Trane SYS-APM001-EN System Controls Variable condenser water flow, Chiller-tower-pump balance

Page 98

System Controls

Variable condenser water flow

Chiller-tower-pump balance

There are times when a system designer may choose to vary the condenser water flow in addition to, or instead of, the cooling-tower fan speed. This may be beneficial in systems with high pumping power. If a variable-speed drive is installed, the flow may be reduced and the pump power can be reduced substantially—approximately with the cube of the speed. Attempting to vary both the pump and the tower fan speeds is complex and requires adequate time for design and implementation.

Keep the flow through the condenser above the minimum allowable flow rate for the chiller’s condenser. The operator should regularly log the condenser approach temperature (the temperature difference between the condenser’s refrigerant temperature and the condenser-water leaving temperature) to ensure that the tubes are not becoming fouled. The approach temperature may be monitored using a chiller plant management system.

Tower and/or tower nozzle design can affect the allowable condenser-water flow. If the flow drops below the manufacturer’s specified limit, the water is no longer evenly distributed over the tower fill. This results in a decrease in cooling-tower heat-transfer effectiveness. In extreme cases, it can also result in water freezing in the cooling tower. If variable tower flow is a consideration, contact the cooling-tower manufacturer to determine the flow limit and possibly choose nozzles or cooling-tower configurations that can handle variable-water flow.

Most water-cooled, chilled-water systems use a constant condenser water flow rate. However, the condenser water flow rate can be varied between the minimum and maximum flows allowed for the specific chiller (refer to product catalog or selection program).

But reducing the condenser water flow rate affects the power consumption of the pumps, chiller, and cooling tower, as described below:

•Condenser water pump: Pump power is reduced because both the flow rate and the pressure drop through the piping and condenser are reduced.

•Chiller: Compressor power is increased because, as the flow rate decreases, the temperature of the water leaving the condenser increases. At a given load, this increases the compressor lift and, therefore, its energy use.

•Cooling tower: As explained above, the temperature of the water returning to the cooling tower is warmer. This increases the effectiveness of the heat exchanger. But the water flow rate is decreased, which can either improve or reduce the effectiveness of the cooling tower. So, for a given load, reducing the flow rate through the cooling tower sometimes decreases and sometimes increases energy use.

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Chiller System Design and Control

SYS-APM001-EN

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Contents May Page Chiller System Design and Control Preface Contents 100 Primary System Components ChillerPrimary System Components Chiller evaporatorEffect of chilled-water temperature Effect of chilled-water flow rate and variationEffect of condenser-water flow rate Effect of condenser-water temperatureWater-cooled condenser Air-cooled versus water-cooled condensers MaintenanceAir-cooled condenser Packaged or Split System?Low-ambient operation Energy efficiencyLoads Air-cooled or water-cooled efficiencyThree-way valve load control Two-way valve load controlVariable-speed pump load control Face-and-bypass dampersChilled-Water Distribution System Chilled-water pumpManifolded pumps Distribution pipingPump per chiller Pumping arrangements Constant flow systemPrimary-secondary system Condenser-Water SystemCooling tower Variable-primary systemEffect of ambient conditions on cooling tower performance Condenser-water pumping arrangementsEffect of load on cooling tower performance Single tower per chillerRecommended chiller-monitoring points per Ashrae Standard Unit-Level ControlsChiller control Centrifugal chiller capacity control Centrifugal chiller with AFDAFD on both chillers Application Considerations Small Chilled-Water Systems 1-2 chillersCondensing method Application Considerations Constant flowVariable flow Parallel or series Application ConsiderationsNumber of chillers Part load system operationPreferential vs. equalized loading and run-time Mid-Sized Chilled-Water Systems ChillersManaging control complexity Large chilled-water system schematic Large Chilled-Water Systems + Chillers, District CoolingWater PowerPipe size Chiller Plant System Performance Chiller performance testingLimitations of field performance testing ControlsSYS-APM001-EN SYS-APM001-EN System Design Options Guidance for Chilled- and Condenser-Water Flow RatesSystem Design Options Chilled-Water TemperaturesStandard rating temperatures Standard rating flow conditions Condenser-Water TemperaturesChilled- and Condenser-Water Flow Rates System Design Options Selecting flow rates DP2/DP1 = Flow2/Flow11.85 Low-flow conditions for cooling tower Base Case Low FlowTotal system power Component Power kW Base Case Low Flow System summary at full loadCoil response to decreased entering water temperature Chilled water system performance at part loadSmaller tower Entering fluid temperature, F CCooling-tower options with low flow System designΔT2 = 99.1 78 = 21.1F or 37.3 25.6 = 11.7C Same tower, smaller approachSame tower, larger chiller Same tower, smaller approach Present Smaller ApproachRetrofit opportunities Retrofit capacity changes Larger Present Chiller Same towerCost Implications Misconceptions about Low-Flow Rates Misconception 1-Low flow is only good for long piping runsKWh SYS-APM001-EN System Configurations Parallel ChillersSystem Configurations Parallel chillers with separate, dedicated chiller pumpsSeries Chillers Series chillersPrimary-Secondary Decoupled Systems Hydraulic decouplingCheck valves System Configurations Production Production loopSystem Configurations Distribution Distribution-loop benefits of decoupled system arrangementTertiary or distributed CommonCampus Decoupled system-principle of operation Tertiary pumping arrangementFlow-sensing Temperature-sensingFlow-based control Subtracting a chiller Multiple chilled-water plants on a distribution loopAdding a chiller Pump control in a double-ended decoupled system Double-ended decoupled systemChiller sequencing in a double-ended decoupled system Variable-Primary-Flow Systems Other plant designsAdvantages of variable primary flow Operational savings of VPF designsChiller selection requirements Dispelling a common misconceptionFlow, ft.water Flow rate Managing transient water flows Flow-rate changes that result from isolation-valve operationSystem Configurations System design and control requirements Effect of dissimilar evaporator pressure dropsAccurate flow measurement Chiller sequencing in VPF systems Bypass flow controlAdding a chiller in a VPF system Flow-rate-fluctuation examplesSubtracting a chiller in a VPF system Sequencing based on loadOther VPF control considerations Select slow-acting valves to control the airside coilsPlant configuration Consider a series arrangement for small VPF applicationsGuidelines for a successful VPF system Chiller selectionChiller sequencing Plant configurationBypass flow Airside controlCondenser Free Cooling or Water Economizer Heat RecoveryChilled-Water System Variations Plate-and-frame heat exchangerChilled-Water System Variations Refrigerant migrationRefrigerant migration chiller in free-cooling mode Well, river, or lake waterPreferential Loading Preferential loading parallel arrangementPreferential loading sidestream arrangement Sidestream plate-and-frame heat exchangerSidestream with alternative fuels or absorption Chilled-Water System VariationsPreferential loading series arrangement Sidestream system controlSeries-Counterflow Application Series-series counterflowCondensers Unequal Chiller SizingEvaporators Amount of Fluid in the Loop System Issues and ChallengesLow ΔT Syndrome System response to changing conditions System Issues and ChallengesChiller response to changing conditions ExampleType and size of chiller ContingencyMinimum capacity required Water and electrical connections System Issues and Challenges Location of equipmentAlternative Energy Sources Ancillary equipmentThermal storage Plant ExpansionAlternative fuel Flow rate out of range Retrofit OpportunitiesApplications Outside the Chiller’s Range System Issues and Challenges Temperatures out of range Precise temperature controlPrecise temperature control, multiple chillers Chilled-Water System Control Chilled water reset-raising and loweringSystem Controls Chilled-water pump controlNumber of chillers to operate Critical valve reset pump pressure optimizationSystem Controls VFDs and centrifugal chillers performance at 90% load Condenser-Water System ControlMinimum refrigerant pressure differential Chillers DifferenceCondenser-water temperature control Cooling-tower-fan controlChiller-tower energy balance Chiller-tower energy consumptionSystem Controls Variable condenser water flow Chiller-tower-pump balanceDecoupled condenser-water system Effect of chiller load on water pumps and cooling tower fansCDWP-2 Failure Recovery Failure recoveryConclusion Glossary Glossary Pumps systemGlossary References Plant. Idea 88th Annual Conference Proceedings 1997References Engineering July102 Index AshraeIndex 105 106 Page Trane

SYS-APM001-EN specifications

The Trane SYS-APM001-EN is an advanced control system designed for HVAC (Heating, Ventilation, and Air Conditioning) applications, specifically tailored to enhance energy efficiency and system performance. This comprehensive solution integrates cutting-edge technologies to optimize climate control in commercial and industrial environments.

One of the main features of the SYS-APM001-EN is its intuitive user interface. The system is equipped with a large, easy-to-read display that provides real-time data on system performance, energy usage, and environmental conditions. This user-friendly interface makes it simple for operators to monitor and adjust settings, ensuring optimal comfort levels and efficient energy consumption.

Another key characteristic of the SYS-APM001-EN is its advanced data analytics capabilities. The system collects and analyzes data from various sensors throughout the building, providing insights into occupancy patterns, equipment performance, and energy consumption trends. This data-driven approach allows facility managers to make informed decisions about system adjustments, predictive maintenance, and energy savings.

The SYS-APM001-EN also boasts robust integration capabilities. It can seamlessly connect with a variety of building management systems (BMS) and other third-party devices. This interoperability enables a cohesive operational ecosystem where HVAC systems can communicate and cooperate with lighting, security, and fire safety systems, enhancing overall building efficiency.

Energy efficiency is a hallmark of the SYS-APM001-EN, as it implements sophisticated algorithms to optimize system operation. These algorithms adjust equipment performance in real-time based on current conditions, thereby reducing energy waste and lowering operational costs. The system is designed to support multiple energy-saving strategies, including demand-controlled ventilation and optimal start/stop scheduling.

Additionally, the SYS-APM001-EN is built with scalability in mind, accommodating facilities of various sizes and configurations. Whether it’s a small office building or a large industrial complex, the system can be tailored to meet specific needs, ensuring that HVAC performance aligns with operational goals.

In conclusion, the Trane SYS-APM001-EN is an innovative HVAC control solution that emphasizes user experience, data-driven decision-making, and energy efficiency. With its advanced features and technologies, it is an essential tool for optimizing building performance and enhancing occupant comfort while reducing environmental impact.
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