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Sizing Pipes for Efficiency

Sizing Pipes for Efficiency. Learning Outcomes. Upon completion of this training one should be able to : Compare pipe sizing methods Understand the impact of pipe sizing on the system performance Apply ASHRAE Standard 90.1 to pipe sizing Understand how VV/VS pumping influences pipe sizing

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Sizing Pipes for Efficiency

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  1. Sizing Pipes for Efficiency

  2. Learning Outcomes Upon completion of this training one should be able to: Compare pipe sizing methods Understand the impact of pipe sizing on the system performance Apply ASHRAE Standard 90.1 to pipe sizing Understand how VV/VS pumping influences pipe sizing Utilize life cycle cost economics to justify the use of Magna3 in both new and renovated systems

  3. Overview Pipe Sizing Considerations Pipe Sizing Methods Work Through a Pipe Sizing Example Discuss Pump & System Energy Costs as They Relate to Pipe Sizing

  4. Importance Pipe size selection impacts: • Pump head • Hydronic system performance • Energy consumption

  5. Sizing Considerations Pipe size depends on: • Material • First cost • Pump energy costs • Internal pipe erosion • Noise • Budget

  6. Pipe Material • Material selection influences pipe size • Nominal pipe size may be the same but different inside diameter (free area) • Influencing the friction loss and velocity

  7. Copper has the more restrictive ID Nominal 2” Copper ID=1.985” Nominal 2” Steel ID=2.067”

  8. Typical Procedure Size pipe based on: • Constant Friction Rate • Velocity • Use rule of thumb or common values

  9. Constant Friction Rate • Range: 1’/100’ - 4’/100’ • 2.5’/100’ used on average (ASHRAE Fundamentals 2009 Chpt 22) • 4’/100’ when > 2” pipe diameter

  10. Velocity • Define a maximum (Common: 4 fps ≤ 2”, 8 fps > 2”) • Limited primarily for noise & erosion • Higher values acceptable when air is removed from system • ASHRAE Fundamentals 2009 Chapter 22

  11. Velocity - Material Impact Maximum velocity per Copper Tube Handbook* • Chilled Water 8 fps • Hot Water (<140ºF) 5 fps • Hot water (>140ºF) 3 fps ≤ ½” diameter pipe, lower velocities should be used due to craftsmanship and abrupt changes in flow direction Higher velocities acceptable in chilled water because the air is more easily removed than in hot water. *Copper Development Association

  12. Commercial Steel Pipe (schedule 40) • ASHRAE Fundamentals 2009 Chapter 22 Figure 4

  13. Commercial Steel Pipe (schedule 40) • ASHRAE Fundamentals 2009 Chapter 22 Figure 4 2.5’/100’ hd loss

  14. Commercial Steel Pipe (schedule 40) • ASHRAE Fundamentals 2009 Chapter 22 Figure 4 2.5’/100’ hd loss 4’/100’ hd loss

  15. Commercial Steel Pipe (schedule 40) • ASHRAE Fundamentals 2009 chapter 22 Figure 4 2.5’/100’ hd loss 4’/100’ hd loss 4 fps

  16. Commercial Steel Pipe (schedule 40) • ASHRAE Fundamentals 2009 chapter 22 Figure 4 2.5’/100’ hd loss 4’/100’ hd loss 4 fps

  17. Schedule 40 Steel Pipe Sizing Chart

  18. Copper Tubing (Types K, L, M) • ASHRAE Fundamentals 2009 chapter 22 Figure 5 2.5’/100’ hd loss 4’/100’ hd loss 4 fps

  19. Copper Type L Pipe Sizing Chart

  20. Material Comparison Copper Steel

  21. Noise • Noise velocity limits are difficult to pin point as it is dependent on many variables: • Insulation • Number of turns, fittings, valves • Air quantity • Partial flow • Typically not a significant concern as long as entrained air has been eliminated from a closed loop system.

  22. Erosion • Velocities < 10 fps – erosion is not significant as long as there is no cavitation • ASHRAE Fundamentals 2009 Chapter 22

  23. Aging • Build up and increased roughness occurs in pipe over time • Narrow the pipe free area increasing head • Often ignored • Unpredictable • Research data is not available • A greater concern for open systems

  24. Example

  25. Example • 4 Story Office Building • Located in Houston, Texas • HVAC system: Fan Coil Units with Chilled Water coils

  26. Zoning 2 3 1 4 5 6 Basement Mechanical Room

  27. Zoning 1 2 3 4 5 6 8 7 11 9 10 Main Floor 13 12

  28. Zoning 3 2 1 4 7 6 5 9 8 2nd/3rd Floor 10 11

  29. Riser Steel Schedule 40 2.5’/100’ Copper 2.5’/100’ 3RD 23.7 GPM 2”, 2” 22.3 GPM 2”, 2” 2ND 46 GPM 2½”, 2½” 24.3 GPM 2”, 2” MAIN 70.3 GPM 3”, 3” 10.7 GPM 1¼”, 1¼” BASE 81 GPM 3”, 3”

  30. Steel Schedule 40 2.5’/100’ Copper 2.5’/100’ Example Fan Coil Unit 0-3 (2.2) 0-2 (2.2) ¾”, 1” 1¼”, 1¼” 0-1 (0.9) 1”, 1” ½”, ½” 0-4 (1.7) 0-5 (1.7) 1¼”, 1¼” 0-6 (1.1) 3”, 3” co Basement 3”, 3” MECH ROOM (0.8)

  31. Steel Schedule 40 2.5’/100’ Copper 2.5’/100’ Example 1-1 (1.5) 1-2 (0.95) 1-3 (0.8) Fan Coil Unit 1-4 (1.6) 1¼”, 1¼” 1”, 1” 1-5 (1.9) 1¼”, 1¼” 1-8 (1.9) 1 ¼”, 1 ½” 1-7 (2.0) 1-11 (1.4) 1½”, 1½” 1-10 (1.0) 1-9 (2.0) 2”, 2” co Main Floor 1-12 (3.7) 1-13 (4.9)

  32. Steel Schedule 40 2.5’/100’ Copper 2.5’/100’ Example 2-2 (2.1) 2-3 (1.2) Fan Coil Unit 2-4 (2.0) 1”, 1” 2-7 (1.5) 1¼”, 1¼” 1¼”, 1¼” 2-1 (1.6) 2-6 (1.3) 2-5 (3.0) 2-9 (2.6) 1¼”, 1½” 1½”, 2” 2-8 (3.0) co 2nd Floor 2-11 (2.2) 2-10 (1.9) 2”, 2”

  33. Steel Schedule 40 2.5’/100’ Copper 2.5’/100’ Example 3-3 (1.3) 3-2 (2.2) Fan Coil Unit 3-4 (2.1) 3-7 (1.6) 1”, 1” 1¼”, 1½” 3-1 (2.2) 3-5 (3.0) 3-6 (1.4) 1½”, 1½” 3-9 (2.8) 3-8 (3.1) 2”, 1½” 3rd Floor 3-11 (2.2) 3-10 (1.9) 2”, 2”

  34. Riser Steel Schedule 40 2.5’/100’ 4’/100’ 4fps(≤2”); 8fps(>2”) 23.7 GPM 2”, 2”,1½” 3RD 22.3 GPM 2”, 1½”,1 ½” 2ND 46 GPM 2½”, 2½”,2½” 24.3 GPM2”, 2”,1 ½” MAIN 70.3 GPM 3”, 2½”,2½” 10.7 GPM 1¼”, 1¼”,1” BASE 81 GPM 3”, 3”,2½”

  35. Example Steel Schedule 40 2.5’/100’ 4’/100’ 4fps(≤2”); 8fps(>2”) ¾”, ¾”, ¾” 0-2 (2.2) 0-3 (2.2) 1 ¼”, 1”,1” 0-1 (0.9) 1” 1” ¾” ½” ½” ½” 0-4 (1.7) 0-5 (1.7) 1¼”, 1¼”,1” 0-6 (1.1) 3” 3” 2½” 2½” 2½” 2½” co Basement MECH ROOM (0.8)

  36. Example Steel Schedule 40 2.5’/100’ 4’/100’ 4fps(≤2”); 8fps(>2”) 1-3 (0.8) 1-1 (1.5) 1-2 (0.95) 1¼” 1” 1” 1-4 (1.6) 1¼” 1” 1” 1” ¾” ½” 1-5 (1.9) 1-8 (1.9) 1¼”, 1¼”, 1¼” 1-7 (2.0) 1-11 (1.4) 1½”, 1¼”, 1¼” 1-10 (1.0) 1-9 (2.0) co MainFloor 1-12 (3.7) 1-13 (4.9) 2” 2” 1½”

  37. Example Steel Schedule 40 2.5’/100’ 4’/100’ 4fps(≤2”); 8fps(>2”) 2-3 (1.2) 2-2 (2.1) 2-4 (2.0) 1”, ¾”,½” 2-7 (1.5) 1¼”, 1¼”, 1” 1¼”, 1¼”, 1¼” 2-1 (1.6) 2-5 (3.0) 2-6 (1.3) 2-9 (2.6) 1¼”, 1¼”, 1” 1½”, 1½”, 1½” 2-8 (3.0) co 2nd Floor 2-11 (2.2) 2-10 (1.9) 2”, 1½”, 1½”

  38. Example Steel Schedule 40 2.5’/100’ 4’/100’ 4fps(≤2”); 8fps(>2”) 3-2 (2.2) 3-3 (1.3) 3-4 (2.1) 3-7 (1.6) 1”, 1”, 1” 1¼”, 1¼”, 1” 1½” 1¼” 1¼” 3-1 (2.2) 3-5 (3.0) 3-6 (1.4) 3-9 (2.8) 3-8 (3.1) 2”, 1½”, 1½” 3rd Floor 3-11 (2.2) 3-10 (1.9) 2”, 2”, 1½”

  39. Pump Energy Costs • Pressure drop (head) • Hours of operation • Annual flow profile • Pump control: constant vs variable pump flow • Energy rates • Efficiency of the pump

  40. Pressure Drop • Energy must exerted to overcome resistance seen by the critical circuit • Poor hydronic system design and pipe lay out influences energy consumed • Items that impose resistance: • Valves • Coils • Fittings • Pipe Manufacturer Literature ASHRAE Tables

  41. Pipe Resistance • Based on pipe size, flow, and material, length Example: 3” Schedule 40 pipe with 80 GPM, 50’ long 1.5’ of Head/100’ of pipe length 50’ of pipe X1.5’/100’ = 0.75’ Hd 1.5’/100’ • ASHRAE Fundamentals 2009 Chapter 22 Figure 4

  42. Fitting Resistance • Based on pipe size and velocity ASHRAE Fundamentals 2009 Chapter 22

  43. Pipe Resistance • Based on pipe size, flow, and material, length Example: 3” Schedule 40 pipe with 81 GPM 3.3 fps Velocity = 3.3 fps • ASHRAE Fundamentals 2009 Chapter 22 Figure 4

  44. Fitting Resistance • Based on pipe size and velocity • ASHRAE Fundamentals 2009 Chapter 22 90⁰ Elbow Resistance = 8.1’ of straight pipe

  45. Fitting Resistance • ASHRAE Fundamentals 2009 Chapter 22

  46. Fitting Resistance • Based on pipe size and velocity Example: 3.5 FPS, 3” Steel pipe 45⁰ Elbow Multiply by the 0.7 correction value Resistance = 8.1’ x 0.7 5.7’ of straight pipe

  47. Pressure Drop Calculation • The calculation is cumbersome and time consuming • Often simplified • Sized pipe using 2.5’/100’, apply this value to the total pipe length of critical circuit • Much of the pipe likely to operate at less than 2.5’/100’ at full load as in example • More common to multiply value by a factor such as 1.5 • Result: Over estimated head

  48. ASHRAE Standard 90.1-2010 Prescriptive Path requirements Section 6.5.4.5 – Hydronic Systems and Control

  49. Hours of Operation

  50. ASHRAE Standard 90.1-2010 • Example: Schedule 40 pipe with 81 GPM • → 3” pipe using traditional sizing methods

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