Catalogue

34 CAB-PRC001-EN
Controls
Sequence of Operation
Fan Speed Switch
Off: Fan is turned off, two-position damper option spring-returns closed.
High, Medium, 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.
Auto (Fan Cycling): Fan and fresh air damper cycle with control valve option to maintain setpoint
temperature. In heating mode it cycles from off to low (factory default that can be field-adjusted
using Rover service software). When heating is not required, the fan is off and the fresh air damper
option closes. The fan can also be field-configured (using Rover) to run at a user-defined speed
when the fan speed switch is in the auto position.
Low, Medium, 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.
Auto: Fan speed control in the auto setting allows the modulating (three-wire floating point) control
valve option and three-speed fan to work cooperatively to meet precise capacity requirements,
while minimizing fan speed (motor/energy/acoustics) and valve position (pump energy). 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 medium speed and the water valve repositions
to maintain an equivalent capacity. The reverse sequence takes place with a decrease in required
capacity.
Low, Medium, High: The fan will run continuously at the selected speed and the valve option will
cycle to meet setpoint.
Tracer UC400
Off: Fan is off; control valve options and fresh air damper options close.
Auto: Fan speed control in the auto setting allows the modulating (three-wire floating point) control
valve option and three-speed fan to work cooperatively to meet precise capacity requirements,
while minimizing fan speed (motor/energy/acoustics) and valve position (pump energy). 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 medium speed and the water valve repositions
to maintain an equivalent capacity. The reverse sequence takes place with a decrease in required
capacity.
Low, Medium, High: The fan will run continuously at the selected speed and the valve option will
cycle to meet setpoint.
Occupied Mode
In Occupied Mode, the UC400 controller maintains the space temperature based on the occupied
space temperature setpoint ± occupied offset. The controller uses the occupied mode as a default
mode when other forms of occupancy request are not present and the fan runs continuously. The
outdoor air damper, if present, will close when the fan is OFF. The temperature setpoints can be
local (hard wired), communicated, or stored default values (configurable using the Tracer TU
service tool).
Unoccupied Mode
In unoccupied mode, the UC400 controller attempts to maintain the space temperature based on
the unoccupied heating or cooling setpoint. The fan will cycle between high speed and OFF. In
CAB-PRC001-EN.book Page 34 Tuesday, May 8, 2012 10:11 AM