Megging - Grundfos SQ Serie Montage- Und Betriebsanleitung

Fault
3. The pump runs at
reduced capacity.
4. Frequent starts
and stops.

10.1 Megging

Megging of an installation incorporating SQ/SQE
pumps is not allowed, as the built-in electronics may
be damaged. See fig. 13.
L
C
C
C
N
PE
Fig. 13
Cause
a) The drawdown is larger than
anticipated.
b) The valves in the discharge pipe
are partly closed/blocked.
c) The discharge pipe is partly
choked by impurities (ochre).
d) The non-return valve of the pump
is partly blocked.
e) The pump and the riser pipe are
partly choked by impurities
(ochre).
f) The pump is defective.
g) Leakage in the pipework.
h) The riser pipe is defective.
i) Undervoltage has occurred.
a) The differential of the pressure
switch between 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 supply voltage is unstable.
e) The motor temperature gets too
high.
C
U
U
U
Remedy
Increase the installation depth of the pump,
throttle the pump or replace it by a smaller
model to obtain a smaller capacity.
Check and clean/replace the valves,
if necessary.
Clean/replace the discharge pipe.
Pull out the pump and check/replace the
valve.
Pull out the pump. Check and clean or
replace the pump, if necessary. Clean the
pipes.
Repair/replace the pump.
Check and repair the pipework.
Replace the riser pipe.
Check the power supply.
Increase the differential. However, the stop
pressure must not exceed the operating
pressure of the pressure tank, and the start
pressure should be high enough to ensure
sufficient water supply.
Adjust the intervals of the electrodes/level
switches to ensure suitable time between
the cutting-in and cutting-out of the pump.
See installation and operating instructions
for the automatic devices used. If the
intervals between stop/start cannot be
changed via the automatics, the pump
capacity may be reduced by throttling the
discharge valve.
Pull out the pump and clean/replace the
non-return valve.
Check the power supply.
Check the water temperature.
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