Technical information

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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.
4.11 Sealed water Systems
The installation must comply with the appropriate
requirements of the current issue of BS4814,
BS5449, BS6759, BS6798 and BS7074 Part 1
and 2.
See diagram 4.3 for a suggested layout.
4.12 Safety Valve
A safety valve must be fitted to a sealed
system.
It shall be preset, non-adjustable with a lift pressure
of 3 bar, incorporating seating of a resilient material,
a test device and a connection for drain.
The drain from the safety valve must be routed
outside the building, must not discharge above
an entrance or window or any type of public
access area, be clear of any electrical fittings and
positioned so that any discharge can be seen.
4.13 Expansion Vessel
A diaphragm type expansion vessel, conforming
to the current issue of BS4814 (see also BS7074
Part 1 and 2) must be connected at a point close
to the inlet side of the circulating pump, see the
diagrammatic layout, diagram 4.3 unless laid down
differently by the manufacturer.
The expansion vessel volume depends on the
total water system volume and the initial system
design pressure. For any system an accurate
calculation of vessel size is given in the current
issue of BS5449 and BS7074 Part 1.
Example: For an initial design pressure of 0.7
bar, the minimum total vessel volume required is
0.063 x Total System Volume.
NOTE: A higher initial design pressure requires
a larger volume expansion vessel.
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”.
The charge pressure must not be less than the
static head of the system, that is, the height of the
highest point of the system above the expansion
vessel.
4.14 Pressure Gauge
A pressure gauge with a set pointer and covering
at least 0 to 4 bar (0 to 60 lb/in2) shall be fitted
permanently to the system in a position where it
can be seen when filling the system.
4.15 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. It must be
suitable for working at a gauge pressure of 0.35
bar above the safety valve setting.
4.16 Water Makeup
Provision should be made for replacing water loss
from the system using a make up bottle mounted
in a position higher than the top point of the
system, connected through a non-return valve to
the return side of either the heating circuit or the
hot water cylinder.
Alternatively, provision for make up can be made
using a filling loop.