Expansion vessel
The table shows the maximum system
volume that the integral expansion
vessel can sustain under different
charge pressure conditions. If the sys-
tem volume exceeds that shown, an
additional expansion vessel must be
fitted and connected to the heating
system primary return pipe as close
as possible to the appliance. If an
extra vessel is required, ensure that
the total capacity of both vessels is
adequate.
Further details are available in the
current issues of BS 5449 and BS
6798.
Note
If the pressure gauge rises by 1.5 bar
when the appliance is at maximum
temperature with all radiators in circu-
lation an extra expansion vessel is
required.
Vessel charge and initial system
pressure
bar
0.5
1.0
1.5
psi
7.3
14.5
21.5
Total water content of system
using 8 litre capacity expansion
vessel supplied with appliance
litres
106
75
42
gallons
23
16.5
9
For systems having larger capa-
city, multiply the total system ca-
pacity in litres by the factor to
obtain the total minimum expan-
sion vessel capacity required
0.0833
0.11
0.16
Installation Requirements
(cont.)
26
Preparing for installation
58
62
670
GB
