© 2007 ASHRAE Hong Kong Chapter Slide 1

Fundamentals of Water System Design

17, 18, 24, 25 January 2007

ASHRAE Hong Kong Chapter Technical Workshop

© 2007 ASHRAE Hong Kong Chapter Slide 2

Chapter 8:Matching Pumps to Systems

1. Matching the Pump to the System2. Parallel Pumping3. Series Pumping4. Standby Pumps 5. Trimming Pump Impellers6. Two-speed Pumping7. Variable-speed Pumping8. Source Distribution Pumping

© 2007 ASHRAE Hong Kong Chapter Slide 3

Typical System Curve

© 2007 ASHRAE Hong Kong Chapter Slide 4

Pump Curve and System Curve

© 2007 ASHRAE Hong Kong Chapter Slide 5

Shift of System Curve

© 2007 ASHRAE Hong Kong Chapter Slide 6

Pump Curve for Parallel Operation

© 2007 ASHRAE Hong Kong Chapter Slide 7

Operating Conditions forParallel Pump Installation

© 2007 ASHRAE Hong Kong Chapter Slide 8

Piping Schematic of Parallel Pumps

© 2007 ASHRAE Hong Kong Chapter Slide 9

Pump Curve for Series Operation

© 2007 ASHRAE Hong Kong Chapter Slide 10

Operating Conditions for Series Pump

© 2007 ASHRAE Hong Kong Chapter Slide 11

Piping Schematic of Series Pumps

© 2007 ASHRAE Hong Kong Chapter Slide 12

Standby Pump

© 2007 ASHRAE Hong Kong Chapter Slide 13

Pump Affinity Laws

Speed Change Impeller Diameter Change

Flow:

Pressure:

Power:

⎟⎟⎠

⎞⎜⎜⎝

⎛=

1

212 N

NQQ ⎟⎟⎠

⎞⎜⎜⎝

⎛=

1

212 D

DQQ

2

1

212 ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

NNpp

2

1

212 ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

DDpp

3

1

212 ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

NNPP

3

1

212 ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

DDPP

© 2007 ASHRAE Hong Kong Chapter Slide 14

Pump Operating Points

© 2007 ASHRAE Hong Kong Chapter Slide 15

Two-Speed Pumping

© 2007 ASHRAE Hong Kong Chapter Slide 16

Typical Impeller Performance Curve

© 2007 ASHRAE Hong Kong Chapter Slide 17

Two-Speed Pumping Example

% ChangeFlow Power

46 1658 2778 57100 100

© 2007 ASHRAE Hong Kong Chapter Slide 18

Typical Direct Return System

© 2007 ASHRAE Hong Kong Chapter Slide 19

Pressure Loss With Two-Way Valves

© 2007 ASHRAE Hong Kong Chapter Slide 20

Proportional Controller and AFD

© 2007 ASHRAE Hong Kong Chapter Slide 21

Measuring Δp in Direct Return System

End of last riser, or highest

pressure drop

© 2007 ASHRAE Hong Kong Chapter Slide 22

Differential Pressure Control Curve Above Piping Friction Loss

© 2007 ASHRAE Hong Kong Chapter Slide 23

Measuring Δp in Reverse Return System

Central or typical zone

© 2007 ASHRAE Hong Kong Chapter Slide 24

Pressure Reduction WithChange in Pump Speed

25%

© 2007 ASHRAE Hong Kong Chapter Slide 25

Pumping Power ReductionWith Change in Pump Speed

12.5%

© 2007 ASHRAE Hong Kong Chapter Slide 26

Primary-SecondaryPumping Concept

(decoupler)

constant flow variable flow

© 2007 ASHRAE Hong Kong Chapter Slide 27

Primary-SecondaryVariable Speed Pumping

© 2007 ASHRAE Hong Kong Chapter Slide 28

Distributed Variable Speed Pumping