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4 Heating System
4.1 General
The boiler is for use only with sealed central heating systems.
The safety valve is an integral part of the boiler and it cannot
be adjusted.
The digital readout on the controls fascia indicates the system
pressure when there is no demand.
The circulation pump is integral with the boiler.
4.2 Expansion Vessel
The boiler has an integral expansion vessel with a capacity of
8 litres (1.76 gallons), with a charge pressure of 0.5bar.
NOTE: The expansion vessel volume depends on the total
water system volume and the initial system design pressure.
Guidance on vessel sizing is also given in the current issue of
BS5449 and BS7074 Part 1, for IE refer to the current edition
of I.S.813 “Domestic Gas Installations”.
4.3 Flow Rate
If it is necessary to alter the flow rate, the system can be
fitted with a lockable balancing valve in the main flow or
return pipes shown as valve “A” in diagram 4.1. The flow rate
through the boiler must not be allowed to fall below that given
in diagram 1.2.
4.4 Bypass
The boiler is fitted with an automatic bypass.
Diagram 4.2 shows the pump head remaining for the heating
system depending on the bypass setting and the speed
setting of the pump, see section 11 Commisioning.
Ensure that under no circumstances does the flow rate drop
below the figure specified, refer to diagram 1.2 and section
11.6.
The installation of the boiler must comply with the
requirements of the current issue of BS6798, in Ireland,
refer also to the current edition of I.S.813 “Domestic Gas
Installations”.
In GB it is necessary to comply with the Water Supply (Water
Fittings) Regulations 1999 (for Scotland, the Water Byelaws
2000, Scotland).
To comply with the Water regulations your attention is drawn
to: The Water Regulations guide published by the Water
Regulations Advisory Service (WRAS) gives full details of the
requirements.
In IE the requirements given in the current edition of I.S.813
“Domestic Gas Installations” and the current Building
Regulations must be followed.
4.5 Filling the Sealed System
NOTE: The water pressure at the boiler must be at least
1.2bar to enable filling the boiler to a minimum pressure. The
boiler is supplied with a filling device, see diagrams 4.1 and
4.3.
This filling device is designed to enable the filling and
pressurisation of the system in the event of loss of pressure.
Diagram 4.1
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