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30
AST 14 C 258/00
AIR/GAS MIXING UNIT
The air/gas mixture is generated thanks to the air flow through the vacuum developed by
the fan and sent to the gas valve mechanism.
When the fan is powered it creates a vacuum proportional to its speed ensuring a mixture
with constant ratio from the maximum to the minimum power. The fan impeller, besides
sucking the combustion air, mixes the air and gas quantity before conveying them to the
burner through the suitable pipe.
The mixer is connected to the fan intake opening and features a mechanism able to
increase or decrease the air and gas flow rate according to the required power ensuring a
very low minimum modulation of the boiler. In particular, inside the mixture, there is a
double deflector that at the minimum power closes (by gravity) the gas outlet of one nozzle
and half passage of combustion air. Upon fan power increase, such deflectors are opened
by vacuum allowing the passage of both air and gas:
Open deflectors
Closed deflectors
INLET
GAS
AIR
COMBUSTION
INLET
AIR/GAS
MIXTURE TO
BURNER
