Dry-Running Protection - Grundfos CU 301 Notice D'installation Et De Fonctionnement

5.7 Dry-running protection

The purpose of dry-running protection is to protect a
pump in case of insufficient water flow.
This built-in dry-running protection makes the
conventional external dry-running protection device
unnecessary.
No additional cables to the motor are required.
The dry-running protection is active after 30 seconds
of operation.
The dry-running settings shown in section 9.
Technical data are built into the pump and
automatically transmitted to CU 301. These settings
can be changed via Grundfos GO Remote.
When air enters the pump together with water, the
pump power decreases, and pressure drops,
causing the motor to increase speed.
If the power consumption falls below the dry-running
setting for an accumulated time of 5 seconds, and
the motor speed is within 1,000 rpm of the maximum
speed setting as defined in the section 6.3.8
Maximum speed, CU 301 stops the pump and
signals a dry-running alarm.
When the motor stops, the dry-running indicator light
is permanently on. See fig. 16, pos. A.
14
PSI
100
90
80
70
60
50
40
Fig. 16 Dry-running indicator light
Possible cause
The pump performance
is too high compared to
the well yield.
The well screen is
blocked.
Restarting
After 5 minutes (factory setting), or the period set in
Grundfos GO Remote, the motor restarts
automatically. See section
restarting.
A
Remedy
Replace the pump with
a smaller one.
Reduce the pump
performance using
Grundfos GO Remote.
See section
6.3.8 Maximum speed.
Well service is required.
6.3.5 Automatic