Uc400 Sequence Of Operation; Power-Up Sequence (Uc400); Random Start (Uc400); Occupancy Modes (Uc400) - Trane HUV Installation, Operation And Maintenance Manual

Startup
tool. If the zone sensor switch is disabled, the controller
resorts to its stored configuration default fan speeds for
heating and cooling, unless the controller receives a
communicated fan input.
When the fan switch is in the off position, the controller
does not control any unit capacity. The unit remains
powered and all outputs drive to the closed position. Upon
a loss of signal on the fan speed input, the controller
reports a diagnostic and reverts to using the default fan
speed.
On/Cancel Buttons (Tracer ZN520)
Momentarily pressing the on button during unoccupied
mode places the controller in occupied bypass mode for
120 minutes. You can adjust the number of minutes in the
unit controller configuration using Rover service tool. The
controller remains in occupied bypass mode until the
override time expires or until you press the Cancel button.
Communication Jack (Tracer ZN520)
Use the RJ-11 communication as the connection point
from Rover service tool to the communication link—when
the communication jack is wired to the communication
link at the controller. By accessing the communication jack
via Rover, you can access any controller on the link.
Communications (Tracer ZN520)
Tracer ZN520 controller communicates via Trane's LonTalk
protocol. Typically, a communication link is applied
between unit controllers and a building automation
system. Communication also is possible via Rover, Trane's
service tool. Peer-to-peer communication across
controllers is possible even when a building automation
system is not present. You do not need to observe polarity
for LonTalk communication links.
The controller provides six 0.25-inch quick-connect
terminals for the LonTalk communication link connections,
as follows:
• Two terminals for communication to the board
• Two terminals for communication from the board to
the next unit (daisy chain)
• Two terminals for a connection from the zone sensor
back to the controller
Table 26. Zone sensor wiring connections (Tracer ZN520)
TB1 Description
1 Space temperature / timed override detection
2 Common
3 Setpoint
4 Fan mode
5 Communications
6 Communications
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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
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
input BI1.
• A timed override request from a Trane zone sensor (see
"Timed Override Control (UC400), " p.
• 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
(UC400)").
79).
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