The SETBACK item sets an alternate control set point, typically
used when the laboratory is unoccupied. The SETBACK control
set point can be for either face velocity or flow control,
depending on the setting of menu item SETBACK CONTROL
MODE. The FHC50 controller will maintain this set point when
normal operating conditions exist.
If SETBACK CONTROL MODE = VelSideWall, VELSashPos or
VelSide+Sash, enter a value between 60 to 980 ft/min.
If SETBACK CONTROL MODE = Flow, enter a value between 0
and 10,000 cfm.
A SETBACK condition is initiated when the SETBACK key has
been pressed, the SETBACK contact input has been closed, or
a command is received through network communications.
WARNING: The Model FHC50 may not maintain the fume
hood’s containment at low SETBACK face
velocities.
The SETBACK CNTRL POS item is used to program a setback
mode fixed damper or venturi valve position. The menu item
SETBACK CONTROL MODE must be set to FIXED POS to
enable the SETBACK CNTRL POS menu item. During
SETBACK, the controller will set the control output to the value
programmed for SETBACK CNTRL POS.
NOTE: To shutdown a fume hood with the Model FHC50
controller, set the SETB CTRL MODE item to Fixed
Position and the SETBACK CNTRL POS item to 0%.
WARNING: The Model FHC50 may not maintain the fume
hood’s average face velocity or flow at the setback
set point item value when a SETBACK CNTRL
POS has been programmed. The average face
velocity or exhaust flow may fall below the setback
alarm value; this could result in a setback velocity
or flow alarm condition.
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