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Central Chiller Plants

Presenter: John Vucci

Associate Director HVAC Systems

University of Maryland

College Park, Maryland

Institute for Facilities Management

Dallas, Texas

February 3, 2014

Course 319

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

Ultrasonic Flow Measurement

3 wire platinum RTD

Basic DesignChiller design is constant flow variable temperature

CHW pumping is constant flowCW 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

6,400 Ton Variable flow chiller plant serving 21 buildings consists of 2-1,900 Tr chillers & 1-2,600 Tr chiller

2,600 TR electric chiller

1,900 Tr Steam driven chiller

1,900 Tr Steam driven 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

High efficiency purges

Venting emergency relief piping to atmosphere

Emergency ventilation capability where CFM = 100 x G0.5 (where G is the mass of the largest refrigerant system)

When occupied; General ventilation @ 0.5 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 MaintenanceCleaning 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%.

Local Condenser gantry rig for head removal. Ideas for plant consideration is not normally presented by the design team

Technician using tube cleaning for annual cleaning of condenser tubes

Planning for Expansion

Original 2,000 Tr TES Plant

New 2007 2,000 Tr Addition

Additional Space allowed for 1,600 Tr addition

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.

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/TrCooling 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.

4,160 VAC Variable Speed Drive

2,000 Ton R-134a Centrifugal Chiller

Condenser Water Treatment

ASHRAE 15 Refr. Exhaust & Refr. Specific Monitor

Primary Variable

Flow VFD

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Operation

Plant flexibility

Operations maintenance

Closing Questions