Catalogue

44 UNT-PRC001-EN
Controls
In the stand-alone configuration, UC400 receives operation commands from the zone sensor and/
or the auto changeover sensor (on auto changeover units). The entering water temperature is read
from the auto changeover sensor and determines if the unit is capable of cooling or heating. The
zone sensor module is capable of transmitting the following information to the controller:
• Timed override on/cancel request
• Zone setpoint
• Current zone temperature
• Fan mode selection (off-auto-high-med-low)
For optimal system performance, fan-co
il units can operate as part of an Integrated Comfort
System (ICS) building automation system controlled by Tracer Summit. The controller is linked
directly to the Summit control panel via a twisted pair communication wire, requiring no additional
interface device (i.e., a command unit). The Trane ICS system can monitor or override UC400
control points. This includes such points as temperature and output positions.
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. 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. In cooling mode, the fan cycles from off to medium 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. The fan can also be field-
configured (using Rover) to run at a 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. 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 three-speed fan to work cooperatively to meet precise capacity requirements,
while minimizing fan speed (motor/energy/acoustics/dehumidification) 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 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
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
Sequence of Operation
UNT-PRC001-EN.book Page 44 Tuesday, May 8, 2012 10:54 AM