Switches And Sensors - Grundfos SE1 50 Installation And Operating Instructions Manual

7.2 Switches and sensors

All SE1 and SEV pumps have thermal protection
incorporated in the stator windings.
7.2.1 Thermal switch, PT1000 and thermistor
(PTC)
Pumps without sensor
Pumps without sensor have a thermal switch or a
PTC thermistor.
Through the pump controller safety circuit, the
thermal switch stops the pump by breaking the circuit
in case of overtemperature (approximately 150 °C).
The thermal switch recloses the circuit after cooling.
For pumps equipped with a PTC thermistor, connect
the thermistor to either the PTC relay or the IO
module to break the circuit at 150 °C.
The maximum operating current of the thermal switch
is 0.5 A at 500 VAC and cos φ 0.6. The switch must
be able to break a coil in the supply circuit.
Pumps with sensor
Pumps with sensor have either a thermal switch and
a Pt1000 sensor or a PTC thermistor in the windings,
depending on the installation site.
Through the pump controller safety circuit, the
thermal switch or the thermistor stops the pump by
breaking the circuit in case of overtemperature
(approximately 150 °C). The thermal switch or the
thermistor recloses the circuit after cooling.
The maximum operating current of both the Pt1000
and the thermistor is 1 mA at 24 VDC.
Measure the motor winding resistance to find out
whether the pump is fitted with a thermal switch or a
PTC thermistor. See table below.
Without ca-
ble
Thermal
< 50 mΩ
switch
PTC ther-
> 100 mΩ
mistor
Non-explosion-proof pumps
When closing the circuit after cooling, the thermal
protection restarts the pump automatically through
the controller. Pumps with 4 kW and larger motors
sold in Australia or New Zealand are fitted with a PTC
thermistor.
With 10 m With 15 m
cable cable
< 320 mΩ < 390 mΩ
> 370 mΩ > 440 mΩ
Explosion-proof pumps
The thermal protection of explosion-proof
pumps must not restart the pump automat-
ically. This ensures protection against
overtemperature in potentially explosive
environments. In pumps with sensor, this
can be done by removing the short circuit
between terminals R1 and R2 in the IO
113.
See electrical data in the IO 113 installation and
operating instructions.
Do not install the separate motor-protec-
tive circuit breaker or control box installed
in potentially explosive environments.
7.2.2 WIO sensor
The WIO sensor measures the water content in the
oil and converts the value into an analog current
signal. The two sensor conductors are for power
supply as well as for carrying the signal to the IO 113.
The sensor measures the water content from 0 to 20
%. It also sends a signal if the water content is
outside the normal range (warning), or if there is air in
the oil chamber (alarm).
The IO 113 module must be configured to
stop explosion-proof pumps in case the
WIO sensor sends an alarm signal.
The pump must not restart automatically.
The sensor is fitted in a stainless steel tube for
mechanical protection.
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