Random Start; Occupancy Modes; Timed Override Control - Trane BCHE Installation, Operation And Maintenance Manual

3. The controller reads all input local values to determine
initial values.
4. The random start timer begins.
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.
• A communicated signal from either a Tracer
BAS.
A communicated request, from either a Tracer
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
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
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default setpoint values (configurable using the Tracer
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
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 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
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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.

Timed Override Control

If the controller has a timed override option (ON/CANCEL
buttons), pushing the ON button initiates a timed override
on request. A timed override on request changes the
occupancy mode from unoccupied mode to occupied
bypass mode. In occupied bypass mode, the controller
controls the space temperature based on the occupied
heating or cooling setpoints. The occupied bypass time,
which resides in the controller and defines the duration of
the override, is configurable from 0 to 240 minutes (default
value of 120 minutes). When the occupied bypass time
expires, the unit transitions from occupied bypass mode to
unoccupied mode. Pushing the CANCEL button cancels
the timed override request. In addition, it will end the timed
override before the occupied bypass time has expired and
transition the unit from occupied bypass mode to
unoccupied mode.
If the controller is in any mode other than unoccupied mode
when the ON button is pressed, the controller still starts the
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