Domestic Hot Water Circuit - Baxi 424 Combi 2 Installation And Service Manual

5 Before installation
Fig.29 Circuit plan
G
B
C
D
E
Combi 2
36
5.7.2
A
B
C
A
D
E
F
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F
All DHW circuits, connections, fittings, etc. should be fully in accordance
with relevant standards and water supply regulations.
PN-0000350
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 IS 813 Domestic Gas Installations.
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 WCs) may affect the DHW
function of the boiler. In these instances the fitting of a backflow prevention
device and expansion vessel is recommended.
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.

Domestic hot water circuit

Boiler
Expansion vessel
Check valve
Pressure reducer
Stop tap
To hot tap
Other tap outlets
Important
In instances where the mains water supply incorporates a non-
return backflow prevention device, or any other device that
includes one*, it is possible for a build-up of pressure to occur. This
may result in damage to the boiler and other appliances. To
prevent damage to the boiler it is strongly recommended that a
suitable mini expansion vessel is fitted on the mains water inlet
between the boiler and the non-return device.
*(The manufacturer of the device should be consulted if there is
any doubt regarding the presence of a non-return feature).
Even in circumstances where a non-return device is not fitted any
future modifications to the mains inlet (e.g. fitting of a water meter)
should be considered and an expansion vessel fitted. Main cannot
accept any responsibility for damage to the boiler if these
recommendations are not followed.