Protection Against Electro-Chemical Corrosion - Grundfos SRG 60 Hz Installation And Operating Instructions Manual

5.5.2 Gearbox protection
The gearbox is monitored for the ingress of water by a leak
sensor incorporated in the gearbox.
If the monitoring function is required, the leak sensor must be
connected to a Grundfos relay.
The cable between the relay and the pump must not
be longer than 164 ft (50 m).
For a longer distance, use an additional, screened cable. An
external alarm indicator, if any, must be connected to the
potential-free outputs, terminals 1 and 3 or 4, respectively.
Maximum load: 250 V, 5 A.
When the Grundfos leakage relay is connected, a current of up to
10 mA will flow through the leak sensor (terminals 5 and 7 in fig.
13 connected to wires 21 and 22). If water penetrates into the oil
chamber, the relay will trigger an alarm signal and/or switch off
the motor.
See wiring diagram in fig. 11 or 12.
Leak sensor
• Two conductors (terminals 21 and 22).
• Maximum operating voltage: Approx. 12 V.
• Maximum current: 1 to 10 mA.
DANGER
Electric shock
Death or serious personal injury
- When adjusting the relay, beware of electric
voltage.
Do not check the leak sensor with an ohmmeter or
other measuring instruments. The leak sensor is an
electronic component.
5.5.3 Overload relays
The motor must be protected against overload via a thermal delay
relay according to local regulations. The relay must be adjusted
to the rated current stated on the nameplate.

5.6 Protection against electro-chemical corrosion

Two different metals or alloys cause electro-chemical corrosion if
they are connected by an electrolyte. This applies if more than
one pump is installed in the same tank. We recommend the
following additional protection:
• galvanic separation of the earth conductor from the neutral
conductor
• galvanic separation of the mains supply by means of an
isolation transformer
• anode kit.
The earth conductor must be separated in such a way as to
ensure that no direct current can flow through it. It must still
function as a protective conductor. This can be achieved with a
limiting unit (polarization cell or anti-parallel diode) or an isolation
transformer.
2
3
Fig. 13 Protection from electro-chemical corrosion
Pos. Designation
1 Limiting unit
2 Earth conductor
3 Isolation transformer
When using an isolation transformer, the ratio
between starting current and rated current (I
must not be altered.
L1
L2
L3
N
PE
1
2
/I )
A N
11