Low Loss Header - Viessmann Vitodens 300-W Technical Manual

Design information
– Vitodens 200-W up to 35 kW
– Vitodens 222-W
– Vitodens 300-W, 11 and 19 kW
■ For the Vitodens 300-W, 26 and 35 kW a mounting frame with
expansion vessel and valves is available as an accessory (see
page 50).
Determine the size of the expansion vessel to be installed in accord-
ance with EN 12828.
If the integral expansion vessel or that supplied as an accessory is
inadequate, install a suitably sized expansion vessel on site.

Low loss header

Application
Design rules for system hydraulics:
■ When balancing the low loss header, adjust the flow rate on the
equipment side to approx. 10 to 30 % below the flow rate on the
system side (reducing the return temperature).
■ The low loss header should be sized for the max. flow rate which
may occur in the overall system.
The low loss header separates the heat generator circuit (boiler cir-
cuit) from the downstream heating circuits.
Install a low loss header if the max. flow rate of an individual design
is greater than the corresponding value shown in the "Specification"
table.
For installation designs in conjunction with low loss headers, see
"System examples".
Heat generator circuit
The circulation pump in the Vitodens must be able to supply the
required water volume against the (mostly low) pressure drop of the
heat generator circuit; the pressure drop of the low loss header is
negligible. The pump diagrams serve to determine the correct resid-
ual head for the internal pipe diameters, subject to the water volume
circulating in the boiler circuit.
Heating circuit
The heating circuit pumps to be installed on site must be able to
deliver the water volume in the heating circuits against their pressure
drop. They must be sized accordingly.
Principle of operation
T1
6
V primary
T2
V Heating water volume in the boiler circuit (approx. 10 to
primary
30 % less than V
V Heating water volume, heating circuit
secondary
T Flow temperature, boiler circuit
1
T Return temperature, boiler circuit
2
T Flow temperature, heating circuit
3
T Return temperature, heating circuit
4
Q Amount of heat supplied by the boiler
primary
Q Amount of heat transferred by the heating circuit
secondary
VIESMANN
88
(cont.)
T3
V second.
T4
)
secondary
Note
When hydraulically connecting the diaphragm expansion vessel,
make sure that there is always a connection between the diaphragm
expansion vessel and the heat generator.
For example, when the thermostat valves are closed and if the
3-way diverter valve is set to "DHW".
V < V
primary secondary
T > T
1 3
≃ T
T
2 4
Q = Q
primary secondary
Note
Thermometers in the flow and return of the low loss header make
adjustments easier.
Low loss header in conjunction with Divicon
For further details, see the technical guide to the Vitodens 200-W, 45
to 150 kW.
Low loss header
– R ¾
– R 1
– R 1¼
Divicon heating circuit distributor
– R ¾
– R 1
– R 1¼
599
120 180 120
A
B
C
HV HR
HR Heating return
HV Heating flow
A Divicon heating circuit distributor
B Manifold
C Low loss header
Max. flow rate
in m 3 /h
4.5
4.5
7.5
1.0
1.5
2.5
VITODENS