12
Safety valve setting (bar)
3.0
Initial system pressure (bar)
1.0
1.5
Total water content of system
VESSEL VOLUME (L)
litres
25
2.7
3.9
50
5.4
7.8
100
10.9
15.6
125
13.6
19.5
150
16.3
23.4
175
19.1
27.3
200
21.8
31.2
225
24.5
35.1
250
27.2
39.0
275
30.0
42.9
300
32.7
46.8
325
35.7
50.7
350
38.1
54.6
375
40.9
58.5
400
43.6
62.4
425
46.3
66.3
450
49.0
70.2
475
51.8
74.1
500
54.5
78.0
For system volumes other than
those given above, multiply
0.109
0.156
the system volume by the factor
across
13,3
400
ft
mbar
10
300
6,7
200
3,3
100
0
0
200
400
600
800 1000 1200 1400 1600
l/h
Q
fig. 8
GW 402/2
3.7.5 Expansion vessel
An expansion vessel is incorporated
into the boiler suitable for a sealed
heating system with a maximum water
content of 100 litres.
If the nominal capacity of the built in
expansion vessel is not sufficient for
the heating system (for instance in
case of modernisation of old open
systems) an additional expansion
vessel can be installed external to the
boiler. It should be fitted in the return
pipe as close as possible to the boiler
in accordance with BS 5449: Part 1.
Guidance on the sizing of an
additional expansion vessel is given in
Table 2.
3.7.6 Circulating pump
The circulating pump is included in the
boiler. The pump head available for
the heating system is shown in fig. 8.
3.7.7 System by-pass
An automatic system by-pass is
included within the boiler. The boiler
is suitable for use in systems with
thermostatic radiator valves and no
additional by-pass is required.
3.7.8 Venting
The boiler is fitted with an automatic
air vent. Additional provision should
be made to enable the heating system
to be vented during filling and
commissioning either by automatic air
vents or manually.
3.7.9 DHW expansion vessel
accessory
A DHW expansion vessel kit (Art. No.
8070) is available as an optional
accessory from Vaillant Ltd. This
expansion vessel kit should be fitted
to the boiler whenever either a stop
valve of the loose jumper type or a
non return valve are present in the
cold water mains supply to the boiler
(fig. 9).
Table 2: Sizing of Additional Expansion Vessel
D.H.W. expansion
vessel fitted to the boiler
Non return
valve
Stop valve
Mains water
supply
fig. 9
GW 494/1
