Grundfos SP Series Installation And Operating Instructions Manual page 22

Fault Cause
4. Frequent a) The differencetial
starts of the pressure
and switch between
stops. the start and stop
pressures is too
small.
b) The water level
electrodes or level
switches in the
reservoir have not
been installed
correctly.
c) The non-return
valve is leaking or
stuck half-open.
d) The tank
precharge
pressure of the
tank is too small
low.
e) The tank is too
small.
f) The diaphragm of
the tank is
defective.
22
Remedy
Increase the
differencetial. The stop
pressure must not
exceed the operating
pressure of the pressure
tank, and the start
pressure must be high
enough to ensure
sufficient water supply.
Adjust the intervals of
the electrodes/ or level
switches to ensure
suitable time between
the cutting-in and
cutting-out of the pump.
See installation and
operating instructions for
the electrodes or /level
switches. If the intervals
between stop/and start
cannot be changed via
the automatics, the pump
performance may be
reduced by throttling the
outlet valve.
Pull out the pump and
clean or replace the
valve.
Adjust the tank
precharge pressure of
the tank in accordance
with its installation and
operating instructions.
Increase the capacity of
the tank by replacing it or
supplementing it with an
additional another tank.
Check the diaphragm
tank.