American Standard UV05 manual Compressor Operation, Ashrae Cycle, Compressor Envelope

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Description of Operation

ASHRAE Cycle II

The UVC supports ASHRAE Cycle II operation. The basis of ASHRAE Cycle II is to maintain the required minimum amount of ventilation whenever possible, which can be increased during normal operation for economizer cooling or CO2 DCV control or reduced to prevent excessively cold discharge air temperatures.

A discharge air temperature sensor is installed in all unit ventilators. If necessary, the ASHRAE II control algorithm overrides room control and modifies the heating, ventilating, and cooling functions (as available) to prevent the discharge air temperature from falling below the VCLL set point.

Compressor Operation

The UVC is configured to operate the compressor as secondary (mechanical) cooling when the economizer is available. When the economizer is not available and the compressor is available, the UVC uses the compressor when cooling is required.

Compressor Envelope

The compressor envelope protects the compressor from adverse operating conditions that can cause damage and or shortened compressor life by ending compressor operation if coil temperatures exceed the defined operating envelope.

For self-contained units, the UVC is configured to monitor both the inside air/refrigerant and outside air/refrigerant coil temperatures to prevent compressor operation under adverse conditions.

For split-system units, the UVC is configured at the factory to only monitor the inside air/ refrigerant coil as part of the compressor envelope function.

Figure 23: Compressor envelope in self-contained units

Evaporator temperature (indoor air coil)

DX cooling

160˚F (71.1˚C)

2

40˚F (4.4˚C)

1

28˚F (-2.2˚C) 120˚F (48.9˚C) Condenser temperature

(outdoor air coil)

Area for compressor operation envelope.

1Area where liquid slugging could occur.

2Area where starving could occur.

Compressor Cooling Lockout

The UVC is configured to lockout compressor cooling when the OA temperature falls below the Compressor Cooling Lockout set point (63.5°F/17.5°C). Below this point, only economizer cooling is available.

McQuay OM 751

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Contents Date November DX Cooling Only Software Model UV05Group Applied Systems Description of Operation UVC Configuration ParametersIntroduction Getting StartedDescription Manual # Model-specific unit ventilator installation literatureAccessory-specific installation literature Software program literature Extreme temperature can damage system componentsDescription Acronym Abr Acronyms/AbbreviationsAcronyms and abbreviations OCS Security Levels Using the Keypad/DisplayDisplay Format Keypad FunctionsArrow Keys Mode KeyON/STOP Key and LED FAN KeyChanging Set Points Using the Keypad/DisplayViewing Actual Indoor Air Temperature IAT Menu ReferenceRW1 Abr Description DefaultChlo State Programming Description of OperationUVC Unit Modes Complete UVC-state diagramDecimal OFF Mode StateUVC state names and numbers Normal UVC modes State namesFan Only Mode State a Night Purge Mode StateCant Heat State State D Emergency Heat Mode Super StateFull Heat State State Heat State State Auto ModeHeat Mode Super State Cant Heat State State B Cool Mode Super StateLow Limit State State E Econ State State Cool mode super state diagramMech State State Econ Mech State StateCant Cool State State C Special Purpose Unit ModesDischarge Air DA Heat State State Low Limit State State FShutdown Mode Pressurize ModeDepressurize Mode Purge ModePriority result Unit Mode PrioritySpecial purpose UVC unit mode priority Normal UVC mode priorityOccupancy mode priority Occupied ModeUnoccupied Mode Standby ModeAdditional Occupancy Features Networked Set Point Offset Capability Space Temperature Set PointsNetworked Space Temperature Sensor Capability Networked Set Point CapabilityEffective Set Point Calculations Remote Wall-Mounted Sensor with +/-3F Adjustment optionalEffective set point calculations Set point calculation examplesExample a Example B Given PI loops Discharge Air Temperature ControlProportional Integral PI Control Loops PI loop listProportional Band PI Control ParametersOccupied, Standby, and Bypass Operation Indoor Air Fan OperationIntegral Time Outdoor Air Damper Operation OA temp sensor Space humidity Economizer enableEconomizer Networked Space CO2 Sensor Capability Networked Space Humidity Sensor CapabilityNetworked Outdoor Humidity Sensor Capability CO2 Demand Controlled Ventilation optionalCompressor Cooling Lockout Compressor OperationAshrae Cycle Compressor EnvelopeOutdoor Air Fan Operation Compressor Minimum On and Off TimersCompressor Start Delay Floating-Point Actuator Auto-Zero, Overdrive and SyncExternal Binary Inputs Unoccupied Input SignalRemote Shutdown Input Signal Ventilation Lockout Input SignalExternal Binary Outputs Exhaust Interlock Input SignalLights On/Off Signal Fault SignalStart/Stop Calculation Exhaust Fan ON/OFF SignalAuxiliary Heat Signal Auxiliary heat start/stop calculationExpansion board Inputs and outputs, software model 05-DX cooling onlyPriority Fault description Reset Keypad Alarm and Fault MonitoringAlarm and fault code summary Discharge Air DX Cooling Low Limit Indication F3 DX Pressure Fault F1Compressor Envelope Fault F2 Space Temp Sensor Failure F0Discharge Air Temp Sensor Failure F7 Condensate Overflow Indication optional F4Space Coil DX Temp Sensor Failure F5 Outdoor Temp Sensor Failure F6Troubleshooting Temperature Sensors Temperature versus resistance Troubleshooting Humidity SensorsRH % VDC mV Troubleshooting Carbon Dioxide CO2 SensorsHumidity versus voltage CO2 versus voltage tableConfiguration Parameter Name Abr Default LUI Menu UVC configuration parameters OMAbr Default LUI Menu OAD Stroke Time Warranty