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15
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 pressure gauge indicates the system pressure.
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 fl ow rate, the system can be fi tted
with a lockable balancing valve in the main fl ow or return pipes
shown as valve “A” in diagram 4.1. The fl ow rate through the
boiler must not be allowed to fall below that given in diagram
1.2.
4.4 Bypass
The boiler is fi tted 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 fl ow rate drop be-
low the fi gure specifi ed, 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 cur-
rent 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 Regula-
tions Advisory Service (WRAS) gives full details of the require-
ments.
In IE the requirements given in the current edition of I.S.813
“Domestic Gas Installations” and the current Building Regula-
tions must be followed.
4.5 Filling the Sealed System
NOTE: The water pressure at the boiler must be at least 1.2bar
to enable fi lling the boiler to a minimum pressure.
4.6 Water Treatment
In the case of an existing system, it is ESSENTIAL that prior to
installing the new boiler the system is thoroughly fl ushed. For
optimum performance after installation of a new system, the
boiler and its associated central heating system should also
be fl ushed. Flushing should be carried out in accordance with
BS7593: 1992 using a cleanser such as Sentinel X300 or X400,
Fernox Restorer or Salamander corrosion guard cleaner.
For long-term corrosion protection, after fl ushing, a suitable in-
hibitor should be used, refer to the current issue of BS 5449
and BS 7593 on the use of inhibitors in central heating systems.
Examples are Sentinel X100 Fernox Protector or Salamander
corrosion guard inhibitor.
Diagram 4.1
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