Zone
Zone
SEQUENCE OF OPERATIONS
VCB-X Controller Field Technical Guide
66
Remote Contact Control, Space Sensor Operation, IAQ
VCB-X Remote Contact Control
A Remote Contact Control option can be con
fi
gured on the VCB-X
Controller to initiate the HVAC Modes of operation. If this option is
con
fi
gured, all Heating, Cooling, and Dehumidi
fi
cation modes will
only be initiated based on 24 VAC wet contact closures on the Forced
Heating, Forced Cooling, and Forced Dehumidi
fi
cation inputs on
the EM2 Expansion Module. This is a single con
fi
guration option
that applies to all three modes.
If both the Forced Heating and Forced Cooling inputs are inactive
or if both are simultaneously active, then the unit is in a Vent mode
(neutral) state. In this condition in the Occupied Mode, only the
fan would be on for ventilation. In this condition in the Unoccupied
Mode, the unit would just be Off.
If Forced Dehumidi
fi
cation is also being used, it will operate in
conjunction with the Forced Heating and Forced Cooling inputs
according to which Dehumidi
fi
cation option you have con
fi
gured.
The four con
fi
guration options are described in the Dehumidi
fi
cation
Mode section on
page 63
.
Space Sensor Operation
Space Sensors are available as a Plain Sensor, Sensor with Override,
Sensor with Setpoint Slide Adjust, and Sensor with Override and
Setpoint Slide Adjust (this is the version that is factory supplied).
An E-BUS Digital Space Sensor is also available with override and
setpoint adjustment capability.
Sensors with Setpoint Slide Adjust can be programmed to allow
Space Setpoint adjustment of up to ± 10° F.
If the Space Temperature is the SAT/Reset Source, then the Slide
Adjust will adjust the HVAC Mode Enable Setpoints and the SAT/
Reset Source Setpoints simultaneously.
During Unoccupied hours, the Override Button can be used to force
the unit back into the Occupied Mode (by pressing the button for
less than 3 seconds) for a user-de
fi
ned override duration of up to
8.0 hours. Pressing the button between 3 to 10 seconds cancels the
override.
IAQ (CO
2
) Control Operation
If you have con
fi
gured the VCB-X Controller to monitor and control
CO
2
levels, the Economizer operation will be modi
fi
ed as follows:
1. If the CO
2
levels remain below the Low CO
2
Level
Setpoint, the Economizer Minimum Position will remain
at its con
fi
gured value.
2. As the level of CO
2
increases above the Minimum CO
2
Level Setpoint, the Economizer Minimum Position will be-
gin to be reset higher. The Economizer Minimum Position
will be proportionally reset higher as the CO
2
rises within
the range set by the Minimum CO
2
Level Setpoint and the
Maximum CO
2
Level Setpoint. If the CO
2
level reaches
the High CO
2
Level Setpoint, the Economizer Minimum
Position will be reset to the Maximum Reset Position.
3. The Maximum Reset Position Setpoint is the highest
the Economizer Minimum Position can be reset to during
CO
2
Control Operation. This setpoint is user-adjustable
and does not keep the Economizer from opening further
during Economizer operation.
4. CO
2
Economizer control cannot be used in conjunction
with Outdoor Air
fl
ow control of the Outdoor Air Damper
in this version.
Revised: 8/7/14
Morning Warm-Up Mode Operation
NOTE:
Morning Warm-Up can now be con
fi
gured for any
application but should not be used on 100% Outdoor
Air Units, since the Outdoor Air Damper remains
closed during Warm Up.
When the VCB-X Controller is con
fi
gured for Morning Warm Up and
switches to the Occupied Mode of Operation (not Override or Force
Mode), the unit compares the Return Air Temperature to a Morning
Warm-Up Target Temperature. If the Return Air Temperature is
below this Setpoint, the Warm-Up Mode is initiated. Heating will
then be controlled to the Warm-Up Supply Air Temperature Setpoint.
This Mode remains in effect until the Return Air Temperature rises
above the Target Temperature or a user-adjustable Time Period
expires. Warm-Up Mode is not initiated by Push-Button Overrides
or Unoccupied Heating demands. The Outdoor Air Damper remains
closed during Warm-Up Mode.
Once the Warm-Up Mode has been terminated, it cannot resume until
the unit has been through a subsequent Unoccupied Mode. Only one
Warm-Up Mode is allowed per Occupied cycle.
If you have stand-alone VAV boxes that need to be forced wide
open during the Warm-Up Mode, you can con
fi
gure one of the
relay outputs to be used during this Mode. If the Warm-Up Mode
is active, the relay is activated. This relay then becomes the Force
Open Command for all VAV boxes to which it is wired.
Morning Cool-Down Mode Operation
When the VCB-X Controller is con
fi
gured for Morning Cool-Down
and switches to the Occupied Mode of Operation (not Override
Mode), the unit compares the Return Air Temperature to a Cool-
Down Target Temperature. If the Return Air Temperature is above
this Setpoint, the Cool-Down Mode is initiated. Cooling will then
be controlled to the Cool-Down Supply Air Temperature Setpoint.
This Mode remains in effect until the Return Air Temperature drops
below the Target Temperature or a user-adjustable Time Period
expires. Cool-Down is not initiated by Push-Button Overrides or
Unoccupied Cooling demands. The Outdoor Air Damper remains
closed during Cool-Down Mode.
