Trane LO - Manual (Page 68)

Tracer ® ZN.520
68 UNT-IOM-6
Heating Cooling
Fan mode Occ. Unocc. Occ. Unocc.
Off Off Off Off Off
Low Low Off/High Low Off/High
Medium Med Off/High Med Off/High
High High Off/High High Off/High
Auto (continuous) Default Off/High Default Off/High
fan sp. fan sp.
During occupied and occupied standby modes, the fan normally is
on. For multiple speed fan applications, the fan normally operates at
the selected or default speed (off, high, medium, or low). When fan
mode is auto, the fan operates at the default fan speed.
During unoccupied mode, the controller controls the fan off. While
unoccupied, the controller heats and cools to maintain the unoccu-
pied heating and cooling setpoints. In unoccupied mode, the fan is
controlled on high speed only with heating or cooling.
The unit fan is always off during occupied, occupied standby, and
unoccupied modes when the unit is off due to a diagnostic or when
the unit is in the off mode due to the local zone sensor module, a
communicated request, or the default fan speed (off).
If both a zone sensor module and communicated request exist, the
communicated request has priority.
Tracer ® ZN.520 does not support fan cycling in occupied mode. The
fan cycles between high speed and off in the unoccupied mode only.
The controller’s cascade control algorithm requires continuous fan
operation in the occupied mode.
When a heating output is controlled off, the Tracer ® ZN.520 controller
automatically holds the fan on for an additional 30 seconds. 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 delay is normally applied to control the fan; otherwise, the fan
off delay does not apply.
Continuous Fan
Operation
Fan Cycling
Operation
Fan Off Delay