Trane SYS-APM001-EN System Issues and Challenges, Low ΔT Syndrome, Amount of Fluid in the Loop

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System Issues and Challenges

Low ΔT Syndrome

For many years the “low ΔT syndrome” debate has raged.27, 28 The symptom of the problem is that, in large systems, return-water temperature is too low, thus not allowing the chillers to fully load. Many system operators simply turn on more pumps and chillers to satisfy flow requirements, which wastes energy. For primary-secondary systems, some system designers advocate putting a check valve in the bypass line—thus putting chilled-water primary and secondary pumps in series and varying the flow through chiller evaporators. Other designers install primary pumps that are larger than necessary and “over pump” chillers at part-load conditions. These solutions are all “band-aids” and do not treat the source of the problem. Coad14 points to the fact that a properly operating hydraulic system will work as designed and explains the fallacies in the check valve and over pumping approaches. (Refer to the “Check valves” sidebar on page 46.) Taylor29 recommends that a number of mitigating procedures be implemented to eliminate the problem. They include:

•Eliminating three-way valves

•Ensuring that airside control is not causing the problem

•Properly maintaining the system, including regular air filter changes, coil cleaning, control calibration, and proper setpoints

Before applying band-aid approaches in an attempt to “fix” symptoms such as low ΔT syndrome, ensure that the system is operating properly using some or all of the procedures Taylor29 discusses. In addition to these procedures, simply reducing the chilled-water supply temperature will have the effect of raising the system return-water temperature in systems using two-way valves.

Amount of Fluid in the Loop

Two questions must be answered when determining how much fluid is necessary to maintain proper chilled-water-system control:

•How fast can the specific chiller respond to changing conditions?

•How fast can the system respond to changing conditions?

The amount of fluid the loop requires to operate properly is related to the larger of these two answers. Note that both answers describe an amount of time.

Required Volume = Flow Rate × Loop Time

Where:

•Required Volume = the amount of fluid in the coil, pipes, evaporator barrel, storage tank, etc., in gallons [liters]

SYS-APM001-EN

Chiller System Design and Control

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Contents May Page Chiller System Design and Control Preface Contents 100 Chiller Primary System ComponentsChiller evaporator Primary System ComponentsEffect of chilled-water flow rate and variation Effect of chilled-water temperatureWater-cooled condenser Effect of condenser-water temperatureEffect of condenser-water flow rate Air-cooled condenser MaintenanceAir-cooled versus water-cooled condensers Packaged or Split System?Energy efficiency Low-ambient operationAir-cooled or water-cooled efficiency LoadsTwo-way valve load control Three-way valve load controlFace-and-bypass dampers Variable-speed pump load controlChilled-water pump Chilled-Water Distribution SystemPump per chiller Distribution pipingManifolded pumps Constant flow system Pumping arrangementsCooling tower Condenser-Water SystemPrimary-secondary system Variable-primary systemEffect of load on cooling tower performance Condenser-water pumping arrangementsEffect of ambient conditions on cooling tower performance Single tower per chillerChiller control Unit-Level ControlsRecommended chiller-monitoring points per Ashrae Standard Centrifugal chiller with AFD Centrifugal chiller capacity controlAFD on both chillers Small Chilled-Water Systems 1-2 chillers Application ConsiderationsVariable flow Application Considerations Constant flowCondensing method Number of chillers Application ConsiderationsParallel or series Part load system operationManaging control complexity Mid-Sized Chilled-Water Systems ChillersPreferential vs. equalized loading and run-time Large Chilled-Water Systems + Chillers, District Cooling Large chilled-water system schematicPipe size PowerWater Limitations of field performance testing Chiller performance testingChiller Plant System Performance ControlsSYS-APM001-EN SYS-APM001-EN Guidance for Chilled- and Condenser-Water Flow Rates System Design OptionsStandard rating temperatures Chilled-Water TemperaturesSystem Design Options Chilled- and Condenser-Water Flow Rates Condenser-Water TemperaturesStandard rating flow conditions System Design Options Selecting flow rates Low-flow conditions for cooling tower Base Case Low Flow DP2/DP1 = Flow2/Flow11.85System summary at full load Total system power Component Power kW Base Case Low FlowChilled water system performance at part load Coil response to decreased entering water temperatureCooling-tower options with low flow Entering fluid temperature, F CSmaller tower System designSame tower, smaller approach ΔT2 = 99.1 78 = 21.1F or 37.3 25.6 = 11.7CSame tower, smaller approach Present Smaller Approach Same tower, larger chillerRetrofit capacity changes Larger Present Chiller Same tower Retrofit opportunitiesCost Implications Misconception 1-Low flow is only good for long piping runs Misconceptions about Low-Flow RatesKWh SYS-APM001-EN Parallel Chillers System ConfigurationsParallel chillers with separate, dedicated chiller pumps System ConfigurationsSeries chillers Series ChillersHydraulic decoupling Primary-Secondary Decoupled SystemsCheck valves Production loop System Configurations ProductionDistribution-loop benefits of decoupled system arrangement System Configurations DistributionCampus CommonTertiary or distributed Tertiary pumping arrangement Decoupled system-principle of operationFlow-based control Temperature-sensingFlow-sensing Adding a chiller Multiple chilled-water plants on a distribution loopSubtracting a chiller Double-ended decoupled system Pump control in a double-ended decoupled systemChiller sequencing in a double-ended decoupled system Other plant designs Variable-Primary-Flow SystemsOperational savings of VPF designs Advantages of variable primary flowDispelling a common misconception Chiller selection requirementsFlow, ft.water Flow rate Flow-rate changes that result from isolation-valve operation Managing transient water flowsSystem Configurations Effect of dissimilar evaporator pressure drops System design and control requirementsAccurate flow measurement Bypass flow control Chiller sequencing in VPF systemsFlow-rate-fluctuation examples Adding a chiller in a VPF systemSequencing based on load Subtracting a chiller in a VPF systemSelect slow-acting valves to control the airside coils Other VPF control considerationsConsider a series arrangement for small VPF applications Plant configurationChiller selection Guidelines for a successful VPF systemBypass flow Plant configurationChiller sequencing Airside controlChilled-Water System Variations Heat RecoveryCondenser Free Cooling or Water Economizer Plate-and-frame heat exchangerRefrigerant migration Chilled-Water System VariationsWell, river, or lake water Refrigerant migration chiller in free-cooling modePreferential loading parallel arrangement Preferential LoadingSidestream plate-and-frame heat exchanger Preferential loading sidestream arrangementChilled-Water System Variations Sidestream with alternative fuels or absorptionSidestream system control Preferential loading series arrangementSeries-series counterflow Series-Counterflow ApplicationEvaporators Unequal Chiller SizingCondensers Low ΔT Syndrome System Issues and ChallengesAmount of Fluid in the Loop Chiller response to changing conditions System Issues and ChallengesSystem response to changing conditions ExampleMinimum capacity required ContingencyType and size of chiller Alternative Energy Sources System Issues and Challenges Location of equipmentWater and electrical connections Ancillary equipmentAlternative fuel Plant ExpansionThermal storage Applications Outside the Chiller’s Range Retrofit OpportunitiesFlow rate out of range Precise temperature control System Issues and Challenges Temperatures out of rangePrecise temperature control, multiple chillers System Controls Chilled water reset-raising and loweringChilled-Water System Control Chilled-water pump controlSystem Controls Critical valve reset pump pressure optimizationNumber of chillers to operate Minimum refrigerant pressure differential Condenser-Water System ControlVFDs and centrifugal chillers performance at 90% load Chillers DifferenceCooling-tower-fan control Condenser-water temperature controlChiller-tower energy consumption Chiller-tower energy balanceChiller-tower-pump balance System Controls Variable condenser water flowEffect of chiller load on water pumps and cooling tower fans Decoupled condenser-water systemCDWP-2 Failure recovery Failure RecoveryConclusion Glossary Pumps system GlossaryGlossary Plant. Idea 88th Annual Conference Proceedings 1997 ReferencesEngineering July References102 Ashrae IndexIndex 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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