Trane Zone Controller, N512, CNT-SVX07C-EN manual Filter-maintenance timer, Freeze avoidance

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Chapter 5 Sequence of operations

Filter-maintenance timer

The filter-maintenance timer tracks the amount of time (in hours) that the fan is enabled. The Maintenance Required Timer Setpoint (config- urable using the Rover service tool) is used to set the amount of time until maintenance (typically, a filter change) is needed. If the setpoint is config- ured to zero, the filter-maintenance timer is disabled.

The controller compares the fan-run time to Maintenance Required Timer Setpoint. Once the setpoint is reached, the controller generates a Mainte- nance Required diagnostic. When the diagnostic is cleared, the controller resets the filter-maintenance timer to zero, and the timer begins accumu- lating fan-run time again.

Freeze avoidance

Freeze avoidance is used for low ambient temperature protection. It is ini- tiated only when the fan is off. The controller enters the freeze-avoidance mode when the outdoor air temperature is below the Freeze Avoidance Setpoint (configurable using the Rover service tool). The controller dis- ables freeze avoidance when the outdoor air temperature rises 3°F (1.7°C) above the Freeze Avoidance Setpoint.

When the controller is in freeze-avoidance mode:

•Valves are driven open to allow water to flow through the coil

•Fan is off

•Face-and-bypass damper (when present) is at full bypass

•Economizing is disabled

•The outdoor/return air damper is closed

•DX cooling is off

•Electric heat stages are off

Freeze protection (discharge air temperature low limit)

The controller monitors the discharge air temperature with a 10 kΩ ther- mistor wired to analog input AI2. The freeze-protection operation is initi- ated whenever the discharge air temperature falls below the Discharge Air Temperature Low Limit. The Discharge Air Temperature Low Limit is configurable using the Rover service tool. During freeze protection, the controller increases the heating capacity or decreases the cooling capacity in order to raise the discharge air temperature above the low limit. If the discharge air temperature remains below the low limit for 3 minutes, the controller generates a Discharge Air Temp Limit diagnostic. See Table 16 on page 59 for the effects of this diagnostic on outputs.

50	CNT-SVX07C-EN

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Contents Installation and Operation Tracer ZN521 Zone Controller Page CNT-SVX07C-EN April CNT-SVX07C-EN Tracer ZN521 Zone Controller Installation and Operation CNT-SVX07C-EN Contents Sequence of operations Status indicators for operation and communication Troubleshooting Index Overview and specifications Product descriptionDimensions Storage environmentClearances Plastic-cover model dimensions and clearances Agency listing/compliance Additional componentsTracer zone temperature sensor options Damper actuatorsZone humidity sensor CO2 sensorOverview and specifications Input/output terminal wiring AC-power wiringGeneral wiring information Communication-link wiring and addressing General wiring information Location recommendations Operating environment requirementsMounting recommendations Mounting the Tracer ZN521 zone controllerTypical applications for the Tracer ZN521 zone controller Application SpeedfanMultiple DehumidificationControlValve Economizing HeatElectricBI1 Low-coil-temperature detection Binary inputsBI2 Condensate overflow Binary inputsBI3 Occupancy or generic binary input BI4 Fan statusZN Zone temperature Analog inputsGND Ground terminals Analog inputsFAN Fan mode input AI1 Entering water temperatureSET Local setpoint AI2 Discharge air temperature AI3 Outdoor air temperature or generic temperatureAI4 configuration options and associated measurement ranges Configuration Measurement rangeAI4 Universal 4-20 mA AI4 terminal wiring CO2 measurement Binary outputs Generic binary outputBinary output functions Binary output FunctionsWiring requirements and options Overriding binary outputsRequired controller inputs for proper operation Function Input source For more information SeeTwo-pipe hydronic-cooling unit Two-pipe hydronic-heating unit Two-pipe hydronic heating/cooling unit with auto changeover Four-pipe hydronic heating/cooling unit Four-pipe heating/cooling unit with auto changeover Two-pipe heating unit with DX cooling Electric heat unit with DX cooling Electric heat unit Two-pipe heating unit with face-and-bypass damper Two-pipe heating/cooling unit with face-and-bypass damper Four-pipe heating/cooling unit with face-and-bypass damper Input/output functions and wiring for typical applications Power-up sequence Random startOccupied mode Unoccupied modeOccupied standby mode Occupancy modesOccupied bypass mode Timed override controlZone temperature control Cascade zone controlSimplified zone control Heating or cooling mode Discharge air temperingMorning warm-up Morning cool-downEntering water temperature sampling function Fan operationExhaust control Exhaust controlValve operation Modulating valve operationModulating valve calibration Valve control optionsModulating outdoor/return air dampers Two-position valve operationIsolation-valve operation Two-pipe operationModulating outdoor air damper position Ashrae Cycle 1 conformance Ashrae Cycle 2 conformanceEconomizing free cooling Two-position control of a modulating outdoor air damper Face-and-bypass damper operationDX cooling operation Face-and-bypass, isolation-valve operationElectric heat operation Baseboard heat operationDehumidification Peer-to-peer communication Unit protection strategiesSmart reset Low-coil-temperature protectionFan off delay Condensate overflowFilter-maintenance timer Freeze protection discharge air temperature low limitFreeze avoidance Test button Tracer ZN521 zone controller circuit boardManual output test For non OutputClose damper, air Outdoor Open damper, air Outdoor Step Result BOP1 BOP2 BOP3 BOP4 BOP5 BOP6 BOP7 BOP8 BOP9Service pin button Red LED Service indicatorInterpreting LEDs LED activity ExplanationGreen LED Status indicator Yellow LED Communications indicatorDiagnostics Types of diagnosticsTable of diagnostics DiagnosticsDiagnostic Probable cause Consequences Type Fan unaffectedValved unaffected PositionDamper unaffected Status indicators for operation and communication Fan does not energize Probable cause ExplanationTroubleshooting Valves remain closedValves remain open DX or electric heat does not energizeOutdoor air damper remains closed Outdoor air damper remains openOutdoor air damper remains open Troubleshooting Index NumericsIndex Index Index Page Trane