Trane Tracer Unit Ventilator, ZN.520 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 Tracer ZN.520 for Classroom Unit Ventilator Installation Owner DiagnosticsInstallation of New Units Start-up ProceduresPower Up Sequence Tracer ZN.520 Overview General InformationGeneral Information Tracer ZN.520 unit controller circuit board Controller Circuit Board FeaturesService Controller FeaturesTypical Components Peer-to-Peer Communications Communication ConfigurationsIntegrated Comfort System Communication Interface Stand-AloneInteroperability Characteristic End Device SpecificationsStandard End Devices DescriptionStandard End Devices Way Control Valve Time clock Zone sensor Dpdt Control Transformer Specifications Installation and WiringBinary Inputs Generic/baseboard Heat Binary Output Binary OutputsAnalog inputs Analog InputsMounting Vertical classroom unit ventilator end pocket Power WiringProper zone sensor placement Installing the Wall- Mounted Zone Sensor OptionalHumidity and CO2 Sensors Typical Wiring Diagram-Wall Mounted Zone Sensor Typical Wiring Diagram-Unit Mounted Zone Sensor Typical Wiring Diagram-Unit Input and output summary Input/Output SummaryInput/Output Summary Configurable parameters ConfigurationCooling source Heating sourceBinary Outputs1 Binary Inputs1 Binary input summary ConfigurationAnalog Inputs1 Analog input summaryEnd Device Configurations Fan ConfigurationFan configuration ranges DefaultDischarge air limit ranges Default Valid range Setpoint defaults Default Valid rangeSetpoints Discharge Air LimitsPower-Up Control Wait Occupied Bypass TimerMaintenance Timers Unit Identification Tag Location IdentifierWinking Unit Operation Power-UpHeating And Cooling Changeover Logic OccupancyHeat/Cool Changeover logic Cooling Operation Fan Off DelayHeating Operation Fan OperationFace-and-Bypass Damper Operation Valve OperationExhaust fan/damper operation Modulating ValvesWater assumption chart Entering Water Temperature SamplingUnit Configuration Temperature Assumed1DX Operation Economizer OperationElectric Heat Operation Baseboard Heat OperationOutput Overrides Filter Status/ Maintenance TimerFan Status Other ModesSimple data sharing application Data Sharing-LonWorksMore 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 Red Service LED TroubleshootingBlack Service Push Button Yellow Comm LEDExit6 Test ProcedureTroubleshooting Entering Water Temperature Failure Space Temperature FailureDischarge Air Temperature Limit Outdoor Air Temperature FailureDiagnostics Troubleshooting Translating Multiple Diagnostics Fans Rover service toolValves 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 Probable Cause Explanation Outdoor air damper stays openReplacing Circuit Boards Tracer ZN.520 Unit Controller ReplacementFan Switch Resistance Values Hardwired Setpoint AdjustmentHardwired Thermistor Values AppendixBinary Configuration Appendix-Binary ConfigurationBinary configuration details Binary input or output FunctionEffective heat/ cool mode output nvoHeatCool Heat/cool mode input NviHeatCoolAppendix-Unit Operation Unit Operation Based On The Effective HEAT/COOL OutputAppendix-Unit Operation Appendix-Data Lists Configuration properties1Data Lists Input/output listing1Appendix-Timeclock Setting the Time ClockSet the Time and Day Set the ProgramOverride Program Manual Operation Review and Change ProgramsAppendix-Timeclock Appendix-Location Identifier Location Identifier Location Identifier Location Identifier Trane Company
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