Installation and setting of overpressure by-pass valves (not included)
In case of fixed-speed circulation pump, the booster kit can be equipped with a differential overpressure valve, cod. 508141. The by-pass setting range is
0.2
÷
0.6 bar, and it should be adjusted slightly above the pressure drop value of the most disadvantaged circuit. The by-pass kit must be installed between the
unit and the users. The black knob must be located in correspondence of the return line (Fig. 4).
System installation
MULTIMIX-C
is available as a wall-mounted unit with insulation shell (‘I’ in product code) or as a recessed unit housed in a metal box (‘C’ in product code). Main
dimensions are reported in Fig. 1, for 2-way wall-mounted unit (Fig. 1a), 3-way wall-mounted unit (Fig. 1b), 2-way recessed unit (Fig. 1c) and 3-way recessed
unit (Fig. 1d), respectively. Instructions for the installation of each type of unit can be found in Fig. 11 and Fig. 12, respectively.
Connection to piping system
MULTIMIX-C
comes in several pre-assembled configurations. The only operations to perform are the connection to the boiler circuit and to the secondary
distribution circuits. Pay attention to the prescribed flow direction. Red colour indicates flow lines (from the boiler, in the separator/manifold; to the users, in
the distribution kits). Blue colour indicates the return lines (to the boiler, in the separator/manifold; from the users, in the distribution kits). While performing
the connections, make sure not to overstress the threads.
CConnection to the distribution circuits
To connect kits to distribution circuits, the following fitting types can be used: for multilayer pipes, press-fittings MP 5608 or screw-fittings RA 761N; for
polyethylene pipe, screw-fittings RP 731N.
Connection to the primary (boiler) circuit
To connect the ball valves pre-installed on the separator/manifold to the primary circuit, the following fittings can be used: for multilayer pipe, press-fittings
MP 5608 or screw-fittings RA 761N; for polyethylene pipe, screw-fittings RP 731N.
+
Important.
In case screw-fittings are used, respect the recommended torque: [20
÷
30] N
·
m for multilayer pipe; [30
÷
40] N
·
m for polyethylene
pipe.
Adjustment
Mixing unit: system adjustment
Secondary by-pass pre-setting
In the mixing unit, water flow temperature is adjusted by a mixing valve, which is controlled automatically by a dedicated actuator (thermostatic head or
servomotor). The system can be adjusted close to the design conditions by adjusting the secondary by-pass (B8 in Fig. 2). When opened by the correct number
of turns, the secondary by-pass exerts a pre-mixing function and increases the circulating flow rate, thus optimising the mixing valve operation. The correct
number of turns can be estimated as it follows:
1. Obtain the following design information (in maximum load conditions):
• Q
1
: hot water to mixing valve [m
3
/h]
• Q
2
: mixed water to distribution circuit [m
3
/h]
• Kv
v
: flow coefficient of the mixing valve ‘hot’ way [m
3
/h/bar
0.5
], when fully open (Fig. 9c)
2. Compute the necessary flow rate through the by-pass in the maximum load conditions, that is, when the mixing valve is fully open:
Q
b
=
Q
2
−
Q
1
[
m
3
/
h
]
3. Compute the pressure drop across the mixing valve ‘hot’ way. When the valve is fully open, this path is assumed in parallel to the secondary by-pass, so
the pressure drops across the two paths are the same:
∆
p
=
Q
1
Kv
v
2
[
bar
]
4. Compute the flow coefficient of the secondary by-pass:
Kv
b
=
Q
b
√
∆
p
m
3
/
h
bar
0
.
5
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