Grundfos CU 301 Instrucciones De Instalación Y Operación página 10

If the pump speed reduces without any pressure
drop being registered, this indicates that no water
is consumed. The diaphragm tank is filled with
water and the pump stops.
2
1
10 s 10 s
Flow detection every 10 seconds during
operation
Pos. Description
1 Flow detection
2 Pressure
3 Time
If the pump goes into low flow
shutdown and it cannot reach the
boost pressure, it will time-out and stop
to prevent it from running with no flow.
System limits
Even though, CU 301 controls the pressure within
± 3 psi, bigger pressure variations may occur in
the system. If the consumption is suddenly
changed, for example if a tap is opened, the water
must start flowing before the pressure can be
made constant again. Such dynamic variations
depend on the pipes, but, typically, they will lie
between 7 and 14 psi
If the desired consumption is higher than the
quantity the pump is able to deliver at the desired
pressure, the pressure follows the pump curve as
illustrated in fig. Possible pressure variations
during constant-pressure
2
1
A
4
3
7
Possible pressure variations during constant-
pressure operation
10
3
operation.
5
6
8
Pos. Description
Stop
1
+ 7 psi
2 Pressure
Start
3
- 7 psi
4 Controlling ± 3 psi
5 Dynamic variations ± 7 psi
6 Flow
7 0.18
8 gpm
A Pressure set
4.2 System sizing
To ensure the correct function of the system, it is
important that the pump is sized properly.
During operation, CU 301 controls the pump
speed within the range from 3000 rpm to 10,700
rpm. See fig. Pump curves at 3000 rpm and
10,700 rpm.
We recommend that you follow the guidelines
below:
5
2
1
3
Pump curves at 3000 rpm and 10,700 rpm
Pos. Description
1 Maximum head at rated flow
2 Pump curve at 3000 rpm
3 Minimum head at no flow
4 Pump curve at 10,700 rpm
5 H [m]
Q
6
rated flow
7 Q [gpm]
4
6
7