Assortment / System Description

Room pressurization and fume hood control
Fume hood
21
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21.9.5 Stabilizing jet
The stabilizing jet feature is used to monitor and control a fume hood stabilizing
jet fan. The status of the stabilizing jet fan is shared with other functions to
determine exhaust volume setpoints and generate alarms. The stabilizing jet
fan is turned on and off based on fume hood sash position and, fume exhaust
air volume flow.
A differential pressure switch is normally used to determine if the stabilizing jet
fan is operating properly. Occasionally a differential pressure switch is not
installed. The stabilizing jet alarm will always be off when the binary input for
the differential pressure switch is not present.
Description Parameter Default value
Setpoint for stabilizing jet fan speed
▶ The speed signal to the stabilizing jet fan when
the fan is operating. Set according to the fume hood
manufacturer’s instruction.
SpStbFanSpd 42 [%]
Switch-off sash position for stabilizing jet fan
▶ The stabilizing jet fan will be off when the sash is
below this position. Set according to the fume hood
manufacturer’s instruction. Only used with
FhSash15.
SwiOffSshpFan 4.0 [cm]
1.6 [in]
Switch-on sash position for stabilizing jet fan
▶ The stabilizing jet fan will be on when the sash is
above this position. Set according to the fume hood
manufacturer’s instruction. Only used with
FhSash15.
SwiOnSshpFan 8.0 [cm]
3.1 [in]
Switch-off area for stabilizing jet fan
▶ The stabilizing jet fan will be off when the face
area is less than this value. Set according to the
fume hood manufacturer’s instruction. Only used
with FhSash11…14.
SwiOffAreaFan 0.06 [m
2
]
0.65 [ft
2
]
Switch-on area for stabilizing jet fan
▶ The stabilizing jet fan will be on when the face
area is greater than this value. Set according to the
fume hood manufacturer’s instruction. Only used
with FhSash11…15.
SwiOnAreaFan 0.12 [m
2
]
1.29 [ft
2
]
Switch-off point for exhaust air volume flow for
stabilizing jet fan
▶ The stabilizing jet fan will be turned off if
FhAirFlEh < SwiOffAflEhFan for a time longer than
DlyOffFanAirFl. Set according to the fume hood
manufacturer’s instruction.
SwiOffAflEhFan 150 [m
3
/h]
88.3 [ft
3
/min]
41.67 [l/s]