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3 Operation
3.4
Monitor storage tanks and react to a dry run
Table 3-3
No.
1.
To avoid the pump running dry in this cooling water system, a three-pole wire electrode is used
for monitoring the water level in the storage tank.
2.
For an electrode, the reference point (M), the
minimum fill level (Min) and the maximum fill
level (Max) are set.
3.
The three-pole wire electrode is connected to
the SIRIUS monitoring relay.
4.
The functional principle of the SIRIUS
monitoring relay is based on the measurement
of the electric resistance of the fluid between
two diving probes (Min, Max) and a reference
terminal (M). If the measured value is lower
than the sensitivity (R sens) set in the SIRIUS
monitoring relay at the front, the relay will
change its switching position.
The monitoring relay is used in the operating
mode "dry run protection" (setting "OV"). It
changes its switching position (time diagram
out: OVER), as soon as the fluid level Max is
reached. It switches back to its original
position, as soon as the Min probe does not
touch the fluid any longer.
5.
The SIRIUS monitoring relay is wired to a
digital input of the LOGO! logic module. If a dry
run is detected, the release for the V20
frequency converter is stopped.
At the Min and Max terminals of the SIRIUS monitoring relay, other resistance
Note
sensors in the range of 5 to 100kOhm, e.g. photo sensors, temperature sensors,
distance transducers on a resistance basis, can also be connected. Therefore,
the monitoring relay is not only suitable for level monitoring of fluids.
Set23_RegSim
Entry ID: 23753479,
V2.3.S,
Function
02/2014
Comments
Max
Min
M
The monitoring relay has two operation
modes, which can be selected by means of
two switches in the device:
•
dry run protection, switch position OVER
•
overflow protection, switch position
UNDER
12
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