Trane ZN.520 manual Output Overrides, Fan Status, Filter Status/ Maintenance Timer, Other Modes

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Unit Operation

than or equal to the configurable exhaust enable setpoint. This is useful for exhaust fans designed to offset the added economizer ventilation.

The exhaust fan is disabled when the outdoor air damper position drops 10% below the exhaust en- able point. If the exhaust fan en- able setpoint is less than 10%, the Tracer ZN.520 controller energizes the exhaust fan at the enable point and disables it when the outdoor air damper closes.

Output Overrides

Manual Output Test

Manual output test allows the bi- nary outputs to be energized in a predefined sequence.(For more in- formation see, Manual Output

Test, on page 48 for more informa- tion.)

Water Valve Override

To enable quicker water balanc- ing, the controller allows a user to specify the desired state of all wa- ter valves. The values supported are:

qOpen all valves

qClose all valves

The valves in the system will re- main open for two hours or until normal operation is resumed.

The Tracer Summit or the Rover service tool is required to access this feature.

Fan Status

There are two ways to do fan sta- tus monitoring:

1.The status of the fan is reported based on the state of the binary output(s) dedicated to fan control. The fan status is reported as HIGH or LOW whenever the corresponding binary output is directed ON.

The fan status is reported as OFF when none of the fan out- puts are directed ON.

2.The Tracer ZN.520 controller has a binary input available for a fan status device (current sensing relay or differential pressure switch) which can provide feedback of fan opera- tion. If the device does not indicate fan operation after 1

minute, a unit shutdown is ini- tiated, and the unit is latched

OFF.

Filter Status/ Maintenance Timer

The unit filter status\maintenance timer is based on the cumulative run hours of the unit fan. The con- troller compares the fan run time against an adjustable fan run hour limit and recommends unit main- tenance as required.

The Rover service tool is used to edit the maintenance required set- point time. Once the setpoint limit is exceeded, the controller gener-

ates a MAINTENANCE REQUIRED infor-

mational diagnostic. When the maintenance required setpoint time is set to zero, the controller disables this feature.

You can use the Trace Summit or the Rover service tool to clear the

MAINTENANCE REQUIRED informa-

tional diagnostic. Once the diag- nostic is cleared, the controller resets the fan run time to zero and begins accumulating fan run hours again.

Note: If at any time the unit loses power, the timer is reset to zero.

Other Modes

DEHUMIDIFICATION

Note: If the unit is in the unoccupied mode, the dehumidification routine will not operate

Dehumidification is possible when mechanical cooling is available; the heating capacity is in the re- heat position; and the space rela- tive humidity setpoint is valid.

The controller starts dehumidify- ing the space when the space hu- midity exceeds the humidity setpoint. The controller continues to dehumidify until the sensed hu- midity falls below the setpoint mi- nus the relative humidity offset.

The controller uses the cooling and reheat coils simultaneously to dehumidify the space. When de- humidifying, the discharge air temperature is controlled to main- tain the space temperature at the current setpoint.

Economizing is disabled during the dehumidification mode.

Note: While in the dehumidification mode, if there is a call for capacity by the unit, the zone temperature setpoint will take priority over the relative humidity setpoints.

DEFROST

For defrost operation, a sensor is wired in series with the DX cooling relay. When a defrost condition is detected, the condensing unit is disabled, and the unit is placed in the DEFROST mode.

During DEFROST the condensing unit is OFF the outside air damper is set to the minimum positions, and the fan will continue to oper- ate as continuous. The unit will re- main in the DEFROST mode until the senor resets at 48°F. The unit will return to NORMAL operation af- ter the mode is discontinued.

FREEZE AVOIDANCE

FREEZE AVOIDANCE is used as low

ambient temperature protection, and is only invoked when the fan is OFF. This includes the UNOCCUPIED mode when there is no call for ca- pacity, or any other time the fan is

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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 boardController Features ServiceTypical Components Communication Configurations Peer-to-Peer CommunicationsIntegrated Comfort System Stand-Alone Communication InterfaceInteroperability 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 LimitsOccupied Bypass Timer Power-Up Control WaitMaintenance Timers Location Identifier Unit Identification TagWinking 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 Valves stay closed Probable cause Possible ExplanationValves stay open Probable cause Possible Explanation DX/Electric Heat Outside Air DamperOutdoor 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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