baltur BTG 20 LX Notice D'instructions page 41

the control box "locks". Note that some "locks" at the first stage
are normal since in the valve ramp pipes there is still air that
must be discharged before having a stable flame.
To "unlock", press the "unlock" push button. At the first stage
there may occur further "locks" due to:
a) The gas pipes have not been sufficiently air-bled, and thus the
gas quantity is not sufficient to allow a stable flame.
b) The "lock" with presence of flame may be caused by instability
of the same in the ionisation zone for an incorrect air/
gas ratio. Remedy is by varying the quantity of supplied
air and/or gas so as to find the correct ratio. The same
problem may be caused by a wrong air/gas distribution
in the combustion head. Remedy is by operating on the
combustion 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 adjustments: see instructions elating to
the gas valve model MB-VEF... Afterwards, check the supplied
gas quantity by reading the meter. If necessary, adjust the
gas output and the relevant combustion air by operating as
described above. Then, check the combustion with the special
instruments (see chapter "Combustion control").
12)After adjusting the "minimum", set the modulation switches
to MAN (manual) and MAX (maximum) position. The air
regulation servomotor sets to "maximum" and as a conse-
quence, 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 multiplying the hourly
output (m3/h) by 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 flow rate automatically adjust to the air
supply. Then, operate on the cam regulating the air damper
maximum aperture position (see dr. n° 0002934320). Reduce
the aperture 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...
14)Afterwards, check the combustion with the special instruments
and if necessary, check the existing regulation (air and optio-
nally gas). Check with the special instruments that the carbon
oxide (CO) percentage in the flue gas does not exceed the
maximum admissible value of 0.1% and that CO2 does not
exceed 10% for methane. (See chapter "Combustion 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, set the modulation switch to MIN.
17) When the air servomotor is set to minimum, and it is necessary
to change the combustion conditions (gas/air), see the instruc-
tions for regulating gas valves model MB-VEF...
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 automatic modulation operation.
20) The air pressure switch has the function of locking the control
box if the air pressure is not correct. 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 (insuffi-
cient air pressure), the control box performs 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 operation 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 auto-
matic control; thus, the contact provided 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 maximum),
if installed, have the function of preventing the burner from
operating when gas pressure does not range in the expected
values. From the specific function of the pressure 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 pressure 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 electrically connected in series; thus, the start (intended
as circuit opening) of any one of the gas pressure switches
does not allow starting the control box and thus, the burner.
When the burner is operating (flame on), the start of the gas
pressure switches (circuit opening) causes the immediate shut
down of the burner. Upon the general test and inspection of
the burner, it is necessary to check the correct operation of
the pressure switches. By suitably acting on the respective
regulation members, make sure that the pressure switch starts
(circuit opening), thus shutting down the burner.
22) In case of UV photoelectric cell, after at least one minute from
ignition extract the photoelectric cell from its housing. When
the UV photoelectric cell is extracted from its housing, it cannot
"see" the ultraviolet radiation emitted by the flame and thus,
the relevant relay de-energises. The burner immediately shuts
down in "lock". A light greasiness strongly affects the passage
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