Zone
Zone
VCB-X CONFIGURATION
VCB-X Operator Interface SD
46
Setpoint Screen #20 - Cool Reset Source
Setpoints - Low Space/High Reset/VFD
VCBX Spts ID 101
Cool Rst Source Spts
If Low Spc: 70.0
º
F
Then Hi Rst: 55
If no SAT Reset Source has been con
fi
gured in Con
fi
guration Screen
#9 and the unit has not been con
fi
gured for Single Zone VAV, then this
screen will read, “No Cool Rst Con
fi
g” and will not be used. If the
unit has been con
fi
gured for Single Zone VAV, see the last paragraph
for this screen.
If a Reset Source has been con
fi
gured in Con
fi
guration Screen #9, the
third line will display “If Low Spc”, “If Low OAT”, “If Low RAT”, or
“If Low VFD” – depending on the Reset option that has been chosen.
This screen will then allow you to input the lower limit for the Reset
Source on Line 3. Line 4 (Then SAT) will show the corresponding Sup-
ply Air Cooling Hi Rst Setpoint that was entered on Setpoint Screen #18.
Please note that the Rst Limit value cannot be changed on this screen; it
is simply displayed from what was entered on the Setpoint Screen #18.
The value on Line 3 corresponds to the value on Line 4. So, if the Space
Temperature Sensor has been con
fi
gured as the Reset Source, then when
the Space Temperature is at or below the Low Spc Setpoint, the Supply
Air Cooling Setpoint will be reset to its highest value, the Cooling Hi
Rst Value. Then, as the Space Temperature moves from this low value
(Low Spc) to its high value (Hi Spc) con
fi
gured on Setpoint Screen #19,
the Supply Air Cooling Setpoint will be proportionally reset from the
Hi Rst Limit Setpoint to its SAT Setpoint.
Cooling Supply Air Reset Setpoints Examples:
Space Temperature Cooling Reset of SAT Setpoint:
Space Temp (Hi Spc) = 75
˚
F SAT Stpt (SAT) = 55
˚
F
Space Temp (Low Spc) = 72
˚
F SAT Stpt (Hi Rst) = 65
˚
F
VFD Percentage Cooling Reset of SAT Setpoint:
VFD Percentage (Hi VFD) = 100% SAT Stpt (SAT) = 55
˚
F
VFD Percentage (Low VFD) = 30% SAT Stpt (Hi Rst) = 65
˚
F
VCBX Spts ID 101
SZ VAV Fan Cool Rst
If Low Spc: 70.0
º
F
Then VFD: 30%
If this unit was con
fi
gured for Single Zone VAV application on Con
fi
gura-
tion Screen #7, this screen will appear. In the Cooling Mode, the Supply
Fan VFD speed will proportionally modulate as the Space Temperature
rises within the range set on this screen and the previous screen. Upon
entering the Cooling Mode, the fan will start at the Min Cooling VFD
VCB-X Setpoint Screens
Setpoint Screen #19 - Cool Reset Source
Setpoints - High Space/SAT/VFD
VCBX Spts ID 101
Cool Rst Source Spts
If Hi Spc: 75.0
º
F
Then SAT: 55
If no SAT Reset Source has been con
fi
gured in Con
fi
guration Screen
#9 and the unit has not been con
fi
gured for Single Zone VAV, then this
screen will read, “No Cool Rst Con
fi
g” and will not be used. If the
unit has been con
fi
gured for Single Zone VAV, see the last paragraph
for this screen.
If a Reset Source has been con
fi
gured in Con
fi
guration Screen #9, the
third line will display “If Hi Spc”, “If Hi OAT”, “If Hi RAT”, or If Hi
VFD” – depending on the Reset option that has been chosen. This screen
will then allow you to input the upper limit for the Reset Source on Line
3. Line 4 (Then SAT) will show the corresponding Supply Air Cooling
Setpoint that was entered on Setpoint Screen #18.
Please note that the SAT value cannot be changed on this screen; it is
simply displayed from what was entered on Setpoint Screen #18. The
value on Line 3 corresponds to the value on Line 4. So, if the Space
Temperature Sensor has been con
fi
gured as the Reset Source, then when
the Space Temperature is at or above the Hi Spc Temperature Setpoint,
the Supply Air Cooling Setpoint will be reset to its lowest value, the
SAT Setpoint. Then, as the Space Temperature moves from this high
value (Hi Spc) to its low value (Low Spc) con
fi
gured on Setpoint Screen
#20, the Supply Air Cooling Setpoint will be proportionally reset from
the SAT Setpoint to the Hi Rst Limit Setpoint.
See Cooling Supply Air
Reset examples under Setpoint Screen #20.
VCBX Spts ID 101
SZ VAV Fan Cool Rst
If Hi Spc: 75.0
º
F
Then VFD: 100%
If this is was con
fi
gured for Single Zone VAV application on Con
fi
gura-
tion Screen #7, this screen will appear. In the Cooling Mode, the Supply
Fan VFD speed will proportionally modulate as the Space Temperature
rises within the range set on this screen and the next screen. Upon enter-
ing the Cooling Mode, the fan will start at the Min Cooling VFD Speed
(entered on Setpoint Screen #16) and modulate up to 100% as the Space
Temperature rises from the Low Spc Setpoint (entered on the next screen)
to the Hi Spc Setpoint entered on this screen. So, on this screen the Hi
Spc Setpoint will correspond to the 100% VFD speed. Please note that
the VFD speed is
fi
xed at 100% on this screen and cannot be changed.
See Single Zone VAV Reset example under Setpoint Screen #20.
Description
Minimum
Default
Maximum
If Hi Space
1ºF
(-17.2
º
C)
75ºF
(24
º
C)
150ºF
(65.5
º
C)
