Dry-Running Protection - Wilo Rexa PRO Notice De Montage Et De Mise En Service

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is connected to the pipe system on the suction and
pressure sides at the specified point in the machine
room. The pump itself is not immersed in the fluid.
The pipe system on the suction and pressure sides
must be self-supporting, i.e. it may not be sup-
ported by the pump. In addition, the pump connec-
tion to the pipe system must be free of stress and
vibrations. We therefore recommend using elastic
connection pieces (expansion joints).
The following operating parameters must be ob-
served for dry well installation.
• The max. fluid temperature and ambient tempera-
ture is 104 °F (40 °C).
• Specifications for "non-immersed operating mode"
The pump is not self-priming, so the hydraulics
housing must be completely filled with the fluid.
The minimum level in the collector tank must
be at the same height as the upper edge of the
hydraulics housing.
CAUTION: beware of burns!
The housing parts can heat up to well above
104 °F (40 °C). There is a risk of burns! After
switching it off, let the pump cool down to am-
bient temperature.
Fig. 4.: Stationary dry well installation
1 Collector tank
2 Machine room
3 Gate valve
4 Non-return valve
Work steps
1. Installing the pump: about 3-5 h
• Check that the pipe system is secured firmly.
• Secure lifting equipment to the pump with a
shackle, lift the pump, and then lower slowly on
to the pipe system.
• When lowering the pump, be mindful of the pow-
er supply cables.
• When the pump is resting on the piping, fasten
the pump to the pipe system on the suction and
pressure sides.
• Route the power supply cables in accordance with
local requirements.
• Have the electrical connections made by a quali-
fied electrician.
2. Install optional accessories, such as dry-running
protection or level controls.
3. Starting up the pump: about 2-4 h
• As described in the "Commissioning" section
• Open slide valves on suction and pressure sides.
• Vent the pressure pipe.
5.3.5. Level control
Level control can be used to detect fluid levels and
to switch the pump on and off automatically. The
fluid levels can be recorded using float switches,
18
5 Expansion joint
6 Pump
7 Min. water level
8

Dry-running protection

pressure and ultrasound measurements, or elec-
trodes.
Note the following:
• When using float switches, ensure that they can
move freely in the operating area.
• The water level must not fall below the minimum.
• The maximum switching frequency must not be
exceeded.
• If the fluid levels fluctuate strongly, then level
control should be implemented using two measur-
ing points as standard. This allows larger intervals
before control is triggered.
Installation
For correct installation, please see the installation
and operation instructions for the level control
device.
Observe the information on the maximum switch-
ing frequency and the minimum water level!
5.4. Dry-running protection
To ensure the necessary cooling, the pump may
need to be immersed when in operation, depend-
ing on the operating mode. In addition, it is also
important to ensure 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 rec-
ommend installing a dry-running protection system.
This can be implemented using float switches or
electrodes. The float switch or electrode is fixed in
the sump and switches off the pump when the wa-
ter level falls below the minimum coverage level. If
the dry-running protection only includes one floater
or electrode and the fluid levels deviate significant-
ly, then the pump may switch 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 implemented using a level control relay.
INSTALLATION
WILO SE 2014-11 V05 Letter