Siemens 125-5033 - Manual (Page 20)

Fume Hood Controller Owner's Manual
12 Siemens Building Technologies, Inc.
Basic Operation
The Fume Hood Controller provides Direct Digital Control (DDC) technology for controlling
fume hood face velocities in a manifolded fume hood exhaust system.
High and Low Exhaust Flow Control
The Fume Hood Controller can operate at two different setpoints, described as HI flow and
LOW flow setpoints. The low setpoint can be set to zero to send the controller into an OFF
mode. The OFF mode shuts off the flow alarms and closes the exhaust flow control device
and allows the controller to go into a standby mode of operation.
The Operators Display Panel (ODP) can display HI/LOW setpoint or output exhaust flow in
CFM. Due to display limits, the actual number displayed is CFM divided by 10.
Control Loops
The PID loop controls the exhaust flow control device based on the values of the exhaust
flow and the flow setpoint. The loop output controls the supply and exhaust through a time
modulation scheme. The control loopout ranges from -100 to 100%.
• -100% is the maximum supply that closes the exhaust flow control device at full
speed.
• 0% holds the exhaust flow control device at its current position.
• 100% is the maximum exhaust that opens the exhaust flow control device at full
speed.
Electronic
The controller sends a separate signal to each of the two inputs that reside on the AO-E
module. For values of 100% to 0%, the controller sends a decreasing percentage of the full
signal length to the retract input. For values of 0% to -100%, the controller sends an
increasing percentage of the full signal to the extend input.
Pneumatic
The controller sends a separate signal to each of the two solenoids that reside on the AO–P
module. For values of 100% to 0%, the controller sends a decreasing percentage of the full
signal length to the exhaust solenoid. For values of 0% to -100%, the controller sends an
increasing percentage of the full signal length to the supply solenoid.
Calibration
Air Velocity Sensor - Calibration of the controller's air velocity sensor is periodically required
to maintain accurate air velocity readings.