Owner manual

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 tted 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

ttings 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 tted permanently to the system

in a position where it can be seen when lling 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.