Building Automation System Support Sequences; Occupancy Mode; Timed Override; Unit Stop - Trane Symbio 700 Controller 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.

Unit Stop

The Unit Stop feature allows for immediate shutdown of all devices in the equipment when initiated.
When a Unit Stop request is received, the following actions are taken:
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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:
• Idle [1]— Controller will not override Unoccupied Mode.
• On [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.
• Cancel [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.
All equipment control binary outputs are de-energized
– Indoor fan
ACC-APG002A-EN