baltur COMIST 180 DSPNM User Instruction Manual page 26

• The air pressure switch locks the equipment if air pressure
is not at the expected value. The pressure switch must be
set to close the contact which should be closed during the
operation, when the air pressure in the burner reaches the
sufficient value. The pressure switch connection circuit is self
controlling. Therefore, the contact which is meant to be closed
in a non operating state (fan stopped and thus no air pressure in
burner), should in fact be in this state, otherwise the command/
control equipment will not be switched on (burner remains
inoperative). Please note that if the contact meant to be closed
during operation does not close (insufficient air pressure), the
equipment carries out its cycle but the ignition transformer is not
switched on and the fuel valves do not open. As a result, the
burner stops in a blocked state. To ensure the air pressure switch
correct operation, with burner at the minimum output, increase
the adjustment value until reaching the triggering value which
must be followed by the immediate burner shutdown. To unblock
the burner, press the special pushbutton and return the pressure
switch regulator to a sufficient value in order to measure the air
pressure existing during the pre-ventilation phase.
• The gas pressure control switches (minimum and maximum)
prevent the burner from operating when gas pressure is not
between the expected range. The specific function of the
pressure control switches clearly reveals that the pressure switch
for controlling minimum pressure must use the contact which is
closed when the pressure switch detects a pressure value above
the value it is set to; on the other hand, the pressure switch
for controlling maximum pressure must use the contact that is
closed when the pressure switch detects a pressure lower than
the value it is set to. The minimum and maximum gas pressure
switches must be set when testing the burner, on the basis of
the pressure measured in each case. The pressure switches
are connected in series, so the triggering (circuit opening) of
any of them, does not allow the equipment, and so the burner,
to start. When the burner is working (flame on), tripping of the
gas pressure switches (opening the circuit) will shut down the
burner immediately. When testing the burner, it is very important
to check that the pressure switches are working properly. With
appropriate regulation of the regulation components, we can be
sure that the pressure switch will be tripped (opening the circuit)
and shut down the burner.
• Check that the flame supervision device (UV photocell) is
operating correctly by sliding it out of its seat on the burner and
checking that the burner effectively locks out.
• Check that the boiler thermostats or pressure switches are
operating correctly (they must cause the boiler to shut down
when they intervene).
air regULaTiOn On THe COmBUsTiOn HeaD
The combustion head is provided with a regulation device that
closes (forward movement) or opens (backward movement) the air
passage between disk and head. By closing the passage, it is thus
possible to obtain a high pressure upstream of the disk also for low
flow rates. High velocity and turbulence ensure a better penetration
in the fuel, an optimum mixture and good flame stability.
It may be necessary to have high air pressure upstream of the disk
to prevent flame pulsations. This condition is indispensable when the
burner works with a pressurized furnace and/or has a high heat load.
From what said above it is evident that the device closing the air
on the combustion head must be set to such position as to always
obtain, behind the disk, a very high air pressure value.
It is recommended to provide an air closure on the head, such to
require a considerable opening of the air damper that regulates the
burner fan intake flow. Obviously this condition must occur when
the burner operates at the maximum required output.
In practice, start by adjusting the device that closes the air on the
combustion head to an intermediate position, turning on the burner
for a preliminary adjustment as described above.
When the maximum desired output is reached, correct the position
of the device which closes air on the combustion head by moving it
forward or backward so that the air flow is appropriate for the output,
with the air regulation damper noticeably open.
When reducing the air passage on the combustion head, make sure
not to completely close it. Perfectly centre the combustion head with
respect to the disk. A combustion head not perfectly centred to the
disk could lead to a wrong combustion and overheat the same head
causing its early wearing. Check it by looking through the inspection
hole on the burner rear side, and then fully tighten the screws that
lock the air regulation device on the combustion head.
Check that ignition is correct because if the regulator is shifted
forward, the outgoing air speed may be too high to permit
ignition. If this happens, gradually move the regulator back to
a position in which ignition takes place correctly, and accept
this as the final position. It should also be remembered that,
for the 1st flame, it is preferable to limit the quantity of air
to that which is strictly indispensable in order to have safe
ignition even in the most difficult circumstances.
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