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6.0 System Details
13
© Baxi Heating UK Ltd 2007
6.8 Domestic Hot Water Circuit (Fig. 7)
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. 7
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 Reducer
Valve
Stop Tap
Fig. 7