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ADJUSTING THE AIR ON THE COMBUSTION HEAD (see BT 8608/1)
The combustion head is equipped with a regulation device that restricts (moves forwards) or opens up (moves
backwards) the air fl ow between the diffuser disc and the head. Closing the passageway therefore generates high
pressure upstream from the diffuser disc even at low fl ow-rates Being at high speed and somewhat turbulent, the
air penetrates the fuel better, giving an excellent mix and good fl ame stability.
High air pressure upstream from the diffuser disc may be necessary to prevent fl ame pulsation; this condition is
practically essential when the burner is working on a pressurized chamber and/or at high thermal loads.
It is clear from the above description that the device which closes off the air in the combustion head must be
brought into a position which always gives decidedly higher air pressure behind the diffuser disc.
It is recommended that adjustment be carried out to provide on-head air closure that requires considerable opening
of the air gate which adjusts the burner fan intake fl ow; this condition must, of course, be obtained when the burner
is working at maximum desired fuel fl ow-rates. In practice adjustment must be begun with the on-head air closure
device in an intermediate position and by igniting the burner for approximate regulation as described previously.
When maximum desired fuel fl ow rates are reached correct the position of the device which closes off combustion
head air: do this by shifting forwards or backwards so that an air fl ow compatible with fuel fl ow is obtained with
the air intake fl ap wide open. When restricting air fl ow on the combustion head avoid complete closure. Check for
perfect centering with respect to the diffuser disc. Please note that imperfect centering with respect to the diffuser
disc may lead to poor combustion and excessive heating of the head with consequent rapid deterioration. Check
by looking through the spy-hole on the rear part of the burner and then tightening (all the way) the screws that
hold the combustion head air regulation device in position.
N.B. Check that ignition occurs properly:
if the regulator has shifted forwards the high speed of the outgoing air may make ignition diffi cult.
Should such a situation occur shift the regulator back a little at a time until it is in a position that gives regular
ignition and take this as the defi nitive setting.
It should be pointed out, once again, that for the 1st stage it is preferable to limit the air quantity to an indispensable
minimum so as to ensure secure ignition even under the most diffi cult conditions.
ADJUSTING THE DISTANCE BETWEEN THE DIFFUSER DISC AND THE NOZZLE
The burners are equipped with a device that allows adjustment of the distance between the diffuser disc and the
nozzle. The distance between diffuser disc and nozzle is set by the manufacturer and must only be reduced if it
is noted that the atomized fuel cone exiting the nozzle wets the diffuser disc and consequently stains it.
CHECKS
Once the burner is operating check the safety devices (photoresistance, shutdown, thermostats).
1) The photoresistance is the fl ame control device. It must therefore cut in if, during operation, the fl ame goes
out (carry out this check at least 1 minute after fl ame ignition).
2) The burner must shut itself down and stay off when, during ignition and within the control set time, the fl ame
fails to appear. Shutdown immediately cuts fuel fl ow, stops the motor and therefore the burner and causes
the shutdown warning light to come on. To check photoresistance effi ciency proceed as follows:
a) start the burner.
b) at least 1 minute after ignition extract the photoresistance by removing it from its housing and simulate a
"no fl ame" situation by covering the photoresistance (obscure the photoresistance support window with a
rag). The fl ame should go out (with control box LAL 1.25 the burner shuts down).
c) If, with control box OR 3/B, the photoresistance is kept in the dark the burner re-ignites but the photoresi-
stance does not "see" the light and the burner shuts down in a time determined by program settings. The
burner can only be reset by pressing the appropriate push-button.
3) To check thermostat effi ciency run the burner until the water in the boiler reaches a temperature of at least 50° C
and then act on the thermostat control knob, lowering the temperature setting until the "click" of the opening
switch is heard and simultaneous burner shutdown is observed. The thermostat must trip within a maximum
"lag" of 5 - 10° C with respect to the control thermostat (boiler thermometer). If this is not so modify the ther-
mostat scale calibration so that it corresponds with thermometer settings.
TWO STAGE HEAVY OIL BURNER
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0006080415 ed2005/08
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