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6.0 System Details
13
© Baxi Heating UK Ltd 2009
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. The Water Regulations recommendations for England
and Wales prohibits backflow from appliances into the
wholesome water supply due to thermal expansion.
However this type of instantaneous combination boiler,
with less than 15 litres of stored capacity, does not
require any backflow prevention device as any thermal
expansion is accommodated within the appliance.
It is possible in certain circumstances that other cold
water demands (e.g. washing machines, flushing of W.C.s)
may affect the DHW function of the boiler. In these
instances the fitting of a backflow prevention device and
expansion vessel is recommended.
4. Also if there is an existing check valve, loose jumpered
stop cock, water meter or water treatment device
already fitted to the wholesome water supply connected
to the boiler domestic hot water (DHW) inlet supply
then a suitable expansion device may be required.
5. 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
*See 6.8 for instances when
these items may be required