Trane LO manual Fan Mode Operation, Tracer ZN.520

Tracer® ZN.520

Unit diagnostics can affect the Tracer® ZN.520 controller operation, causing unit operation to be defined as abnormal. Refer to the Troubleshooting section for more information about abnormal unit operation.

The heating output is controlled based on the heating capacity. At 0% capacity, the heating output is off continuously. Between 0 and 100% capacity, the heating output is controlled according to modulating valve logic (modulating valves) or cycled on (2-position valves). As the load increases, modulating outputs open further and binary outputs are energized longer. At 100% capacity, the heating valve is fully open (modulating valves) or on continuously (2-position valves).

The Tracer® ZN.520 fan output(s) normally run continuously during the occupied and occupied standby modes, but cycle between high and off speeds with heating/cooling during the unoccupied mode. When in the occupied mode or occupied standby mode and the fan speed is set at the high, medium, or low position, the fan runs continuously at the selected speed. Refer to the Troubleshooting section for more information on abnormal fan operation.

When the unit’s supply fan is set to auto, the controller’s configura- tion determines the fan speed when in the occupied mode or occu- pied standby mode. The fan runs continuously at the configured heating fan speed or cooling fan speed. For all fan speed selections except off, the fan cycles off during unoccupied mode.

The economizer outdoor air damper is never used as a source of heating. Instead, the economizer damper (when present) is only used for ventilation; therefore, the damper is at the occupied minimum position in the occupied mode. The damper control is primarily associated with occupied fan operation.

Fan Mode Operation	For multiple fan speed applications, the Tracer® ZN.520 controller
	offers additional fan configuration flexibility. Separate default fan
	speeds for heating and cooling modes can be configured. The fan
	runs continuously for requested speeds (off, high, medium, or low).
	When the fan mode switch is in the Auto position or a hardwired fan
	mode input does not exist, the fan operates at the default configured
	speed. See Table 21 on page 67 for default fan configuration for heat
	and cool mode. During unoccupied mode, the fan cycles between
	high speed and off with heating and cooling fan modes. If the re-
	quested speed is off, the fan always remains off.
	During dehumidification, when the fan is on Auto, the fan speed can
66	UNT-IOM-6