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Central Chiller Plants
Institute for Facilities Management
Dallas, Texas
February 3, 2014
Course 319
Presenter: John Vucci
Associate Director HVAC Systems
University of Maryland
College Park, Maryland
Seminar Course Objectives
Provide an introduction to the Planning and Design
Process when considering the upgrade of Central Plants
Discuss the basics of Central Plant Designs
Review industry guidelines and standards applicable to
developing efficient Central Plants
Discuss examples of Central Plant Designs
Planning Decisions
Sustainability in Design
What type of Central Plant is best for the
application
Single Building
Multiple Facilities connected
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Today’s Concepts of Green and
Sustainable Design
Sustainability: Providing for the needs of the present without
detracting from the ability to fulfill the needs of the future
Green and sustainable design achieves a balance of high
performing buildings over the life of a facility (CHP) by,
Minimizing natural resource consumption
Minimizing emissions
Minimizing solid waste and liquid effluents
Minimizing negative impacts on site ecosystems
Maximizes quality of indoor environment
Information from ASHRAE Green Guide: the design and construction and
operation of sustainable buildings – 2nd edition 2006
Today’s Concepts of Green and
Sustainable Design
Implementing Green/Sustainable design may
raise the first cost of the purchase
G/S designs evaluate and contribute to LCC
through energy efficiency and operational
flexibility rather than simple focus on first cost
Design Considerations
The Architects Team
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Design
Peak design vs. Diversified or part load operation
Constant Primary/Variable Secondary
Primary Variable Flow
Constant Flow
Hybrid Designs (using different technologies)
Demand Management of energy Consumption
Metering & Controls Integration
Ancillary Systems (water Treatment, Refrigeration MER
Ventilation)
Useful Guides and References
ASHRAE Guideline 22: Instrumentation for monitoring Central Chilled
Water Plant Efficiency
ASHRAE Standard 15 - 2007: Safety Standard for Refrigeration
Systems
ASHRAE Handbook 2008: Chapter 2 Decentralized Cooling
and Heating
ASHRAE Handbook 2008: Chapter 3 Central Cooling and
Heating Plants
ASHRAE Handbook 2008: Chapter 11 District Heating and
Cooling
Future Standard: ASHRAE SPC – 184 MOT Field Testing Package
Chillers
ASHRAE / ARI
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Temperature, Flow and BTUH Metering
GPC-22 & SPC-184
3 wire platinum RTD Ultrasonic Flow
Measurement
Basic Design
Chiller design is constant flow variable temperature
CHW pumping is constant flow
CW pumping is constant flow
CW temperature is controlled by some means (VFD shown)
Basic Design
Typically these systems were designed in the past with three-way control
valves across the distribution load. Newer single designs can utilize
variable CHW flow with two – way modulating valve control changing the
original design concept to variable flow constant temperature.
Oversized chiller with installed plate
& frame heat exchanger connected
to another building utilizes variable
2-way control valve. Original 3-way
control valve provides plant
minimum flow requirements.
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Primary-Secondary Design
Primary Variable Flow
2,600 TR
1,900 Tr 1,900 Tr electric
Steam Steam chiller
driven driven
chiller chiller
6,400 Ton Variable flow chiller plant serving
21 buildings consists of 2-1,900 Tr chillers &
1-2,600 Tr chiller
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Thermal Energy Storage - ICE
Hydronic Decoupler or
Crossover
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Chiller Plant Refrigerant
Containment, Ventilation and Safety
Spring loaded relief valves Emergency ventilation capability where
CFM = 100 x G0.5 (where G is the mass of the
High efficiency purges largest refrigerant system)
Venting emergency relief piping to When occupied; General ventilation @ 0.5
atmosphere cfm/SF and volume not to exceed a MER
temperature rise of 18oF
Chiller Plant Refrigerant
Containment, Ventilation and Safety
Refrigerant Transfer Equipment for total
removal of refrigerant from chiller. Where
multiple chillers in a Central Plant are present
the storage vessel is sized to hold the largest
charge.
Planning for Maintenance
Service access for repairs, equipment access need to be
considered
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Planning for Maintenance
Cleaning condenser tubes can be one of the most cost effective measures of a
maintenance program.
Clean condenser heat transfer is critical to the efficient operation of a chiller.
Discussions with manufacturers identify for every 1 oF increase in
condenser water temperature compressor energy consumption increases
by 2%.
Technician using Local Condenser gantry rig for head
tube cleaning for removal. Ideas for plant consideration
annual cleaning of is not normally presented by the design
condenser tubes team
Planning for Expansion
Following the construction of a new Biosciences building (1,400 Tons Peak) a
2,000 Ton chiller addition was constructed to expand an existing 2,000 Ton –
8,900 Tr/Hr TES ICE Plant. Shell construction occurred parallel to the new facility
during summer 2007 the chiller equipment was installed and commissioned for
readiness. The original Plant decouples the ethylene glycol Primary from water
secondary. The 2,000 TR Plant addition now base loads the summer daily
diversified peak of 1,800 tons of capacity, with the TES ICE storage used for Univ.
Demand Response Program.
Original 2,000 New 2007
Tr TES Plant 2,000 Tr
Addition
Additional Space allowed for
1,600 Tr addition
Components of the Plant designed with sustainability,
Chiller: .62 Kw/Tr @ Design 2,000 tons with VFD operation was factory
performance tested @ 9% (180 Tr) at .36 Kw/Tr
Cooling Tower: Uses 2 VFD’s for each fan set to supply 65 oF CWS
CHW Variable 125 HP Pumps: Use VFD to pump CHW from design 4,000 GPM to
minimum flow (2,000 GPM) as needed.
Primary
Variable
Flow VFD
4,160 VAC Variable
Speed Drive
ASHRAE 15 Refr.
Exhaust & Refr.
Specific Monitor
Condenser Water 2,000 Ton R-134a
Treatment Centrifugal Chiller
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Operation
Plant flexibility
Operations maintenance
Closing Questions
