Glow-worm hxi and Gas Valve - Manual (Page 18)

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4 Water System
Diagram 4.3
12999
4.5 Bypass
A system bypass will be required fitted at least 1.5 metres away
from the boiler, refer to the current issue of the central heating
system specifications (CHeSS).
4.6 Water Treatment
In the case of an existing installation, it is ESSENTIAL that prior
to installing the new boiler the system is thoroughly flushed. For
optimum performance after installation of a new system, the
boiler and its associated central heating system should also be
flushed. Flushing should be carried out in accordance with
BS7593: 1992 using a cleanser such as Sentinel X300 or X400,
or Fernox Superfloc.
For long-term corrosion protection, after flushing, an inhibitor
suitable for stainless steel exchangers 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 and Fernox.
4.7 Open (Vented) Water System
The boiler must be supplied from an unrestricted water supply
taken from a feed and expansion cistern situated at a maximum
height of 27 metres (90ft) above the boiler.
The cold feed must be 15mm minimum size.
The vent must rise continuously and be unrestricted.
It is important that the relative positions of the pump, cold feed
and open vent are as shown in diagram 4.2.
4.8 Combined Feed and Vent
For combined feed and vent, a 22mm pipe must be fitted in
accordance with BS 5449.
4.9 Domestic Hot Water Cylinder
SINGLE FEED INDIRECT CYLINDERS ARE NOT SUITABLE
The domestic hot water cylinder must be of the double feed fully
indirect coil type.
4.10 Domestic Hot Water System - unvented
General - All domestic hot water circuits, connections, fittings
must be in accordance with the relevant standards and water
supply regulations.
For GB: Guidance G17 to G24 and recommendation R17 to
R24 of the Water Regulations Guide.
For IE: The current edition of I.S.813 "Domestic Gas Installations".
Where a storage system will not have a vent to atmosphere the
installation must comply with the building regulations and local
Water Company bylaws, see also the current issue of BS5546
and BS6700.
If fitting to an existing system the local authority should be
informed.