Emerson Understanding Hot Gas Bypass Operation and Adjustment in Electronic Hot Gas Bypass Valves
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System Operation, Testing and Maintenance

Hot Gas Bypass

Operation

The hot gas bypass valve is installed between the compressor discharge piping and suction piping, bypassing the condenser and evaporator coils. The discharge gas mixes with the suction gas, raising the suction temperature and pressure and decreasing the mass flow through the evaporator. The higher suction temperatures could cause compressor overheating, therefore a separate liquid quenching valve is provided to mix refrigerant from the system liquid line with the discharge gas before mixing with the suction gas entering the compressor.

During normal operation, when the evaporator is under full load the hot gas bypass equalizer pressure will remain high enough to keep the valve port closed. If the evaporator load decreases, the evaporator temperature and pressure will drop. When the suction pressure reduces below the hot gas bypass valve setting the hot gas bypass valve opens diverting some of the refrigerant flow back to the compressor suction. The liquid quenching valve bulb senses this increased superheat and opens, allowing liquid refrigerant to mix with the discharge gas, desuperheating it.

Proper mixing of the three refrigerant paths ensures stable operation and system performance. The liquid quenching valve bulb must be located downsteam of all these connections to control superheat at the compressor inlet. Superheat settings for the liquid quenching valve are chosen to maintain consistency with the system expansion valve. During hot gas bypass operation higher superheats, 50- 60°F (19 to 15°C), may be observed at the compressor. The liquid quenching valve is internally equalized and superheat is not adjustable.

Adjustment

1.Install the suction and discharge pressure gauge.

2.Adjust temperature setpoint to call for cooling so that the refrigeration compressor will run continuously.

3.Remove the TOP adjusting nut from the valve.

4.Insert an Allen wrench in the brass hole at top of valve in adjusting port and turn CLOCKWISE if a higher evaporator temperature is required. Adjust no more than 1/4 turn at a time. Let the system stabilize for 15 minutes before determining if additional adjustment is necessary.

5.After obtaining the suction pressure required, reinstall cap tightly making sure there are no leaks.

6.Let the evaporator operate for approximately 10 to 15 minutes to make sure the suction pressure is within the range desired.

7.There may be a fluctuation of approximately 3 to 6 PSIG (21 to 41 kPa) on the evaporator due to the differential on the hot gas bypass.

8.Return temperature setpoint to the desired setting.

Figure 30 Hot gas bypass

Liebert® Mini-Mate2™

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Contents Liebert Mini-Mate2 Page Table of Contents Microprocessor Control System Performance Microprocessor ControlsAlarms System OPERATION, Testing and MaintenanceTables Important Safety Instructions Liebert Mini-Mate2 Product Model Information Air-cooled systems-indoor centrifugal condensing unitsPFH 0 67 a a L System configurations-60 Hz System configurations-50 HzIntroduction Standard FEATURES-5 TON Systems Evaporator Section-Split SystemCondensing Unit Section-Split System Chilled Water UnitsOther Standard Control Features System ControlsSwitches and Motors ReheatHumidifier SensorsOptional Configurations-Water/Glycol Condensing Units Optional Configurations-Prop Fan Condensing UnitsFree-Cooling Optional Configurations-Chilled Water Units SHIP-LOOSE ACCESSORIES-FIELD-INSTALLED Ship-Loose Accessories-Field-Installed Site Preparation and Installation Installation ConsiderationsRoom Preparation Location Considerations Air-cooled systemsCeiling Unit Weights Unit weightsCooling Drycooler Cooling UnitsInstalling the Ceiling Units Close Coupled InstallationsEquipment Inspection Upon Receipt Evaporator Air Distribution Filter BoxConnections for Ducted Systems Piping Connections and Coolant Requirements Drain LineHumidifier Water Supply Line Evaporator external static pressureRecommended refrigerant line sizes Equivalent lengths for various pipe fittings, ft mEquivalent Pipe Liquid Suction Length, ft m Copper PipeVertical rise above evaporator/maximum Pipe length and condenser elevation relative to evaporatorVertical fall below evaporator Total refrigerant = Units and Lines Quick Connect FittingsRefrigerant charge Line charges refrigerant per 100 ft m of Type L copper tubeDPN000218 Threaded rod and hardware kit installation Electrical ConnectionsPower Connections Control ConnectionsEvaporator unit electrical connections Close coupled installation Piping Connections DuctingGeneral Considerations Considerations for Specific ApplicationsAIR-COOLED Dimensional Data AIR Cooled AIR-COOLED Weight, lb kg Outdoor Air-Cooled Condensing Unit InstallationModel # 60Hz 50Hz Rev Condensing Unit Fluid Requirements Water/Glycol Piping ConsiderationsRegulating Valve WATER/GLYCOL Dimensional Data WATER/GLYCOL DPN000214 Hot Water Reheat Coil Optional free-cooling coil 3-way valve on water/glycol unitsChecklist for Completed Installation Feature Overview Microprocessor ControlMain Menu Menu SetpointsActive Alarms StatusTime DateSetup Operation Restart Time DelayShow DIP Switch 2 C/F DegreesChange Passwords Setup functions, default values and allowable rangesFunction Default Range Calibrate SensorsAlarm Enable Alarm Time DelayCommon Alarm Enable Alarm default time delaysCustom Alarms Standard Custom Alarm MessagesCustom Text LCD Display ContrastRun Diagnostics Available On Rev 1.001.0 and higher Equipment Options SwitchesEquipment switch settings unit control board Switch settings wall box boardTest Outputs Test Control BoardControl menu Control board-inside evaporator Wall box boardHumidity Control Temperature ControlSystem Performance Microprocessor Controls Humidification Operation Load Control FeaturesCommunications Alarms Definitions and Troubleshooting AlarmsCustom Alarms High Head PressureTemperature Humidifier Problem AlarmHigh Water Alarm Air-Cooled SystemsOptional/Custom Alarms Maintenance and Component Operation System TestingSystem OPERATION, Testing and Maintenance Blower System Air DistributionBlower Removal Refrigeration SystemGlycol Solution Maintenance Discharge PressureThermostatic Expansion Valve Air-Cooled Condensing UnitsHot Gas Bypass Hot gas bypassReplacement Procedures Compressor ReplacementMechanical Failure Electrical FailureReplace a Failed Compressor Steam Generating Humidifier-Operation Procedures Humidifier Circuit Board Adjustments Humidifier control board DIP switch settingsReplacing the Humidifier Canister AmpsMaintenance Inspection Checklist Troubleshooting TroubleshootingSymptom Possible Cause Check Or Remedy Cooling cycle too Display ProblemShort Display freezesNe t Ppor t Is tTwor k Care

MINI-MATE2 specifications

The Emerson MINI-MATE2 is a cutting-edge temperature and pressure monitoring device specifically designed for the needs of the refrigeration and HVAC industries. Known for its reliability and user-friendly interface, this compact unit serves as a key tool for technicians and facility managers looking to optimize system performance while ensuring compliance with safety standards.

One of the main features of the MINI-MATE2 is its advanced digital display, which allows users to easily monitor and interpret temperature and pressure readings in real-time. Its highly responsive sensors ensure accurate data collection, vital for maintaining optimal operating conditions. Moreover, the device supports a wide range of refrigerants, making it versatile for different applications, from walk-in coolers to commercial refrigeration systems.

The MINI-MATE2 utilizes state-of-the-art technology to enhance efficiency and performance. Equipped with Bluetooth connectivity, it allows for wireless communication with mobile devices, enabling technicians to track readings and receive alerts remotely. This feature not only improves convenience but also helps in quick decision-making, ensuring timely interventions when anomalies are detected.

Another significant characteristic is its robust construction. Built to withstand harsh environments, the MINI-MATE2 features a durable casing that protects it from physical impacts and environmental factors. This resilience ensures longevity, making it a cost-effective investment for any facility.

In addition, the MINI-MATE2 is designed with user-friendliness in mind. Its intuitive interface means that even technicians with limited experience can easily navigate its functionalities. Quick setup and straightforward operation allow for rapid adoption and extensive use in a variety of settings.

Finally, the MINI-MATE2 also includes built-in data logging capabilities. Users can record historical data for analysis and reporting purposes, which is essential for performing trend analysis and identifying potential issues before they escalate. By providing a comprehensive overview of system performance, the MINI-MATE2 empowers users to make informed decisions that can lead to improved energy efficiency and reduced operational costs.

Overall, the Emerson MINI-MATE2 is an indispensable tool for modern refrigeration and HVAC applications, combining cutting-edge technology, user-friendly design, and essential features to support efficient system management.
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