VCB-X Controller Field Technical Guide
INPUTS & OUTPUTS
57
VCB-X Controller Inputs
VCB-X Controller Inputs
AI1 - Space Temperature Sensor Input
The Space Temperature Sensor will initiate Occupied Heating and
Cooling modes if the unit is con
fi
gured for Space Temperature
control. It is always the sensor used to initiate Unoccupied Heating
and Cooling modes. If the Space Temperature Sensor used is
equipped with the optional Push-Button Override feature, this input
will detect user overrides and switch the unit from the Unoccupied
Mode back to the Occupied Mode operation for a user-adjustable
amount of time. The Space Temperature can also be con
fi
gured to
reset the Supply Air Temperature Setpoint.
AI2 - Supply Air Temperature Sensor Input
Once the unit is in the Heating or Cooling Mode (based on the
temperature at the mode enable sensor), the unit will control the
staging or modulation of the heating or cooling sources to maintain
a Heating or Cooling Supply Air Setpoint. The HVAC unit must
always have a Supply Air Temperature Sensor installed.
AI3 - Outdoor Air Temperature Sensor Input
The Outdoor Air Temperature is used to lock out Heating or Cooling
to conserve energy at whatever temperature you deem appropriate
for each Mode of Operation. This sensor is also used to initiate
Heating and Cooling modes on a Make Up Air unit. The Outdoor
Air Temperature Sensor can also be used for Pre-Heater operation
and for Low Ambient Protection operation.
NOTE:
For AI1 through AI3, all Temperature Sensors must
be Thermistor Type III which provide 77.0°F @ 10K
Ohms Resistance.
AI4 - Digital Compressor Discharge
Temperature Sensor lnput
The Digital Compressor Discharge Temperature Sensor monitors
the discharge temperature from the Digital Compressor to protect
against overheating.
AI5 - Space Temperature Sensor Slide Adjust
If the Space Temperature Sensor being used has the optional Slide
Adjust feature, its AUX output is connected to this input. The Slide
Adjust control is used to vary the HVAC Mode Heating and Cooling
Setpoints by a user-con
fi
gured maximum amount.
If the Space Temperature is con
fi
gured as the SAT Reset Source, the
Slide Adjustment adjusts both the HVAC Mode Enable Heating and
Cooling setpoints and the SAT Reset Source Heating and Cooling
setpoints simultaneously by a user-con
fi
gurable maximum amount.
BI1 - Emergency Shutdown Input
This wet contact input is used to initiate shutdown of the HVAC
unit when a N.C. Smoke Detector (by others), Firestat (by others),
or other shutdown condition (by others) contact is opened. The
controller remains active and can initiate alarm relays.
BI2 - Proof of Flow Input
A Proof of Flow Switch (by others) that provides a wet contact
closure whenever the HVAC unit Supply Fan is operating can be
connected to this input. If the Proof of Flow Switch contact opens
while the Supply Fan is operating, all Heating and Cooling is
suspended or disabled.
BI3 - Dirty Filter Contact Closure Input
This wet contact input is required for Filter Status Indication and
requires a Differential Pressure Switch to initiate a Dirty Filter alarm.
BI4 - Defrost Coil Temperature Switch Input
This wet contact input monitors a Defrost Coil Temperature Switch
on air to air heat pump units. If the compressors are operating in the
Heating Mode and this switch closes, it will initiate a Defrost Mode.
NOTE:
The Binary Inputs require wet contacts (24 VAC
only) to recognize an active input. If you provide dry
contacts, the contact closure will not be recognized.
All Binary Inputs are optional. This means that you
must con
fi
gure the VCB-X Controller to recognize
these input signals.
