Dry-Running Protection; Electrical Connection - Wilo Rexa CUT Serie Einbau- Und Betriebsanleitung

INSTALLATION
• If the fill levels fluctuate strongly, then a level
control should be made on two test points as
standard. This means larger differential gaps are
reached.
Installation
For correct installation, please see the installation
and operation instructions for the level control
device.
Observe the information on the maximum
switching frequency and the minimum water
level!

5.4. Dry-running protection

To ensure the necessary cooling, the pump must
be immersed when in operation, depending on
the operating mode. In addition, make sure that
no air enters the hydraulics housing.
The pump must therefore always be immersed
in the fluid up to the top edge of the hydraulic
housing or, if applicable, up to the top edge of
the motor housing. For optimum operational
reliability, we recommend installing a dry-running
protection system.
Correct running is ensured by float switches or
electrodes. The float switch or electrode is fixed
in the pump chamber and switches off the pump
when the water level falls below the minimum
coverage level. If the dry-running protection
only includes one floater or electrode and the fill
levels deviate significantly, then the pump may
turn on and off constantly! This can result in the
maximum number of motor activations (switching
cycles) being exceeded.
5.4.1. Remedies for avoiding excessive switching
cycles
• Manual reset
The motor is switched off when the water level
falls below the minimum coverage level and
switched back on when a sufficient water level is
reached.
• Separate reactivation point
A second switching point (additional floater or
electrode) is used to obtain a sufficient difference
between the activation and deactivation points.
This prevents constant switching. This function
can be put into effect with a level control relay.

5.5. Electrical connection

ELECTROCUTION hazard!
Incorrect electrical connections can cause fa-
tal electric shocks. Electrical connections may
only be carried out by a qualified electrician
approved by the local energy supply company,
in accordance with locally applicable regula-
tions.
Installation and operating instructions Wilo-Rexa CUT
INCORRECT connection can result in danger!
With Ex-rated pumps, the power supply cable
must be connected outside the potentially
explosive area, or inside a housing with igni-
tion protection conforming to DIN EN 60079-
0! Non-observance may lead to fatal injury
due to explosion!
• Always have the connection carried out by
a qualified electrician.
• Note the additional information about this in
the appendix.
• The mains connection current and voltage must
be as stated on the rating plate.
• Connect the power supply cable in accordance
with the applicable standards and regulations and
according to the conductor assignment.
• Any available monitoring equipment, e.g. for
thermal motor monitoring, must be connected
and tested to ensure that it is working properly.
• For three-phase AC motors, a clockwise rotating
field must be available.
• Ground the pump properly.
Pumps that are permanently installed must be
grounded in compliance with nationally applica-
ble standards. If a separate grounding conductor
is available, it must be connected to the marked
hole or earth terminal (;) using a suitable screw,
nut, toothed washer and flat washer. The cross
section of the cable for the grounding conductor
connection must correspond to the local regula-
tions.
• A motor protection switch must be used for
motors with a free cable end. We recommend
using a residual-current device (RCD).
• Switchgear must be purchased as accessories.
5.5.1. Mains fuses
The back-up fuse must be rated according to the
starting current. You will find the starting current
on the rating plate.
Only slow-blow fuses or K characteristic auto-
matic cut-outs may be used as a back-up fuse.
5.5.2. Checking the insulation resistance and moni-
toring devices before commissioning
If the values measured deviate from the specifi-
cations, moisture may have penetrated into the
motor or the power supply cable or the monitor-
ing unit may be defective. Do not connect the
pump and consult Wilo customer service.
Insulation resistance of the motor winding
Before connecting the power supply cable, the
insulation resistance must be tested. This can be
measured with an insulation tester (measuring
voltage = 1000 V):
• On initial commissioning: insulation resistance
may not be less than 20 MΩ.
• For further measurements: value must be larger
than 2 MΩ.
For motors with an integrated capacitor, the
windings must be short-circuited before check-
ing.
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