How to Convert and Optimize

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• How to Convert and Optimize
• Primary/Secondary Pumping Systems
• to Variable Flow Primary Systems

Presented By Hemant Mehta, P.E.
WMGroup Engineers, P.C.
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History of Variable Primary Flow Projects

• King Saud University - Riyadh (1977)
• Louisville Medical Center (1984)
• Yale University(1988)
• Harvard University (1990)
• MIT(1993)
• Amgen (2001)
• New York-Presbyterian Hospital (2002)
• Pennsylvania State Capitol Complex (2005)
• Duke University (2006)
• NYU Medical Center (2007)
• Memorial Sloan-Kettering Cancer Center (2007)

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King Saud University Riyadh (1977)

• 60,000 ton capacity with 30,000 tons for first
  phase
• Six 5,000 ton Carrier DA chillers
• Seven 10,000 GPM 240 TDH constant speed pumps
• Major Problem Too much head on chilled water
  pumps
• Lesson Learned Be realistic in predicting growth

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Louisville Medical Center (1984)

• Existing system (1984)
• Primary/Secondary/Tertiary with 13,000 ton
  capacity
• Current System (2007)
• 120 feet TDH constant speed primary pumps with
  building booster pumps 30,000 ton capacity
• Changed the heads on some of the evaporator
  shells to change number of passes
• Primary pumps are turned OFF during winter, Early
  Spring and Late Fall. Building booster pumps are
  operated to maintain flow.

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Yale University (1988)

• Existing system (1988)
• Primary/Secondary/Tertiary with 10,500 ton
  capacity
• Current System (2007)
• 180 feet TDH VFD / Steam Turbine driven variable
  flow primary pumps 25,000 ton capacity
• Changed the heads on some of the evaporator
  shells to change number of passes

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Amgen (2001)

• Creation of a computerized hydraulic model of the
  existing chilled water plant and distribution
  system
• Identification of bottlenecks in system flow
• Evaluation of existing capacity for present and
  future loads
• Two plants interconnected Single plant operation
  for most of the year, second plant used for
  peaking
• Annual Energy Cost Savings 500,000

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Additional Variable Primary Flow Projects

• Harvard University (1990)
• MIT(1993)
• New York-Presbyterian Hospital (2002)
• Pennsylvania State Capitol Complex (2005)
• Duke University (2006)
• NYU Medical Center (2007)
• Memorial Sloan-Kettering Cancer Center (2007)

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Duke University Background

• CCWP-1 plant was built four years ago
• CCWP-2 design was 90 complete (Primary/Secondary
  pumping)
• We were retained by Duke to peer review the
  design
• Peer review was time sensitive
• Plant design for CCWP-2 was modified to Variable
  Primary pumping based on our recommendations

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Duke CCWP-1 Before
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Duke CCWP-1 After

• Dark blue pipe replaces old primary pumps

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Duke Levine Science Research Center CHW System
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Duke CIEMAS Building CHW System
90 closed
Triple duty valves 50 closed
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Duke CIEMAS Building AHU-9
Balancing valve 50 closed
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NYU Medical Center (2007)

• Plant survey and hydraulic model indicated
  unnecessary pumps
• 1,300 horsepower of pumps are being removed,
  including 11 pumps in two brand new chiller
  plants
• 300,000 implementation cost
• 460,000 annual energy savings

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NYU Medical Center (2007)

• Plant survey and hydraulic model indicated
  unnecessary pumps
• 1,300 horsepower of pumps are being removed,
  including 11 pumps in two brand new chiller
  plants
• 300,000 implementation cost
• 460,000 annual energy savings

8 Pumps Removed
3 Pumps Removed
7 Pumps Removed
3 Pumps Removed
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Memorial Sloan-Kettering - Before
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Memorial Sloan-Kettering - After
Bypass or removal of pump
Bypass or removal of pumps
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Pump Cemetery
To date we have removed several hundred large
pumps from our clients chilled water systems
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Good Engineers Always Ask Why?

• Why does the industry keep installing
  Primary/Secondary systems?
• Why dont we get the desired system ?T?
• Why does the industry allow mixing of supply and
  return water?

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Good Engineers Always Ask Why?

• Why does the industry keep installing
  Primary/Secondary systems?
• Why dont we get the desired system ?T?
• Why does the industry allow mixing of supply and
  return water?
• Answer To keep consultants like us busy!
• Why change?

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Reasons to Change

• Chiller manufacturing industry supports the
  concepts of Variable Primary Flow
• Evaporator flow can vary over a large range
• Less space is required for fewer pumps
• Lower first cost and operating costs

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Change is Starting Around the World

• Most of the large district cooling plants in
  Dubai currently use Primary/Secondary pumping
• By educating the client we were able to convince
  them that this is not necessary
• We are now currently designing three 40,000 ton
  chiller plants in Abu Dhabi using Variable
  Primary Flow as part of a 6.9 billion
  development project

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Design Guidelines of A Primary Variable Flow
System

• Main Equipment
• Minimize amount of installed equipment
• Estimate maximum chiller capacity required with
  full build-out of your campus
• Use 350 SF/Ton as a guideline for most building
  types
• Multiple Plants/ Virtual Central System
• Review your existing system and decide your needs
  for ultimate build-out

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Design Guidelines of A Primary Variable Flow
System

• Chillers
• Renegotiate with manufacturer to provide maximum
  capacity based on the chiller selection.
• Keep flow velocity around 6.5 ft/sec at peak
• Chilled Water Pumps
• Variable Frequency Drive
• Review feasibility of oversizing pumps in lieu of
  providing a standby pump

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Design Guidelines of A Primary Variable Flow
System

• Condenser Water Pumps
• Variable Speed Condenser Water Pumps?
• Cooling Towers
• Design for at least 2F higher wet bulb
  temperature than normal design wet bulb
• Specify full flow coverage at 50 of peak flow
• Pressurization Tank
• City water pressure may be adequate
• Tank May not be required for large system
• Air Separators
• Not required

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Design Guidelines of A Primary Variable Flow
System

• Controls
• Flow control valves on CHWR and CWR lines to each
  chiller
• Chilled water differential pressure bypass valve
  at the plant
• Differential pressure sensors at the
  hydraulically most remote buildings
• Flow meters on CHWR and CWR lines to each chiller
• Outside air weather station
• Temperature and humidity sensors for cooling
  tower controls
• Learn the behavior of your system
• Remember
• You can not manage what you do not measure

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Design Guidelines of A Primary Variable Flow
System

• Chilled water flow controls and site differential
  pressure
• Master Control
• CHWP VFD is controlled to maintain required
  differential pressure at remote buildings
• Sub Master Control
• Provide to maintain individual chiller minimum
  flow

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Variable Volume Primary System Flow Diagram
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Variable Volume Primary System Flow Diagram
Chillers
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Variable Volume Primary System Flow Diagram
CHW Pumps
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Variable Volume Primary System Flow Diagram
DP Bypass
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Variable Volume Primary System Flow Diagram
Condensers
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Variable Volume Primary System Flow Diagram
Control Valves
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Variable Volume Primary System Flow Diagram
CW Pumps
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Variable Volume Primary System Flow Diagram
Cooling Towers
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Summary

• There are many chilled water plants with
  significant opportunities for improvement
• WM Group has a proven record of providing smart
  solutions that work
• We will be happy to review your plant logs with
  no obligation

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• Thank You
• Hemant Mehta, P.E.
• President
• WMGroup Engineers, P.C.
• [phone]
• hmehta_at_wmgroupeng.com