11
221954D
3.8 Inhibitor
Attention is drawn to the current issue of BS5449 and BS7593
on the use of inhibitors in central heating systems.
If an inhibitor is to be used, contact a manufacturer or
Glow-worm, for their recommendations as to the best product
to use.
When installing in an existing system take special care to drain
the entire system, including the radiators, then thoroughly
cleaning out before installing the boiler whether or not adding an
inhibitor.
3.9 Sealed Water Systems
The installation should comply with the appropriate requirements
of the current issue of BS4814, BS5449, BS6759, BS6798 and
BS7074 Part 1 and 2.
3.10 Safety Valve
A safety valve must be fitted to a sealed water system.
It shall be preset, nonadjustable with a lift pressure of 3bar,
incorporating seating of resilient material, a test device and a
connection for drain.
The drain from the safety valve must be routed clear of any
electrical fittings and positioned so that any discharge can be
seen.
3.11 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, unless laid down differently by the manufacturer.
The expansion vessel volume depends upon the total water
system volume and the initial system design pressure. For any
system an accurate calculation of the vessel size is given in the
current issue of BS7074 Part 1.
Example. For an initial system design pressure of 0.7bar the
minimum total vessel volume required is 0.063xTotal 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.
The water content of the boiler is given in Data Table 1.
3.12 Pressure Gauge
A pressure gauge with a set pointer and covering at least the
range of 0 to 4bar (0 to 60lb/in
2
) shall be permanently fitted to
the system in a position where it can be seen when filling the
system.
3.13 Domestic Hot Water Cylinder
SINGLE FEED INDIRECT CYLINDERS ARE NOT SUITABLE.
The domestic hot water cylinder must be if the indirect coil type.
It must be suitable for working at a gauge pressure of 0.35bar
above the safety valve setting.
3 Water Systems
Diagram 3.2
28mm
PIPE
FLOW
RETURN
4273
1metre Min.
27 metres
Max.
INDIRECT
CYLINDER
ALTERNATIVE
SYSTEM
CONTROL
VALVES
HEATING
SYSTEM
PUMP
FULLY PUMPED CIRCULATION
BYPASS (DIAGRAMMATIC)
BYPASS 28mm
MIN WITH
LOCKSHIELD
VALVE
22mm VENT & 15mm COLD FEED
TO BE FITTED IN ACCORDANCE
WITH BS 5449
6459
3.14 Domestic Hot Water System - Unvented
Where a storage system will not have a vent to atmosphere the
installation must comply with Building Regulations and the
Local Water Company Byelaws, see also the current issue of
BS6700.
If fitting into an existing system, the local authority must also be
advised.
3.15 Filling a Sealed Water System
Provision for filling the system at low level must be made.
The installation should comply with the appropriate requirements
of the current issue of BS 5449.
3.16 Water Make-up
Provision must be made for replacing water lost from the
system. A make up vessel mounted above the highest point of
the system and connected through a non-return valve to the
system on the return side of either the hot water cylinder or
heating system.
Alternatively provision for make up can be made by a filling loop.