Installation and Maintenance Manual

Startup
UNT-SVX07D-EN 99
UC400 Sequence of Operation
The UC400 controller will operate to maintain the space
temperature setpoint. This section provides information
about sequence of operations.
Power-up Sequence (UC400)
When 24Vac power is initially applied to the UC400
controller, the following sequence occurs:
1. The Power Marquee LED turns on as red, then flashes
green, and then turns a solid green.
2. All outputs are controlled OFF and all modulating
valves and dampers close.
3. The controller reads all input
local values to determine
initial values.
4. The random start timer begins (refer to the following
section, “Random Start (UC400)”).
5. The random start timer expires.
6. Normal operation begins,
assuming there are no
generated diagnostics. If any points are in fault or
alarm mode, the Power Marquee LED flashes red.
Important: Flashing red does
not indicate that the
UC400 controller will fail to operate.
Instead, the point(s) that are in fault or alarm
mode should be checked to determine if the
status of the point(s) is acceptable to allow
equipment operation.
Random Start (UC400)
Random start is intended to prevent all units in a building
from energizing at the same time. The random start timer
delays the fan and any heating or cooling start-up from 5
to 30 seconds.
Occupancy Modes (UC400)
Occupancy modes can be controlled in the following ways:
• The state of the local (hard wired) occupancy binary
in
put BI1.
• A timed override request from a Trane zone sensor (see
“Timed Override Control (UC400),” p. 100).
• A communicated signal from either a Tracer SC or BAS.
A communicated request, from either
a Tracer SC or BAS,
takes precedence over local requests. If a communicated
occupancy request has been established, and is no longer
present, the controller reverts to the default (occupied)
occupancy mode after 15 minutes (if no hard wired
occupancy request exists). The UC400 controller has the
following occupancy modes:
• Occupied
• Unoccupied
• Occupied standby
• Occupied bypass
Occupied Mode (UC400)
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 (UC400)
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 addition, the outdoor air damper
remains closed, unless economizing. The controller
always uses the stored default setpoint values
(configurable using the Tracer TU service tool), regardless
of the presence of a hard wired or communicated setpoint
value.
Occupied Standby Mode (UC400)
The UC400 controller is placed in occupied standby mode
only when a communicated occupied request is combined
with an unoccupied request from occupancy binary input
BI1. In occupied standby mode, the controller maintains
the space temperature based on the occupied standby
heating or cooling setpoints. Because the occupied
standby setpoints have a typical temperature spread of 2°F
(1.1°C) in either direction, and the outdoor air damper is
closed, occupied standby mode reduces the demand for
heating and cooling the space. The fan will run as
configured (continuously) for occupied mode. The
controller always uses the stored default setpoint values
(configurable using the Tracer TU service tool), regardless
of hard wired or communicated setpoint values. In
addition, the outdoor air damper uses the economizer
occupied standby minimum position setpoint to reduce
the ventilation rate.
Occupied Bypass Mode (UC400)
The UC400 controller is placed in occupied bypass mode
when the controller is operating in the unoccupied mode
and when either the timed override ON button on the
Trane zone sensor is pressed or the controller receives a
communicated occupied bypass signal from a BAS. In
occupied bypass mode, the controller maintains the space
temperature based on the occupied heating or cooling
setpoints. The fan will run as configured (continuous or
cycling). The outdoor air damper closes when the fan is
OFF. The controller remains in occupied bypass mode
until either the CANCEL button is pressed on the Trane
zone sensor or the occupied bypass time (configurable
using the Tracer TU service tool) expires. The temperature
setpoints can configured as local (hard wired),
communicated, or stored default values using the Tracer
TU service tool.
UNT-SVX07_-EN.book Page 99 Friday, April 27, 2012 9:40 AM