14
5 Water Systems - Open Vented
Diagram 5.3
12999
5.7 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 5.2.
5.8 Combined Feed and Vent
For combined feed and vent, a 22mm pipe must be fitted in
accordance with BS 5449.
5.9 Safety Valve
A safety valve need not be fitted to an open-vented system.
5.10 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.
5.11 DHW. 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.
Diagram 5.2
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