Sequence Of Operation - Trane UniTrane Installation, Operation And Maintenance Manual

The appropriate control valve will actuate assuming the
following conditions:
• Room temperature should be greater than 55°F and
less than 85°F .
• For a 2-pipe fan-coil unit with an entering water
temperature sensor, the water temperature input is
appropriate for the demand placed on the unit. For
example, cooling operation is requested and cold
water (5° lower than room temperature) flows into the
unit.
• Select the correct temperature setpoint.
Note: Select and enable zone sensor temperature
settings to prevent freeze damage to unit.
UC400-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.
In DX/HP mode, the fan is limited to factory selected single
speed operation.
Low/Med/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).
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
UNT-SVX07J-EN
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.
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
Startup
116).
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