Glow-worm Flexicom hx - Manual (Page 14)

14
5 Water Systems - Sealed
5.12 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 5.4 for a suggested layout.
5.13 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.
5.14 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 5.4.
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 mini-
mum total vessel volume required is 0.063 x Total System
Volume.
NOTE: A higher initial design pressure requires a larger vol-
ume 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.
Diagram 5.4
14017
5.15 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.
5.16 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.