11
45
44
43
42
41
30
4.4
Open-loop and Closed-loop
Control System
The Central extraction system is equipped
with automatic electronic control. The
frequency inverter (33) is actuated via the
control board (41) with the vacuum sensor
accommodated in the electronics housing
(30). The frequency inverter generates a
rotating field with a variable frequency for
infinite motor (27) speed adjustment at
the blower (26). Since the vacuum is
regulated to a constant level, irrespective
of the number of suction units open,
suction at the various work spaces
30 Housing for electronic control
41 Control board
42 Lower control threshold potentio-
meter (black)
43 Control setpoint potentiometer
(suction, red))
44 Upper control threshold potentio-
meter (black)
45 Microswitch
4.5.1
Changing the Rate of Suction
The rate of suction can be increased by
turning the red potentiometer (43)
clockwise.
Only make slight changes. If the rate of
suction of the extraction system has
declined considerably, it is not normally
due to the setting. Clean the pipes or
change the filter. Consult our service
technicians.
Fig. 11: Housing with control board
remains constant. Motor speed, and
hence the suction capacity of the extraction
system, is constantly being adjusted to
current demand. On a daily average the
extraction system only runs at a fraction
of its maximum capacity. That ensures a
long service life, low noise levels and
minimal energy costs. The lower threshold
potentiometer (42) and the upper
threshold potentiometer (44) are specially
set by our fitters for your laboratory using
an air flow meter when the system is
being installed. This basic setting must
not be changed.
4.5
Changing the Settings of the
Extraction System
1. Turn OFF at the power switch (5).
2. Remove the mains coupling from
plug (2).
3. Unscrew the cover from the
electronic control housing (30).
4.5.2
Changing the Holding Time for
Maximum
In the preset (15 min) the first switch is
in the ON position (top). Every switch
which is in the ON position extends
holding time by 15 minutes.
Example: 3 switches in the ON position
results in a period of 3 x 15 minutes = 45
minutes.
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