American Standard UV05 Cool Mode Super State, Low Limit State State E, Cant Heat State State B

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Description of Operation

Note – The OAD is considered to be in “alarm” when the OAD is forced below the active minimum position in the Low Limit state. This is not an actual unit “alarm” or “fault” condition, but only a condition used for the purpose of transition arguments.

Low Limit State (State E)

The Low Limit state is a “non-normal” state the UVC can go into while Heat mode is active when the unit reaches 100% heating and still cannot meet the current DATS (see “Discharge Air Temperature Control” on page 29) required to maintain the effective heating set point (see “Space Temperature Set Points” on page 26). This is likely to occur only if the OA temperature is very cold, the OA damper minimum position is set too high, the unit ventilator is oversized for the application, or if the electric heating has failed, or is set incorrectly.

When the Low Limit state becomes active, the Low Limit PI-loop can override the OA damper position (see “Outdoor Air Damper Operation” on page 32) and adjust the OA damper toward closed as necessary to maintain the current DATS (see “Discharge Air Temperature Control” on page 29).

Cant Heat State (State B)

The Cant Heat state is a “non-normal” state the UVC can go to when Heat mode is active. An

IAT or DAT sensor fault during the Heat mode causes the UVC to make this state active.

When the Cant Heat state becomes active, no heating or ventilation takes place. The OA damper goes to the minimum position unless it is forced closed by other functions such as freezestat (T6) or morning warm-up.

Cool Mode (Super State)

When in Cool mode the UVC uses primary cooling (economizer) and secondary cooling (mechanical, DX) as needed to maintain the effective cooling set point (see “Space Temperature Set Points” on page 26). The keypad/display or network connection can be used to force the unit into the Cool mode. When the UVC is in Auto mode, it is “normal” for the UVC to “idle” in Cool mode when there is no need to switch to another mode. The Cool mode super state consists of the following UVC states: Econ Mech [1], Mech [2], Econ [3], DA Heat [4], Low Limit [F], and Cant Cool [C].

When the Cool mode super state becomes active, the UVC will automatically determine which

UVC state to make active based upon the transitions for each state.

If the space temperature drops below EHS, and the Emergency Heat function is enabled, the

UVC will be forced into the Emergency Heat mode (see “Emergency Heat Mode (Super

State)” on page 16).

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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
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