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Best Practice Design

Discover the essential best practices for optimizing pump designs in HVAC systems. This guide focuses on impeller optimization for both constant and variable speed pumps, detailing strategies for trimming impellers, applying affinity laws, and understanding system curves to reduce operating costs. Learn about the implications of equipment oversizing and compliance with ASHRAE 90.1 for pumps above 10HP, ensuring you balance first costs with operational efficiency. Explore primary piping design for hot and chilled water systems and maintenance tips for key components like strainers and separators.

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Best Practice Design

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  1. Best Practice Design

  2. Best Practice Design Optimize Pump Impeller • Why • Constant speed pump • Variable speed pump

  3. Best Practice Design Why Equipment over-sizing Cost penalty Mandate by ASHRAE 90.1 when > 10HP Optimize Pump Impeller

  4. Best Practice Design Constant speed pump 4 • Trim the impeller • Utilize the affinity laws • Follow the system curve • Save operating cost • First costs

  5. Best Practice Design Variable speed pump • Impeller optimization • Follows affinity laws • First cost impacts • Does not correct for poor engineering • Over-sized pumps minimize turndown ratio • Over-sized pumps and motors operate at lower efficiencies

  6. Best Practice Design Primary Piping for Hot Water Systems • Pump out of a boiler • Keep the boiler at the lowest possible pressure • Remember NPSH! P2 P1 Boiler 1 Boiler 2

  7. Best Practice Design Primary Piping for Chilled Water Systems • Pump into a chiller • Largest pressure drops after the pump Chiller Chiller Chiller Primary Pumps

  8. Condenser Water Piping Condenser Water Piping Tips • Installation • Maintenance

  9. Condenser Water Piping Condenser Pump Cooling Tower Evaporator Condenser Chiller Sediment and Air Separator 9 • Installation • Pump suction flooded • Watch NPSHa

  10. Condenser Water Piping Cooling Tower Evaporator Condenser Obstacle Chiller Condenser Pump 10 • Operation • Air pockets • End of curve

  11. Condenser Water Piping Cooling Tower Condenser Pump Evaporator Condenser Sediment/Air Separator And Relief Valve: Alternate Locations Chiller 11 • Maintenance • Strainers • Air vents

  12. Best Practice Design System Bypass Options Secondary CS Pump(s) Supply Chiller 2 Chiller 3 Chiller 1 Pump Controller Common Pipe Return

  13. Best Practice Design System Bypass Options • Locate bypass near end of system • Locate bypass near end of major loops • Selectively leave 3-way valves • Bypass with pressure activated control • Variable speed considerations

  14. 120 100 % Speed 110 100 90 80 70 Head 60 30% Speed 50 40 30 20 10 0 % Flow 60 70 80 90 100 0 10 20 30 40 50 Best Practice Design • Below 30% speed: CS, but still VV Effect at program minimum VFD speed

  15. Pump 1 Variable Speed: 500GPM @ 100 Ft 1000 GPM Wrong! Pump 2 Constant Speed: 500 GPM @ 100 Ft 1000 GPM Mixing CS and VS Pumps Best Practice Design

  16. ∆P Sensor Pump Controller Best Practice Design Sensor Location Secondary Pumps Supply Chiller 3 Chiller 1 Chiller 2 VFDs Return Primary Pumps

  17. Best Practice Design Sensor Location • The Traditional Way • Hydronically, the farthest load • Typically the largest, farthest load • Maximize the variable head loss • Multiple sensors are a benefit

  18. Best Practice Design • Optimized solution not only for the pumps, but for the total system conditions • Proportional pressure, calculated • Proportional pressure, measured • FLOWADAPT and AUTOADAPT 18

  19. Best Practice Design • Uncontrolled • Constant pressure • Proportional pressure (calculated) • Proportional pressure (measured) • Temperature control 100 80 60 40 20 0 1. Effect in % H 2. 3. 4. 5. 0 20 40 60 80 100 Flow in % 25% 100% Q Get Additional Energy Savings 19

  20. Best Practice Design - Demand More Total Efficiency vs. Control Modes

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