Installation Manual
6.0 System Details
12
6.8 Domestic Hot Water Circuit (Fig. 6)
1. All DHW circuits, connections, fittings, etc.
should be fully in accordance with relevant
standards, the Water Supply (water fittings)
Regulations and the Water Bylaws (Scotland).
2. Your attention is drawn to:
Schedule 2, Section 6 of the Publication Water
Regulations Guide which relates to backflow
prevention.
3. A single check valve must be fitted as shown in
Fig. 6 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.
Boiler
Other Tap
Outlets
Expansion
Vessel
To Hot
Taps
Check
Valve
Pressure
Reducer Valve
Stop Tap
Fig. 6