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must be designated as a standby pump, i.e. at
maximum extraction, one pump is always decom-
missioned or on stand-by. To ensure that all the
pumps are used equally, the control unit cycles the
pumps continuously, i.e. the order of switching on
and the allocation of the base load/peak load or
standby pump functions change regularly.
The diaphragm pressure vessel (total content
approx. 8 litres) which can be installed as a retrofit
kit accessory option on systems with Helix EXCEL
pumps) performs a certain buffering function on
the pressure sensor and prevents oscillation of the
control system when switching the system on and
off. It also guarantees low water extraction (e.g.
for very small leaks) from the storage volume at
hand without switching on the base-load pump.
This reduces the switching frequency of the
pumps and stabilises the operating status of the
pressure boosting system.
CAUTION! Risk of damage!
To protect the mechanical seal or slide bearing,
do not allow the pumps to run dry. If the pumps
run dry they may develop leaks.
Various kits are offered as accessories for direct
connection to the public water mains as protec-
tion against low water level (WMS) (14) (Fig. 6a
and 6b). Each kit incorporates a built-in pressure
switch (22). This pressure switch monitors the
supply pressure and if the pressure is low it sends
0,37
1 pump
2 pumps
3 pumps
4 pumps
(*) Values for 50 Hz (fixed speed) with tolerance of +3 dB(A)
In the following overview, pumps of the standard
series MVIE Helix VE up to a maximum motor
1 pump
2 pumps
3 pumps
4 pumps
(**) Values for 60 Hz (variable speed) with tolerance of +3 dB(A)
Lpa = workplace-related emission level in dB(A);
LWA = Sound-pressure level in dB(A) indicated from Lpa = 80 dB(A)
36
0,55
0,75
56
57
58
59
60
61
61
62
63
62
63
64
1,1
2,2
63
67
66
70
68
72
69
73
a switching signal to the control device.
An installation point for this purpose is provided as
standard at the inlet manifold pipe.
In the case of an indirect connection (system sep-
aration through non-pressurised break tank), a
level-dependent signal transmitter must be pro-
vided and installed in the break tank as a dry-run-
ning protection device. If a Wilo break tank is
installed (as in Fig. 13a) a float switch is already
included in the scope of delivery (see Fig. 13b).
For existing onsite tanks, the Wilo range offers
various signal transmitters for retrofitting (e.g.
float switches WA65 or low water electrodes with
level relays).
WARNING! Health hazard!
Only materials that have no adverse effects on
the quality of the water may be used for drink-
ing water systems!
6.4 Noise
Pressure boosting systems are supplied with dif-
ferent types of pumps and a variable number of
pumps, as listed under point 5.1. No specific over-
all noise level can therefore be listed here for all
variants of pressure boosting systems.
In the following overview, pumps of the standard
series MVI/Helix V up to a maximum motor power
of 7.5 kW are taken into account without fre-
quency converters:
Nominal motor power (kW)
1,1
1,5
2,2
59
60
63
62
63
66
64
65
68
65
66
69
power of 7.5 kW are taken into account with fre-
quency converters:
Nominal motor power (kW)
4
72
75
77
78
(LWA=91 dB(A))
3
4
5,5
66
68
70
70
71
73
72
73
75
73
74
76
5,5
7,5
74
74
77
77
79
79
80
80
(LWA=91 dB(A))
WILO SE 04/2013
7,5
70
73
75
76
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