Astra G-18 MS Manuale di installazione e sfruttamento - Pagina 5

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the heating system, it is necessary to install a four-way mixing valve between the boiler

and the heating system. Water temperature supplied from the boiler during exploitation

should be no less than 70°C.

WARNING! In order to guarantee a natural water circulation in the boiler, the pipeline

between the boiler and the four-way mixing valve (boiler – four-way mixing valve – boiler) should be of

the same diameter and meet the diameter of the boiler connection branches (see fig. 4, I - boiler ring).

Four-way mixing valve should be installed above the boiler.

The boiler will operate in the most effective and economic way, if a circulating pump is

installed in the system. It should be installed behind the water supplied by the four-way

mixing valve in the pipe. This guarantees a constant water flow in the heating system.

The boiler may also operate in a natural circulation (gravitational, without a pump)

system, however in this case, it won't be totally used and its operation conditions won't

be optimal. In case when reconstruction of natural (gravitational) circulation systems is

performed by installing the pump, in order to avoid emergencies, when the pump is

broken, it should be installed on the edging line together with reverse valves, as shown

in fig. 4 and 5. The pump is controlled with the electronic controller of boiler and is

connected to the electric socket on the rear wall of the boiler.

Dirt collector should be installed in the returning water pipe of the heating system.

Boiler room should be ventilated. The required airflow necessary for combustion and

ventilation should be also guaranteed. For this purpose, boiler room doors should have

grille or there should be a gap between the doors and the floor. If there is no possibility

to bring air in from another rooms or the house is very tight, it will be necessary to

make an opening in the exterior wall. Air quantity should be no less than 1, 6 m

per hour. Cross-section area of the opening should be no less than 0,001 m

required air quantities and areas of the opening are presented in the table below.

Boiler type

Required air quantity

per hour, m

Area of airflow

opening, m

For example: the area of airflow opening should be 0,025 m

the height of the gap under the door - about 4 cm when door width is 60 cm.

Put the boiler on the hard (e.g. concrete) and even ground, closer to the chimney pot.

Leave at least 600 mm gap between the back wall of the boiler and building structure for boiler

servicing and cleaning. The smallest distance between a lateral wall of the boiler and building structure

is 400 mm. If building structure is of the flammable materials, this distance should be doubled. At least

800 mm gap should be left from the other side of the boiler to have an access to the backside of the

boiler, its servicing and cleaning. From three sides of the boiler the floor of 300 mm and from the front

of the boiler the floor of 500 mm should be of inflammable materials. Screw supporting legs in to the

base of the boiler and level the boiler with screw nuts using a level.

Smoke exhaust opening of the boiler should be connected with the chimney by a metal

pipe. Internal diameter of the metal connecting pipe should be at least of the external diameter of the

smoke exhaust opening of the boiler. To improve the traction, a connecting pipe between the boiler and

the chimney should be installed with an inline towards the boiler. All junctions should be carefully

tightened by a heat-resistant material.

If the boiler is installed higher than the heating equipment, the water level measuring

instrument must be installed in the heating system.

When the boiler is installed in the open heating system, on the highest point of the heating

system there has to be mounted the open expansion vessel. The volume of expansion vessel has to

be about 10 % of the total volume of water in the heating system (including the volume of the boiler).

The diameter of the overflow pipe of the expansion vessel has to exceed the diameter of

the safety inlet pipe by one unit.

Safety return pipe has to be connected to the return pipe of the heating system and to the

bottom of the expansion vessel.

It is forbidden to install any fittings in the safety inlet and return pipes between the boiler

and expansion pipe.

Chimney requirements. It is recommended to install acid-resistant stainless steel shell

into the stone chimney. It improves traction of the chimney and protects the stone chimney from

destruction due to the condensate (moisture) impact. Internal diameter of the shell should be no less

than the external diameter of the smoke exhaust opening of the boiler. Chimney shell may be round or

G-18

G-25

G- 31,5

0,018

0,025

G- 40

0,025

0,03

/kW. The

G- 50

G- 80

128

0,05

0,08

or 250 cm

, i.e. 16x16 cm; or

/kW

G- 100

160

0,1