Plastec Variable Air C - Manual (Page 3)

When the fume extraction fan is running, it causes negative pressure inside
the fume cupboard. If the sash is lowered, the negative pressure become more
intense causing air to be drawn through the sash opening at an increased velocity.
Conversely, if the sash is raised the negative pressure becomes less intense and air
velocity reduces.
If an opening is made in the wall of the fume cupboard, air will enter it at a
velocity determined by the same negative pressure that is drawing air into the
sash opening. By sensing the air velocity through an opening, we can determine
its level at the sash opening.
PLASTEC ® AirControl Type C exploits this by the placing of a numerical sensor,
or thermal anemometer into a hole in the cupboard and sending the air velocity
measurement obtained to a display on the fascia panel. Based on air velocity
measured, Plastec
® AirControl C will send a signal to an inverter to either increase
or decrease fan speed.
The air velocity level is displayed on the fascia either by LED illumination or
digital read-out. An audible alarm will also sound if the air velocity is too low.
Operating Principle
SENSOR
Airflow Monitor
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.plas
tecv
ent.net
2216 60th Drive East • Bradenton, Florida 34203
(941) 751-7596 • Fax (941) 751-7598 • www.plastecvent.net 3
Laboratory Airflow Monitors & Controls
TYPE C STANDARD & NIGHT SETBACK
LED & DIGITAL - VAV SYSTEM