Servicing Manual
11
Description
ILL. 4: particolare testa di combustione
A certain amount of air coming from the fan flows around the combustion head, and, depending on the
air lock setting, a part of it - the so-called primary air - flows inside the burner head. The primary air is
distributed and mixed with the atomized fuel jet exiting the nozzle by means of a baffle disc. To get good
combustion and therefore high efficiency, the adjustment of the primary air/fuel ratio must be very
accurate. For this purpose, please carefully follow the setting specifications and instructions contained in
this manual.
The burner head includes :
nozzle holder
air lock
baffle disc (whirl disc)
fuel nozzle
ignition electrode
flame sensor (photoresistor)
The fuel coming out of the nozzle is atomized and mixed with primary air. Additional circumferential
openings on the burner head allow another amount of air, called secondary air, to flow into the chamber.
That is an additional air delivery that completes combustion.
During the whole ignition sequence the electrodes are powered by the high voltage transformer and
produce a spark that ignites the fuel-air mixture.
The function of the whirl disc is to induce a rotational component in the primary air flow and therefore to
decelerate it : this way the mixing of fuel and air is increased and the combustion improved.
The combustion chamber is made of stainless steel. It includes :
a rear end on which the combustion head is fitted
a front end with hole on direct heaters, without hole on indirect heaters
a front flame shield on direct heaters
the heat exchanger with gas passageways
the exhaust gas flue collar
the protection shield around the chamber
a manually resettable overheat thermostat
2.5 ELECTRICAL BOARD
