For suitable means of water softening, see the Vitoset pricelist.
Expansion vessels
In accordance with EN 12828, water heating systems must be equip-
ped with a diaphragm expansion vessel (DEV).
An expansion vessel (12 litre capacity) is integrated into the Vitola-
dens 333-F.
A mounting frame with expansion vessel (18 litre capacity) and valves
is available as an accessory for the Vitoladens 300-W.
Its design matches that of the boiler and it is fitted behind the Vitola-
dens 300-W.
The size of the expansion vessel is subject to the heating system
specification and should be checked in each case (see page 55).
If the expansion vessel available as an accessory is insufficient, install
a suitably sized expansion vessel on site.
If the Vitoladens 300-W is installed with a self-supporting mounting
frame, the on-site expansion vessel may also be fitted to that mounting
frame.
Mounting frame with expansion vessel
Testing the expansion vessel inside the mounting frame
Expansion vessel in the mounting frame (accessories)
Pre-charge pressure
0.75 bar
Blow-off pressure
2.5 bar
Capacity
18 litres
When making the hydraulic connections, check that the size of the
expansion vessel matches the system conditions.
The following steps will enable you to make a rough check.
V
DEV
= f ((V
A
+ V
K
) A
f
+ 2.4)
V
DEV
= Volume of the expansion vessel
f
= Expansion factor (= 2 for expansion vessel)
V
A
= System volume
V
K
= Boiler water volume
A
f
= Heating water expansion factor
Example:
System:
■ Vitoladens 333-F
■ Boiler water volume 12 litres
■ Rated output 23.5 kW
■ Panel radiators
■ System volume approx. 120 litres
■ Heating system 70/50 ºC
Calculation:
Heating system 70/50 ºC: average water temperature approx. 60 ºC
A
f
= 0.0171
V
DEV
= 2 · ((120 + 12)· 0.0171 + 2.4)
V
DEV
= 9.3 litres
Result:
The integral expansion vessel (12 litre capacity) is sufficiently
large for this system.
Note
If the expansion vessel is insufficient, connect an adequately sized
expansion vessel to the heating flow of the Vitoladens.
Calculating the heating system volume (approximate values)
A
B
C
D
5
10
20
30
40
50
0
130
200
400
600
800
1000
Output in kW
System volume in litres
A
Convector heaters
B
Panel radiators
C
Radiators
D
Underfloor heating
Calculating the expansion factor A
f
Average water temp. [ºC]
Expansion factor A
f
50
0.0121
60
0.0171
70
0.0228
Low loss header
Application
Design rules for system hydraulics:
■ When balancing the low loss header, adjust the flow rate on the
boiler side to approx. 10 to 30 % lower than the flow rate on the
system side (reducing the return temperature).
■ The low loss header should be sized for the max. volume flow that
may occur in the overall system.
The low loss header separates the heat source (boiler circuit) from the
downstream heating circuits.
Install a low loss header if the max. flow rate in that case exceeds
1390 l/h.
For installation diagrams, see the corresponding sample application.
Subject to the individual system type, the boiler circuit and the heating
circuit are sized independently of each other.
Design information
(cont.)
VITOLADENS 300-W
/
VITOLADENS 333-F
VIESMANN
55
5822 425 GB
5
