed by a commercial building used for fans and pumps(1.5 Quads)Of the 1.5 Quads: 5% for heating water pumps2% for condenser water pumps2% for chilled water pumpsWhere did the electricity come from? Coal generated51% (1.968 billion kWh)Nuclear20% (754 billion kWh)Natural Gas16.1% (1.141 billion kWh)Hydroelectric7% (273 billion kWhPetroleum (oil)3% (109 billion kWh)Source – USGBC & EIA Annual Energy Outlook 1998, ref 1Variable Flow Pumps – Control StrategiesBBT Conference – Feb 4/5, 2015Presented by Steve ThompsonVP - Residential Product Management – Taco Inc.Mobile (401) 441-2934E Mail: stetho@taco-hvac.com 29

VALVE BYPASS W/VALVE TERMINAL UNIT PRIMARY PUMP DIFF. PRESSURE TRANSMITTER CONTROL VALVE BYPASS W/VALVE TERMINAL UNIT PRIMARY PUMP DIFF. PRESSURE TRANSMITTER 80’ setpoint 17’ setpoint Location of P Transmitters Effeciencies are dramatically affected Differential Temperature Delta-T le

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