Sealed Primary Systems; Gas Supply - Worcester 24CDi Installation And Servicing Instructions

7. Sealed Primary Systems

See Figs. 5, 6 and 6a
7.1 The system must comply with the requirements of BS 6798
and BS 5449.
7.2 The appliance must not be operated without the system
being full of water, properly vented and pressurised.
7.3 The pressure relief valve operates at 3 bar (45lb/in
discharge must be directed away from electrical components or
where it might be a hazard to the user.
7.4 The pressure gauge indicates the system pressure which
must be maintained.
7.5 The 10 litre expansion vessel is charged to 0.5 bar and is
suitable for a static head of 5 metres (17.5ft). The pressure can be
increased if the static head is greater than 5 metres (17.5ft).
7.6 With an initial system pressure of 0.5 bar, a system capacity
of about 72 litres can be accommodated. Refer to BS 7074 for
more information. The charge pressure can be increased but with
a decrease in system volume.
7.7 The appliance includes a system filling link.
7.8 Water loss must be replaced.
7.9 Repeated venting loses water from the system. It is essential
that this water is replaced and the system pressure maintained.
Refer to Section 13 Commissioning.
7.10 Connections to the mains water supply must not be made
without the authority of the local Water Company.
Fig. 5. Sealed primary water system.
Lockshield
valve
NOTE: A drain cock should be installed at
the lowest point of the heating circuit and
beneath the appliance.
Fig. 6. Filling Loop.
Filling Key
2
). The
Radiator
valve
Grey filling
knob
7.11 The pump is set at maximum and must not be adjusted.
7.12 Connections in the system must resist a pressure of up to
3bar.
7.13 Radiator valves must conform to BS2767:10.
7.14 Other valves used should conform to the requirements of
BS1010.
7.15 No special system inhibitor is needed.

8. Gas Supply

8.1 The boilers require a gas flow in m
24CDi
28CDi
35CDi II
Check that the supply system can accommodate this together
with any other appliances connected to it. Refer to Table 7.
8.2 A natural gas appliance must be connected to a governed
meter.
8.3 There must be a pressure of 20mbar (G20) or 37mbar (G31)
at the inlet to the appliance. This is equivalent to a pressure of
18.5 - 19.0mbar (G20) or 35 - 35.5mbar (G31) at the inlet
pressure tapping on the gas valve.
Automatic
air vent
Heating
return
Heating
flow
Fig. 6a. Filling Key inserted for filling.
8
3 /h of:
NG (G20) LPG (G31)
2.9 1.13
3.3 1.3
4.16 1.6
Mains cold
water
Expansion
vessel
Hot water out
British Standard
stop valve.
Fixed spindle type
Water main
Always remove key
after filling