Description, Operating principle, Gas/air setting – DE DIETRICH INNOVENS MCA 25_28 BIC User Manual

Page 10: Combustion, Heating and domestic hot water production, 3 description, 1 operating principle

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3 Description

3.1

Operating principle

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).

3. Description

MCA 25/28 BIC

9

31/08/2011 - 300024163-001-B

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