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Pressure gauge and filling loop
Primary
The pressure gauge and the filling loop should
be fitted at the system filling point which it is
recommended should be adjacent to the
boiler.
There shall be no permanent connection to
the mains water supply for filling the system,
even through a non-return valve without
the approval of the Local Water Authority.
The approved filling loop supplied with the
appliance should be disconnected after
commissioning the system.
Pressure relief valve
Primary
The pressure relief valve must be fitted in the
boiler flow pipe adjacent to the boiler. There
must no isolating valves or any such devices
between the boiler and the pressure relief
valve. The pressure relief valve should be fitted
in a position where it is accessible for testing/
inspection.
The method of fitting should ensure that
discharge of water or steam cannot create a
hazard to persons in or about the premises or
damage to electrical components or wiring and
the point of discharge shall be clearly visible.
Expansion vessel
Primary
The expansion vessel is designed be sited on
top of the appliance and connected to the
15mm copper pipe provided at the top of the
appliance (see figure 2.3).
The expansion vessel must accommodate the
change in volume of system water when heated
from 10
o
C to 110
o
C (see BS 5449:1990 clause
16.2). When calculating the system water
content, the water content of the primary heat
exchanger (see table 2.1) must be included.
The expansion vessel requirements are shown
in table 3.1.
Note 1
After first filling the system to a pressure of 1.0
bar at mains supply temperature (typically 15
o
C
in summer), the total system (space heating and
hot water) should be heated to its maximum
temperature. If the primary pressure gauge
indicates 2.6 bar or higher, then an additional
expansion vessel may be required.
Note 2
If the system pressure required is more than 1.0
bar, then the expansion vessel charge pressure
should be adjusted to match the primary
system pressure and the expansion vessel size
recalculated accordingly.
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1.0 DESIGN
1.3 SYSTEM DETAILS
