Orion System VCM-X Modular E-BUS - Manual (Page 53)

VCM-X Modular E-BUS Controller Technical Guide
SEQUENCE OF OPERATIONS
53
VCM-X E-BUS Operation Modes
Occupied/ Unoccupied Mode of
Operation
The VCM-X E-BUS Controller can utilize several methods for determin-
ing 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 VCM-X 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 VCM-X E-BUS
Controller 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.
Internal 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 66 for more
information on the Optimal Start feature.
Push-Button Override Signal
During Unoccupied hours, you can force the VCM-X E-BUS Control-
ler 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 VCM-X E-BUS Controller to Normal Unoc-
cupied 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 7 possible HVAC Modes of Operation. They are as follows:
• Vent Mode
• Cooling Mode
• Dehumidifi cation Mode
• Heating Mode
• Heat Pump
• 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, Return, or
Outdoor Air Temperature Sensor is selected as the HVAC Mode Enable
Sensor. Vent Mode can also occur if the Supply Air Temperature Sensor
is the HVAC Mode Enable Sensor and the VCM-X has been confi gured
for Remote Forced Heating and Cooling. See the Remote Control of
HVAC Mode section on page 60 for complete details.
NOTE: During Vent Mode, all Cooling and Heating Stages are
deactivated and the Economizer Damper is maintained at a Minimum
Position to provide fresh air into the building. 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 Tem-
perature is above the HVAC Mode Enable Cooling Setpoint. Unoccupied
Cooling Mode only occurs if a Space Temperature Sensor is connected
to the VCM-X or a broadcast of Space Temperature is being received
from an Averaging Broadcast Controller and only then if the Space
Temperature is above the Cooling Setpoint plus the Night Offset value.
The Mechanical Cooling will be disabled if the Outdoor 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 Outdoor 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 Economizer has been enabled for operation, it is used as the fi rst
stage of Cooling, and the Mechanical Cooling will be activated if nec-
essary. See the Economizer Operation section on page 54 for a more
detailed operating sequence.
No matter which Sensor is confi gured for the HVAC Mode Enable or
if the Remote BAS sets the Mode through Remote Forced Cooling, the
Supply Air Temperature is always regulated to the Active Supply Air
Cooling Setpoint while in the Cooling Mode.