Appendix
en
Installation and operating instructions Wilo-Rexa CUT GE
37
13
Appendix
13.1
Tightening torques
Rust-free screws A2/A4
Threaded
Tightening torque
Nm
kp m
ft·lb
M5
5.5
0.56
4
M6
7.5
0.76
5.5
M8
18.5
1.89
13.5
M10
37
3.77
27.5
M12
57
5.81
42
M16
135
13.77
100
M20
230
23.45
170
M24
285
29.06
210
M27
415
42.31
306
M30
565
57.61
417
Geomet-coated screws (strength 10.9) with Nord-Lock washer
Threaded
Tightening torque
Nm
kp m
ft·lb
M5
9.2
0.94
6.8
M6
15
1.53
11
M8
36.8
3.75
27.1
M10
73.6
7.51
54.3
M12
126.5
12.90
93.3
M16
155
15.81
114.3
M20
265
27.02
195.5
13.2
Operation with frequency con-
verter
The motor in series design (confirming to IEC 60034‑17) can be operated with a fre-
quency converter. Contact customer service if the rated voltage is over 415 V/50 Hz or
480 V/60 Hz. Because of the additional heating caused by harmonics, the rated power
of the motor must be around 10 % more than the power requirement of the pump. For
frequency converters with a low-harmonic output, it may be possible to reduce the
10 % power reserve. A reduction of the harmonic waves is achieved with output filters.
The frequency converter and filter must be compatible.
The configuration of the frequency converter depends on the rated motor current. Care
must be taken to ensure that the pump operates without jerking or vibration, especially
in the lower speed range. Otherwise, the mechanical seals can leak or be damaged. The
flow rate in the pipe must also be observed. If the flow rate is too low, the greater the
risk is of solids depositing in the pump and piping. A minimum flow rate of 0.7 m/s
(2.3 ft/s) with a pumping pressure of 0.4 bar (6 psi) is recommended.
It is important that the pump operates across the entire control range without vibra-
tions, resonance, oscillation or excessive noise. Increased motor noise caused by the
harmonics of the power supply is normal.
During parameterisation of the frequency converter, observe the setting of the quad-
ratic pump curve (U/f curve) for pumps and fans! The U/f curve ensures that the output
voltage at frequencies less than the rated frequency (50 Hz or 60 Hz) is adjusted to the
power requirement of the pump. Newer frequency converters feature an automatic
power optimisation function - this automation achieves the same effect. For the fre-
quency converter setting, refer to its installation and operating instructions.
Faults with the motor monitoring may occur on motors operated with a frequency con-
verter depending on the type used and installation conditions present. The following
measures can help to reduce or avoid these faults:
▪ Keeping within the limit values stated in IEC 60034‑25 for overvoltages and rise speed.
Output filters may need to be installed.
▪ Vary the pulse frequency of the frequency converter.
