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6.0 SYSTEM DETAILS
12
Publication No. 5111811
6.8 Domestic Hot Water Circuit
1. All DHW circuits, connections, fittings, etc. should
be fully in accordance with relevant standards and
water supply regulations.
2. Your attention is drawn to:
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”.
3. A single check valve must be fitted as shown in
Fig. 10 to prevent backflow to the supply pipe and to
ensure the efficient operation of the expansion vessel
which is required to accommodate the thermal
expansion of the water.
4. When the domestic water system includes any
device which prevents water expanding back
towards the supply (check valve, loose jumpered
stopcock, water meter, water treatment device) then
an expansion vessel must be fitted (eg. Zilmet 160ml,
R
1
/
2
15bar).
5. If the hot water expansion is not provided for, then
high pressures can develop which may result in
damage to fittings and devices on the system.
6. The boiler’s maximum working mains pressure is 8
bar, therefore all pipework, connections, fittings, etc.
should be suitable for pressures in excess of 8 bar. A
pressure reducing valve must be fitted for pressures
in excess of 8 bar. The manufacturer of any outlet
fittings, such as a shower valve, may require a lower
maximum pressure. The pressure reduction must
take account of all fittings connected to the DHW
system.
6.9 Showers
1. If a shower control is supplied from the appliance
it should be of the thermostatic or pressure balanced
type. Thermostatic type shower valves provide the
best comfort and guard against water at too high a
temperature. Existing controls may not be suitable -
refer to the shower valve manufacturer.
6.10 Hard Water Areas
1. If the area of the installation is recognised as a
HARD WATER AREA then a suitable device should
be fitted to treat the mains water supply to the boiler.
Contact your Water Distribution Company for advice
on suitable devices.
Boiler
Other Tap
Outlets
Expansion
Vessel
To Hot
Taps
Check
Valve
Pressure
Reducing Valve
Stop Tap
Fig. 10