Trane ZN.520, Tracer Unit Ventilator manual Heat/Cool Changeover logic

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Unit Operation

4 = Night Purge (air changeover) not supported

5= Pre-cool (morning cool down)

6= Off (no unit operation allowed)

7= Test (special test mode)

8= Emergency Heat not supported

9 = Fan Only (no heating or cooling allowed)

All other enumerations will be in- terpreted as Auto.

As the controller automatically de- termines its heating or cooling mode, it changes from cool to heat or from heat to cool, while the error (integrated over time between the active setpoint and the space tem-

perature) is (900°FhSec). Integra- tion only begins once the heating and cooling capacity is equal to 0% or the discharge air temperature is being limited by the discharge air temperature control limits.(See

Figure 17: “Heat/Cool Changeover logic”).

Figure 17: Heat/Cool Changeover logic

If the measured space temperature is 69 °F and the active cooling set- point is 72 °F, the error between the space temperature and the set- point is three degrees. If the same error exists for one minute (60 sec- onds), the integration term is

(3 °Fh60 Sec) or (180 °Fh Sec).

The Tracer™ ZN.520 Unit Control- ler changes from heating to cool- ing and cooling to heating when the integration term exceeds

(900 °FhSec). Along with satisfy- ing the integration for heating and cooling changeover, the measured space temperature must fall out- side the setpoint range. This means the space temperature must be greater than the active

cooling setpoint or lower than the active heating setpoint.

Example: If the cooling setpoint is 75 °F and the heating setpoint

70 °F, any space temperature greater than 75 °F or less than 70 °F is outside the setpoint range.

Once the integration term is satis- fied and the space temperature is outside the setpoint range, the controller changes modes. Howev- er, before the unit's heating or cooling capacity ramps up, the controller checks to make sure it is capable of heating or cooling.

For some units, heating and cool- ing capability exists with local re- sources such as electric heat or

compressors. For these units, cen- tral heating or cooling plan opera- tion is not required for heating or cooling because they are capable of providing their own local heat- ing or cooling.

For 2-pipe changeover and 4-pipe changeover units with hydronic ca- pacity, heating and cooling is pro- vided through hydronic. For those hydronic, central heating or cool- ing plant operation is required for the unit to deliver heating or cool- ing. To determine whether the cen- tral plant is providing the desired water temperature, an entering water temperature sensor (either hardwired or communicated) must be present.

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Contents Installation Owner Diagnostics Tracer ZN.520 for Classroom Unit VentilatorStart-up Procedures Installation of New UnitsPower Up Sequence General Information Tracer ZN.520 OverviewGeneral Information Controller Circuit Board Features Tracer ZN.520 unit controller circuit boardService Controller FeaturesTypical Components Peer-to-Peer Communications Communication ConfigurationsIntegrated Comfort System Communication Interface Stand-AloneInteroperability Standard End Devices End Device SpecificationsCharacteristic DescriptionStandard End Devices Way Control Valve Time clock Zone sensor Dpdt Control Transformer Installation and Wiring SpecificationsBinary Inputs Binary Outputs Generic/baseboard Heat Binary OutputAnalog Inputs Analog inputsMounting Vertical classroom unit ventilator end pocket Wiring PowerInstalling the Wall- Mounted Zone Sensor Optional Proper zone sensor placementHumidity and CO2 Sensors Typical Wiring Diagram-Wall Mounted Zone Sensor Typical Wiring Diagram-Unit Mounted Zone Sensor Typical Wiring Diagram-Unit Input/Output Summary Input and output summaryInput/Output Summary Cooling source ConfigurationConfigurable parameters Heating sourceBinary Outputs1 Analog Inputs1 Binary input summary ConfigurationBinary Inputs1 Analog input summaryFan configuration ranges Fan ConfigurationEnd Device Configurations DefaultSetpoints Setpoint defaults Default Valid rangeDischarge air limit ranges Default Valid range Discharge Air LimitsPower-Up Control Wait Occupied Bypass TimerMaintenance Timers Unit Identification Tag Location IdentifierWinking Heating And Cooling Changeover Logic Power-UpUnit Operation OccupancyHeat/Cool Changeover logic Heating Operation Fan Off DelayCooling Operation Fan OperationExhaust fan/damper operation Valve OperationFace-and-Bypass Damper Operation Modulating ValvesUnit Configuration Entering Water Temperature SamplingWater assumption chart Temperature Assumed1Electric Heat Operation Economizer OperationDX Operation Baseboard Heat OperationFan Status Filter Status/ Maintenance TimerOutput Overrides Other ModesData Sharing-LonWorks Simple data sharing applicationMore complex data sharing application Heating And Cooling Changeover Logic Heat/Cool Changeover logic Cooling Operation Valve Operation Entering Water Temperature Sampling Economizer Operation Output Overrides Data Sharing-LonWorks More complex data sharing application Black Service Push Button TroubleshootingRed Service LED Yellow Comm LEDTest Procedure Exit6Troubleshooting Discharge Air Temperature Limit Space Temperature FailureEntering Water Temperature Failure Outdoor Air Temperature FailureDiagnostics Troubleshooting Translating Multiple Diagnostics Rover service tool FansValves stay closed Probable cause Possible Explanation ValvesValves stay open Probable cause Possible Explanation Outside Air Damper DX/Electric HeatOutdoor air damper stays closed Probable cause Explanation Outdoor air damper stays open Probable Cause ExplanationTracer ZN.520 Unit Controller Replacement Replacing Circuit BoardsHardwired Thermistor Values Hardwired Setpoint AdjustmentFan Switch Resistance Values AppendixBinary configuration details Binary input or output Appendix-Binary ConfigurationBinary Configuration FunctionAppendix-Unit Operation Heat/cool mode input NviHeatCoolEffective heat/ cool mode output nvoHeatCool Unit Operation Based On The Effective HEAT/COOL OutputAppendix-Unit Operation Data Lists Configuration properties1Appendix-Data Lists Input/output listing1Set the Time and Day Setting the Time ClockAppendix-Timeclock Set the ProgramReview and Change Programs Override Program Manual OperationAppendix-Timeclock Appendix-Location Identifier Location Identifier Location Identifier Location Identifier Trane Company
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