Grundfos ALPHA2 L 15-50 Montageanleitung Seite 36

For information, the following is a list of the pump's operating faults:
Fault Control
The circulator is not
running
"POWER ON"
indicator lamp
Cause
panel
a) An installation fuse is
blown
b) The circuit breaker
controlled by current or
Lamp off
voltage has tripped
c) The circulator is faulty
a) The power supply voltage
Only the is off. Possibly too low.
b) The circulator is blocked
is on
Page 12 of 12
Solution
Replace the fuse.
Reset the circuit breaker.
Replace the circulator.
Check that the power supply is within the
specified range
Remove any impurities.