Product Overview

System operation
The job of the by-pass valve is to maintain the pump operating
point as close as possible to its nominal value (point A on the graph
shown below). If the by-pass valve is not used, when the flow rate
in the circuit decreases due to partial closure of the two-way valves,
the head loss in the circuit increases, point B.
The by-pass valve, set to the nominal head value of the pump,
enables to limit the pressure increase, by-passing the flow rate ΔG.
This behaviour is guaranteed at any closing condition of the system
regulating valves. In fact, once the position of the valve control
knob has been established, the trigger pressure value is more or
less constant as the discharge flow rate varies (see hydraulic
characteristic diagrams).
A proper valve sizing must guarantee a sufficient flow rate by-pass
to keep the pump at its nominal operating point in all system
operating conditions, for example when the first thermostatic valves
are closed.
Flow rate G
Δp
Δp
NOMINAL
Pump curve
Δp constant
on the circuit
Circuit resistance curve
with regulating valves
partially open
Circuit resistance curve with
regulating valves fully open
A
B
ΔG
50% 100%
Operating principle
When the spring (1) compression is adjusted using the control knob (2), the force
balance acting on the obturator (3) changes, thus modifying the trigger pressure value
of the valve. The obturator opens, activating the by-pass circuit, only when it is subjected
to a differential pressure sufficient to generate a thrust greater than the thrust exerted
by the contrast spring. This allows the flow discharge through the outlet (4), limiting the
difference in pressure between the two points in the system where the valve is fitted.
1
2
3
4
5
Regulating valve
TOTAL LOAD PARTIAL LOAD
mH
2
O
1
2
3
4
5
6
mH
2
O
1
2
3
4
5
6
Setting
To regulate the valve, turn the knob to the required value on the
graduated scale: the values correspond to the differential pressure in
metres w.g. to open the by-pass.
To carry out rapid adjustment of the by-pass valve it is possible to use
the following practical method, which can be applied, for example, to
the system in an apartment fitted with thermostatic valves: the system
must be operating, the regulating valves must be fully open and the
by-pass valve must be set to the maximum value (a). Close approximately
the 30% of the thermostatic valve. Gradually open the valve using the
control knob. Use a thermometer, or simply your hand, to check that
the hot water is flowing into the by-pass circuit (b).
As soon as a rise
in the temperature is noted, open the thermostat valves again and
check that the hot water stops flowing into the by-pass (c). Lock the
knob in this position (d) with the fixing screw (5).
➪
➪
➪
➪
mH
2
O
1
2
3
4
5
6
mH
2
O
1
2
3
4
5
6
mH
2
O
1
2
3
4
5
6
mH
2
O
1
2
3
4
5
6
a) b)
c) d)