14
Expansion vessel.
The following table gives the maximum system vol-
ume that the integral 7 l expansion vessel can sustain
under different temperature conditions. If the system
volume exceeds that shown, an additional expansion
vessel must be fitted and connected to the heating
system primary return pipe as close as possible to
the appliance. If an extra vessel is required, ensure
that the total capacity of both vessels is adequate. If
the pressure gauge indicates 2.2 bar or greater when
the appliance is at maximum temperature with all
radiators in circulation an extra expansion vessel is
required.
Pressure relief valve
A pressure relief valve set 3 bar (43.5psi) is fitted and
a discharge pipe is routed to the outside of the appli-
ance. This discharge pipe should be extended to ter-
minate safely away from the appliance to a point
where a discharge would not cause damage to per-
sons or property but would be detected. The pipe
should be able to withstand boiling water, be a mini-
mum of 15mm in diameter, and not include any
upward pipe runs or horizontal runs prone to freezing.
4.9 D.H.W
. SYSTEMS
- Check that mains supply pressure is within the pre-
scribed limits (refer to 'technical data' page 7) If nec-
essary, a pressure reducing valve should be fitted to
the mains supply before D.H.W. inlet connection.
- The DHW performance is summarised in the graph:
- The final 1000 mm (40 in) of the mains supply pipe
to the boiler must be copper.
- If the appliance is installed in an area where the
temporary hardness of the water supply is high, say
over 150 ppm, the fitting of an in line scale inhibitor
may be an advantage.
- Devices capable of preventing the flow of expan-
sion water: e.g. non return valves and/or loose -
jumpered stop cocks should not be fitted unless sep-
arate arrangements are made for expansion water.
- If a non-return valve is fitted in the incoming water
supply - e.g. in line with scale inhibitor then a D.H.W.
expansion vessel MUST be obtained and fitted.
- For specific information relating to fittings
(exAmPLe:. Shower, washing machines etc.) suitable
for connection in the D.H.W. circuit, consult the Local
Water Undertaking, however the following informa-
tion is given for guidance.
Domestic hot/cold water supply taps and mixing
taps - All equipment designed for use at mains water
pressure is suitable.
Showers - Any mains pressure shower is suitable,
but if the unit has a loose head which may become
immersed in bath water either an anti-syphonage
device must be fitted, or the length of the flexible
hose must be reduced so that it cannot fall closer
than 13 mm (1/2 in) to the top of the bath.
