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in the combustion head. Remedy
is by operating on the combus-
tion head regulation device, by
adjusting the closing or opening
of the air passage between head
and gas diffuser.
11) Set the burner to minimum flame
(modulation servomotor set to
minimum), check the quantity
and appearance of the flame
making the necessary adjust-
ments: see instructions elating to
the gas valve model MB-VEF..,
DMV-VEF.. Afterwards, check
the supplied gas quantity by
reading the meter. If necessary,
adjust the gas output and the
relevant combustion air by oper-
ating as described above. Then,
check the combustion with the
special instruments (see chapter
"Combustion control".
12) After adjusting the "minimum",
set the modulation switch to
MAX (maximum). The air regu-
lation servomotor sets to "maxi-
mum" and as a consequence,
also the gas supply reaches
the "maximum". The quantity of
supplied gas is then checked
by reading the meter. With
burner ignited at the maximum
existing output, measure the
gas flow rate by calculating the
difference between two reads
performed after one minute from
one another. By multiplying the
measured value by sixty, a sixty-
minute flow rate – that is, one
hour – is obtained. By multiply-
ing the hourly output (m
the gas heat value, you obtain
the delivered power in Kcal/h,
which must correspond or be
very close to that required by
the burner (lower heat value
for methane = 8550 Kcal/h).
Avoid operating the burner if
the flow rate is more than the
admissible for the boiler so as
to prevent possible damages
to the same. Shut down the
burner after the two meter
reads.
13)To change the maximum gas
output, operate on the air flow
rate regulator since the gas
All manuals and user guides at all-guides.com
flow rate automatically adjust
to the air supply. Then, oper-
ate on the cam regulating the
air damper maximum aperture
position (see dr. n° 0002933220
- 0002933490). Reduce the ap-
erture angle of the air damper
to reduce the gas flow rate, and
vice versa. To change the gas/
air ratio, see instruction of gas
valve MB-VEF.., DMV-VEF..
14)Afterwards, check the combus-
tion with the special instru-
ments and if necessary, check
the existing regulation (air and
optionally gas). Check with the
special instruments that the
carbon oxide (CO) percent-
age in the flue gas does not
exceed the maximum admis-
sible value of 0.1% and that
CO
does not exceed 10% for
2
methane. (See chapter "Com-
bustion control")
15) After adjusting the operation
to the high flame (maximum)
you must operate so that the
air regulation servomotor sets
to the minimum to perform the
control also in this position.
16) To set the air – and thus gas
– regulation servomotor to the
minimum, the modulation switch
must be pressed to MIN.
17) When the air servomotor is set
to minimum, and it is necessary
to change the combustion condi-
tions (gas/air), see the instruc-
tions for regulating gas valves
/h) by
model MB-VEF.., DMV-VEF..
3
18) It is advisable to perform the
combustion control using the
instruments and, if necessary,
change the previous regulation
also in some intermediate points
of the modulation stroke.
19) Now, check the correct auto-
matic modulation operation
now check correct automatic
modulation operation, inserting
the boiler's previously removed
4-pole plug.
20) The air pressure switch has the
function of locking the control box
if the air pressure is not correct.
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The pressure switch must thus
be set to start by closing the
contact (a normally open contact)
when air pressure in the burner
reach a sufficient value. Note
that if the normally open contact
does not close (insufficient air
pressure), the control box per-
forms its cycle but the ignition
transformer does not start, the
gas valves do not open and as a
consequence, the burner stops in
lock. To check the correct opera-
tion of the air pressure switch,
set the burner to the minimum
output, increase the regulation
value so as to check when it
should start to immediately "lock"
the burner. Unlock the burner by
pressing the special push button
and restore the pressure switch
regulation to a sufficient value to
detect the existing air pressure
during the pre-ventilation step.
The pressure switch connection
circuit provides for the automatic
control; thus, the contact pro-
vided to be closed when at rest
(fan off, and thus, absence of
air pressure in the burner) must
implement this condition, or the
control box does not start (the
burner remains off).
21) The gas pressure control
switches (minimum and maxi-
mum), if installed, have the
function of preventing the burner
from operating when gas pres-
sure does not range in the
expected values. From the
specific function of the pres-
sure switches, it is evident that
the minimum pressure control
switch must used the contact
that is closed when it detects
a higher pressure than that to
which it is set, the maximum
pressure control switch must
use the contact that is closed
when it detects a lower pres-
sure than that to which it is set.
Therefore, the gas maximum
and minimum pressure switch
regulation must be performed
during the burner general test
and inspection, based on the
pressure measured each time.
Pressure switches are electri-
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