Orion System SA E-BUS Controller - Manual (Page 41)

SA E-BUS Controller Technical Guide
Sequence of Operations
41
Mode of Operation Overview
Occupied/ Unoccupied Mode of
Operation
The SA E-BUS Controller can utilize several methods for determining
the Occupied Mode of Operation. These are as follows:
• Forced Schedule
• Remote Forced Occupied Signal
• Internal Week Schedule
• Push-Button Override Signal
Forced Schedule
The SA E-BUS Controller can be forced into the Occupied Mode by
inputting a Forced Schedule from any operator interface.
Remote Forced Occupied Signal
When this wet contact input closes, it will force the SA E-BUS Con-
troller into the Occupied Mode. When the Remote Forced Occupied
Signal is removed, the controller will revert to the Unoccupied Mode
of operation if no Internal or External Schedule has been confi gured or
is in effect when this occurs.
NOTE: When using Remote Forced Occupied Mode, set all the
Internal Week Schedules to ‘0’ so that the Internal Schedule always
commands the Unoccupied Mode.
In ternal Week Schedule
An Internal Week Schedule, which supports up to two start/stop events
per day, is available for determining Occupied and Unoccupied Sched-
ules. If you are using the Internal Schedule, an Optimal Start calcula-
tion is also available. See the Scheduling Section on page 52 for more
information on the Optimal Start feature.
Push-Button Override Signal
During Unoccupied hours, you can force the SA E-BUS Controller back
to Occupied operation by pressing the Override Button on the Space
Temperature Sensor for a period of less than 3 seconds. This initiates the
Override or resets the Override Timer back to zero during Unoccupied
hours of operation.
During Override operations, you can cancel the Override by pressing the
Override Button for a period of time between 3 seconds and 10 seconds.
This restores the SA E-BUS Controller to Normal Unoccupied Operation.
If the Override Button is held for more than 10 seconds, it causes a Space
Sensor Failure Alarm. This is due to the fact that the Override Button
actually shorts the Space Temperature Sensor input to ground. If this
input is shorted to ground or left fl oating with no Space Temperature
Sensor detected for more than 10 seconds, it is considered a Space
Temperature Sensor failure.
You can still use the Space Temperature Sensor input for an Override
Command even when a Space Temperature Sensor is not connected.
Simply provide a Momentary Push-Button connected between AI1
and the Ground Terminal on the same terminal block. Follow the same
procedure for initiating Overrides, even on Supply Air Temperature
Controlled Cooling-Only HVAC units.
HVAC Modes of Operation
There are 8 possible HVAC Modes of Operation. They are as follows:
• Vent Mode
• Cooling Mode
• Dehumidifi cation Mode
• Heating Mode
• Heat Pump
• Water Side Economizer
• Warm-Up Mode
• Off Mode
Vent Mode Operation
This Mode only applies to the Occupied Mode of Operation. The Vent
Mode is defi ned as the Supply Fan running with no Heating, Cooling,
or Dehumidifi cation demand.
Vent Mode can occur during the Occupied Mode if the Space or Entering
Air Temperature Sensor is selected as the HVAC Mode Enable Sensor.
NOTE: During Vent Mode, all Cooling and Heating Stages are
deactivated. The Static Pressure is still maintained by the Supply
Fan VFD or Zoning Bypass Damper Signal since the Supply Fan
is still operating in this Mode.
Cooling Mode Operation
Occupied Cooling Mode occurs whenever the HVAC Mode Enable
Temperature rises one deadband above the HVAC Cooling Mode En-
able Setpoint. The unit will leave the Cooling Mode when the HVAC
Mode Enable Temperature falls one deadband below the HVAC Mode
Enable Cooling Setpoint. Unoccupied Cooling Mode only occurs if a
Space Temperature Sensor is connected to the SA E-BUS Controller
or a broadcast of Space Temperature is being received from a General
Broadcast Controller and if the Space Temperature is above the Cool-
ing Setpoint.
The Mechanical Cooling will be disabled if the Entering Air Tempera-
ture is below the Cooling Lockout Setpoint by 1°F. This gives a 2°F
hysteresis around the Cooling Lockout Setpoint to prevent unwanted
cycling in and out of Mechanical Cooling Mode. If the Entering Air
Temperature disables the Mechanical Cooling while it is currently
operating, the Mechanical Cooling will stage off if all staging and run
times are satisfi ed.
If the Water Side Economizer has been enabled for operation, it is used as
the fi rst stage of Cooling, and the Mechanical Cooling will be activated
if necessary. See the Water Side Economizer Operation section on page
43 for a more detailed operating sequence.
No matter which Sensor is confi gured for the HVAC Mode Enable, the
Supply Air Temperature is always controlled to the Active Supply Air
Temperature Setpoint while in the Cooling Mode.