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Trane TRG-TRC016-EN manual Capacity, notes, Chiller-PlantControl, period four

Models: TRG-TRC016-EN

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Capacity

period four

Chiller-Plant Control

notes

load indicators

Capacity

supply-water temperature

flow meter

return-water temperature

chiller-plant controller

Figure 93

Another method of monitoring system cooling load is to measure the system water flow rate and temperatures directly, and then calculate the load. Although it would appear that direct measurement of the actual system load would be an excellent way to determine when to turn chillers on and off, this method has several drawbacks. It requires the use of flow meters with high accuracy and high turndown capacities. Although flow meters have become more accurate and less expensive, they require special installation conditions for reliable accuracy—conditions seldom achievable in real installations. Also, the equipment typically requires regular calibration. For these reasons, direct measurement of load has not been used as much as the simple and reliable methods discussed previously.

An alternate way to monitor chiller load is by measuring the current draw of the chiller motor. By itself, this does not provide an adequate control indicator, but when used in conjunction with other information, such as system supply-water temperature, it can be effective. System supply-water temperature is used to determine when to turn an additional chiller on, and operating chiller compressor-motor current draw is used to determine when a chiller can be turned off.

The most effective load indicator for any chilled-water system is dependent on the design of that system. Creative designers have used the control strategies as described here and in various combinations to effectively control a wide variety of chiller plants. It is highly recommended that one of the first tasks undertaken in the design process is to create a simplified flow diagram and a load model of the system that allows for the evaluation of various control strategies and sensor placements. This will help to ensure that effective chiller-plant control can be implemented.

TRG-TRC016-EN

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Trane TRG-TRC016-EN manual Capacity, notes, Chiller-PlantControl, period four

Contents

TRG-TRC016-EN Air Conditioning Clinic Chilled-WaterSystemsOne of the Systems Series BUSINESS REPLY MAIL BUSINESS REPLY MAILTHE TRANE COMPANY Attn: Applications Engineering 3600 Pammel Creek Road La Crosse WIComment Card Response CardChilled-WaterSystems One of the Systems SeriesThe Trane Company Chilled-WaterSystemsOne of the Systems Series A publication of A Trane Air Conditioning Clinic PrefaceChilled-WaterSystems Contents period two Chilled-WaterSystem Designperiod three period fourTRG-TRC016-EN notes period oneTypes of Water Chillers Types of Water Chillersperiod one Driving Sourcesnotes Types of Water ChillersVapor-CompressionCycle notesTypes of Water Chillers period oneCompressor Types notesTypes of Water Chillers period oneVariable-SpeedDrives notesTypes of Water Chillers period oneCondenser Types Air-Cooledor Water-Coolednotes Types of Water ChillersMaintenance Tower maintenance Freeze protection Makeup waternotes Types of Water ChillersLow Ambient Operation notesTypes of Water Chillers period oneEfficiency notesTypes of Water Chillers period oneComparison notesTypes of Water Chillers period onePackaged Air-CooledChiller notesTypes of Water Chillers period oneRemote Evaporator Barrel notesTypes of Water Chillers period oneRemote Air-CooledCondenser notesTypes of Water Chillers period oneIndoor Air-CooledCondenser notesTypes of Water Chillers period oneAbsorption Refrigeration Cycle notesTypes of Water Chillers period oneAbsorption Chillers Offer Choice Waste heat recovery Cogenerationnotes Types of Water ChillersAbsorption Chiller Types notesTypes of Water Chillers period oneEquipment Rating Standards notesTypes of Water Chillers period onePart-LoadEfficiency Rating notesTypes of Water Chillers period oneStandard Rating Conditions notesTypes of Water Chillers period oneFlow Rates and Temperatures notesTypes of Water Chillers period onenotes Types of Water Chillersperiod one Flow Rates and TemperaturesASHRAE/IESNA Standard 90.1–1999 Electric Vapor-CompressionChillersnotes Types of Water ChillersWater-CooledAbsorption Chillers notesTypes of Water Chillers period oneASHRAE Standard 15–1994 Safety standard for refrigerating systemsnotes Types of Water Chillersperiod two Chilled-WaterSystem DesignChilled-WaterSystem Design period twoperiod two Chilled-WaterSystemnotes Chilled-WaterSystem DesignLoad-TerminalControl Options notesChilled-WaterSystem Design period twoperiod two Three-WayValve ControlChilled-WaterSystem Design Two-WayValve Control notesChilled-WaterSystem Design period twoFace-and-BypassDamper Control notesChilled-WaterSystem Design period twoChiller Evaporator Flow notesChilled-WaterSystem Design period twoSingle-ChillerSystem notesChilled-WaterSystem Design period twoMultiple-ChillerSystems notesChilled-WaterSystem Design period twoSingle Pump Parallel Configurationnotes Chilled-WaterSystem DesignDedicated Pumps notesChilled-WaterSystem Design period twoFigure 43 shows an example of the pump–systemcurve relationship. When both pumps are operating, the system receives 100 percent of design flow. When only one pump is operating, the intersection of the pump’s performance curve with the system curve results in about 65 percent of design flow notesChilled-WaterSystem Design period twoChillers Piped in Series Series Configurationnotes Chilled-WaterSystem DesignEqual Set Points notesChilled-WaterSystem Design period twoStaggered Set Points notesChilled-WaterSystem Design period twoPrimary-SecondaryConfiguration Primary-SecondaryDecoupled ConfigurationChilled-WaterSystem Design period twoPrimary-SecondarySystem Rules notesChilled-WaterSystem Design period twoProduction Loop notesChilled-WaterSystem Design period twoManifolded Production Pumps notesChilled-WaterSystem Design period twoperiod two Distribution LoopChilled-WaterSystem Design notes Chilled-WaterSystem Designperiod two Primary-SecondarySystem RulesVarying Distribution Flow notesChilled-WaterSystem Design period twoMultiple Distribution Pumps notesChilled-WaterSystem Design period twoA variation of the multiple-pumpconfiguration is to use separate pumps to deliver water to specific, dedicated loads. An example is a chilled-watersystem serving a college campus. Separate distribution pumps supply water to the east A, west B, and central C portions of the campus. A primary advantage of this configuration is flexibility. Expanding the system can be achieved by simply adding another distribution pump to the existing plant and connecting it to the piping that runs to the new building notesChilled-WaterSystem Design period twoTertiary Pumping notesChilled-WaterSystem Design period twoDistribution Loop Characteristics notesChilled-WaterSystem Design period twonotes Chilled-WaterSystem Designperiod two Primary-SecondarySystem RulesSystem Operation notesChilled-WaterSystem Design period twoDeficit Flow notesChilled-WaterSystem Design period twoExcess Flow notesChilled-WaterSystem Design period twoControl of Primary-SecondarySystem notesChilled-WaterSystem Design period twoTypes of Fluid Flow Meters Chilled-WaterSystem Designperiod two Pressure-basedTemperature-BasedCalculations notesChilled-WaterSystem Design period twoperiod three System VariationsSystem Variations period threeperiod three Fuel Choice OptionsSystem Variations absorption thermal storageChiller Efficiency Improvements System Variationsperiod three Low-FlowSystemsGreater Focus on System Efficiency Trend Toward Lower Flow Ratesnotes System VariationsLow-FlowSystems notesSystem Variations period threeVariable-Primary-FlowSystems notesSystem Variations period threeCritical VPF System Requirements notesSystem Variations period threePreferential Chiller Loading notesSystem Variations period threeSidestream Configuration notesSystem Variations period threeHeat-RecoveryChiller Heat Recoverynotes System VariationsHeat-RecoveryChiller Options notesSystem Variations period threeHeat-RecoveryChiller Efficiency notesSystem Variations period threeControl of a Heat-RecoveryChiller notesSystem Variations period threeAsymmetric Design notesSystem Variations period threeSwing Chiller notesSystem Variations period threenotes System Variationsperiod three Swing Chiller“Free” Cooling notesSystem Variations period threePlate-and-FrameHeat Exchanger notesSystem Variations period threeRefrigerant Migration notesSystem Variations period threeApplication Outside Range of Chiller notesSystem Variations period threeperiod four Chiller-PlantControlChiller-PlantControl period fourperiod four Chiller Controlsnotes Chiller-PlantControlWhat Is Important? When to turn a chiller on or offHow to recover from an equipment failure How to optimize system efficiencyChiller Sequencing notesChiller-PlantControl period fourTemperature notesChiller-PlantControl period fourFlow notesChiller-PlantControl period fourCapacity notesChiller-PlantControl period fourChiller Rotation notesChiller-PlantControl period fourWhen the system consists of chillers with different capacities, efficiencies, or fuel types, the question of which chiller to turn on or off next becomes more complex. Although each system requires a complete analysis, there are some general principles that apply to most systems notesChiller-PlantControl period fourHeat Recovery preferentially-loaded heat-recoverychillernotes Chiller-PlantControlThe variable-primary-flowsystem, introduced in Period Three, is designed to operate with variable flow through the chiller evaporators. Sequencing chillers in this type of system cannot be based solely on temperature, because in a properly-operatingsystem the supply- and return-watertemperatures will be nearly constant. Determining when to turn chillers on or off is not a simple task. For control stability and chiller reliability, the flow rates through the chillers, and the rate of flow change, must be kept within allowable ranges notesChiller-PlantControl period fourSystem Failure Recovery Failure Recovery and Contingency Planningnotes Chiller-PlantControlContingency Planning notesChiller-PlantControl period fourSystem Timers System TuningLoad-confirmationtimer Staging-intervaltimerUnload Before Start notesChiller-PlantControl period fourSoft Loading notesChiller-PlantControl period fourChilled-WaterSet Point Control notesChiller-PlantControl period fourSystem Optimization notesChiller-PlantControl period fourChilled Water Reset notesChiller-PlantControl period fourCondenser-WaterTemperature notesChiller-PlantControl period fourperiod four Control of Condensing PressureChiller-PlantControl Operator Training and Support notesChiller-PlantControl period fourOperator Interface notesChiller-PlantControl period fourASHRAE Guideline Chiller-PlantControlperiod four chiller operating logperiod five ReviewReview period fiveperiod five Review—PeriodTwoParallel configuration Series configuration notesReview—PeriodThree Heat recovery Asymmetric designnotes ReviewReview—PeriodFour Chiller sequencing Failure recoveryContingency planning System tuning notesReview period fivenASHRAE Handbook – Refrigeration nASHRAE Handbook – Systems and EquipmentQuestions for Period QuizQuestions for Period 9Why does a variable-primary-flowVPF system require a bypass in the system? QuizQuestions for Period Questions for PeriodAnswers Answers 12Sequencing 13Decreases; increasesGlossary Glossary decoupled system See primary-secondarysystemGlossary swing chiller A smaller-capacitychiller used in a multiple-chillersystem. It is alternated on and off between the larger chillers operation to serve as a smaller, incremental step of loading notesGlossary The Trane Company