Low Loss Header - Viessmann Vitodens 200 Technical Manual

3.4 Low loss header

3.4 Low loss header
Application
Design rules for system hydraulics:
H Generally install a low loss header
when cascading several Vitodens
boilers.
H When adjusting the low loss header
set the volume flow on the boiler side
approx. 10 to 30 % lower than the
volume flow on the system side
(lowering the return temperature).
H Size the low loss header to the max.
volume flow which occurs in the total
system.
The low loss header decouples the heat
generator circuit (boiler circuit) and the
downstream heating circuits.
Install a low loss header if the max.
volume flow of an individual design is
greater than the values shown in the
following table.
3
Principle of operation
T1
V
V
primary
T2
118
For installation diagrams, see the
corresponding application example.
Boiler
Vitodens 200
Vitodens 300,
4.2 kW 13.0 kW
Vitodens 300,
6.6 kW 26.0 kW
Vitodens 300,
8.7 kW 35.0 kW
Vitodens 300,
12.2 kW 49.0 kW
Vitodens 300,
16.6 kW 66.0 kW
Vitodens 333
Vitodens 343
Boiler circuit and heating circuit
are sized independently of each other,
subject to the individual system type.
V
T3
primary
V
secondary
secondary T
1
T
2
T4
T
3
T
4
Q
primary
Q
secondary
Max. volume flow
l/h
1 400
1 000
1 400
1 600
3 500
3 500
1 400
1 000
Heating water volume heat
generator circuit
(approx. 10 30 % smaller than
V )
secondary
Heating water volume
heating circuit
Flow water temperature
boiler circuit
Return water temperature
boiler circuit
Flow temperature
heating circuit
Return temperature
heating circuit
Heat volume supplied by the
heat generator
Heat dissipated by the
heating circuit
Boiler circuit
The circulation pump in the Vitodens
must be able to supply the required water
volume against the mostly low
pressure drop of the boiler circuit; the
pressure drop of the low loss header is
negligible. Subject to the water volume
circulating in the boiler circuit, the
respective residual head may be
determined for the sizing of the internal
pipes using the pump diagrams;
alternatively the variable speed pump for
the Vitodens 300 and 333 can be adjusted
accordingly.
Heating circuit
The central heating pumps to be installed
on-site must be able to transfer the water
volume in the heating circuits against
their pressure drop; size the pumps
accordingly.
V < V
primary secondary
T > T
1 3
T ]T
2 4
Q = Q
primary secondary
Note
Suitable thermometers in the flow and
return of the low loss header make
adjustments easier.
VITODENS