Combustion; Heating And Domestic Hot Water Production; Control System; Adjustment - REMEHA Calenta 25s Installation And Service Manual

3. Technical description
14
3.3.2.

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.
3.3.3.

Heating and domestic hot water production

On heating and domestic hot water production type boilers, an
integrated plate exchanger heats the domestic water. A 3-way valve
determines whether the heated water is fed into the heating system
or the plate exchanger. A pick-up sensor signals that a hot water tap
is being opened. 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. In comfort mode, if there is no hot water draw-off, the
boiler handles the periodic reheating of the plate exchanger. Any
limescale particles are kept out of the plate exchanger by a self-
cleaning water filter (self-cleans once every 76 hours).
3.3.4.

Control system

The boiler command, called Comfort Master
heat supply. This means that the boiler treats external negative
influences in a practical manner (notably when the water-flow is
insufficient or there are problems with air supply). In the presence of
such influences, the boiler doesn't switch into locking mode, but first
reduces his power and, depending on the nature of the
circumstances, will be temporarily out of service (blocking or stop).
The boiler will continue to supply heat as long as the situation does
not become dangerous.
3.3.5.

Adjustment

The power of the boiler can be adjusted in the following ways:
4 On/Off setting
The output between the minimum and maximum values varies
based on the heating flow set point temperature.
4 Adjustable control
The output between the minimum and maximum values varies
based on the heating flow temperature determined by the
modulating control system.
4 Analogue setting (0-10 V)
Calenta 25s - 28c - 35s - 40c
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