Grundfos CU 301 Manuel D'instructions page 11

3.2 Dry-running protection
The purpose of the dry-running protection is to pro-
tect the pump in case of insufficient water flow.
The dry-running protection makes the conventional
dry-running protection unnecessary.
No additional cables to the motor are required. The
dry-running settings shown in section 8. Technical
data, are built into the pump and automatically trans-
mitted to the CU 301. These settings can be
changed via the R100.
When air enters the pump together with water, the
pump power decreases, and pressure drops, caus-
ing the motor to increase speed. If the power con-
sumption falls below the dry run setting for an accu-
mulated time of 5 seconds, and the motor speed is
within 1,000 rpm of the maximum speed setting as
defined in the section 5.3.6, the CU 301 stops the
pump and declares a dry-running alarm.
When the motor is stopped, the dry-running indicator
light is permanently on, see fig. 13, pos. A.
PSI
100
90
80
70
60
50
40
Fig. 13 Dry-running indicator light
Possible cause
The pump performance
is too high compared to
the well yield.
Well screen is blocked.
Restarting
After 5 minutes (factory setting) or the period set by
means of the R100, display 5.3.4 Automatic restart,
the motor will restart automatically.
A
Remedy
Replace the pump with
a smaller one.
Reduce pump perfor-
mance using the R100,
display 5.3.6 Maximum
speed.
Well service is required.
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