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English (US)
8.1 Thermal protection of the stator
Thermal switches
• Standard KPL and KWM 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, e.g.
302 °F (150 °C), the switch will open the circuit and stop the
motor.
• When the windings have cooled to normal temperature, the
switch will close the circuit and the motor can be restarted.
The thermal switches are connected in series in a separate circuit
in the power or control cable. See section
The thermal switches must be connected to the motor protection
safety circuit in the control cabinet
Technical data for thermal switches:
• Two conductors
• operating voltage of switch: 12-250 VAC.
• maximum switching current: 2.5 A at cos
φ
= 1.
Thermistors
Standard KPL and KWM pumps incorporate one Pt100 thermistor
for analog measurement of stator temperature.
The thermistor is connected in a separate circuit in the power or
control cable. See section
The thermistor must be connected to a Pt100 relay in the control
cabinet, preferably Grundfos IO 113.
The resistance of the Pt100 thermistor varies with the
temperature, and has approximately the following values:
• 100
Ω
at 32 °F (0 °C).
• 138.5
Ω
at 212 °F (100 °C).
• approx. 107.8
Ω
at indoor temperature (68 °F (20 °C)).
8.2 Moisture switches
The KPL and KWM pumps have two moisture switches (one
positioned in the terminal box and 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
.
They must also be connected to the safety circuit of the separate
pump controller.
Technical data of moisture switches:
• Two conductors
• operating voltage of switch: 12-250 VAC.
• maximum switching current: 2.5 A at cos
φ
= 1.
8.3 Thermal protection of the bearings
Standard KPL and KWM pumps incorporate one Pt100 thermistor
for analog measurement of the temperature of the lower and the
upper bearing.
The thermistor is connected in a separate circuit in the power or
control cable. See section
.
The thermistor must be connected to a Pt100 relay in the control
cabinet, preferably Grundfos SM-113 or IO-113.
The resistance of the Pt100 thermistor sensor varies with the
temperature, and has approximately the following values:
• 100
Ω
at 32 °F (0 °C).
• 138.5
Ω
at 212 °F (100 °C).
• approx. 107.8
Ω
at indoor temperature.
The following temperature limits are defined:
• 194 °F (90 °C): alarm for bearing temperature.
• 266 °F (130 °C): pump stop caused by high bearing
temperature.
Checks to be made after installation of the pump:
1. Using a multimeter, check whether the resistance at room
temperature (68 °F (20 °C)) is approx. 107.8
Ω
.
2. Using a multimeter, check whether the insulation between
circuit and stator housing is outside the measuring range (not
measurable).
3. Carry out similar measurements at the end of the power
supply cable.
During pump check, the Pt 100 sensor must be connected to a
recording device.
Caution
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.
Caution
Do not use a megohmmeter to test this alarm due
to the low resistance of the sensor circuits.
Caution
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.
Caution
Do not use a megohmmeter to test this alarm due
to the low resistance of the sensor circuit.
