Fundamentals Of Hydronic System Design
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This document provides an agenda for a class on hydronic system design fundamentals. The agenda includes: 1. A short introductory class on very basic hydronic system concepts and taking notes. 2. A general class covering: - Design problem analysis - System design and calculations - Pump selection - Control and system balancing - Advanced concepts 3. Review of key hydronic system design concepts like Bernoulli's equation, pressure units, and air management in hydronic systems. 4. Overview of the closed loop hydronic system design method including calculating facility load, selecting heat transfer devices, calculating system flows, schematically designing piping, and addressing piping configurations.
Fundamentals Of Hydronic System Design
- 1. Agenda 1. “Short Class” Fundamentals of Hydronic System Design 1. Very Fundamental 2. You take notes May 8, 2009 ASHRAE Region 6 2. General Class Flow Chapters Region Conference 1. Design Problem Mark Hegberg 2. System Design & Calculation Product Manager, Danfoss Heating Controls 3. Pump selection 4. Control & System Balance 5. Advanced Concepts Daniel Bernoulli Bernoulli Equation V12 P1 V2 P P2 z1 z 2 2 2 HL V2 2g ρ1 2g ρ2 HL Z2 P1 V1 Z1 1
- 2. Bernoulli’s Equation... Pressure Units • Elevation - Potential Energy Of The System, Lifting The Fluid Standard 14.7 PSIA • Fluid Velocity: Kinetic Energy and Effects of Gravity or Atmospheric • Pressure & Density: Flow Energy Work Done On Pressure 0 PSIG Surroundings By Fluid Z Elevation V2 Fluid Velocity In Pipe 2g Perfect 0 PSIA P Pressure or Vacuum -? PSIG ρ Fluid Density HL Head Loss Hair Gear Spring Units: Pointer • Inches Difference • Feet Link In Length • Millimeters Bourdon • Meters Tube Sector Liquid Fill & Pinion • Water • Oil Stationary • Mercury Socket Pressure Connection 2
- 3. Pressure • Or Another Way Of Looking At It; 1' 1' 62.34 Lb. 1Ft 2 Ft 3 144 In2 Water 1' 62.34 Lb Lb. 0.443 12" In2 or 2.31Ft Or: 0.433 psi / Ft. 12" Ft 1PSI • A 231 Foot Long Manometer Is Inconvenient for Measuring 100 PSI, and In The Old Days A Common Dense Fluid Was Mercury... 1' Standard 14.7 PSIA Atmospheric or 1' 844.87 Lb. 1Ft 2 0 PSIG Pressure Ft 3 144 In2 Mercury 1' 844.87 Lb Lb. ≈30 In Hg 5.87 In2 or 0.17 Ft 12" Ft 1PSI 0 PSIA Perfect or or 12" Vacuum -? PSIG 2.04 In Hg 1PSI 3
- 4. Standard Atmospheric Pressure Standard 14.7 PSIA Atmospheric or Lb Lb In Hg 1 0 PSIG 14.7 2 11 2 2.04 7 In Hg Pressure in in PSI 2 ≈30 In Hg 11 PSIA Perfect 0 PSIA Perfect or Vacuum -? PSIG Vacuum Pressure Static Pressure • For this class our reference will be; • Static Pressure Is The Elevation • It’s Created By The Weight Of A Vertical Column Of Water 4
- 5. And That Other Unit of Measure? Feet of Head Feet of Head Why Use Pump Head? Pump Rated For 30 Ft Head @ Flow Density = 62.34 lbs/cu ft Density = 60.13 lbs/cu ft Density = 57.31 lbs/cu ft • Remember Bernoulli Really Described Energy 62.34 144 = 0.43 psi/ft 2.3 ft / psi 60.13 144 = 0.41 psi/ft 2.44 ft / psi 57.31 144 = 0.40 psi/ft 2.5 ft / psi • Pumps Do "Work" On The Water 30 ft X .43psi/ft =12.9psi 30 ft X .41psi/ft =12.3psi 30 ft X .40psi/ft =12.0psi 12.9 psi X 2.3 ft/psi = 30 ft 12.3 psi X 2.44 ft/psi = 30 ft 12.0 psi X 2.5 ft/psi = 30 ft • Work Is Measured In Ft-Lbs • Water Is Measured In Pounds 92.9 psi 92.3 psi 92.0 psi Ft - Lb P=12.9 P=12.3 P=12.0 Lb 80.0 psi 80.0 psi 80.0 psi Water @ 60 F Water @ 200 F Water @ 300 F 5
- 6. Review Design Problem • Pumps Do The Work: They Add Energy To the Fluid System • Three Story Building – We “Pump” Pounds of Fluid – Four Zones Per Floor – Work Measured In Foot-Pounds – Each Zone 14 Tons Air Conditioning – Foot-Pounds of Work Per Pound Fluid Pumped – 168 Total Tons • Pounds Cancel; We’re Left With Feet or “Head” – Evaluate at Constant Entering Air 78½°F DB, • “Density Independent” 65½°F WB • Three Components To Total Head (Work) – 42°F EWT, 16 ½°F ΔT – Elevation, Velocity, Pressure • Work Done on System Components – Head or Pressure Losses Develop “Flat” Layout 6
- 7. Closed Loop Hydronic System Design Method Air Management How Does It Work? • Air Is In Water, and Goes 1. Calculate Facility Load Into and Comes Out Of • Pumps Provide Solution As A Function Of Set Space Design Criteria Differential Pressure By Pressure & Temperature Converting Electrical Building Code Requirements Energy To Move Water ASHRAE Requirements Standard 62.2; Air/Ventilation Requirements Standard 90.1; Energy Pump Standard 55; Thermal Comfort Coil Standard 111; Test & Balance • Adds Heat Guideline 1; Commissioning • Rejects Heat Examine Load Requirements • Changes Water Temperature Source Zone Distribution • BTU/Hour Pipes HVAC Method • Pipes & Coils Provide “Resistance” You Use Diversity; Do Not Use Diversity When Sizing Pipes & Pumps Energy In Form of Pressure To Move Water System Load System Impacts • •ASHRAE’s Latest: 1998 “Cooling && ASHRAE’s Latest: 1998 “Cooling Heating Load Calculation • Heat Transfer Becomes Water Flow Heating Load Calculation Principles” (RP-875) Pedersen, Principles” (RP-875) Pedersen, – Over Estimation Causes Over Calculation of Flow Fisher, Spitler, Liesen Fisher, Spitler, Liesen • •Air Conditioning Contractors of – Energy Efficiency Impacted Air Conditioning Contractors of America America – Leads To Bigger Coils & Oversized Control Valves • •Manufacturer Load Programs Manufacturer Load Programs • Controllability Impacted – System Load – System Load – Block Load • Changes Desired Coil Performance – Block Load • •“Old” Carrier Manual “Engineering “Old” Carrier Manual “Engineering Guide for System Design” (1963) Guide for System Design” (1963) 7
- 8. Closed Loop Hydronic System Design Method Calculate Flow 2. Select Heat Transfer Devices Source; Desired System Operating Differential • Flow Temperature Load; Coil that offers required performance at calculated gain conditions Heating, Cooling & De-Humidification Operating system differential temperature Q m cP ΔT 3. Calculate and “Analyze” System Flows lb. min Btu Q 8.34 60 GPM 1 (TLvg TEnt ) Total System Flow gal hr lbm F Zone Flow Q 500 Flow T Can the required operating differential temperature be achieved? Alternative piping and pumping considerations Required Water Flow Thank You! Scott Blackmore & B&G System Syzer Q 500 q ! T (14 12,000) 500 q 16.5 (14 12,000) • Scale 1 q 20 gpm • Align 16½°F ΔT 500 16.5 • 168(,000) • 80 GPM / Floor • Read Flow • 240 GPM Building 8
- 9. 240 160 80 Hydronic Coil Heat Transfer 40 40 40 80 80 80 20 20 20 20 20 20 40 40 40 40 40 40 • Air Side Heat Transfer • Water Side Heat Transfer 20 20 20 20 20 20 q UA( LMTD ) q=mcp(t2-t1) 80 80 80 40 40 40 Where LMTD is the air- water log mean Where t is the water temperature difference temperature rise 240 160 80 2 Pipe Control Hot 120% Water Hot Water Coil Heat Transfer Hot Water Coil Heat Transfer Performance Vs. Water Side ΔT Performance Vs. Water Side ΔT Coil M C 97.5% 100% The coil Heat The coil performance Transfer performance is not linear is not linear % Heat Transfer 80% T °Δ T 20 T °Δ t1 60 60% Al t2 Al 40% 20% 75% 90% Design Design 0% Flow Flow % Water Flow 9
- 10. Coil Heat Transfer General Coil Notes 100% 4 Row Tot Total Heat Transfer 90% 4 Row Sens 4 Row Lat • Traditionally, sensible heat transfer is 80% 5 Row Tot 5 Row Sens controlled by throttling flow 5 Row Lat 100% • Coil performance tends to be non-linear Percentage Heat Transfer 6 Row Tot 70% 6 Row Sens 6 Row Lat Sensible Heat Transfer 60% – More non linear with low water ΔT (6ºF) 50% – More linear with higher water ΔT (16ºF) 40% 50% • Coil pressure drop affects 30% – Main & branch pipe sizing 100% 20% – Control valve operation (valve authority) 10% 50% – System balance Latent Heat Transfer 0% 0% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percentage Water Flow Rate 4. Schematically Design Piping General Notes: Air Bind Select Terminals / Heat Transfer Coils Component Drops • Adequate Operating Differential To Create Flow Note Coil Characteristic for Temperature Drop Locate Terminals / Heat Transfer Coils Address Area Fit Constraints 1½’ – Size of Unit 3’ Air – Area of Application Water Examine Piping Geography A B Develop Pipe Sizing Criteria Select Control Valve Supply Main Return Main Examine Valve Authority 10
- 11. General Notes: Air Bind General Notes: Air Bind • Adequate Operating Differential To Create Flow 1½’ 3’ Air 3’ Water Riser Water Level 1’ Displaced By 1’ B Supply Main Return Main B B Supply Main Return Main B ΔH A to B = 1’ ΔH A to B = 5’ General Notes: Air Bind Ensure Adequate Differential Potential For Air Binding Low Pressure Drop Low Pressure Drop High Pressure Drop 3’ Supply Main A B Supply Main Return Main B ΔH ΔH A to B = 5’ B Return Main 11
- 12. Avoid Ghost Flow Circuits Piping Configuration • Single Pipe Systems – Single Load – Multiple Load Open • Two Pipe Systems (Supply & Return) A – Constant Flow Single & Multiple Load – Variable Flow Single & Multiple Load Closed B • Hybrid Systems – Bypass Systems – Primary-Secondary-Tertiary Single Pipe System Single Pipe Grid Coil • Depending On “T” Advantages: Branch Loss – General Guidance: “B” • Simple System! Length Should Be Twice That of “A” • Less Costly Piping – High Potential of Air B Binding In Grid Disadvantages: – Raising Water Temperature To Compensate Causes Panel • Simple System! Flux To Be Too High • Zone Temperature Control • Guidance: Intertwined Matched Tagged To Serpentine Coils (Most Pex Source Production A Based Systems Wind Up This Way) 12
- 13. Closed Loop Circulating System Two Pipe, Direct Return Definition: Elevation Differences Do Not Cause Flow Definition: Contact With Air At One Location Or Less Two Pipe Distribution System Two Pipe Variable Flow Riser (Main) Distribution System Supply Advantages: Disadvantages: Old Balancing Technique; • 2:1- BRPDR 90% design Branch • Water Flow Is Variable • Chiller Sees Variable Flow flow at all terminals – Saves Pump HP • Flow Through Coil Is • 1:1- 80% • Water Coil Provides Better Throttled Creating Variable Control of Temperature & Return Water Temperature Humidity To Chiller • Temperature To Each Coil Is • Must Balance Coil Branches Return Constant Per Chiller In Relation To Each Other Riser (Main) 13
- 14. 2 Pipe Direct Return Has Unequal Differential Pressures Two Pipe Constant Flow Distribution System Advantages: 100% Supply • Source Sees “Constant” Flow • Water Coil Provides Better Control of Temperature & Humidity • Temperature To Coil Is Constant ΔP3 T Per Source Head ΔP1 ΔP2 Disadvantages: • Water Flow Is “Constant” • Flow Through Coil Is Throttled Creating Variable Return Water Return Temperature To Source • More Components: Valves 0 • Must Balance Coil Bypass Pipe ΔP Distance From Pump Two Pipe Variable Flow Reverse Return System 2 Pipe Reverse Return Has More Equal Differential Pressures 100% ΔP1 ΔP2 ΔP3 Head 0 Distance From Pump 14
- 15. Applying Reverse Return Calculating Friction Head Loss • Loads Should All Be Within 25% Of Each Other • hf = Energy Lost Through Friction Expressed As Fluid • If Zone Control Is Used, All Branches Should Feet Of Head, Feet Of Fluid L V 2 Flowing Be In Similar Zones hf f D 2g • f= Friction Factor • You May Still Have To Balance System • L= Length Of Pipe Darcy-Weisbach Eqn. • D= Pipe Diameter • V= Fluid Average Velocity, Ft/Sec (Flow / Pipe Area) • g= gravitational constant 5. Size Piping & Calculate Drops Design Criteria For Balanced Piping Size Pipes In Branches First 2-10 FPS / 1’-4.5’ P Per 100’ (Steel) Determine Highest Branch Drop & Length Examine Pressure Drops Closely For Hydronic Balance Add Coil Drop – Branch To Riser Pressure Drop Ratio Helps System Balance In Tolerance Valve Drop Equal To Coil & Pipe or PICV pressure drop • 4:1 95% Design Flow All Circuits Select Branch To Riser Pressure Drop Ratio • 2:1 90% Design Flow Calculate Mains • 1:1 80% Design Flow Divide Worst Branch PD By Ratio, and Then 2 (S&R) • Constant Speed Pump Divide Riser Total Drop By Pipe Length (Target Design Rate) Examine Target Rate • Issues – Within ASHRAE Guidelines – Equipment Room Piping – Enough Pipe Length vs. TEL Of Fittings Size Risers – Variable Speed Calculate System & Branch Drops 15
- 16. 240 160 80 240 GPM 160 80 40 100’ 20’ 20’ 100’ B 20’ C 20’ 40 GPM 1 40 40 40 30’ 30’ A 80 80 80 80 3 30’ 30’ 20’ 20 20 20 20 20 20 4 20 20 5 6 2 30’ 30’ 30’ Source Source 40 40 40 40 40 40 40 GPM 40 GPM 30’ 30’ 30’ 7 8 20 20 20 20 20 20 F 10 20 20 9 30’ 80 80 GPM 11 80 80 30’ 40 40 40 30’ 30’ 40 GPM 100’ E 20’ D 20’ 12 240 160 80 240 GPM 160 80 Flow Segment A B C 1-2 2-3 3-4-6 3-5-6 6-7 2-8 8-10-11 8-9-11 11-7 7-12 D E F Calculate Friction Losses Size Length HF Rate HF Friction Loss Fittings • Know Length Of Pipe Service Valves Coil Control Valve – Work Darcy-Weisbach Equation Balance Valve Source – Use Design Tool Total • Count Fittings Path Path Total A-1-2-3-4-6-7-12-F – Example: I’m applying stock head loss A-1-2-3-5-6-7-12-F A-1-2-8-10-11-7-12-F A-1-2-8-9-11-7-12-F – You In Practice: Don’t do this! • Determine Branch & Riser Losses A-B-1-2-3-4-6-7-12-E-F A-B-1-2-3-5-6-7-12-E-F A-B-1-2-8-10-11-7-12-E-F A-B-1-2-8-9-11-7-12-E-F A-B-C-1-2-3-4-6-7-12-D-E-F – Coils, Specialty Devices A-B-C-1-2-3-5-6-7-12-D-E-F A-B-C-1-2-8-10-11-7-12-D-E-F – Trying To Get Rough Cut for Control & Balance Valves A-B-C-1-2-8-9-11-7-12-D-E-F 16
- 17. Copper Pipe Friction Loss Friction Loss Charts Head Loss Due To Friction, Ft. Per 100 Ft. Pipe • Published by ASHRAE & Hydraulic Institute • D/W Eqn. Add 15%! Add 15%! Volumetric Flow Rate, GPM 2” 3¼ Scale 2 Pipe Sizing Scale 3 Velocity Check 17
- 18. 2” 3.6 Pipe Sizes ½”-2” Fitting Pressure Loss Fitting Loss Pictogram • Variety of Fitting Loss Methodologies Accuracy Varies Widely Elbow Equivalents (Least Accurate) Total Equivalent Length “K” Factor (Current ASHRAE Recommendation) V2 Hf = K 2g 18
- 19. Fitting Pressure Loss How Do Fitting Drops Stack Up? Rahmeyer “K” hf hf % TEL hf % K hf Over Over GPM TEL “K” “K” K2 K2 hf 2” 90° Steel Elbow (K=1) 15 .04 .03 26 .505 98 <3FPS 20 .07 .03 127 .535 -18 • 1961 H/I TEL 8.5’ 25 .11 .09 24 .535 51 30 .15 .13 18 .543 56 • ASHRAE - H/I “K” Factor 35 .20 .17 15 .552 57 40 .26 .23 15 .561 55 • ASHRAE RP-968 45 .33 .29 15 .57 53 50 .39 .35 .626 45 >11FPS – (Rahmeyer); K Factor varies 10 widely as a function of 116 1.9 1.91 0 .71 41 velocity • Organize through spreadsheet Moving Towards Pump Selection… SEGMENT A B C 1-2 2-3 3-4-6 3-5-6 6-7 2-8 8-10-11 8-9-11 11-7 7-12 D E F Flow 240 160 80 80 40 20 20 40 40 20 20 40 80 80 160 240 Size Length 4" 100' 3" 20' 2.5" 20' 2.5 30 1.5 1.25 1.25 1.5 30 60 60 30 1.5 30 1.25 60 1.25 60 1.5 30 2.5 30 2.5" 20' 3" 4" 20' 100' • Friction Losses Unaccounted for; HF Rate 3 5.5 4.5 4.5 12.5 9 9 12.5 12.5 9 9 12.5 4.5 4.5 5.5 3 – Control Valve Friction Loss 3 1.1 0.9 1.35 3.75 5.4 5.4 3.75 3.75 5.4 5.4 3.75 1.35 0.9 1.1 3 Fittings 2 2 2 2 2 2 2 2 2 2 2 2 Service Valves 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Coil 17 17 17 17 Control Valve • Need to understand “controls” Balance Valve Source – Balance Valve 30 Total 5 3.1 2.9 3.35 7.75 26.4 26.4 7.75 7.75 26.4 26.4 7.75 5.35 4.9 5.1 37 PATH TOTAL • Need to understand “balance” A-1-2-3-4-6-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-1-2-3-5-6-7-12-F – Suction Diffuser 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-1-2-8-10-11-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-1-2-8-9-11-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-B-1-2-3-4-6-7-12-E-F A-B-1-2-3-5-6-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 • Should understand pumps 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-1-2-8-10-11-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-1-2-8-9-11-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 – Pump Discharge Valve(s) A-B-C-1-2-3-4-6-7-12-D-E-F 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 A-B-C-1-2-3-5-6-7-12-D-E-F A-B-C-1-2-8-10-11-7-12-D-E-F 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 • Should understand pumps and systems 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 A-B-C-1-2-8-9-11-7-12-D-E-F 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 19
- 20. Room Air Re-circulated Automated Control Heated Room Controller Unit Heater Control Signal Actuator Hot Water Coil Blower Add Valves Automated Control Theory Energy is lost Energy is lost Disturbances proportionally to proportionally to the outside the outside Heat Gains • Solar temperature temperature • Change Weather q = UA(Ti-TO) ) q = UA(T -T i O • People Manipulate Coil Control Water Blower Temperature The controller output signal Flow Process The controller output signal acts in a proportional manner acts in a proportional manner to the difference in the actual to the difference in the actual from the desired temperature from the desired temperature adding what is lost adding what is lost 20
- 21. Theory A Fairly Simple Concept... Disturbances • Unaccounted for Changes In • We control for comfort as indicated by Heat Gains Differential Head • Friction Head Loss temperature Water Flow Distribution Air Flow • Pressure Control – Humidity Control “Implied” By Coil Selection Dynamics • Various levels of implementation Manipulate Coil – Economic Criteria Control Water Blower Temperature – Process Criteria Flow Process – Paradigm Criteria Proportional Control Proportional Control SP + e t K Ke e ns MV - e po 0-10 VDC Output es Output Error 0-10 VDC rR Signal SP Control Signal ea Lin “Control Theory” e - Error y 0-10 VDC t Output 0-10 VDC SP Control Signal Room Controller Room Controller Actuated Valve Actuated Valve 21
- 22. Proportional Control Traditional 2 Way Valve Temperature Control M C • Controller controls y because response t is predictable 0-10 VDC Output 0-10 VDC SP Control Signal T • Variable coil flow Room Controller • Variable system y flow • “Why” variable (y-yi)=K(t-ti) speed pumping Actuated Valve can be used y = Valve Position yi = Initial Valve Position t = Temperature ti = Initial Temperature K = Constant (gain) Valve Characteristic • ASHRAE Research (RP-5) Boiled It Down To This 100% – Just About Every HVAC Text On Valves Uses This Type of Figure Quick Opening 90% – The Coil Gain (Proportional Band) Isn’t the Same As The 80% Controllers… Why We Use An Equal Percentage Valve 70% Controlled Coil Characteristic Valve Characteristic Relationship % Branch Flow 60% Linear n 50% Ga i 40% in Ga 30% in Ga 20% Gain 10% Equal Percentage 0% 0% 20% 40% 60% 80% 100% % Valve Lift Source: ASHRAE Handbook 22
- 23. Linear Stem Valves (Globe) Controllability ~ Constants • Constant Differential Pressure Keeps Predictable Flow Characteristic Coil 1% 8% To Select Properly; • Required Flow Rate (GPM) • Select Differential Pressure TC Valve – Magnitude Depends On; Throttle In • Control; Open-Closed/Modulating Here 90% Time • Hydraulic Design Philosophy; Balanced, Unbalanced, Branch & Riser Pressure Drops • Pump Control; Constant vs. Variable Speed • Required Valve Authority – Consider Characteristic Requirement Adjustment Proportional Action THROTTLING % 100 0% 10% 100% • Two Position POSITION OF CONTROLLED DEVICE Room Temperature 75 Set Point % OF STROKE 50 25 Valve Position Open 0 0 25 50 75 100 CONTROLLED VARIABLE % OF CONTROLLER SCALE 23
- 24. Proportional Action Valve Description • Proportional Positioning • Many terms describe valves Room Temperature • Flow Coefficient Set Offset Point – CV – Rangeability Open Valve Position Closed Control Valve Integration Flow Coefficient EQUAL PERCENTAGE CHARACTERISTIC 100 75 % OF FLOW 50 25 y 0 0 25 50 75 100 ΔP q CV % OF VALVE STROKE SG 24
- 25. Flow Coefficient Rangeability Max Flow Q q 500(t ent t lvg ) Heat Transfer Min Flow • With & W/O Actuator ΔP Units = PSI • Without Actuator, 30:1 Flow q CV • With Actuator, 100+:1 SG Water = 1 • Globe Valves “De-Facto” Standard • Ball Valve… Calculate Desired Live with Available The Goal; Make the red line straight and 100% to 100% Authority 100% istic Ch ar act er • Valve authority affects controllability C oil 80% • The Controller cannot control properly ic ist = PMIN / PMAX rity er ct t ho ra ha 60% Au lC Return Supply % ro tic nt 50 Co ris te 40% ac ar Ch PENT % Eq 20% PMAX PMIN Maximum Valve Stroke 0% 0% 20% 40% 60% 80% 100% 120% 140% PLVG 25
- 26. Valve Authority Valve Characteristic and Authority 100% Return Supply 90% 80% .1 70% = β % Branch Flow .3 60% .50 β= 1. 0 50% = β β= 40% CV2 CV1 CV2 30% Constant Flow Coefficient 20% Valve Specification C V1 C V2 Valve Specification Pipe 10% • Modified Equal Percentage Valve • Modified Equal Percentage Valve • Globe Pattern C VSYS • Globe Pattern Coil • 2” Size • 2” Size • 30:1 Rangeability Service Valves 0% • 30:1 Rangeability Balancing Valves Variable: Control Valve C2 C2 V1 V2 0% 20% 40% 60% 80% 100% % Valve Lift Selection Understand Hydraulics • Required Flow Rate (GPM) 100% • Select Differential Pressure ΔP1 ΔP2 – Magnitude Depends On; • Control; Open-Closed/Modulating Head • Hydraulic Design Philosophy; Balanced, ΔP1+ΔP2 ΔP2 ΔP3 Unbalanced, Branch & Riser Pressure Drops • Pump Control; Constant vs. Variable Speed • Required Valve Authority – Consider Characteristic Requirement 0 • Solve Algebraically Distance From Pump 26
- 27. Balance Valve Considering Our Example • Temperature Control Valves Balance: – Electronically Actuated – Farthest Circuit (Highest Head Loss) 108.6’ – Characteristic for control – Middle Circuit; 100.8’ – About 8’ required to balance • Temperature Control Valves Static Balancing Valve Require Balancing Valves – Closest Circuit; 92.6’ – About 16’ required to balance – “Static”; “Circuit Setter”: Constant Control Valve: speed flat curve pumping systems with “low” head loss distribution – 50% Authority means 108’ (47 psi) selection pressure systems drop! A 216 foot head pump!! – “Dynamic” or Automatic Flow Options: Limiting; Variable Speed Variable Flow Pumping Systems –? Dynamic Balancing Valve Cartridge SEGMENT A B C 1-2 2-3 3-4-6 3-5-6 6-7 2-8 8-10-11 8-9-11 11-7 7-12 D E F Flow 240 160 80 80 40 20 20 40 40 20 20 40 80 80 160 240 • Actually calculate and show all fittings and losses… Size Length HF Rate 4" 100' 3 3" 20' 5.5 2.5" 20' 4.5 2.5 30 4.5 2 30 1.5 1.5 60 60 2 30 3.25 3.75 3.75 3.25 2 30 1.5 60 3.25 3.75 1.5 60 2 30 3.75 3.25 2.5 30 4.5 2.5" 20' 4.5 3" 4" 20' 100' 5.5 3 Friction Loss 3 1.1 0.9 1.35 0.98 2.25 2.25 0.98 0.98 2.25 2.25 0.98 1.35 0.9 1.1 3 Fittings SEGMENT A B C 1-2 2-3 3-4-6 3-5-6 6-7 2-8 8-10-11 8-9-11 11-7 7-12 D E F Service Valves Flow 240 160 80 80 40 20 20 40 40 20 20 40 80 80 160 240 Coil 17 17 17 17 Size 4" 3" 2.5" 2.5 1.5 1.25 1.25 1.5 1.5 1.25 1.25 1.5 2.5 2.5" 3" 4" Control Valve Length 100' 20' 20' 30 30 60 60 30 30 60 60 30 30 20' 20' 100' Balance Valve HF Rate 3 5.5 4.5 4.5 12.5 9 9 12.5 12.5 9 9 12.5 4.5 4.5 5.5 3 Source 30 Friction Loss 3 1.1 0.9 1.35 3.75 5.4 5.4 3.75 3.75 5.4 5.4 3.75 1.35 0.9 1.1 3 Total 3 1.1 0.9 1.35 0.98 19.3 19.3 0.98 0.98 19.25 19.25 0.98 1.35 0.9 1.1 33 Fittings 2 2 2 2 2 2 2 2 2 2 2 2 Service Valves 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 PATH Coil 17 17 17 17 TOTAL Control Valve A-1-2-3-4-6-7-12-F 3 1.35 0.98 19.3 0.98 1.35 33 59.9 Balance Valve A-1-2-3-5-6-7-12-F 3 1.35 0.98 19.3 0.98 1.35 33 59.9 Source 30 A-1-2-8-10-11-7-12-F 3 1.35 0.98 19.25 0.98 1.35 33 59.9 Total A-1-2-8-9-11-7-12-F 3 1.35 0.98 19.25 0.98 1.35 33 59.9 5 3.1 2.9 3.35 7.75 26.4 26.4 7.75 7.75 26.4 26.4 7.75 5.35 4.9 5.1 37 PATH A-B-1-2-3-4-6-7-12-E-F 3 1.1 1.35 0.98 19.3 0.98 1.35 1.1 33 62.1 TOTAL A-B-1-2-3-5-6-7-12-E-F 3 1.1 1.35 0.98 19.3 0.98 1.35 1.1 33 62.1 A-1-2-3-4-6-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-B-1-2-8-10-11-7-12-E-F 3 1.1 1.35 0.98 19.25 0.98 1.35 1.1 33 62.1 A-1-2-3-5-6-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-B-1-2-8-9-11-7-12-E-F 3 1.1 1.35 0.98 19.25 0.98 1.35 1.1 33 62.1 A-1-2-8-10-11-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-1-2-8-9-11-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-B-C-1-2-3-4-6-7-12-D-E-F 3 1.1 2.9 1.35 0.98 19.3 0.98 1.35 0.9 1.1 33 65.9 A-B-C-1-2-3-5-6-7-12-D-E-F 3 1.1 2.9 1.35 0.98 19.3 0.98 1.35 0.9 1.1 33 65.9 A-B-1-2-3-4-6-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-C-1-2-8-10-11-7-12-D-E-F 3 1.1 2.9 1.35 0.98 19.25 0.98 1.35 0.9 1.1 33 65.9 A-B-1-2-3-5-6-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-C-1-2-8-9-11-7-12-D-E-F 3 1.1 2.9 1.35 0.98 19.25 0.98 1.35 0.9 1.1 33 65.9 A-B-1-2-8-10-11-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-1-2-8-9-11-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 • Upsize pipe; Ignore fitting & service valve losses A-B-C-1-2-3-4-6-7-12-D-E-F A-B-C-1-2-3-5-6-7-12-D-E-F 5 5 3.1 3.1 2.9 2.9 3.35 3.35 7.75 26.4 7.75 7.75 26.4 7.75 5.35 5.35 4.9 4.9 5.1 5.1 37 37 108.6 108.6 • 40% Reduction in head A-B-C-1-2-8-10-11-7-12-D-E-F A-B-C-1-2-8-9-11-7-12-D-E-F 5 5 3.1 3.1 2.9 2.9 3.35 3.35 7.75 7.75 26.4 7.75 26.4 7.75 5.35 5.35 4.9 4.9 5.1 5.1 37 37 108.6 108.6 • Why did we do this… 27
- 28. Control Valve System Syzer: Scale Five • We reduced head loss to 66’ 66’ • We want 50% Authority, so size valve for ____ – 66’ (28.6 PSI) q CV ! P 66 20 GPM C V 2.31 20 C V 3.74 3.75 66 2.31 Control Valve Selection Control Valve Selection • Required CV = 3.75 • Pipe Size = 1½” There is an awful lot that goes into understanding valve selection • Rules of Thumb – One valve isn’t necessarily better than another – One pipe size smaller – 5 PSI; CV = 9 – Long discussion on hydraulics Remember we reduced pump head 40% only to have to double it for the control valve – 108 Feet to 66 Feet to 132 Feet; Net result 24 foot increase – Skipping a long introduction; Apply dynamic pressure compensating control valves (i.e. “PICV”) tp reduce required head losses, and factor back in estimates for fittings and service devices • Which one do you believe? • Selected on flow requirement 28
- 29. Pressure Independent Pressure Independent Control Valves Control Valves • Pressure is kept constant across temperature control orifice by modulating pressure regulator Two Integrated Valves One Body Technology Changes… • Selection by flow rate • Problem is head loss – 1½” valve has maximum flow of 44 – Head loss is required for (standard) valves to work GPM P1 P2 P3 • Differential pressure • Still, “old” design guidance is good – 2-5 PSI design head loss – Proven – 2-50 PSI operating differential – Essential element was to drive down head loss i.e. make • TC Valve always has 100% the system more energy efficient through larger pipe authority sizes… – Integrated pressure regulator – We can easily get to 110 feet, can also upsize main piping M maintains set pressure • May be easily adjustable • 240 GPM @ 110 -120 Ft. • Eliminates need for extraneous • Pick a pump P1 P2 P3 balancing valves 29
- 30. What is a centrifugal pump? Motor Centrifugal Pumps • Three Basic Components (Driver) Coupler Volute Impeller Bearings Volute Pump Shaft Impeller Seal Base • Other Components Based On Design End Suction Pump End Suction Pump • Single Suction Impeller • Broad Range of Flow • HVAC Workhorse Base Mounted Close Coupled Bell & Gossett Series 1510 Bell & Gossett Series 1510 30
- 31. Line Mounted Pump Small Circulators…”Boosters” • Concept of pumped HVAC goes back to 1920’s • Transition from gravity hot water heating to forced circulation • “Boosters”; industry workhorse until ’80s Bell & Gossett Series 100 Bell & Gossett Series 100 • ≈ 100 GPM, 40 Ft. Wet Rotor Circulator Pumps Range In Size Greatly! Double Suction Impeller Circulator 5 GPM 15,000 GPM 31
- 32. Why So Many Pumps? Bernoulli’s Theorem •Function of a Flow, Head, Speed, Impeller b Profile, Force •Application – HVAC Pa Va2 Pb Vb2 – Wells Za Zb W 2g W 2g – Irrigation – De-watering The total head of a fluid at “a” is equal to the – etc. total head at “b”, provided that there’s no loss due to friction or work, and no gain due to the application of work. Impeller Pump Impeller 32
- 33. Single Suction Impeller Impeller and volute End Suction Pump; Single Suction Impeller Discharge Discharge Typical Impellers Gauge Taps Gauge Taps Bearing Bearing Shaft Shaft Suction Suction Slinger Slinger Ring Ring Seal Seal Single Suction Double Suction Drain Drain 33
- 34. Impeller Dynamics Impeller Dynamics VR VS VR VS 80% VT ion ion VT tat tat Ro Ro VT = Tangential VT = Tangential Velocity Velocity VR = Radial VR = Radial Vanes Velocity Velocity VS = Vector Sum Trimmed VS = Vector Sum Full Impeller Size Impeller Q 2 80%Q1 80% Seals Impeller Types • Open • Semi-open Environment Vessel Wall • Closed - Single suction Shaft - Double suction Process • Non-clogging Fluid Leakage • Axial flow • Mixed flow 34
- 35. Typical Mechanical Seal Pump Seal Detail Stationary Assembly Graphite Seal Ring Ceramic Seal Insert Compression Ring Retainer (Sec Seal) Gasket Secondary Seal (Seal Bellows) Impeller • Normal to HVAC Pump Construction – Circulating fluid flushes and cools faces – “2” Seals Rotary Assy – Many seal materials based on application Seal Lubrication Seal Cavity – Separate surfaces – Prevent contact of high surface points – Reduce friction / heat – Carry away the heat that is generated Lubricant Stationary Ceramic Rotating Graphite Heat Separation 35
- 36. Suction Piping Detail Why 5 Diameters? 5 dia. RIGHT WRONG 1. Pipe supported 1. Pipe weight hangs 2. Length of suction on pump flange. piping allows even 2. Short suction pipe impeller loading results in uneven impeller loading. Suction Diffusers Suction Diffusers 36
- 37. Construction Installation Orifice Cylinder Full-Length Straightening Vanes Bronze Start-Up Strainer EPDM O-Ring Suction Diffuser Pump Curve From System Access Required To Pump Support Straightening Foot Vanes 37
- 38. Curve Construction Water Horsepower Input 1 Head Capacity 2 Horsepower Input Total Head In Feet Total Head In Feet 3 Water H.P. Input 4 Capacity In US Gallons Per Minute Capacity In US Gallons Per Minute Water horsepower BHP and WHP Head Capacity Horsepower Input Total Head In Feet WHP=Flow x Head x SG÷3960 H.P. Lost To Friction B.H.P. Input To Shaft & Recirc. WHP Capacity In US Gallons Per Minute 38
- 39. Brake Horsepower Pump Efficiency Flow X Head x Sp. Gr. BHP = 3960 x ηPump x ηMotor Where: WaterHP BHP Horsepower provided at the motor shaft ηpump Flow Head GPM through the pump feet of head developed by the pump Brake HP ηPump efficiency of the pump at the operating point 3960 constant required to provide consistent units Sources Of Inefficiency Pump Efficiency Curve Maximum Head Capacity Efficiency • Bearing friction At This Point • Seal Total Head In Feet • Fluid friction Efficiency • Recirculation Efficiency • Shock losses Capacity In US Gallons Per Minute 39
- 40. Multiple Impeller Curves Higher RPM Pumps Efficiency Curves Efficiency Curves Total Head In Feet Total Head In Feet Capacity In US Gallons Per Minute Capacity In US Gallons Per Minute Speed Effects Pump Impeller vs. Horsepower 1100 RPM 1700 RPM 3500 RPM 9½" 8¾ 8" Total Head In Feet Total Head In Feet 7¼" 15 HP 10 HP 7.5 HP 5 HP Capacity In US Gallons Per Minute Capacity In US Gallons Per Minute 40
- 41. Speed vs. Horsepower Non-Overloading Non-Overloading 9½" Motor Selection Motor Selection Total Head In Feet 15 HP 1750 RPM 3 HP 10 HP 2 HP 7.5 HP 5 HP Capacity In US Gallons Per Minute Net Positive Suction Head Required Why Worry About Cavitation? • Noise • Performance • Damage • To What? – Pipes – Valves – Pumps 41
- 42. Pump Curve What’s Going On? From Increase (Turb c Shock ller ss e) s ce Lo Impe ulenc n Los ure auli n Minimum Head Frictio Minimum Head Entra Press Hydr Required To Required To Prevent Cavitation Prevent Cavitation 3 NPSHR 5 NPSHR 20 4 Pressure 1 2 NPSHR NPSHR 10 0 1 2 3 4 5 Hydraulic Institute Standards • ANSI/HI 9.6.1 (1998) • NPSHR – NPSHR Of A Pump Is The NPSH That Will Cause The Total Head (First Stage Head For Multi-Stage 3% Head 3% Head Pumps) To Be Reduced 3%, Due To Flow Blockage Deviation NPSHR NPSHR Deviation From Cavitation Vapor In The Impeller Vanes & Induced & Induced 20 Cavitation Cavitation NPSHR 10 NPSHR 0 42
- 43. NPSHA NPSH Margin Recommendations NPSHR • Cavitation Does Not Start At NPSHR • Cooling Towers – Low Energy 1.3 or 3 Feet Whichever Is Greater – High Energy 1.5 or 5 Feet Whichever Is Greater • The Starting Point Of Cavitation Is Referred To As Incipient Cavitation • General Industry – Low Energy 1.1 or 2 Feet Whichever Is Greater – Incipient Cavitation Can Be From 2 to 20 Times the 3% NPSHR Value – High Energy 1.2 or 3 Feet Whichever Is Greater – Magnitude Depends On Pump Design • Building Services – Low Energy 1.1 or 2 Feet Whichever Is Greater – High Energy 1.3 or 5 Feet Whichever Is Greater Issues Avoiding The Issue • Extra Margin May Be Required To Account For Pump Wear • Choose The Head • Suction Piping Right Pump – In General >5 Diameters LONG Radius Elbow – Avoid Pump – >8 Diameters Short Radius Elbow Curve Extremes – Manifolds L1 Head D2/D1 L1 L2 L2 D2 D2 ≥0.3 ≥2D1 ≥5D2 L2 ≥0.3 ≥2D1 ≥5D2 D1 Flow Design Flow 43
- 44. Shape of The Curve Affinity Laws GPM Capacity Ft. Head Brake H.P. Steep Curve 2 3 D D D Diameter Q 2 2 Q1 H2 2 H1 P2 2 P1 D D Total Head In Feet BEP D1 1 1 Flat Curve 2 3 R R R Q 2 2 Q1 H2 2 H1 Speed R P2 2 P1 R R1 1 1 Q = Flow H = Head P= Power Capacity In US Gallons Per Minute D = Imp. Diam. R = Speed on on Pump Selection for Why is Pump Requirement 240 GPM @ 120 Feet? lati lati ircu ircu Best Operation Rec Rec Characteristic • Pump Energy Is Absorbed By System tion rge Life ~ MTBF cha η Suc • How Much? Dis η x 0.92 High Temperature Rise Low Flow Cavitation Low Bearing & Seal Life Best Practice – Pump Is Putting Energy In That Meets The Specific Reduced Impeller Life P BE -10% to +5% Flow And Head That System Will Take Of BEP η x 0.53 – What Will The System Take… As Much As Pump Will ring Better Practice Give! % Head Bea e -20% to +10% l Lif Sea & Low • The Flow In The System Is A Balance Of The Pump η x 0.1 Capacity and The System Capacity Cavitation Good Practice % Reliability -30% to +15% • We Need To Understand Pumps and Systems % Flow 44
- 45. Closed Loop Circulating System Closed Loop Circulating System Pa V2 P V2 Pa V2 P V2 Za a EP b Zb b hf Za a EP b Zb b hf W 2g W 2g W 2g W 2g B A B A P P V2 V2 EP b a Zb Za b a hf W W 2g 2g EP hf Calculated Pump Requirement • Add All Terminal Flows – Total All Branch Flows In GPM • Select Greatest Hydraulic Pressure Loss Circuit – Branch Loss + Shared Riser Piping; 66 Feet of Head – Pressure Independent Control Valve; 11 Feet – Total Head Loss 110 - 119 Feet if we worry about fittings, service valves, etc. • Pump Requirement Is Required Flow @ Required Head; 240 GPM @ 120 Feet of head 45
- 46. 5¾” • “2½AB” Operating Point – 240 GPM @ 120 Ft – η = 74% – 10 HP @ Design – 15 HP Motor for NOL Plot Your Pump Curve… Analyze System Flow & Head Relationship 140 130 2 120 Q 2 h2 110 100 Q h 90 80 1 1 • Q1 = Know (design) Flow 70 60 50 • Q2 = Final Flow 40 30 • h1 = Know (design) Head 20 10 • h2 = Final Head 0 0 50 100 150 200 250 300 350 400 450 500 46
- 47. Draw System Curve Pumps in Parallel 140 2 130 Q2 h System Head 120 Q 2 110 100 1 h1 90 1/2 system flow 80 Flow Head 70 250 155 60 220 120 50 160 63 40 120 36 1/2 system flow 30 60 9 20 0 0 10 • Size pump piping for total flow 0 0 50 100 150 200 250 300 350 400 450 500 • Select pumps for ½ design flow and full head 100 90 80 70 60 50 Specification Specification 40 30 •• 1400 Total GPM 1400 Total GPM •• 72.5 Ft. Head 72.5 Ft. Head 20 •• 2 2 Pumps In Parallel Pumps In Parallel •• 4 4 BC Pump BC Pump 10 0 10 20 30 40 50 60 70 80 90 0 10 11 12 0 0 0 0 0 0 0 0 0 00 00 00 47
- 48. 48 00 00 22 12 00 21 00 00 11 20 00 19 00 10 00 18 00 17 0 90 00 16 00 0 15 80 00 14 00 70 0 13 00 12 0 00 60 11 00 10 0 50 850 GPM 0 90 0 80 40 0 0 70 0 0 60 30 0 50 0 0 20 40 0 30 0 10 0 20 0 10 0 0 100 90 80 70 60 50 40 30 20 10 0 100 0 90 80 70 60 50 40 30 20 10 00 00 12 22 00 21 00 11 00 20 00 19 00 10 00 18 00 0 17 90 00 16 0 00 80 15 00 14 70 0 00 13 00 12 0 60 00 11 00 0 10 50 0 90 0 0 80 40 0 70 550≈ GPM 0 0 30 60 0 50 0 20 0 40 0 30 0 10 0 20 0 10 0 0 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0
- 49. 49 00 00 22 22 00 00 21 21 00 00 20 20 00 00 Design Point 1400 @ 72.5’ 19 19 00 00 18 18 00 00 17 17 00 00 16 16 1050 @ 72.5’ 00 Operates To 00 One Pump 15 15 And Is On 00 00 Curve 14 14 00 00 13 13 00 00 12 12 00 00 11 11 00 00 10 10 0 0 90 90 0 0 80 80 0 0 70 70 0 0 60 60 0 0 50 50 Operates At Each Pump 700 @ 72.5’ 0 0 40 40 0 0 30 30 0 0 20 20 0 0 10 10 0 0 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 00 00 22 22 00 00 21 21 00 00 20 20 00 00 19 19 00 00 18 18 Q2 h2 Q h 1 1 1400 GPM @ System Curve 00 00 72.5' Head Fixed Point 17 17 00 00 16 16 00 00 15 15 2 00 00 14 14 00 00 13 13 00 00 12 12 00 00 11 11 00 00 10 10 0 0 90 90 0 0 80 80 0 0 70 70 0 0 60 60 0 0 50 50 0 0 40 40 0 0 30 30 0 0 20 20 0 0 10 10 0 0 0 100 90 80 70 60 50 40 30 20 10 100 90 80 70 60 50 40 30 20 10 0
- 50. 100 100 Check Pump Horsepower Operating Points 90 90 Design Point 80 80 1400 @ 72.5’ 70 70 60 60 50 50 40 20 HP 40 15 HP 30 30 20 10 HP 20 10 10 0 0 10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 0 10 11 12 13 14 15 16 17 18 19 20 21 22 0 10 11 12 13 14 15 16 17 18 19 20 21 22 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Parallel Pumping Problem • Selection – One Half Design Flow At Design Head – Two Equally Sized Pumps – PUMP CONTROLLER • Technique – Safety: System Curve Intersects Both Curves At Design Condition • Benefit – Instead of 2 full sized pumps, 2 half size – Staging; Most of year is with one pump not two 50
- 51. 195 GPM 81% Design 210 GPM • 1 Pump: 87% Design Flow Discussion Primary-Secondary System Allows Separation of Equipment Losses • Same pump, different size impellers depending on accuracy of calculation • 80%+ design flow on one pump operation, reasonable efficiency 66% • 7.5 BHP • Backup pump with low hours 51
- 52. Primary Secondary Issue What Is Primary Secondary? What Is Primary Secondary? • Coordination of Primary & Secondary Flows – Causes Mixing – Mixing Point Moves • Method Of Breaking Systems Into Smaller More • Returning to Source, Poor ΔT Manageable Sub-Systems • Returning to Field, Reduced Heat Transfer Performance • Hydraulically and Thermodynamically Isolates One & Increased System Flow System From Other • Traditional VSVF Systems; “Low Delta T” • Instead Of One Large Pump Two (or more) Small Pumps – Move Towards VSVF Primary & Secondary SEGMENT A B C 1-2 2-3 3-4-6 3-5-6 6-7 2-8 8-10-11 8-9-11 11-7 7-12 D E F Primary Secondary Layout Flow 240 160 80 80 40 20 20 40 40 20 20 40 80 80 160 240 Size 4" 3" 2.5" 2.5 1.5 1.25 1.25 1.5 1.5 1.25 1.25 1.5 2.5 2.5" 3" 4" Length 100' 20' 20' 30 30 60 60 30 30 60 60 30 30 20' 20' 100' HF Rate 3 5.5 4.5 4.5 12.5 9 9 12.5 12.5 9 9 12.5 4.5 4.5 5.5 3 Friction Loss 3 1.1 0.9 1.35 3.75 5.4 5.4 3.75 3.75 5.4 5.4 3.75 1.35 0.9 1.1 3 Fittings 2 2 2 2 2 2 2 2 2 2 2 2 Service Valves 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Coil 17 17 17 17 Control Valve Balance Valve Source 30 Total 5 3.1 2.9 3.35 7.75 26.4 26.4 7.75 7.75 26.4 26.4 7.75 5.35 4.9 5.1 37 PATH TOTAL A-1-2-3-4-6-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-1-2-3-5-6-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-1-2-8-10-11-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-1-2-8-9-11-7-12-F 5 3.35 7.75 26.4 7.75 5.35 37 92.6 A-B-1-2-3-4-6-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-1-2-3-5-6-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-1-2-8-10-11-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-1-2-8-9-11-7-12-E-F 5 3.1 3.35 7.75 26.4 7.75 5.35 5.1 37 100.8 A-B-C-1-2-3-4-6-7-12-D-E-F 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 A-B-C-1-2-3-5-6-7-12-D-E-F 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 A-B-C-1-2-8-10-11-7-12-D-E-F 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 A-B-C-1-2-8-9-11-7-12-D-E-F 5 3.1 2.9 3.35 7.75 26.4 7.75 5.35 4.9 5.1 37 108.6 • Two pumps – Source 240 GPM @ 30 Ft. – Load 240 GPM @ 90 Ft. 52
- 53. Further Definition Further Definition • Primary: 240 GPM@ 58 Ft. 4.7 BHP • Three Secondary Pumps (Floor Zones) 80 GPM@53 Ft Discussion Implied Control • Horsepower 10.25 • Controllability ~ Constants – 3 x 1.85 •Water Flow: Keep System – 1 x 4.7 Differential Pressure Constant • Smaller pumps less expensive, but maybe not in total – Old Paradigm: Apply Constant Speed Flat Curve Pumps • Easier expansion, simpler management – Adjust All Hydronic Loops To Same – May offer operating benefit to non-variable flow Friction Loss source 53
- 54. Horsepower Is Reduced Variable Speed Pumping • Controllability ~ Constants – Water Flow: Keep System Differential Pressure Constant • New Paradigm: Variable Speed Pumps 5 HP – System Differential Changes In Reaction To Valve Position 3 HP – Control Valve Requires the Same Control Influence as Previously, But Lower Differential Heads Bring Out Selection Mistakes Variable Speed Pump Paradox Solved, Energy Saved Variable Speed Pump Application • Ideal “Engineering” form of hydronic Speed = 100% control; Energy Saving Head Reduced 80% + – Coils operate 80% year with 50% of flow or less – 50% flow ≈ 12.5% Brake Horsepower 5 HP • In our problem, we would probably go with 2 pumps in parallel at ½ Flow and full head • Review and understand Balancing & Speed = 37% Controls ¼ HP 54
- 55. Typical Variable Speed Setup Example Differential Pressure Sensor Differential Pressure Sensor 100 BV Path P3 C Path P3 D Controlled Head 0 (Constant) Variable Head 20 20 20 Variable Head Pump Control 100 BV Path P2 B Path P2 E 20 ? 20 20 Speed Drive Path P1 Power A 200 F Path With Design Head Both Valves 50% Flow Flow Path 3 100 A-B B-C C-D D-E E-F Path 3 50 A-B B-C C-D D-E E-F Head 20 20 20 20 20 100 Design 20 20 20 20 20 100 Head 5 5 20 5 5 40 Path 2 100 A-B B-E BV E-F Path 2 50 A-B B-E BV E-F Head 20 20 40 20 60 Design 20 20 40 20 60 Balanced 20 60 20 100 Balanced 20 60 20 100 Head 5 ? 5 ? 55
- 56. Paradigm Change Evaluate Using Flow Coefficient 2 Q2 h2 P3 Flow Coefficien t Q h 100 BV 1 1 C Path P3 D C 100 34 V 20 0 20/2.31 • System Curve Implies 1 Flow, 1 Head 20 20 • Variable Speed Does Not Follow; Why? 100 BV P2 Flow Coefficient B Path P2 E 100 Path 2 Path 3 Flow TDH 20 CV 19.6 40 60/2.31 100 100 200 100 20 20 0 100 100 70 100 0 100 30 A 50 50 100 40 0 0 0 20 F Control Area Balancing Implication • This Is The Classic (ASHRAE) Balancing Argument 100 – “Balancing ruins the control valve” 90 • Excess Balancing Valve Drop Causes Skewed Flow Performance 80 – “Must use high performance valve” – “I don’t like the “extra” pressure drop you have to use for a flow 70 limiter…” 60 • No; 80% wrong 50 – 80% Fallacy 40 • Balance provides functionality when all TC valves are open • TC Valve control does not recognize changes in system differential 30 pressure 20 • Flow limiters don’t add extra pressure drop when properly applied – 20% Right? 10 • Static balance does skew improperly sequenced VSVF pump systems 0 • This is a control set point problem, not a balance problem 0 50 100 150 200 56
- 57. G 1 CV g Set Point = 20 Ft 0 2 Plot of Valve & Head Combinations 0 0 0 0 0 1000 X 4 =0 70.0 Valve 6 Closed 845 CV 2 Valve 6 & 5 Closed F f 2 845 60.0 0.7 7.1 7.1 5.7 0.7 2000 X 4 = 0.7 Valve 6-4 Closed 771 CV 50.0 3 E e 2 5.9 5.9 9.5 845+771 1.16 1.16 3000 X 4 = 1.16 Valve 1 Closed 735 CV 40.0 4 d 2 Valve 1 & 2 Closed Head (Feet) D 5.4 5.4 13 2350 1.38 1.38 4000 X 4 = 1.38 30.0 714 5 CV C c 2 20.0 5.1 5.1 16.3 3064 1.5 1.5 Inner Valves Close Head X 4 = 1.5 Outer Valves CLose 701 CV 5000 System Curve 10.0 6 B b 4.9 4.9 19.6 2 Valve 1-3 Closed 3767 1.58 3767 A a 1.58 6000 X 4 = 1.58 0.0 0.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 Flow (USGPM) 3767 GPM @ 32.7’ In VSVF Hydronic Systems of Any Type Variable Speed Pumping 100 The idea of Variable Speed • Control valves will change system flow 90 Pumping is to have even speed transition proportional greater than the control valve selection 80 to changes in head and flow • This can effect control system stability in 70 60 – Chiller staging 50 n=100% – Pump staging 40 n=90% – Other circuits temperature control n=80% 30 • There’s more to it than just the valve! n=70% 20 n=60% n=50% 10 n=40% n=30% 0 0 100 200 300 400 500 600 700 800 900 1000 57
- 58. Variable Speed Pumping Variable Speed Pumping 100 100 90 90 80 80 ΔP ~ Gain 70 70 However, pump and system curve 60 60 intersection should be steep enough so that a change in flow rate actually 50 50 yields a change in differential head 40 40 significant enough to get the control algorithm to modify pump speed in 30 30 a reasonable increment Normal pump control often uses a 20 20 controlled differential pressure across one or more branches that 10 10 indicate changes in building load 0 ΔP (implication) 0 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 Variable Speed Pumping “Traditional” Balance Valves 100 90 80 • Static: Circuit Setter 70 • Dynamic: Griswold, Circuit Sentry Valve ΔP 60 Just Provide Maximum Flow Protection Changes 50 – Static Valves Proportionally Balance; Only Have Radically 40 The old “flat curve” pump characteristic 75% Pump All Valves Get 75% (Constant Speed could hurt system performance, the pump speed controller could easily jump from full Pumps, Not Variable Speed) 30 speed to much less (100% to 40%) causing 20 improper control throughout all affected but non connected loops (Chillers, towers, – Dynamics Clip Excess Flows & Lose Balance Effects pump stage, etc.). Remember: the valve When Required (Variable Speed Pumps) 10 controller always thinks it has a predictable characteristic because of constant ΔP 0 across it. 0 100 200 300 400 500 600 700 58
- 59. Variable Speed Pump Paradox Solved, Energy Saved Variable Speed Pump Paradox • Big Energy Savings Speed = 100% Head Reduced 80% + – Coil; Little Flow… Lots of Heat Transfer – Hydraulics; Change Pump Speed, Change Valve 5 HP and Heat Transfer Predictability… Lose Control • PIC Valves; Can Stop Over Flow and Maintain 100% Valve Authority, 100% Control Predictability Speed = 37% ¼ HP PIC Valves with Flow Setting Summary/Tips • Load analysis • Provide majority of system required features – Tip: If you have to apply a diversity factor do not factor it into pump or pipe sizing. and benefits • Flow – Overflowing coils does not add appreciable heat transfer…it takes surface area. Slightly oversize the coil and then operate at a lower temperature. • Pipe – You only install it once. Spend the money on larger pipe to reduce head loss. Be very judicious in applying any diversity when sizing pipe. • Pumps • Lift & Turn To Percentage of – Often cost more to run in one year than they cost to install. Rated Flow – No head, no flow. • Lack traditional proportionality of – Learn more; study up on variable speed pump application. static balance, although the • Controls “control valve” can now control – Modulate coils and use VS pumps. Carefully coordinate control valve and and provide such…impossible spend the extra cash to apply pressure independent control valves with standard ATC valves 59
- 60. Just About Quittin’ Time! • There’s a lot more to know! – We didn’t cover air and pressure management – Many variations on systems and materials – Practice lots! • We did not cover Open Systems (Cooling Towers) • Most of our discussion is applicable to all system designs – Keep sense of relativity A difference to be a difference must be a big enough difference to make a difference! …Gil Carlson 60