Trane VUV Installation, Operation And Maintenance Manual page 83

UC400-B/Symbio™ 400-B Operation
Controller
Off - Fan is off; control valves and fresh air damper option
close. Low air temperature detection option is still active.
Auto - Fan speed control in the auto setting allows the
modulating (3-wire floating point) or 2-position control valve
option and 1-, 2-, 3- or variable-speed fan to work
cooperatively to meet precise capacity requirement, while
minimizing fan speed (motor/energy/acoustics) and valve
position (pump energy, chilled water reset). As the capacity
requirement increases, the water valve opens. When the fan
speed capacity switch points are reached, the fan speed
ramps up 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 runs continuously at the selected
speed and the valve option will cycle to meet setpoint.
Sequence of Operation
Power-Up Sequence
When 24 Vac power is initially applied to the 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," p.
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 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
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
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," p.
• A communicated signal from either a Tracer® SC or BAS.
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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 controller has the following occupancy
modes:
• Occupied
• Unoccupied
• Occupied standby
• Occupied bypass
Occupied Mode
In Occupied Mode, the 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 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
The 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
The 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
Start-Up
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