baltur COMIST 180 DSPNM, Instruction

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probe, if the burner is a COMIST...MNM (modulating) version,
or on the command of the thermostat or pressure switch of
the 2nd stage, if the burner is a COMIST...DSPNM (two-stage
progressive) version. (See Chapter “Electronic Potentiality
Regulator RWF 40 for the modulating version).
17) The air pressure switch has the job of bringing the control box
to a safety shut down if the air pressure is not at the correct
value.Therefore, the air pressure switch must be regulated in
such a way as to intervene by closing the contact (foreseen to
be closed while working) when the air pressure in the burner
has reached a sufficient level. The pressure switch is self-
controlled and therefore it must close the contact (fan stops
and consequently there is an absence of air pressure in the
burner; if it does not, the control box will not be inserted (the
burner remains at a standstill). It must be specified that if the
contact is not closed during working (insufficient air pressure),
the control box will carry out its cycle, but the ignition transfor -
mer will not be inserted and the gas pilot valves will not open.
Consequently, the burner will go to “shut down”. Check that the
air pressure switch functions properly with burner at minimum
delivery, increase the regulating valve until it reaches intervention
point and the burner should go to shut down. To unblock the
burner, press the special push-button and return the pressure
switch regulator to a sufficient value in order to measure the air
pressure existing during the pre-ventilation phase.
18) The pressure switches which control the gas pressure (mi -
nimum and maximum) have the job of stopping the burner
functioning when the gas pressure is not within the values
specified. From the specific functions of the pressure switches,
it is evident that the pressure switch which controls the mini -
mum pressure must make use of the contact, which is closed,
when it measures a pressure which exceeds that at which it
has been set. The maximum pressure switch must make use
of the contact, which is closed, when it measures a pressure
below that at which is has been set. The minimum and maxi -
mum gas pressure switches should be regulated during the
burner’s general inspection and should be in function with the
pressure found each time. The pressure switches have been
electrically connected in series and therefore the intervention
(by this mean the opening of the circuit) of any one of the gas
pressure switches, will prevent the control box and thus the
burner from starting up. When the burner is operating (flame
lit), the intervention of the gas pressure switches (opening
of the circuit) determines the immediate arrest of the burner.
During the burner’s general inspection, check the correct fun -
ctioning of the pressure switches. By operating the respective
regulating device, it is possible to control the pressure switch’s
intervention (opening of circuit) which causes the burner’s
arrest.
19) Check the efficiency of the flame detector, the UV Cell, by
sliding it out of its seat and verifying the “shut down”.
20) Check the efficiency of the boiler thermostat and pressure switches
(this should result in the burner coming to a standstill).
REGULATION OF THE COMBUSTION HEAD AND
FLAME DISK (See BT 8608/1)
The combustion head is equipped with a regulating device which
closes (by moving forwards) and opens (by moving backwards)
the air passage between the disk and the head. By closing the
passage it is possible to achieve high pressure upstream the disk
and therefore high velocity and turbulance for low inputs as well.
High velocity and air turbulance ensure a better penetration in the
fuel, and are an optimum mixture which ensures less smoke and
good flame stability. It might be necessary to have high air pres -
sure upstream the disk in order to avoid flame pulsation’s and it is
considered practically indispensable when the burner is operating
with a pressurized furnace and/or high thermal load.
It is evident from the above, that the device which closes the air on
the combustion head should be put in such a position as to always
obtain a decidedly high air pressure value behind the disk.
It is advisable to regulate in such a way as to achieve a closing of the
air on the head; this will necessitate a considerable opening of the
air shutter which regulates the flow to the burner’s fan suction.
Obviously, these adjustments should be carried out when the
burner is operating at maximum delivery described. In practice,
start regulating by putting the device which closes the air on the
combustion head in an intermediate position, start up the burner
and make trial adjustments as previously described.
When maximum delivery desired has been reached, proceed with
correcting the position of the device which closes the air on the
combustion head; move it backwards or forwards in such a way as
to obtain an air flow suitable to the delivery, with the air regulation
shutter in suction considerably open. When reducing the air passage
on the combustion head, avoid closing it completely. Proceed with
perfect centering with respect to the disk. It must be pointed out
that, if perfect centering with respect to the disk is not obtained, bad
combustion and excessive heating of the head could occur which
would result in its rapid deterioration.
A control can be carried out by looking through the spy hole situated
at the back of the burner; then tighten home the screws that lock
the position of the air regulation device on the combustion head.
Note: Check that ignition occurs regularly, because when the
device has been moved forwards, it could occur that
the air velocity in exit is so high as to render ignition
difficult. If this happens, move it backwards, gradually,
until it reaches the correct position and ignition occurs
regularly. This position should be definitive. It should
be kept in mind that it is preferable, for the first flame,
to limit the amount of air to that strictly necessary in
order to ensure safe ignition even in difficult circum -
stances.