Precharge Pressure Setting; Pressure Relief Valve; Product Introduction; Product Description - Grundfos CU 301 Notice D'installation Et De Fonctionnement

3.4 Precharge pressure setting

CU 301 is designed to work with a 2 gal diaphragm
tank.
Set the precharge pressure of the diaphragm tank to
70 % of the pressure setting in order to use the tank
to the limit of its capacity. This is of course especially
important when the tank volume is limited to 2 gal.
Use the values in the following table.
Precharge pressure is measured with 0 psi in the
pipeline:
Setting
[psi]
40
50
60
70
80
90
100
If the precharge pressure is higher than the pressure
setting, the system is not able to control the
pressure.

3.5 Pressure relief valve

In order to provide protection against the risk of a
overpressurization, install a pressure relief valve
down stream of the well head. The setpoint of the
pressure relief valve must be at least 30 psi above
the pressure setting. See section
product.
We recommend that the relief valve is plumbed to an
appropriate drainage point.
8
Precharge pressure
[psi]
28
35
42
49
56
63
70
6. Setting the

4. Product introduction

4.1 Product description

The system maintains a constant pressure within the
maximum pump performance despite varying water
consumption.
Figure 5 shows an example of an installation with
constant-pressure control.
1
4
Fig. 5
Pos. Description
1 CU 301
2 Diaphragm tank (2 gal)
3 Pressure sensor
4 SQE pump
The pressure is registered by the pressure sensor,
which transmits a 4-20 mA signal to CU 301. CU 301
adjusts the pump performance accordingly by
changing the pump speed.
Mains borne signalling (power line
communication)
CU 301 and the pump communicate via the power
cable.
This communication principle is called 'mains borne
signalling (power line communication). Using this
principle means that no additional cables to the
pump are required.
The data communication is effected by a high-
frequency signal transmitted to the power cable. The
data is led into the electronics unit by signal coils
incorporated in the motor and CU 301 respectively.
2
3