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Trane TRG-TRC016-EN manual System Failure Recovery, notes, Chiller-PlantControl, period four

Models: TRG-TRC016-EN

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System Failure Recovery

period four

Chiller-Plant Control

notes

System Failure Recovery

▲Maintain flow of chilled water

▲Keep it simple

◆Lock out failed equipment

◆Turn on the next chiller in the sequence

▲Notify the operator▲Allow the operator to intervene

Figure 98

Failure Recovery and Contingency Planning

In addition to normal chiller sequencing, the chiller-plant control system must react when a chiller or another piece of associated equipment fails. Failure recovery, or ensuring the reliable supply of chilled water, is a very important part of the chiller-plant control system, and is an area where many systems have fallen short. This is especially true in field-programmed systems because of the difficulty of thorough debugging.

During periods of equipment malfunction, it is important to focus on the primary goal of the system, which is to provide the required flow of chilled water to the system at the proper temperature. It seems reasonable that the simplest and most reliable failure-recovery sequence is to simply turn on the next chiller in the sequence, and not try to turn several chillers on and off in an attempt to re-optimize the system.

During an equipment failure, it is especially important to notify the operator of the status, as well as to help the operator understand where the problem is and what might be the cause. The control system must also allow the operator to easily analyze the situation and to intervene if the failure condition will exist for an extended period of time. A system that provides this information will ensure that the system itself will be maintained and operated in proper condition.

90	TRG-TRC016-EN

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Trane TRG-TRC016-EN manual System Failure Recovery, notes, Chiller-PlantControl, period four, Notify the operator

Contents

One of the Systems Series Air Conditioning Clinic Chilled-WaterSystemsTRG-TRC016-EN BUSINESS REPLY MAIL BUSINESS REPLY MAILTHE TRANE COMPANY Attn: Applications Engineering 3600 Pammel Creek Road La Crosse WIResponse Card Comment CardChilled-WaterSystems One of the Systems SeriesOne of the Systems Series A publication of Chilled-WaterSystemsThe Trane Company Chilled-WaterSystems PrefaceA Trane Air Conditioning Clinic period two Chilled-WaterSystem Design Contentsperiod three period fourTRG-TRC016-EN period one notesTypes of Water Chillers Types of Water ChillersDriving Sources period onenotes Types of Water Chillersnotes Vapor-CompressionCycleTypes of Water Chillers period onenotes Compressor TypesTypes of Water Chillers period onenotes Variable-SpeedDrivesTypes of Water Chillers period oneAir-Cooledor Water-Cooled Condenser Typesnotes Types of Water ChillersTower maintenance Freeze protection Makeup water Maintenancenotes Types of Water Chillersnotes Low Ambient OperationTypes of Water Chillers period onenotes EfficiencyTypes of Water Chillers period onenotes ComparisonTypes of Water Chillers period onenotes Packaged Air-CooledChillerTypes of Water Chillers period onenotes Remote Evaporator BarrelTypes of Water Chillers period onenotes Remote Air-CooledCondenserTypes of Water Chillers period onenotes Indoor Air-CooledCondenserTypes of Water Chillers period onenotes Absorption Refrigeration CycleTypes of Water Chillers period oneWaste heat recovery Cogeneration Absorption Chillers Offer Choicenotes Types of Water Chillersnotes Absorption Chiller TypesTypes of Water Chillers period onenotes Equipment Rating StandardsTypes of Water Chillers period onenotes Part-LoadEfficiency RatingTypes of Water Chillers period onenotes Standard Rating ConditionsTypes of Water Chillers period onenotes Flow Rates and TemperaturesTypes of Water Chillers period onenotes Flow Rates and TemperaturesTypes of Water Chillers period oneElectric Vapor-CompressionChillers ASHRAE/IESNA Standard 90.1–1999notes Types of Water Chillersnotes Water-CooledAbsorption ChillersTypes of Water Chillers period oneSafety standard for refrigerating systems ASHRAE Standard 15–1994notes Types of Water ChillersChilled-WaterSystem Design period twoChilled-WaterSystem Design period twoChilled-WaterSystem period twonotes Chilled-WaterSystem Designnotes Load-TerminalControl OptionsChilled-WaterSystem Design period twonotes Three-WayValve ControlChilled-WaterSystem Design period twonotes Two-WayValve ControlChilled-WaterSystem Design period twonotes Face-and-BypassDamper ControlChilled-WaterSystem Design period twonotes Chiller Evaporator FlowChilled-WaterSystem Design period twonotes Single-ChillerSystemChilled-WaterSystem Design period twonotes Multiple-ChillerSystemsChilled-WaterSystem Design period twoParallel Configuration Single Pumpnotes Chilled-WaterSystem Designnotes Dedicated PumpsChilled-WaterSystem Design period twonotes Figure 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 flowChilled-WaterSystem Design period twoSeries Configuration Chillers Piped in Seriesnotes Chilled-WaterSystem Designnotes Equal Set PointsChilled-WaterSystem Design period twonotes Staggered Set PointsChilled-WaterSystem Design period twoPrimary-SecondaryDecoupled Configuration Primary-SecondaryConfigurationChilled-WaterSystem Design period twonotes Primary-SecondarySystem RulesChilled-WaterSystem Design period twonotes Production LoopChilled-WaterSystem Design period twonotes Manifolded Production PumpsChilled-WaterSystem Design period twoChilled-WaterSystem Design Distribution Loopperiod two Chilled-WaterSystem Design notesperiod two Primary-SecondarySystem Rulesnotes Varying Distribution FlowChilled-WaterSystem Design period twonotes Multiple Distribution PumpsChilled-WaterSystem Design period twonotes A 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 buildingChilled-WaterSystem Design period twonotes Tertiary PumpingChilled-WaterSystem Design period twoHigher return-watertemperatures Distribution Loop Characteristicsnotes Chilled-WaterSystem DesignChilled-WaterSystem Design notesperiod two Primary-SecondarySystem Rulesnotes System OperationChilled-WaterSystem Design period twonotes Deficit FlowChilled-WaterSystem Design period twonotes Excess FlowChilled-WaterSystem Design period twonotes Control of Primary-SecondarySystemChilled-WaterSystem Design period twoChilled-WaterSystem Design Types of Fluid Flow Metersperiod two Pressure-basednotes Temperature-BasedCalculationsChilled-WaterSystem Design period twoSystem Variations period threeSystem Variations period threeFuel Choice Options period threeSystem Variations absorption thermal storageSystem Variations Chiller Efficiency Improvementsperiod three Low-FlowSystemsTrend Toward Lower Flow Rates Greater Focus on System Efficiencynotes System Variationsnotes Low-FlowSystemsSystem Variations period threenotes Variable-Primary-FlowSystemsSystem Variations period threenotes Critical VPF System RequirementsSystem Variations period threenotes Preferential Chiller LoadingSystem Variations period threenotes Sidestream ConfigurationSystem Variations period threeHeat Recovery Heat-RecoveryChillernotes System Variationsnotes Heat-RecoveryChiller OptionsSystem Variations period threenotes Heat-RecoveryChiller EfficiencySystem Variations period threenotes Control of a Heat-RecoveryChillerSystem Variations period threenotes Asymmetric DesignSystem Variations period threenotes Swing ChillerSystem Variations period threeSystem Variations notesperiod three Swing Chillernotes “Free” CoolingSystem Variations period threenotes Plate-and-FrameHeat ExchangerSystem Variations period threenotes Refrigerant MigrationSystem Variations period threenotes Application Outside Range of ChillerSystem Variations period threeChiller-PlantControl period fourChiller-PlantControl period fourChiller Controls period fourStart–stop Chilled-watertemperature control notesWhen to turn a chiller on or off What Is Important?How to recover from an equipment failure How to optimize system efficiencynotes Chiller SequencingChiller-PlantControl period fournotes TemperatureChiller-PlantControl period fournotes FlowChiller-PlantControl period fournotes CapacityChiller-PlantControl period fournotes Chiller RotationChiller-PlantControl period fournotes When 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 systemsChiller-PlantControl period fourpreferentially-loaded heat-recoverychiller Heat Recoverynotes Chiller-PlantControlnotes The 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 rangesChiller-PlantControl period fourFailure Recovery and Contingency Planning System Failure Recoverynotes Chiller-PlantControlnotes Contingency PlanningChiller-PlantControl period fourSystem Tuning System TimersLoad-confirmationtimer Staging-intervaltimernotes Unload Before StartChiller-PlantControl period fournotes Soft LoadingChiller-PlantControl period fournotes Chilled-WaterSet Point ControlChiller-PlantControl period fournotes System OptimizationChiller-PlantControl period fournotes Chilled Water ResetChiller-PlantControl period fournotes Condenser-WaterTemperatureChiller-PlantControl period fourChiller-PlantControl Control of Condensing Pressureperiod four notes Operator Training and SupportChiller-PlantControl period fournotes Operator InterfaceChiller-PlantControl period fournotes ASHRAE GuidelineChiller-PlantControl period fourReview period fiveReview period fiveReview—PeriodTwo period fiveParallel configuration Series configuration notesHeat recovery Asymmetric design Review—PeriodThreenotes ReviewChiller sequencing Failure recovery Review—PeriodFourContingency planning System tuning notesperiod five ReviewnASHRAE Handbook – Refrigeration nASHRAE Handbook – Systems and EquipmentQuestions for Period QuizQuestions for Period Quiz 9Why does a variable-primary-flowVPF system require a bypass in the system?Questions for Period Questions for PeriodAnswers 12Sequencing 13Decreases; increases AnswersGlossary decoupled system See primary-secondarysystem GlossaryGlossary Glossary notesswing 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 The Trane Company