Preferential Chiller Loading | Trane TRG-TRC016-EN specs

period three

System Variations

notes

Preferential Chiller Loading

equally loaded

preferentially loaded

distribution pump

					e
				ip
			p
		s
	s
	a
p
y
b

absorption chiller

Figure 74

Preferential Loading

To take full advantage of a high-efficiency, heat-recovery or alternate-fuel chiller, the system may need a method to preferentially load these chillers. The following two system configurations are variations of the primary-secondary system.

In the basic primary-secondary system, all operating chillers are loaded to equal percentages. In this first preferential-loading configuration, the preferentially- loaded chiller is moved to the distribution side of the bypass pipe. This chiller is preferentially (or most fully) loaded when it is turned on, because it always receives the warmest system return water. In this example, an absorption chiller is located on the distribution side of the bypass pipe so that it can be preferentially loaded during periods of high electricity costs.

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Trane TRG-TRC016-EN manual Preferential Chiller Loading, Preferential Loading

Contents

Air Conditioning Clinic Chilled-Water Systems Business Reply Mail One of the Systems Series Comment Card One of the Systems Series Publication Trane Company Preface Contents Iii Water systems Types of Water Chillers Compressor-driven heat-driven Driving Sources Vapor-Compression Water Chillers Vapor-Compression Cycle Scroll Reciprocating Helical-rotarycentrifugal Compressor Types Variable-Speed Drives Air-Cooled or Water-Cooled Condenser TypesAir-Cooled or Water-Cooled Condensing Maintenance Low Ambient Operation Efficiency Comparison Packaged or Split Components Packaged Air-Cooled Chiller Remote Evaporator Barrel Remote Air-Cooled Condenser Indoor Air-Cooled Condenser Absorption Water Chillers Absorption Refrigeration Cycle Absorption Chillers Offer Choice Single-effectdouble-effect Direct-fired Absorption Chiller Types Equipment Rating Standards Equipment Rating StandardsAir-Conditioning & Refrigeration Institute ARI Integrated Part-Load Value Iplv Part-Load Efficiency RatingNon-Standard Part-Load Value Nplv Evaporator Condenser Rating Chiller type Flow rate Standard Rating Conditions QBtu/hr = 500 ⋅ flow rate ⋅ ∆T Flow Rates and Temperatures ARI conditions Low-flow conditions Electric Vapor-Compression Chillers ASHRAE/IESNA StandardEnergy Standard Chiller type Capacity Water-Cooled Absorption Chillers Ashrae Standard Chilled-Water System Components Chilled-Water System Design Chilled-Water System Load-Terminal Control Load-Terminal Control Options Three-Way Valve Control Two-Way Valve Control Face-and-Bypass Damper Control Three-way modulating valve Chiller Evaporator FlowConstant flow is most common Variable flow is possible Single-Chiller System Redundancy Part-load efficiency Multiple-Chiller Systems Single Pump Parallel Configuration Dedicated Pumps Percent flow Chillers Piped in Series Series Configuration Equal Set Points Staggered Set Points Primary-Secondary Decoupled Configuration Primary-Secondary Configuration Bypass pipe should be free of restrictions Primary-Secondary System Rules Production Loop Manifolded Production Pumps Distribution Loop Load terminals should use two-way modulating control valves Bypass pipe should be free of restrictions Variable-speed control riding the pump curve Varying Distribution Flow Multiple Distribution Pumps Distribution Tertiary Pumping Distribution Loop Characteristics Primary-Secondary System Rules Primary-Secondary System Operation System Operation Deficit Flow Excess Flow Control of Primary-Secondary System Pressure-based Types of Fluid Flow MetersTurbine and impeller Vortex Magnetic Ultrasonic Temperature-Based Calculations Alternate Fuel Choice Electric Utility Deregulation Indirectly-coupled, gas-engine chillers Fuel Choice Options Low-Flow Systems Chiller Efficiency Improvements Trend Toward Lower Flow Rates Greater Focus on System Efficiency Low-Flow Systems Variable-Primary-Flow Systems Variable-Primary-Flow Systems Critical VPF System Requirements Preferential Loading Preferential Chiller Loading Sidestream Configuration Heat Recovery Heat-Recovery Chiller Heat-recovery Auxiliary Dual condenser Condenser Heat pump Heat-Recovery Chiller Options Mode Heat-Recovery Chiller Efficiency Unloadingwith Control of a Heat-Recovery Chiller Asymmetric Design Asymmetric DesignDifferent chiller Capacities Different chiller Swing Chiller Chiller Free Cooling Free CoolingAirside economizer Waterside economizer Plate-and-Frame Heat Exchanger Refrigerant Migration Application Outside the Operating Range of the Chiller Application Outside Range of Chiller Chiller-Plant Control Chiller Controls What Is Important? Chiller Sequencing Chiller Sequencing Temperature Flow Capacity Chiller Rotation Small electric Chiller largeelectric chiller Heat Recovery Variable-Primary-Flow Systems Failure Recovery and Contingency Planning System Failure RecoveryMaintain flow of chilled water Keep it simple Notify the operator Allow the operator to intervene Contingency Planning System Tuning System TimersLoad-confirmation timer Staging-interval timer Unload Before Start Soft Loading Chilled-Water Set Point Control System Optimization System Optimization Pros Chilled Water ResetCons Tower Condenser-Water Temperature Control of Condensing Pressure Operator Interface Operator Training and Support Operator Interface Ashrae Guideline Vapor-compression water chillers Review-Period One Load-terminal control Review-Period Two Review-Period Three Review-Period Four For more information, refer to the following references Quiz 109 Answers 111 Glossary 113 114 115 Trane Company