Trane UniTrane Installation Operation & Maintenance page 68

Continuous Fan
Operation
Fan Cycling
Operation
Fan Off Delay
68
Table 24. Fan operation in heating and cooling modes
Heating
Fan mode Occ. Unocc.
Off Off
Low Low
Medium Med
High High
Auto (continuous) Default Off/High
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
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.
®
Tracer ZN.520
Cooling
Occ.
Off Off
Off/High Low
Off/High Med
Off/High High
Default
fan sp.
®
ZN.520 controller
Unocc.
Off
Off/High
Off/High
Off/High
Off/High
UNT-IOM-6