9
2.2 Working principle
The Remeha Selecta’s casing serves as a sealed air box, with air drawn in by the
fan. On the outlet side of the fan is a venturi, into which a measured quantity of gas is
injected based on the volume of air available. The fan speed control is dependent on
the settings of the heat requirement and the prevailing temperatures (measured by the
temperature sensors).
The method of gas/air combination ensures that the gas quantity is precisely adjusted
to the air quantity. This creates optimum combustion over the whole heat input range.
The gas/air mixture is mixed in the venturi and then flows to the burner. After com-
bustion, the hot flue gas is directed through a specially designed, high efficiency cast
aluminium heat exchanger with a large surface area, and transferring its heat to the
heating water. The water vapour in the flue gas condenses against the “pins” within the
heat exchanger, and the heat released during this process (the so-called latent or con-
densation heat) is also transferred to the heating water. The condensate water formed
is discharged via a siphon on the bottom of the heat exchanger.
NOTE:
In normal operation, the boiler’s flue gas discharge will produce a visible white
condensing “plume” and care should be taken when choosing a location.
2.3 Combi boiler operation
The Remeha Selecta combi contains a facility for providing domestic hot water in addi-
tion to central heating. The opening of a hot water tap is detected by a temperature
sensor, which is located on the cold water inlet side of the heat exchanger. This sensor
then activates the motorised three-way valve to provide domestic hot water. Once the
demand for hot water stops the motorised valve automatically returns to the central
heating position. This three-way valve is electrically controlled by the control box and
only consumes power when it is changing to a different position.
2.4 Advanced boiler control (‘abc’- control)
An intelligent advanced boiler control (‘
abc’
) continuously monitors the boiler condi-
tions and ensures a very reliable supply of heat. This control system is adept at deal-
ing with negative influences from the system such as flow reduction, airflow problems
and alike. In the event of such influences, the boiler will not go into “lock-out” failure
mode, but will in the first instance modulate back. If necessary, depending on the
nature of the circumstances, it will temporarily switch off (shutdown or control stop),
and then after a short while simply try again.
NOTE:
Provided that the situation is not actually hazardous, the Remeha Selecta will
always try to supply heat. The ‘
abc
’- control prevents unnecessary additional call outs.
Содержание Selecta
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