Building Automation System Support Sequences; Occupancy Mode; Timed Override; Supply Air Tempering - Trane Symbio 700 Application Manual

Building Automation System Support Sequences

Occupancy Mode

During expected occupied periods, the system will control to the user selected cooling and
heating setpoints.
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There are two mechanisms available to control when units should switch between occupied and
unoccupied modes:
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Timed Override

Exceptions to the time-of-day scheduling are required when unusual or difficult to schedule
events cause a space to become occupied during a scheduled unoccupied period. The Timed
Override function provides a mechanism for an occupant to signal the system that the space is
actually occupied and override the time-of-day schedule to provide occupied control for some
limited time period. It also provides a mechanism to return the system to unoccupied mode
when the space is no longer occupied.
There are two methods of requesting or terminating timed override on a Symbio 700 control
system:
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When Timed Override is initiated by any of the above methods, the controller starts a timer using
the user selected Occupied Bypass Time to control the duration of the Timed Override event. The
range for Occupied Bypass Time is 0-240 minutes with a default of 120 minutes.
When the unit is operating in Occupied Bypass mode, the Occupied Bypass Timer duration can
be extended by initiating a Timed Override Request again. This extends the Occupied Bypass
Timer duration by the value of the user selected Occupied Bypass Time.
When Timed Override is terminated by any of the above methods, the controller will exit
Occupied Bypass and will again begin to use unoccupied control setpoints.

Supply Air Tempering

If the Supply Air Tempering function is configured and the Discharge Air Temperature local
sensor is valid, the Space Temperature Control algorithm manages the Supply Air Tempering
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The unoccupied setpoint temperatures are often adjusted higher for cooling (setup) and
lower for heating (setback) to reduce building operating cost.
Regardless of how the (occupied) fan mode is set, the supply fan mode is forced to AUTO
during unoccupied periods to reduce supply fan operating costs.
Building controllers provide signals to the unit to request occupied or unoccupied operation.
Time-of-day scheduling within building controllers typically determine when the switching
should occur.
Stand Alone Unoccupied control is initiated by a contact closure that causes the unit to begin
unoccupied control. In this mode, the controller will use the Unoccupied Cooling and Heating
setpoints to determine capacity control needs. Stand Alone Unoccupied control is only
applicable when the unit is not being controlled by a conventional thermostat interface.
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– Timed Override Request value can be set to 3 discrete values:
• I I d d l l e e [ [ 1 1 ] ] — Controller will not override Unoccupied Mode.
• O O n n [ [ 2 2 ] ] — When the value is changed from Idle to On, the controller overrides
Unoccupied Mode and the unit operates in Occupied Mode. The Occupied Bypass
Timer and the Timed Override Timer is Active is set to 'Active'. The controller remains
in Timed Override for the duration of the Occupied Bypass Time.
• C C a a n n c c e e l l [ [ 3 3 ] ] — When value is changed from On to Cancel, the unit's unoccupied status
is no longer overridden and the Occupied Bypass Timer will be set to 0.
Zone Sensor Initiate/Terminate buttons – Some zone sensors have a Timed Override Initiate
and Terminate buttons.
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