Application
Table Of Contents
- Overview
- Sequence of Operation
- Average Face Velocity Control
- AVS Calibration
- AO2 Flow Signal
- Control Loop - Damper Application
- Venturi Application
- Minimum Exhaust Mode
- Maximum Exhaust Mode
- Warning Limits
- Alarm Limits
- Alarm Output
- Horn Disable
- Sash Area Alarms
- Table Access Feature
- Emergency Mode
- Start-up/Decommission Mode
- Fail Mode
- Wiring Diagrams
- Point Database Application 6741
- Point Database Application 6742
Sequence of Operation
Fail Mode
25
Siemens Industry, Inc. Application Note 140-1344
Restricted 2015-11-09
The digital output DO6 can be used for local indication that the sash was opened after
the hood entered Out of Service mode. The output will remain ON until STARTUP
MODE is changed.
Fail Mode
If the Fume Hood Controller or one of its accessories fails, then a failure mode
sequence is initiated.
Fume Hood Controller – If the Fume Hood Controller power fails, the exhaust damper
goes to the fully opened position. Since there is no power to the controller, no LEDs or
displays are available on the ODP. If the power fails to both the exhaust fan and the
controller, there is no indication except for the absence of the noise that the air makes
during normal operation.
Sash Sensor – If the sash sensor fails, then GEN FAILURE turns ON, and the Fume
Hood Controller maintains flow through the fume hood at an exhaust setpoint
calculated using the value in FAIL AREA and making FACE AREA equal to FAIL
AREA. The ODP displays FFF and GENERAL FAILURE.
Operator Display Panel – If the ODP fails, then the Fume Hood Controller continues to
control the flow. However, displays and audible alarms are not available.
OAVS Sensor – If the OAVS sensor fails or is disconnected, then GEN FAILURE turns
ON, AO2 goes to zero Vdc, and the Fume Hood Controller controls the exhaust
damper to the condition described in AVS FAILMODE. This will be either fully open or
holding the current position. The ODP displays the failure.
(Optional) Differential Pressure Transmitter – If A I3 is used and the differential
pressure transmitter fails by losing the 4 to 20 mA signal, then GEN FAILURE turns
ON, AO2 goes to 0 Vdc, and the Fume Hood Controller controls the exhaust damper to
the condition described in AVS FAILMODE. This will be either fully open or holding the
current position. The ODP displays the failure.
Electronic Actuator – If the actuator fails and flow control is lost, the ODP displays
alarms indicating unsafe operating conditions.
Upon loss of power the actuator will fail based on the related DIP switch settings.
Face Velocity – If the Face Velocity falls out of the safe range of operation, the LOW
ALM or HIGH ALM turns ON and alarms are displayed on the ODP indicating unsafe
operating conditions.