Trane LPC Install And Operation Instructions page 70

Space temperature control: Unoccupied
mode
In unoccupied mode, if configured for
space temperature control, the supply
fan is Off whenever the space
temperature is between the unoccupied
heating and cooling setpoints. If the space
temperature rises above the unoccupied
cooling setpoint the Tracer AH540/541
turns On the supply fan and provides
cooling at the unoccupied cooling
setpoint.
If the space temperature drops below the
unoccupied heating setpoint the control-
ler turns On the supply fan and provides
heating at the unoccupied heating
setpoint.
Discharge air temperature control:
Unoccupied mode
In unoccupied mode, if configured for
discharge air temperature control,
the controller must have either a hard-
wired or communicated space
temperature input from the Tracer
Summit building automation system.
In unoccupied mode, the supply fan is Off
whenever the space temperature
is between the unoccupied heating and
cooling setpoints. If the space
temperature rises above the unoccupied
cooling setpoint the Tracer AH540/541
turns On the supply fan and provides
cooling at the discharge air cooling
setpoint.
If the space temperature drops below the
unoccupied heating setpoint the control-
ler turns On the supply fan and provides
heating at the discharge air heating
setpoint.
Note that primary heating or cooling
capacity is defined by unit type and
whether heating or cooling is enabled or
disabled. For example, if the economizer
is enabled and possible, it will be the
primary cooling capacity. If hydronic
heating is possible, it will be the primary
heating capacity.
Occupied standby mode
If configured for space temperature
control, the controller uses the occupied
standby mode to reduce heating and
cooling demands during occupied
70
Operation
hours when a space is vacant or
unoccupied. For example, the controller
may use occupied standby mode for a
classroom while the studentsare out of
the room. In the occupied standby mode,
the controller uses the occupied standby
cooling and heating setpoints. Because
the occupied standby setpoints typically
cover a wider range than the occupied
setpoints, the Tracer AH540/541
controller reduces the demand for
heating and cooling the space. Also, the
outdoor air economizer damper uses the
economizer standby minimum position to
reduce the heating and cooling demands.
Occupied standby is a mode in which the
controller has received an occupied
request from Tracer Summit, but has also
received a local unoccupied binary input
IN9 signal. For example, an unoccupied
conference room (as sensed by a local
occupancy sensor) in an occupied
building (as commanded by a Tracer
Summit system) is in occupied standby
mode. When the conference room
becomes occupied with people, the local
occupancy sensor changes the controller
mode to occupied.
The controller can be placed into the
occupied standby mode when a commu-
nicated occupancy request is combined
with the local (hard-wired) occupancy
binary input signal. When the communi-
cated occupancy request is unoccupied,
the occupancy binary input (if present)
does not affect the controller occupancy.
When the communicated occupancy
request is occupied, the controller uses
the local occupancy binary input to switch
between the occupied and occupied
standby modes.
During occupied standby mode, the
controller economizer damper position
goes to the economizer standby mini-
mum position. The economizer standby
minimum position can be changed using
the Rover service tool.
When no occupancy request is communi-
cated, the occupancy binary input
switches the controller operating mode
between occupied and unoccupied.
When no communicated occupancy
request exists, the unit cannot switch to
occupied standby mode.
sequence of
operation
Occupied bypass mode
If configured for either space
temperature control or discharge air
temperature control, the controller uses
occupied bypass mode for timed
override conditions. For example, if the
controller is in unoccupied mode and
someone presses the ON button on the
zone sensor, the controller is placed in
occupied bypass mode for 120 minutes
(adjustable) or until someone presses the
CANCEL button on the zone sensor. The
controller can be placed in occupied
bypass mode by either communicating
an occupancy request of Bypass to the
controller or by using the timed override
ON button on the Trane zone sensor.
When the controller is in unoccupied
mode, you can press the ON button on
the zone sensor to place the controller
into occupied bypass mode for the
duration of the bypass time (typically 120
minutes).
If the controller is in the occupied standby
mode, you can press the ON button on
the zone sensor to place the controller
into occupied bypass mode for the
duration of the configured bypass time.
Typically, the controller is in occupied
standby mode rather than occupied
mode because of the local binary
occupancy input.
Sources of occupancy mode control
There are four ways to control the
occupancy mode (see Table O-SO-4):
• Communicated request (usually
provided by the building automation
system or peer device)
• Pressing the zone sensor timed
override ON button (or CANCEL button)
• Occupancy binary input (see
"Occupancy binary input" for more
information)
• Default operation of the controller
(occupied mode)
A communicated request from a building
automation system or another peer
controller can change the controller
occupancy. However, if communication is
lost, the controller reverts to the default
operating mode (occupied) after 15
minutes (configurable, specified by the
"receive heartbeat time"), if no local
hard-wired occupancy signal exists.
LPC-SVX01C-EN