19
Combi 70 & Combi 90 Oil Boilers
d Automatic air vent, fitted to the top of the
boiler, ensures the boiler is vented.
e Filling loop. This must be isolated and
disconnected after filling the system.
3 Using the expansion vessel as supplied and an
initial system pressure (cold) of 0.8 bar, a heating
system volume of approximately 77 or 117 litres
can be used for the Combi 70 and 90 respectively.
For further guidance refer to BS 7074:1.
Refer to section 5.1 for further details of the
expansion vessel.
4 The system design pressure (cold) should be
between 0.5 and 1.0 bar. This pressure is
equivalent to the maximum static head (see Fig.
12) in bar + 0.3 (1 bar = 10.2 metres of water).
5 If thermostatic radiator valves are fitted to all
radiators, a system by-pass must be fitted.
6 Provision should be made to replace water lost
from the system. This may be done manually
(where allowed by the local Water Undertaking)
using the filling loop arrangement supplied with the
boiler.
7 Filling of the system must be carried out in a
manner approved by the local Water Undertaking.
Where allowed, the system may be filled via the
filling loop supplied (the loop arrangement
includes a double check valve assembly).
8 All fittings used in the system must be able to
withstand pressures up to 3 bar.
9 Radiator valves must comply with the requirements
of BS 2767(10):1972.
3 - GENERAL BOILER INFORMATION
10 One or more drain taps (to BS 2879) must be used
to allow the system to be completely drained.
To avoid the danger of dirt and foreign matter entering
the boiler the complete heating system should be
thoroughly flushed out - before the boiler is connected
and then again after the system has been heated and is
still hot. This is especially important where the boiler
is used on an old system.
For optimum performance after installation, this boiler
and its associated central heating system must be
flushed in accordance with the guidelines given in BS
7593:1992 'Treatment of water in domestic hot water
central heating systems'.
This must involve the use of a proprietary cleaner,
such as BetzDearborn's Sentinel X300 or X400, or
Fernox Superfloc. Full instructions are supplied with
the products, but for immediate information, please
contact BetzDearborn on 0151 4209563 or Fernox on
0179 9550811.
For Long term protection against corrosion and scale,
after flushing, it is recommended that an inhibitor such
as Betzdearborn's Sentinel X100 or Fernox MB01 or
Copal is dosed in accordance with the guidelines given
in BS 7593:1992.
Failure to implement the guidelines may invalidate the
warranty.
Fig. 12 - Sealed system
If thermostatic radiator valves are fitted, the
system must incorporate an adequate by-pass.
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