En
gl
is
h (
G
B)
24
8.1.1 Thermal switches
•
Standard pumps incorporate three bimetallic
thermal switches built into the stator windings.
The thermal switches protect the motor against
overheating.
•
When the maximum winding temperature is
reached, for example 125 °C, the switch opens
the circuit and stops the motor.
•
When the windings have cooled to normal
temperature, the switch will close the circuit and
the motor can be restarted. Manual restarting is
necessary.
The thermal switches are connected in series in a
separate circuit in the power or control cables. See
section
The thermal switches must be connected to the
motor protection safety circuit in the control cabinet.
Technical data for the thermal switches:
•
two conductors
•
operating voltage of the switch: 12-250 VAC
•
maximum switching current: 2.5 A at cos
φ
= 1
8.1.2 Pt100 sensor
The sensor is connected in a separate circuit in the
power or control cables. See section
The sensor must be connected to a Pt100 relay in
the control cabinet, preferably a Grundfos SM 113 or
IO 113.
The resistance of the sensor varies with the
temperature. The table below show approximate
values.
8.1.3 Moisture switches
The pumps have two moisture switches:
•
one in the terminal box
•
one in the lower part of the stator housing.
Moisture switches are motor protection devices
protecting the motor from damage due to moisture.
The moisture switches are non-reversing and must
be replaced after they have been activated.
The moisture switches are connected to a separate
circuit via the control cable. See section
.
The moisture switches must also be connected to
the safety circuit of the separate pump controller.
Technical data of moisture switches:
•
two conductors
•
operating voltage of the switch: 12-250 VAC
•
maximum switching current: 2.5 A at cos
φ
= 1
The motor-protective circuit breaker of the
pump controller must include a circuit
which automatically disconnects the power
supply in case the protective circuit of the
pump is opened.
[
Ω
]
[°C]
100
0
138.5
100
107.8
20
Do not use a megohmmeter to test this
alarm due to the low resistance of the
sensor circuits.
The motor-protective circuit breaker of the
pump controller must include a circuit
which automatically disconnects the power
supply in case the protective circuit of the
pump is opened.
