baltur BT 100 DSPN /D, Instruction For Burners Model

Page: 43 / 96

43
17) The minimum-level thermostat closes when fuel in the pre-heater reaches the temperature to which the
thermostat is set. When the minimum level thermostat closes this does not immediately cut-in the burner
command/control equipment. This equipment is cut-in by the regulation thermostat (by commutation contact)
when it switches off the elements because fuel temperature has reached the level set on the regulation
thermostat. Burner start-up therefore begins only when the elements are switched off and maximum pre-
heater temperature has been reached (provided that the boiler and safety thermostats or pressure switches
are cut-in). When the burner is in operation, an auxiliary relay (connected to the minimum level thermostat)
prevents it stopping when the regulation thermostat switches on the contact to cut-in the elements again (see
wiring diagram). When the command/control equipment is cut-in, the burner ignition phases begin. The
programme entails a combustion chamber preventilation phase coupled to precirculation of hot oil at low
pressure over the entire fuel circuit in the burner. Burner ignition is as described in the preceding chapter “Fuel
oil operation”. The burner ignites at minimum level.
18) When the burner operates at minimum level, air should be set to the quantity needed to ensure good combustion.
Screw down or unscrew the adjusting screws near the point of contact with the lever that transmits movement
to the combustion air regulation gate. Air quantity for minimum level should preferably be slight, so that perfect
ignition may be guaranteed even in the most difficult cases.
19) After setting minimum level air, position the modulation switches to “MAN” and “MAX”.
20) The modulation motor begins turning.
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 flame 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 (CO
2
) 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% CO
2
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 variation, 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 CO
2
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 CO
2
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 orange
flame, avoiding a red smoky flame or a white flame 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 ignition,
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 exceeding 2° E. For a guide, see the viscosity-temperature diagram relating to the type of oil used.