Positioning The Pressure Sensor; Precharge Pressure Setting - Grundfos CU 321 Installation And Operating Instructions

1.5 Positioning the pressure sensor

Pressure losses often cause inconvenience to
the user.
The CU 321 keeps the pressure constant in the
place where the pressure sensor is positioned,
see fig. 5.
CU 321
Pressure sensor
Fig. 5 Pressure sensor position
In fig. 5, tap 1 is placed close to the pressure sensor.
Therefore, the pressure will be kept nearly constant
at tap 1, as the friction loss is small. At the shower
and tap 2, the friction loss is greater. This depends
on the piping.
It is recommended that the pressure sensor be
positioned as close to the places of consumption
as possible.
8
Shower
Tap 1
Tap 2

1.6 Precharge pressure setting

The CU 321 is designed to work with a 4 gal.
(minimum) diaphragm tank.
The precharge pressure of the diaphragm tank must
be set to 70% of the pressure setting in order to use
the tank to the limit of its capacity. This is especially
important when the tank volume is limited to 4 gal.
Use the values in the following table. Precharge
pressure is measured with 0 psi in the pipeline:
Setting [psi] Precharge pressure [psi]
40
45
50
55
60
65
70
75
80
85
90
95
100
28
31
35
38
42
45
49
52
56
59
63
66
70