Electrical Connection; Motor Protection - Grundfos SRP Instrucciones De Instalación Y Funcionamiento

7. Electrical connection

The electrical connections must be carried out by a qualified elec-
trician in accordance with local regulations.
All national and local regulations relating to safety and accident
prevention must be observed.
Warning
Before making any electrical connections, make
sure that the fuses have been removed or the
mains switch has been switched to off. Make sure
that the power supply cannot be accidentally
switched on.
The supply voltage and frequency are marked on the pump
nameplate. Make sure that the pump is suitable for the power
supply available at the installation site.
The SRP pump is supplied complete with a power power cable of
30 ft (10 meters), 50 ft (15 meters), or 80 ft (25 meters) as
standard.
The motor is marked either with a Y (star) or a Δ (delta)on motor
nameplate. The right connection has to be made in the external
control panel, using conductors 1 to 6 of the power cable.
Figure 13 shows a schematic drawing of these star and delta
connections. See also section 7.5 Wiring diagrams.
Three-phase motors
W2 U2 V2
U1 V1 W1
L1 L2 L3
Fig. 13 Schematic drawing of delta and star connection
W2 U2 V2
U1 V1 W1
L1 L2 L3

7.1 Motor protection

The pumps are provided with the following type of motor
protection:
Standard SRP pumps incorporate three bimetallic thermal
switches (PTO = Protection Thermique á Ouverture). See fig. 16.
(PTC sensors are available on request).
Function of thermal switches (PTO)
The motor is protected against overheating by three thermal
switches (PTO) connected in series, one switch in each winding.
When the maximum winding temperature is reached, 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.
See notes in fig. 16, section 7.5 Wiring diagrams.
Thermal switches (F6)
• Two conductors (terminals 11 and 12).
• Maximum operating voltage of switch: 250 V.
Maximum switching current: 2.5 A at cos φ = 1.
• Cut-out temperature: 302 °F (150 °C).
Function of PTC sensors
Optional the motor can be protected against overheating by three
thermal sensors connected in series, one in each winding.
When overheated, the motor will stop. Automatic restarting is not
permitted in such cases. This requires a thermistor trigger unit
with a reconnection suppressor in the control circuit of the motor
contactor.
See wiring diagram in fig. 17, section 7.5 Wiring diagrams.
1, 2, 3: PTC sensors:
• Two conductors (terminals 31 and 32).
• Maximum voltage at the terminals: U
• Resistance between terminals 31 and 32:
- at room temperature R = 150 Ω to 750 Ω.
- at cut-out temperature 266 °F (130 °C) R ≥ 4000 Ω.
When the connection at terminals 31 and 32 is
tested, the test voltage must not exceed 2.5 V
Note Note
(AC/DC).
Use an ohmmeter for the test.
= 2.5 V (AC/DC).
max.
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