Fault Finding Chart - Grundfos BM 4 Instrucciones De Instalación Y Funcionamiento

12. Fault finding chart

Before removing the terminal box cover and before any removal/dismantling of the module, make sure that the electricity sup-
ply has been switched off and that it cannot be accidentally switched on.
Fault Cause
1. The unit stops a) No or insufficient water supply. The pres-
occasionally. sure switch has cut out.
One or more
modules stop.
b) The capacity is too small. The flow switch
has cut out.
2. The booster unit a) The fuses are blown.
does not run.
b) The motor starter overload unit has
tripped out.
c) The magnetic coil of motor starter/contac-
tor is short-circuited. (Not cutting in).
d) The control circuit has cut out or is defec-
tive.
e) The motor/supply cable is defective.
3. The booster unit a) No water or too small quantity delivered
runs, but gives to the unit or air in the system.
no water or de-
velops no pres-
sure.
b) Suction parts are blocked.
4. The booster unit a) Wrong direction of rotation.
runs at reduced
capacity (flow
b) The valves on the discharge side are
and pressure).
partly closed or blocked.
c) The discharge pipe is partly blocked by
impurities.
d) The pump is partly blocked by impurities.
e) The pump is defective.
10
Remedy
Check that the pressure switch functions normally and is ad-
justed correctly. Check that the minimum inlet pressure is cor-
rect.
The discharge pipe is totally or partly blocked due to incor-
rectly adjusted manually operated valve, or failure in the mag-
netic or motor-operated valve.
Check these valves.
The flow switch is faulty or incorrectly adjusted. Check/adjust
the switch.
Check and replace both main fuses and/or fuses for control cir-
cuit.
Reset the starter overload. If it trips out again, the voltage
should be checked.
Replace the coil. Check the coil voltage.
Check the control circuit and the contacts in the monitoring de-
vices (pressure switch, flow switch, etc.).
Check motor and cable. See also section 13. Checking of mo-
tor and cable.
Check that the inlet pressure during operation is at least
0.5 bar for BM 4", BM 6", BMB 4" and BMB 6" and 1 bar for
BM 8" and BMB 8". If so, the water supply is OK. Stop and vent
the system. Restart the unit as described in section 8. Opera-
tion.
If the pump is defective, it should be dismantled and repaired/
replaced.
Pull the pump out of the sleeve and clean the suction parts.
See section 7. Liquid filling, module venting and checking of di-
rection of rotation.
Check valves.
Measure the discharge pressure and compare with the calcu-
lated data. Clean or replace the discharge pipe.
Pull the pump out of the sleeve. Dismantle, clean and check
the pump. Any defective parts should be replaced. Clean the
pipes.
Pull the pump out of the sleeve. Dismantle, clean and check
the pump. Any defective parts should be replaced. See section
11. Service manuals.