Trane SYS-APM001-EN manual Condenser-water temperature control, Cooling-tower-fan control

Page 96

System Controls

The flow reduction options include:

• Cooling tower bypass

• Chiller bypass

• One or two throttling valves in the condenser-water pipe with the pump riding its curve

• A variable-speed condenser water pump

After the minimum-pressure differential is reached, the flow may be increased as long as that minimum-pressure difference is maintained. Some designers and operators become concerned with possible fouling of condenser-water tubes during these start-up conditions. There is little to fear due to the short duration of reduced flow operation and the limited occurrences. The advantages and disadvantages of these options are discussed in a variety of publications.36,37

Condenser-water temperature control

Cooling-tower-fan control

Cooling towers operate to produce a desired sump water temperature. As the heat rejection load and ambient wet-bulb temperature change, the cooling tower fans must move more or less air to produce the desired water temperature.

Cycling a single fan. Cycling a single fan on and off is one method to maintain rough water temperature control. Since airflow changes greatly between fan speeds, so does heat rejection. Temperature swings of 7°F to 10°F [3.9°C to 5.6°C] are not uncommon. Some chillers, especially older chillers with pneumatic controls, may operate poorly in response to these changing temperatures. Make sure that the fan does not cycle too often and damage the motor, drive, or fan assembly.

Two-speed fans. The installation of two-speed cooling tower fans is an option that reduces temperature swings. Typically, the low fan speed is between 50 and 70 percent of full speed. Since the heat rejection changes roughly in proportion with the fan speed, the temperature swing will be only 50 to 75 percent of cycling a single fan. Again, take care not to cycle too often between speeds—or the gear box may incur excessive wear and fail. A distinct advantage of two-speed fans is that at low speed, the fan power is greatly reduced. Since the fan power varies with the cube of the speed (approximately) the power at half speed is about 15 percent of full speed.

“Pony” motors. Another option offered by cooling-tower manufacturers is to have two separate motors available to drive the fan. The smaller motor is referred to as a “pony” motor. It operates at two-thirds of the full speed and uses about 30 percent of the full speed power. While controlling the tower, it is important to minimize cycling between speeds.

Variable-speed drives. Because the cost of variable-speed drives for cooling- tower fans has decreased, variable-speed drives have become more

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Chiller System Design and Control

SYS-APM001-EN

Page 95 Page 97
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Page 95 Page 97
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 temperature Water-cooled condenserEffect of condenser-water flow rate Maintenance Air-cooled condenserAir-cooled versus water-cooled condensers 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 pumpDistribution piping Pump per chillerManifolded pumps Pumping arrangements Constant flow systemCondenser-Water System Cooling towerPrimary-secondary system Variable-primary systemCondenser-water pumping arrangements Effect of load on cooling tower performanceEffect of ambient conditions on cooling tower performance Single tower per chillerUnit-Level Controls Chiller controlRecommended chiller-monitoring points per Ashrae Standard Centrifugal chiller capacity control Centrifugal chiller with AFDAFD on both chillers Application Considerations Small Chilled-Water Systems 1-2 chillersApplication Considerations Constant flow Variable flowCondensing method Application Considerations Number of chillersParallel or series Part load system operationMid-Sized Chilled-Water Systems Chillers Managing control complexityPreferential vs. equalized loading and run-time Large chilled-water system schematic Large Chilled-Water Systems + Chillers, District CoolingPower Pipe sizeWater Chiller performance testing Limitations of field performance testingChiller Plant System Performance ControlsSYS-APM001-EN SYS-APM001-EN System Design Options Guidance for Chilled- and Condenser-Water Flow RatesChilled-Water Temperatures Standard rating temperaturesSystem Design Options Condenser-Water Temperatures Chilled- and Condenser-Water Flow RatesStandard rating flow conditions 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 loadEntering fluid temperature, F C Cooling-tower options with low flowSmaller tower 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 arrangementCommon CampusTertiary or distributed Decoupled system-principle of operation Tertiary pumping arrangementTemperature-sensing Flow-based controlFlow-sensing Multiple chilled-water plants on a distribution loop Adding a chillerSubtracting 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 selectionPlant configuration Bypass flowChiller sequencing Airside controlHeat Recovery Chilled-Water System VariationsCondenser Free Cooling or Water Economizer 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 counterflowUnequal Chiller Sizing EvaporatorsCondensers System Issues and Challenges Low ΔT SyndromeAmount of Fluid in the Loop System Issues and Challenges Chiller response to changing conditionsSystem response to changing conditions ExampleContingency Minimum capacity requiredType and size of chiller System Issues and Challenges Location of equipment Alternative Energy SourcesWater and electrical connections Ancillary equipmentPlant Expansion Alternative fuelThermal storage Retrofit Opportunities Applications Outside the Chiller’s RangeFlow rate out of range System Issues and Challenges Temperatures out of range Precise temperature controlPrecise temperature control, multiple chillers Chilled water reset-raising and lowering System ControlsChilled-Water System Control Chilled-water pump controlCritical valve reset pump pressure optimization System ControlsNumber of chillers to operate Condenser-Water System Control Minimum refrigerant pressure differentialVFDs and centrifugal chillers performance at 90% load 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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