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BCXC-SVX01B-EN 53
Start-Up
Additional flexibility built into the controller allows you to enable or disable the local fan switch
input. The fan mode request can be hardwired to any of the Tracer™ ZN controllers or
communicated to the Tracer ZN510 or ZN520 controller. When both inputs are present, the
communicated request has priority over the hardwired input. See Table 19, p. 52.
Fan Speed Switch
Off. Fan is turned off, two-position damper option spring-returns closed.
High or Low. Fan runs continuously at the selected speed. The two-position damper option
opens to an adjustable mechanical stop-position.
Tracer ZN010 and ZN510
Off. Fan is off; control valves and fresh air damper option close. Low air temperature detection
option is still active.
Auto (Fan Cycling). Fan and fresh air damper cycle with control valve option to maintain
setpoint temperature. If the unit has a 2-speed fan, in cooling mode the fan cycles from off to high
and in heating mode it cycles from off to low (factory default that can be field-adjusted using
Rover™ service software). When no heating or cooling is required, the fan is off and the fresh air
damper option closes. Units with 2-speed fans can also be field-configured using Rover to run at
a defined speed when the fan speed switch is in the auto position.
Low or High (Continuous Fan). Fan operates continuously while control valve option cycles to
maintain setpoint temperature. Fresh air damper option is open.
Tracer ZN520
Off. Fan is off; control valve options and fresh air damper options close. The low air temperature
detection option is still active.
Auto. Fan speed control in the auto setting allows the modulating (three-wire floating point)
control valve option and single or two-speed fan to work cooperatively to meet precise capacity
requirements, while minimizing fan speed (motor/energy/acoustics) and valve position (pump
energy/chilled water reset). As the capacity requirement increases at low fan speed, the water valve
opens. When the low fan speed capacity switch point is reached, the fan switches to high speed and
the water valve repositions to maintain an equivalent capacity. The reverse sequence takes place
with a decrease in required capacity.
Units with 2-speed fans on low or high. The fan will run continuously at the selected speed
and the valve option will cycle to meet setpoint.
Continuous Fan Operation
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, or low). When
fan mode is auto, the fan operates at the default fan speed.
During unoccupied mode, the fan is off. While unoccupied, the controller will heat or cool to
maintain the unoccupied heating and cooling setpoints. In unoccupied mode, the fan runs on high
speed only, with heating or cooling. See Table 24, p. 55.
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. See Table 23, p. 55.