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3. Description
3
Description
3.1
Operating principle
9
3.1.1.
Gas/air setting
The casing fitted to the boiler is also used as an air box. Air is sucked
in by the fan and gas injected into the venturi by the fan intake. The
fan rotation speed is set according to the settings parameters, the
thermal energy requirement and the temperatures measured by the
temperature sensors. The gas and air are mixed in the venturi. The
gas/air ratio ensures that the quantities of gas and air are adjusted to
each other. This provides optimum combustion on the entire output
range. The gas/air mixture is fed into the burner on top of the
exchanger.
3.1.2.
Combustion
The burner heats the heating water circulating in the heat
exchanger. At a return temperature lower than around 55°C, the flue
gases cool down to a temperature lower than the dew point, thus
causing the condensation of the water vapour contained in the flue
gases in the back side of the heat exchanger. The heat released
during this condensation process (the latent heat or condensing heat)
is also transferred to the heating water. The cooled combustion gases
are evacuated via the combustion gas outlet flue. The condensation
water is evacuated via a siphon.
3.1.3.
Heating and domestic hot water production
An integrated plate exchanger handles domestic hot water
production. A 3-way valve determines whether the heated water is
fed into the heating system or the plate exchanger. A DHW sensor
signals domestic hot water demands. This signal is transmitted to the
control panel, which then switches the 3-way valve to the hot water
position and trips the heating pump. The 3-way valve is spring-loaded
but only consumes electricity when it switches to another position.
The heating water reheats the domestic water in the plate
exchanger. This water is pumped into the boiler tank to provide a
constant plentiful supply of domestic hot water. In comfort mode, if no
domestic hot water is drawn off, the boiler reheats the plate exchanger
and the boiler tank at regular intervals. Any limescale particles are
kept out of the plate exchanger by a self-cleaning water filter (self-
cleans once every 76 hours).
MCA 25/28 BIC
15/06/12 - 300022162-001-01
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