baltur BT 75 DSPN Manual De Instrucciones página 20

20) T h e m o d u l a t i o n m o t o r b e g i n s t u r n i n g .
Wait until the disk with the adjusting screws has turned through
an angle of about 12° (this corresponds to the space taken
up by three screws) and then stop modulation by resetting
the switch to the "O" position. Do a visual check of the fla-
me and, if necessary, adjust combustion air, following the
instruction at point 18. You should then check combustion
using the appropriate instruments and, if necessary, modify
the previous visual check. The above operation should
be repeated gradually (moving the disk forward 12° each
time) changing, if necessary the fuel-air ratio each time
during the whole modulation movement. It is advisable to
ensure that fuel supply occurs gradually and that maximum
supply occurs at the end of the modulation movement.
This is necessary for modulation to operate gradually. You
may have to change the position of the fuel-control screws to
achieve this. Maximum supply occurs when return pressure
is about 2 ÷ 3 bar less than the delivery pressure (usually
20 ÷ 22 bar). For correct air-fuel ratio, carbon-dioxide (CO2)
level should increase as supply increase, by about at least
10% (at minimum supply) to an optimum level of about 13% at
maximum supply. We do no recommend exceeding the 13%
CO2 level to avoid operation with a rather limited excess of
air, which could cause considerable increase in smoke opacity
(due to unavoidable causes such as atmospheric pressure va-
riation, small dust deposits in the fan air pipes, etc.).
The resulting smoke opaqueness is closely connected to the
kind of fuel used (the latest regulations indicate maximum value
n° 6 on the Bacharach scale). We recommend, if possible,
to keep smoke opacity under level n° 6 of the Bacharach
scale, even though CO2 level could be, as a result, slightly
lower. Lower smoke opacity means less dirt in the boiler and
consequently, its average performance is usually higher,
even though CO2 is slightly lower. Remember that for good
setting, plant water temperature should be steady and the
burner should have been operating for at least fifteen minutes.
If no suitable instruments are available, judge by the
flame colour. We suggest you set to get a light oran-
ge flame, avoiding a red smoky flame or a white fla-
me with too much air fed in. After checking the setting
(air-fuel) is correct, tighten the lock screws of the adjusting
screws.
21) Check that modulation functions automatically by putting the
AUT - O - MAN switch in the "AUT" position and the MIN -
O - MAX switch in the "O" position. In this way, modulation is
activated exclusively by the automatic command of the boiler's
probe, if the burner is a ....MNM (modulating) version, or on
the command of the thermostat or pressure switch of the 2nd
stage, if the burner is a ....DSPN (two-stage progressive)
version. (See booklet "Electronic Potentiality Regulator RWF
40 for the modulating version).
22) Check that the settings of the pre-heater thermostats
do not cause any troublesome conditions (poor igni-
tion, smoke, gas in the pre-heater, etc.). If necessary,
change these values up or down. Keep in mind that the
regulation thermostat should in any case be 15 ÷ 20°
C higher than the minimum level thermostat setting.
The minimum level thermostat must close at the minimum
temperature for good atomisation (nozzle viscosity not excee-
ding 2° E. For a guide, see the viscosity-temperature diagram
relating to the type of oil used.
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