Grundfos SCALA Installation And Operating Instructions Manual page 20

Fault
4. System
overpressure.
5. You can reset
the pump, but
it runs only for
a few
seconds.
6. You can reset
the pump, but
it starts
repeatedly,
immediately
after stopping.
20
Cause
a) The setpoint has been set
too high. The difference
between the outlet
pressure and the inlet
pressure must not exceed
Yes
4 bar (58 psi).
Example: If the required
outlet pressure is 5 bar
(73 psi), the minimum
inlet pressure must be 1
bar (14.5 psi).
b) The maximum pressure
has been exceeded - the
Yes inlet pressure is higher
than 6 bar, 0.6 MPa (85
psi)
c) The maximum pressure
has been exceeded -
equipment elsewhere in
the system causes a high
Yes
pressure at the pump
(e.g. water heater or
defective safety
equipment)
a) Dry running or water
shortage
Yes
b) The inlet pipe is blocked
by impurities
Yes
c) The foot or non-return
valve is blocked in closed
Yes
position
d) Leakage in the inlet pipe
Yes
e) Air in the inlet pipe or the
pump
Yes
a) The internal non-return
valve is defective or
No
blocked in completely or
partly open position.
b) The tank precharge
pressure is not correct.
No
Remedy
Reduce the setpoint to 4
bar (58 psi) + positive
inlet pressure.
Check the inlet
conditions.
Check the installation.
Check the water source,
and prime the pump.
Clean the inlet pipe.
Clean, repair or replace
the foot or non-return
valve.
Repair the inlet pipe.
Prime the inlet pipe and
the pump. Check the
inlet conditions of the
pump.
Clean, repair or replace
the non-return valve.
Adjust the tank
precharge pressure to
70 % of the required
outlet pressure.