49
11.7.42 Dry-running protection (4.4.1)
Fig. 87 Dry-running protection
Description
Dry-running protection is one of the most important monitoring
functions, as bearings and shaft seal may be damaged if the
pumps run dry. Grundfos thus always recommends dry-running
protection.
The function is based on monitoring of the inlet pressure or the
level in a possible tank or pit on the suction side.
Level switches, pressure switches or analog sensors signalling
water shortage at a set level can be used.
There are three different methods for detection of water shortage:
• Pressure switch on suction manifold or float switch/electrode
relay in the supply tank. See section 11.7.43 Dry-running
protection with pressure/level switch (4.4.1.1).
• Measurement of inlet pressure in the suction manifold by
means of an analog pressure transmitter. See section
11.7.44 Dry-running protection with pressure transmitter
(4.4.1.2).
• Measurement of level in the supply tank by means of an
analog level transmitter. See section 11.7.45 Dry-running
protection with level transmitter (4.4.1.3).
Setting via control panel
1. Mark the Settings menu with .
2. Mark Monitoring functions with or , and press .
3. Mark Dry-running protection with or , and press
.
4. Select the method with or , and press .
11.7.43 Dry-running protection with pressure/level switch
(4.4.1.1)
Fig. 88 Dry-running protection with pressure/level switch
Description
This function is primarily used in booster applications. Dry-
running protection can take place by means of a pressure switch
on the suction manifold or a level switch in a tank on the suction
side.
When the contact is open, the CU 351 will register water
shortage after a time delay of approx. 5 sec. It is possible to set
whether the indication is to be just a warning or an alarm stopping
the pumps.
In the display, it is possible to set whether restart and reset of the
alarm is to be automatic or manual.
Setting range
• Selection of digital input for the function.
• Reaction in case of water shortage: Warning or alarm + stop.
• Restart: Manual or automatic.
Setting via control panel
1. Mark the Settings menu with .
2. Mark Monitoring functions with or , and press .
3. Mark Dry-running protection with or , and press
.
4. Mark Pressure/level switch with or , and press .
5. Mark Go to setting of digital input, and press . Now the
display Digital inputs (4.3.7) appears. Set the input to dry-
running protection. Return with .
6. Mark Warning or Alarm + stop with or , and save
with .
7. Mark Manual or Auto with or , and save with .
Factory setting
The setting is done in the start-up wizard and depends on the
application.
TM03 2320 4807
TM03 2329 1109
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