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D E S C R I P T I O N
O P E R AT I O N S AT T W O
STAGE PROGRESSIVE
These burners are of the blown air type
which have a mixture of gas/air at the
combustion head. They are suitable for
use with combustion chambers which
are either raising high pressure or redu-
cing pressure, according to the relative
work curves. Together with excellent
flame stability, these burners are safe
and highly efficient. It is equipped with
a steel flange which slips on the burner
head. When fastening the burner to the
boiler it is necessary to correctly posi-
tion the flange so that the burner head
enters the combustion chamber to the
extent specified by the boiler manufac-
turer.The burner has an electronic
cam mod. MPA 22. The microprocessor-
controlled MPA 22 provides intermittent
operation, controls and monitors
the electronically-modulated fan-equip-
ped gas burners and features two (air/
gas) adjuster motors. When working
as an automatic burner valve seal
control is activated; (for a better un-
derstanding of the MPA 22 read the in-
structions in the attached manual, code
0006080905).
Operation of is of the progressive two-
stage type, so called because the switch
from primary flame to secondary flame
(from minimum to the set maximum)
occurs gradually as regards the delive-
ry of both combustion air and fuel; this
gives considerable advantages in terms
of the pressure stability in the gas feed
line. Delivery rate ranges, approxima-
tely, from 1 to 1/3. Ignition is preceded
by pre-ventilation of the combustion
chamber as per standards, with the air
open: this lasts about 36 seconds. If, at
the end of the ventilation stage, the air
pressure switch detects that pressure
is sufficient, the ignition transformer co-
mes on and, after 3 seconds, the safety
and main valves open in sequence.
The gas reaches the combustion head,
is mixed with the air being delivered by
the fan, and is ignited. Delivery is re-
gulated by the gas throttle valve. Three
seconds after the (main and safety)
valves are opened the ignition tran-
sformer is switched off. The burner is
now on at the ignition point (P0). The
flame is detected by the relative control
device (an ionisation sensor positioned
inside the flame).The programming re-
lay goes beyond the shutdown position
and powers the air/gas delivery regula-
tion servomotors, which go to minimum
O F
(P). If the 2nd stage boiler thermostat
(or pressure switch) – adjusted by a
temperature or
pressure greater than that in the boiler)
allow, the air/gas delivery servomotors
start running and cause a gradual in-
crease is the delivery of gas and com-
bustion air until the maximum flow rates
to which the burner has been set have
been reached (point P9).
N.B. Electronic cam MPA 22 controls
the burner by adjusting the combu-
stion air and gas servomotors ac-
cording to a pre-set curve.
The burner remains in the maximum
delivery position until the temperature
or pressure reaches the limit set for the
intervention of the boiler thermostat (or
pressure switch) of the 2nd stage and
makes the servomotors regulating gas/
air delivery rotate in the opposite sense
of direction. Thus gas delivery and the
relative combustion air are gradually
reduced until they reach minimum va-
lue.
Even with delivery at a minimum, if
the limit (temperature or pressure at
the shut down device (thermostat or
pressure switch) has been regulated is
reached, the burner will be brought to
a standstill. When the temperature or
pressure drops below the intervention
limit set on the shut down device, the
burner will star up again, according to
the programme previously described.
During normal operations, the boiler
30 / 68
000608220_2007/03
thermostat (or pressure switch) of the
2nd stage fitted to the boiler detects the
variations requested and automatically
proceeds with adapting the fuel and
combustion air delivery by inserting the
servomotors which regulates delivery
(gas/air). This will rotate in such a way
as to obtain an increase or a decrease.
With this manoeuvre, the gas/air delive-
ry regulating system try's to equilibrate
the quantity of heat supplied to the boi-
ler with that which the boiler gives to
be utilised.
If the flame does not appear within
THREE seconds of the opening of the
gas valve, the control box goes to "shut
down" (the burner stops completely and
(1) error message 25H) on display.).
To "unblock" the equipment press the
interference
elimination
about half a second (2).
button
for
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