Trane Tracer Unit Ventilator, ZN.520 manual Cooling Operation

Page 47

Unit Operation

The entering water must be five degrees or more above the space temperature to allow hydronic heating, and five degrees or more below the space temperature to al- low hydronic cooling.

If the desired water temperature is available, the unit begins normal heating and cooling operation. If the measured entering water tem- perature is not adequate for the desired heating or cooling, the controller begins the entering wa- ter temperature sampling logic.

The Tracer™ ZN.520 Unit Control- ler operates the modulating valves and dampers based on a heating or cooling capacity calculated by the control algorithm. The control algorithm calculates the heating or cooling capacity based on the measured space temperature, the active setpoint and the discharge air temperature. When the mea- sured space temperature is within the active heating and cooling set- points, the heating and cooling ca- pacity approaches zero.

Cooling Operation

During the COOLING mode, the Tracer ZN.520 controller attempts to maintain the space temperature at the active cooling setpoint. Based on the controller’s occupan- cy mode, the active cooling set- point is one of the following:

qOccupied cooling setpoint

qOccupied standby cooling setpoint

qUnoccupied cooling setpoint

The controller uses the measured space temperature, the active cooling setpoint, and discharge air temperature along with the con- trol algorithm to determine the re- quested cooling capacity of the unit (0-100%). The outputs are con- trolled based on the unit configu- ration and the requested cooling capacity.

Heating Operation

During the HEATING mode, the Tracer ZN.520 controller attempts to maintain the space temperature at the active heating setpoint. Based on the controller’s occupan- cy mode, the active heating set- point is one of the following:

qOccupied heating setpoint

qOccupied standby heating setpoint

qUnoccupied heating setpoint

The controller uses the measured space temperature, the active heating setpoint, and discharge air temperature along with the con- trol algorithm to determine the re- quested heating capacity of the unit (0-100%). The outputs are con- trolled based on the unit configu- ration and the requested heating capacity.

Fan Operation

For multiple fan speed applica- tions, the Tracer ZN.520 controller allows separate default fan speeds to be configured for heating and cooling modes. When the fan mode switch is in the AUTO posi- tion or no hardwired input exists, the fan operates at the configured default fan speed (i.e, HIGH).

The Tracer ZN.520 controller also allows the default fan speed to be configured as AUTO . When the fan speed switch is in the AUTO posi- tion and the default fan speed is configured as AUTO , the unit may change fan speeds based on the requested heating or cooling ca- pacity. In this mode, the unit fan will operate at LOW speed until the requested capacity requires HIGH fan speed operation to maintain space comfort.

The fan mode request can be ei- ther hardwired or communicated to the Tracer ZN.520 controller.

When both are present, the com- municated request has priority over the hardwired input. Addi- tional flexibility in the controller al-

lows the fan speed switch to be disabled. When this occurs, the unit will operate at the default fan speed unless a communicated re- quest is present.

During OCCUPIED, OCCUPIED STANDBY, and OCCUPIED BYPASS

modes, the fan will normally oper- ate continuously at the appropri- ate fan speed. The fan will only be OFF in these modes when the MAN- UAL OUTPUT TEST has been initiat- ed, a latching diagnostic is present, or the communicated or hardwired fan speed is OFF. (See

“Manual Output Test” on page48.for more information.)

During the UNOCCUPIED mode, the unit fan is controlled OFF. When ca- pacity is required to maintain the unoccupied heating or cooling set- point, the unit fan is controlled to high speed regardless of a hard- wired or communicated fan speed.

Table 21: Absolute two-speed fan switch points

Fan Speed

Absolute

Change

Temperature Error

Low to High

2.00

°F

High to Low

1.25

°F

 

 

 

Fan Off Delay

When a heating output is con- trolled off, the Tracer™ ZN.520 Unit Controller automatically holds the fan on for an additional

30seconds. This 30-second delay gives the fan time to blow off any residual heat from the heating source, such as a steam coil. When the unit is heating, the fan off de- lay is normally applied to control the fan; otherwise, the fan off de- lay does not apply.

Fan Start On High Speed

On a transition from off to any oth- er fan speed, the Tracer™ ZN.520 Unit Controller automatically starts the fan on high speed and runs the fan at high speed for 0.5

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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 FeaturesTypical Components Controller FeaturesService Integrated Comfort System Communication ConfigurationsPeer-to-Peer Communications Interoperability Stand-AloneCommunication Interface Description End Device SpecificationsCharacteristic Standard End DevicesStandard 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 Heating source ConfigurationConfigurable parameters Cooling sourceBinary Outputs1 Analog input summary Binary input summary ConfigurationBinary Inputs1 Analog Inputs1Default Fan ConfigurationEnd Device Configurations Fan configuration rangesDischarge Air Limits Setpoint defaults Default Valid rangeDischarge air limit ranges Default Valid range SetpointsMaintenance Timers Occupied Bypass TimerPower-Up Control Wait Winking Location IdentifierUnit Identification Tag Occupancy Power-UpUnit Operation Heating And Cooling Changeover LogicHeat/Cool Changeover logic Fan Operation Fan Off DelayCooling Operation Heating OperationModulating Valves Valve OperationFace-and-Bypass Damper Operation Exhaust fan/damper operationTemperature Assumed1 Entering Water Temperature SamplingWater assumption chart Unit ConfigurationBaseboard Heat Operation Economizer OperationDX Operation Electric Heat OperationOther Modes Filter Status/ Maintenance TimerOutput Overrides Fan StatusSimple 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 Yellow Comm LED TroubleshootingRed Service LED Black Service Push ButtonExit6 Test ProcedureTroubleshooting Outdoor Air Temperature Failure Space Temperature FailureEntering Water Temperature Failure Discharge Air Temperature LimitDiagnostics Troubleshooting Translating Multiple Diagnostics Fans Rover service toolValves stay open Probable cause Possible Explanation ValvesValves stay closed Probable cause Possible Explanation Outdoor air damper stays closed Probable cause Explanation DX/Electric HeatOutside Air Damper Probable Cause Explanation Outdoor air damper stays openReplacing Circuit Boards Tracer ZN.520 Unit Controller ReplacementAppendix Hardwired Setpoint AdjustmentFan Switch Resistance Values Hardwired Thermistor ValuesFunction Appendix-Binary ConfigurationBinary Configuration Binary configuration details Binary input or outputUnit Operation Based On The Effective HEAT/COOL Output Heat/cool mode input NviHeatCoolEffective heat/ cool mode output nvoHeatCool Appendix-Unit OperationAppendix-Unit Operation Input/output listing1 Configuration properties1Appendix-Data Lists Data ListsSet the Program Setting the Time ClockAppendix-Timeclock Set the Time and DayOverride Program Manual Operation Review and Change ProgramsAppendix-Timeclock Appendix-Location Identifier Location Identifier Location Identifier Location Identifier Trane Company