addition, to circulate air in the room,
air vents must be made on the outside
walls for which the surface area must
never be less than 3,000 cm
2
and
5,000 cm
2
for gas with a density grea-
ter than 0.8.
2.2
CONNECTING UP SYSTEM
Before proceeding to connect up the
boiler, you are recommended to make
the water circulating in the piping in
order to eliminate any foreign bodies
that might be detrimental to the ope-
rating efficiency of the appliance.
The unit must be connected up with
rigid pipe fittings which will not subject
it to stress of any kind.
The connections should be easy to
disconnect using pipe unions with
orientable connections.
You are recommended to install suita-
ble shutoff valves on the system flow
and return pipes.
In order to achieve a good water
distribution inside the cast-iron body,
the system flow and return pipes
should be connected to the same side
of the boiler.
The boiler comes supplied standard
with the attachments on the right-hand
side, with the possibility of them being
transferred to the left-hand side.
In that case, move the water distribu-
tor, located on the return header, and
the thermostat bulbs located in the
sheathe, to the same side.
The thermal jump between the system
flow and return pipes should not
exceed 20°C.
For this purpose, it is advisable to
install a mixer valve with correspon-
ding anti-condensation pump.
CAUTION:
The system circulation pump or
pumps must go into action at the
time of boiler ignition.
For this purpose, you are recommen-
ded to use an automatic system of
precedence.
The gas connection must be made
using
seamless
steel
pipe
(Mannesmann type), galvanized and
with threaded joints provided with
gaskets, excluding three-piece connec-
tions, except for initial and end con-
nections.
Where the piping has to pass through
walls, a suitable insulating sleeve must
be provided.
When sizing gas piping, from the
meter to the boiler, take into account
both the volume flow rates (consump-
tion) in m
3
/h and the relative density of
the gas in question.
The sections of the piping making up
the system must be such as to gua-
rantee a supply of gas sufficient to
cover the maximum demand, limiting
pressure loss between the gas meter
and any apparatus being used to not
greater than:
–1.0 mbar for family II gases (natural
gas);
–2.0 mbar for family III gases (butane
or propane).
An adhesive data plate is sticked inside
the front panel; it contains all the tech-
nical data identifying the boiler and the
type of gas for which the boiler is
arranged.
2.3
CHARACTERISTICS
OF FEEDWATER
It is absolutely essential that the
water used for the central heating
system should be treated in the fol-
lowing cases:
–Very extensive systems (with high
contents of feedwater).
–Frequent addition of makeup water
into the system.
–Should it be necessary to empty the
system either partially or totally.
2.3.1 Filter on the gas pipe
The gas valve is supplied ex factory
with an inlet filter, which, however, is
not adequate to entrap all the impuri-
ties in the gas or in gas main pipes.
To prevent malfunctioning of the valve,
or in certain cases even to cut out the
safety device with which the valve is
equipped, install an adequate filter on
the gas pipe.
2.4
SYSTEM FILLING
Filling must be done slowly so as to
allow any air bubbles to be bled off
through the air vents provided on the
heating system.
The pressure of cold charging of the
system, and the pressure of pre-
pressurization of the expansion ves-
sel, must correspond, or in any case
must not be less than, the height of
the static column of the system (e.g.,
for a static column of 5 m, the pre-
pressurization pressure of the
expansion vessel and the charging
pressure must correspond to at
least 0.5 bar).
2.5
CONNECTING UP FLUE
The flue for the atmospherical expul-
sion of the combustion products from
natural draught appliances must meet
the following requirements:
–Be gas-tight to the combustion pro-
ducts, waterproof and thermally
insulated.
–Be built of materials suitable for
keep resisting to normal mechanical
stresses, heat, and the action of
combustion products and their pos-
sible condensates.
–Follow a vertical path and not pre-
sent any throttling throughout its
entire length.
–Be adequately insulated to prevent
phenomena of condensation or
smokes cooling, in particular if loca-
ted outside the building or in unhea-
ted ambiences.
–Be set at an adequate distance
from combustible or easily inflam-
mable material by means of an air
gap or suitable insulating material.
–Have beneath the mouth of the first
smoke duct a chamber for collecting
solid material and any condensate;
the height of the chamber must be
at least 500 mm.
Access to the chamber must be
guaranteed by means of an opening
provided with an air-tight metal door.
–Have a circular, square, or rectangu-
lar internal cross section; in the
case of square or rectangular sec-
tions, the corners must be rounded
off with a radius of not less than 20
mm. However, hydraulically equiva-
lent cross sections are allowed.
– Be equipped with a chimney-pot at
the top, which must be outside the
so-called back-flow zone, so as to pre-
vent the formation of back-flow, which
prevents free discharge of the pro-
ducts of combustion into the atmo-
sphere. Therefore, conform to the
minimum heights indicated in fig. 4.
– Be devoid of mechanical means of
suction located at the top of the pipe.
–No overpressure should be present
in a chimney that passes within or
close up to inhabited rooms.
2.5.1
Sizing of flue
The correct sizing of the flue is an
essential condition for efficient boiler
operation. The main factors to be
taken into consideration for calcula-
ting the section are the heat input of
the boiler, the type of fuel, the percen-
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