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8
The system design should incorporate the connections
appropriate to one of these methods.
e) The following paragraphs outline the specifications of the
items fitted to the boiler.
2.9.1
Pump
The available head shown in fig. 5 is that in excess of the appli-
ance hydraulic resistance, i.e. that available for the system at
any given heating load up to the maximum output in C.H.
mode. Never reduce the pump speed below maximum as this
will reduce D.H.W. output. The pump speed is indicated on the
side of the pump speed selector switch (if fitted).
2.9.2
System volume (total water content)
The following Table gives the maximum system volume that
the integral expansion vessel can sustain under different
charge pressure conditions.
If the system volume exceeds that shown, an additional expan-
sion 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. Further details are available in the
current issues of BS5449 and BS6798.
NOTE: If the pressure gauge indicates 2.65 bar or greater
when the appliance is at maximum temperature with all
radiators in circulation an extra expansion vessel is
required.
2.9.3
Pressure gauge
A pressure gauge is mounted on the appliance facia panel.
2.9.4
Safety valve
A safety valve set at 3 bar (43.5 psi) is fitted to the appliance
and a discharge pipe is routed to outside of the appliance. This
discharge pipe should be extended to terminate safely away
from the appliance and where a discharge would not cause
damage to persons or property but would be detected. The
pipe should be able to withstand boiling water, be a minimum
of 15 mm in diameter, and installed with a continuous fall.
2.10
D.H.W. SYSTEMS
– Check that the mains supply pressure is within the pre-
scribed limits (
Table 4).
If necessary, a pressure reducing valve should be fitted to
the mains supply before the D.H.W. inlet connection.
– A maximum D.H.W. flow rate of: 10.3 l/m (2.3 gpm) for
“FORMAT 80 C”
, 13 l/m (2.9 gpm) for
“FORMAT 100 C”
and 14 l/m (3.1 gpm) for
“FORMAT 110 C”
is recom-
mended. Higher flow rates will not damage the appliance
but may lower the water temperature below an accept-
able level.
– If the appliance is installed in an area where the tempo-
rary hardness of the water supply is high, say over 150
ppm, the fitting of an in line scale inhibitor may be an
advantage. Consult the Local Water Undertaking if in
doubt.
– Devices capable of preventing the flow of expansion water:
e.g. non return valves and/or loose-jumpered stop cocks
should not be fitted unless separate arrangements are
made for expansion water.
– For specific information relating to fittings (eg. Showers,
washing machines etc.) suitable for connection in the
D.H.W. circuit, consult the Local Water Undertaking, how-
ever the following information is given for guidance.
2.10.1 Domestic hot/cold water supply
taps and mixing taps
All equipment designed for use at mains water pressure is
suitable.
2.10.2 Showers
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 temperature. Existing controls may
not be suitable, refer to the shower valve manufacturer.
2.10.3 Bidets
Providing that the appliance is of the over-rim flushing type, the
outlets are shrouded and it is impossible to attach a temporary
hand held spray, no anti syphonage device is necessary.
Vessel charge and initial system
pressure
Total water content of system
using 8 l (1.76 gal) capacity expan-
sion vessel supplied with appliance
For systems having a larger capaci-
ty multiply the total system capacity
in litres (gal) by the factor to obtain
the total minimum expansion vessel
capacity required litres (gal)
bar
psi
l
gal
0.5
7.3
96
21.1
.0833
1.5
21.8
51
11.2
.156
1.0
14.5
74
16.2
.109
TABLE 6
