Zone
Zone
VCB-X CONFIGURATION
VCB-X Operator Interface SD
44
Setpoint Screen #12 - Outdoor Dewpoint
Setpoint
VCBX Spts ID 101
Outdoor Dewpoint
Setpt: 55.0
º
F
On MUA con
fi
gured units (100% or high percentage Outdoor Air units),
or if this is a unit in Hood On MUA operation, Dehumidi
fi
cation will
be initiated if the Outdoor Air Dewpoint rises 2°F above this setpoint.
If the humidity falls 2°F below this setpoint, the unit will leave the
Dehumidi
fi
cation Mode.
Description
Minimum
Default
Maximum
Outdoor Dewpoint
Setpoint
35ºF
(1.7
º
C)
55ºF
(12.8ºC)
80ºF
(26.6ºC)
Setpoint Screen #13 - Indoor RH Setpoint Low
and High Reset Source
VCBX Spts ID 101
Indoor RH Setpt
Lo Rst Src: 50%
Hi Rst Src: 60%
This screen can be used to set the Space Humidity Setpoint and to set
the Space Humidity Reset range used to reset the Suction Coil Tem-
perature Setpoint.
On units where Indoor Humidity is used to initiate Dehumidi
fi
cation
(non MUA units), the Low Reset Source (Lo Rst Src) is the Dehumidi-
fi
cation Setpoint, and as the Indoor Humidity rises above this setpoint,
Dehumidi
fi
cation will be initiated. If the humidity falls 1% below this
setpoint, the unit will leave the Dehumidi
fi
cation Mode.
If no reset of the Coil Temperature Setpoint is desired, set the High Reset
Source (Hi Rst Src) at the same value as the Low Reset Source. If reset
of the Coil Temperature Setpoint is desired, when the Indoor Humidity
rises above the Low Reset Source, Dehumidi
fi
cation will be initiated
and the Coil Temperature Setpoint will be set at the Coil Temperature
High Reset Limit (con
fi
gured in the next screen).
The High Reset Source (Hi Rst Src) is the Indoor Humidity level at
which the Coil Temperature will be reset to the Coil Temperature Low
Reset Limit (con
fi
gured in the next screen). As the Indoor Humidity
rises between the Low Reset Source and the High Reset Source, the
Coil Temperature Setpoint will be proportionally reset between the
Coil Temperature High Reset Limit down to the Coil Temperature Low
Reset Limit.
On MUA units where the Outdoor Dewpoint Setpoint is used to initiate
Dehumidi
fi
cation, this screen is only used to set the Indoor Humid-
ity values that will reset the Coil Temperature Setpoint. As described
above, as the Indoor Humidity rises within the range created by the Low
and High Reset Source Setpoints, the Coil Temperature Setpoint will
be proportionally reset between the High and Low Coil Temperature
Reset Limits.
VCB-X Setpoint Screens
Description
Minimum
Default
Maximum
Indoor RH Setpoint
Low Reset Source
0%
50%
100%
Indoor RH Setpoint
High Reset Source
0%
60%
100%
Setpoint Screen #14 - Coil (Saturation)
Temperature High and Low Reset Setpoints
VCBX Spts ID 101
Coil Temp Setpt
Hi Rst Lmt: 45
º
F
Lo Rst Lmt: 40
º
F
Based on the Indoor Humidity Reset Range con
fi
gured on the previous
screen, the Coil Suction Temperature Setpoint can be reset between
the High Reset Limit (Hi Rst Lmt) and Low Reset Limit (Lo Rst Lmt)
con
fi
gured on this screen during the Dehumidi
fi
cation Mode. See the
description of this reset function on the previous screen. If the High
Reset Limit and the Low Reset Limit are set at the same value, no Coil
Temperature Reset will occur.
Description
Minimum
Default
Maximum
Coil Temp Setpoint
High Reset Limit
35ºF
(1.7
º
C)
45ºF
(7.2
º
C)
70ºF
(21.1
º
C)
Coil Temp Setpoint
Lo Reset Limit
35ºF
(1.7
º
C)
40ºF
(4.4
º
C)
70ºF
(21.1
º
C)
Setpoint Screen #15 - Static Pressure
Setpoint and Deadband
VCBX Spts ID 101
Static Pressure
Setpt: 1.50
Deadband: 0.10
For VAV units, a Supply Fan VFD or Bypass Damper Actuator is used to
maintain the Duct Static Pressure Setpoint. The Static Pressure Output
Signal varies to control to the Static Pressure Setpoint. The Duct Static
Pressure is maintained at this setpoint anytime the Main Fan is running.
The Duct Static Setpoint accuracy is controlled by this value. No Main
Fan VFD changes are made if the static is within this range of this
setpoint.
Description
Minimum
Default
Maximum
Static Pressure Spt
0.10
″
WG
1.50
″
WG
3.0
″
WG
Deadband
0.01
″
WG
0.10
″
WG
0.50
″
WG
