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15
GENERAL REQUIREMENTS
Expansion vessel
The 28 kW boiler incorporates a
10 litre expansion vessel which is
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 R.2.
Table R.2: Sizing of additional expansion vessel
Vessel Volume [L]
Initial system pressure (bar)
1.0
1.5
Pressure relief valve setting (bar)
3.0
Total water content of system
litres
25
50
100
125
150
175
200
225
250
275
300
325
350
375
400
425
450
475
500
2.7
5.4
10.9
13.6
16.3
19.1
21.8
24.5
27.2
30.0
32.7
35.7
38.1
40.9
43.6
46.3
49.0
51.8
54.5
3.9
7.8
15.6
19.5
23.4
27.3
31.2
35.1
39.0
42.9
46.8
50.7
54.6
58.5
62.4
66.3
70.2
74.1
78.0
For system volumes other than those given above,
multiply the system volume by the factor across
0.109
0.156
