22
Sealed Systems
Figure 7-3: Expansion Vessel location
7
.2 System Models
All System models have the following
sealed system components factory
fitted:
• Diaphragm expansion vessel
complying with BS 4814,
p
re-charged at 1.0 bar. Refer to
Section 2.2.
• System pressure gauge, with an
operating range of 1 to 4 bar.
• Pressure relief safety valve
complying with BS 6759 and set to
operate at 2.5 bar.
• Automatic air vent, fitted to the flow
pipe of the boiler, ensures the boiler
is vented.
• Filling loop. This must be isolated
and disconnected after filling the
system.
Refer to Section 2.2 for system volumes
and BS 7074: for further guidance, and
for further details of the expansion
vessel.
The location of the expansion vessel is
shown by the large arrow in Figure 7-3.
The expansion vessel fitted, is supplied
with a charge pressure of 1.0 bar
(equivalent to a max. static head of 10.2
metres). The charge pressure must not
be less than the actual static head at
the point of connection.
Do not pressurise the vessel above
1.5 bar.
The air pressure in the vessel must
be checked annually.
The central heating system volume,
using the expansion vessel as supplied,
must not exceed the recommended
value. Refer to Section 2.2. If the system
volume is greater, an extra expansion
vessel (complying with
BS 4841) must be fitted as close as
possible to the central heating return
connection on the boiler. The charge
pressure of the extra vessel must be the
same as the vessel fitted in the boiler.
Refer to BS 7074:1 for further guidance.
The air charge pressure may be
checked using a tyre pressure gauge on
the expansion vessel Schraeder valve.
The vessel may be re-pressurised using
a suitable pump. When checking the air
pressure the water in the heating
system must be cold and the system
pressure reduced to zero.
!
CAUTION
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