American Standard UV05 manual PI Control Parameters, Proportional Band

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Description of Operation

PI Control Parameters

Associated with each PI loop is a set of two adjustable parameters: Proportional Band and Integral Time. When the unit ventilator is properly sized for the space, the factory settings for these parameters provides the best and most robust control action (see Figure 20).

If field problems arise, first ensure these parameters are set back to the factory default settings. If adjustment is required, only make small adjustments to one parameter at a time. After each adjustment, allow enough time for the system to stabilize before making further adjustments. If you do not have the means to graph the space performance, record the actual measured value and set point for several minutes and then plot the results using a spreadsheet to determine the correct action to change the PI parameter.

CAUTION

Adjusting PI parameters can cause erratic unit operation, and potentially damage the equipment.

PI control parameters should only be adjusted by trained personnel having a complete understanding of how these parameters affect system operation. Generally these parameters do not need to be adjusted from the factory default settings.

Figure 20: Optimized PI loop control

Proportional Band

The proportional band, or proportional action, causes the controlled output to changes in proportion to the magnitude of the difference between the sensor value and set point.

A proportional band setting that is too small (see Figure 21) causes control oscillations that go fully above and below the set point.

Figure 21: Proportional bands

A proportional band setting that is too large (see Figure 21) causes an offset between the actual measured oscillation center and the set point. A small offset is not necessarily a problem since most systems have a small “natural” offset and the integral function automatically works to eliminate or reduce this effect.

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McQuay OM 751

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Contents DX Cooling Only Software Model UV05 Group Applied SystemsDate November Getting Started UVC Configuration ParametersIntroduction Description of OperationModel-specific unit ventilator installation literature Accessory-specific installation literatureDescription Manual # Extreme temperature can damage system components Software program literatureAcronyms/Abbreviations Acronyms and abbreviationsDescription Acronym Abr OCS Keypad Functions Using the Keypad/DisplayDisplay Format Security LevelsFAN Key Mode KeyON/STOP Key and LED Arrow KeysMenu Reference Using the Keypad/DisplayViewing Actual Indoor Air Temperature IAT Changing Set PointsAbr Description Default RW1Chlo Description of Operation State ProgrammingComplete UVC-state diagram UVC Unit ModesNormal UVC modes State names OFF Mode StateUVC state names and numbers DecimalNight Purge Mode State Fan Only Mode State aEmergency Heat Mode Super State Full Heat State StateCant Heat State State D Auto Mode Heat Mode Super StateHeat State State Cool Mode Super State Low Limit State State ECant Heat State State B Cool mode super state diagram Econ State StateEcon Mech State State Mech State StateLow Limit State State F Special Purpose Unit ModesDischarge Air DA Heat State State Cant Cool State State CPurge Mode Pressurize ModeDepressurize Mode Shutdown ModeNormal UVC mode priority Unit Mode PrioritySpecial purpose UVC unit mode priority Priority resultStandby Mode Occupied ModeUnoccupied Mode Occupancy mode priorityAdditional Occupancy Features Networked Set Point Capability Space Temperature Set PointsNetworked Space Temperature Sensor Capability Networked Set Point Offset CapabilityRemote Wall-Mounted Sensor with +/-3F Adjustment optional Effective Set Point CalculationsSet point calculation examples Example a Example B GivenEffective set point calculations PI loop list Discharge Air Temperature ControlProportional Integral PI Control Loops PI loopsPI Control Parameters Proportional BandIndoor Air Fan Operation Integral TimeOccupied, Standby, and Bypass Operation Outdoor Air Damper Operation Economizer enable EconomizerOA temp sensor Space humidity CO2 Demand Controlled Ventilation optional Networked Space Humidity Sensor CapabilityNetworked Outdoor Humidity Sensor Capability Networked Space CO2 Sensor CapabilityCompressor Envelope Compressor OperationAshrae Cycle Compressor Cooling LockoutFloating-Point Actuator Auto-Zero, Overdrive and Sync Compressor Minimum On and Off TimersCompressor Start Delay Outdoor Air Fan OperationVentilation Lockout Input Signal Unoccupied Input SignalRemote Shutdown Input Signal External Binary InputsFault Signal Exhaust Interlock Input SignalLights On/Off Signal External Binary OutputsAuxiliary heat start/stop calculation Exhaust Fan ON/OFF SignalAuxiliary Heat Signal Start/Stop CalculationInputs and outputs, software model 05-DX cooling only Expansion boardAlarm and Fault Monitoring Alarm and fault code summaryPriority Fault description Reset Keypad Space Temp Sensor Failure F0 DX Pressure Fault F1Compressor Envelope Fault F2 Discharge Air DX Cooling Low Limit Indication F3Outdoor Temp Sensor Failure F6 Condensate Overflow Indication optional F4Space Coil DX Temp Sensor Failure F5 Discharge Air Temp Sensor Failure F7Troubleshooting Temperature Sensors Troubleshooting Humidity Sensors Temperature versus resistanceCO2 versus voltage table Troubleshooting Carbon Dioxide CO2 SensorsHumidity versus voltage RH % VDC mVUVC configuration parameters OM Configuration Parameter Name Abr Default LUI MenuAbr Default LUI Menu OAD Stroke Time Warranty