Trane Tracer ZN.520

CNT-SVX04A-EN
Sequence of operation
62
Table 36 Fan operation in heating and cooling modes
The fan is off when:
■ The unit is off due to a diagnostic
■ The unit is off due to the local zone sensor
■ A request for the unit to be off has been communicated
■ The fan is in auto mode, but the default speed is off
If both a zone sensor module and communicated request exist, the
communicated request has priority
Cycling fan operation
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, occupied bypass, and occupied standby modes. Tracer ZN.520 zone
controller does not support fan cycling in occupied mode.
During unoccupied mode, the controller controls the fan off. While unoccupied,
the controller heats and cools to maintain the unoccupied heating and cooling
setpoints. In unoccupied mode, the fan is controlled at high speed only with
heating or cooling.
Fan off delay
When a heating output is controlled off, the Tracer ZN.520 zone 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.
Fan start on high speed
On a transition from off to any other fan speed, the Tracer ZN.520 zone
controller automatically starts the fan on high speed and runs the fan at high
speed for 0.5 seconds for fan coils and for 3.0 seconds for unit ventilators and
blower coils. This provides the ample torque required to start all fan motors
from the off position.
Fan mode
While heating While cooling
Occupied/
Occupied standby/
Occupied bypass Unoccupied
Occupied/
Occupied standby/
Occupied bBypass Unoccupied
Off Off Off Off Off
Low Low Off/High Low Off/High
Medium Medium Off/High Medium Off/High
High High Off/High High Off/High
Auto (continuous) Heat default fan speed Off/High Cool default fan speed Off/High