baltur COMIST 72 DSPGM Manuel D'installation, Utilisation Et Entretien page 24

tion and the MIN - O - MAX switch in the "O" position.
E
In this way, modulation is activated exclusively by
the automatic command of the boiler's probe, if the
N
burner is a COMIST....(modulating) version, or on
the command of the thermostat or pressure switch
G
of the 2nd stage, if the burner is a COMIST...DSPGN
L
(two-stage progressive) version. (See Chapter
"Electronic Potentiality Regulator RWF ... for the
I
modulating version).
17) The air pressure switch has the job of bringing the
S
control box to a safety shut down if the air pressure
H
is not at the correct value. Therefore, the air pres-
sure 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 transformer 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
pushbutton 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 (minimum 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
minimum 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 measu-
res a pressure below that at which is has been
set. The minimum and maximum gas pressure
switches should be regulated during the bur-
ner's general inspection and should be in fun-
ction with the pressure found each time.
T
he pressure switches have been electrically con-
nected 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) de-
termines the immediate arrest of the burner. During
the burner's general inspection, check the correct
functioning 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 "UV pho-
toelectric Cell" sliding it put of its seat on the burner
and verify the "shut down".
20) Check the efficiency of the thermostats 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 burner is equipped with a combustion head which can be
regulated (by moving it backwards or forwards) in such a way as
to close more or open more 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 air turbulence for
low inputs as well. High velocity and air turbulence ensure a better
penetration in the fuel and are therefore an optimum mixture and
allow the burner to operate with good flame stability.
High air pressure, upstream the disk, might be necessary in order
to avoid flame pulsations, and it is considered practically indispen-
sable when the burner is operating with a pressurized furnace and/
or high thermal load.
It is evident from above, that the position of the device which
regulates 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 between the disk and 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 desired.
In practice, commence regulating with the combustion head in an
intermediate position, start up the burner and make a first adjustment
as previously described. When maximum delivery desired has been
reached, proceed with correcting the position of the combustion
head; move it backwards and forwards in such a way as to obtain
an air flow suitable for the light oil delivery with the air regulation
shutter in suction considerably open.
It the combustion head is pushed forwards (which causes a reduction
in the air passage between the head and the disk), avoid closing
it completely. When regulating the combustion head, proceed with
centering it perfectly 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
on the back of the burner.
Then tighten home the screws that lock the combustion head in
position. The distance between the disk and the nozzle, regulated
by the manufacturer, must be reduced only it the atomized fuel cone
coming out of the nozzle wets the disk and fouls it.
20 / 30
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