4 Description of the product
4.1
General description
The Baxi Combi condensing boiler is a gas-fuelled boiler. The purpose of
this boiler is to heat water to a temperature that is lower than boiling point
at atmospheric pressure. It must be connected to a heating installation and
to a domestic hot water distribution system that is compatible with its
power and performance ratings. Features of this boiler:
Low pollutant emissions.
High-efficiency heating.
Combustion products discharged through a coaxial connector.
Front control panel with display.
Lightweight and compact.
4.2
Operating principle
4.2.1
Air-gas adjustment
The air is drawn in by the fan and gas injected directly at the top of the
mixer valve. The fan rotation speed is regulated automatically by the
electronic board based on temperature adjustment and other parameters.
The gas and air are mixed in the manifold. The gas/air ratio ensures that
the quantity of gas and air are adjusted correctly to always obtain optimal
combustion. The gas/air mixture is fed into the burner at the front of the
heat exchanger. The mixture is ignited by the spark electrode.
4.2.2
Combustion
The burner heats the heating water circulating in the heat exchanger.
When the temperature of the combustion gas is lower than the dew point
(around 55 °C), the water vapour contained in the combustion gas
condenses in the flue gas side of the heat exchanger. The heat recovered
during this condensation process (the latent heat or condensing heat) is
also transferred to the heating water. Once cooled, the combustion gases
are discharged through the flue exhaust. The condensed water is
discharged through a trap.
4.2.3
Central heating and domestic hot water production
In boilers used for heating and for producing domestic hot water, an
integrated plate heat exchanger heats the domestic water. The heated
water is then channelled to the heating installation or to the plate heat
exchanger via a diverter valve. A flow sensor detects that a hot water tap
has been turned on and communicates this to the printed circuit board
(PCB), which switches the diverter valve to the hot water position and
activates the pump. The diverter valve is spring-loaded but only consumes
electricity when switching from one position to another. Priority is given to
domestic hot water.
4 Description of the product
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