Sealed Central Heating System; Sealed System - Grant Combi 70 V3 User's Installation Manual

5.12

Sealed central heating system

See Fig. 16
1 The boilers are only suitable for use with a sealed
system complying with the requirements of BS 5449.
The maximum temperature of the central heating
water is 85°C for the Combi V3 and Combi Max
and 80°C for the Vortex Combi models.
Design notes - when designing the system, the
pump head, expansion vessel size, radiator mean
temperature, etc. must all be taken into account.
2 The boilers are supplied with the following items
factory fitted:-
a 12 litre diaphragm expansion vessel complying
with BS 4814, pre-charged at 1.0 bar. A 14 litre
vessel is fitted in the Vortex Combi 36 model.
b System pressure gauge, with an operating range
of 1 to 4 bar.
c Pressure relief safety valve complying with
BS 6759 and set to operate at 2.5 bar. The discharge
pipe must be routed clear of the boiler to a drain,
in such a manner that it can be seen, but cannot
cause injury to persons or property.
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 Refer to Sections 4.1 or 4.2 for system volume and
BS 7074: for further guidance.
Refer to Section 6.8 for further details of the
expansion vessel.
If thermostatic radiator valves are fitted, the
system must incorporate an adequate by-pass.
5 - GENERAL BOILER INFORMATION
Fig. 16 - Sealed system
Combi V3, Combi Max and Vortex Combi models
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.
16) 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. The by-
pass must be an automatic type.
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.
10 One or more drain taps (to BS 2879) must be used
to allow the system to be completely drained.
11 The expansion vessel is connected via a flexible
hose to allow it to be moved to gain access to the
baffle cleaning cover. When replacing the vessel,
care should be taken to ensure that the flexible
connecting hose is not twisted.
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