9
ANCILLARY PUMP (see BT 8666/2)
In some cases (excessive distance or difference in level) it is necessary to install a “loop-type”supply system with an
ancillary pump, which dispenses with the connection of the burner pump directly to the tank.
In this case the ancillary pump can be put into operation when the burner is started up and cut-off when the latter
stops.
The electric wiring of the ancillary pump is made by connecting the coil (220 V) which controls the pump remote
controlswitch to terminals “N”(equipment terminal board)and“L1”(downstream the motor remotecontrolswitch).
It is important to comply strictly with the previsions set forth here below:
- The ancillary pump should be installed as near as possible to the fuel to be sucked.
- Its head should meet the requirements of subject system.
- We recommend a delivery rate equal to at least that of the burner pump.
- Connection pipes should be sized to cope with the delivery rate of the ancillary pump.
- Always avoid to electrically connect the ancillary pump directly to the remote control switch of the burner motor.
DESCRIPTION OF OPERATIONS (see diagram)
Byclosingtheswitchontheburner,andifthethermostats(controlandsafety)allowit,currentflowtothecontrolboxand
activatethemotorand the ignition transformer.
Themotorwillstartupthe fan which will carry out a pre-ventilationwithairfromthecombustionchamber and simultane-
ously the pump which will drive oil through the pipes and expel any gas bubbles through the return pipe.
Duringthepre-ventilation phase the combustion air shutterisactivatedby its motor and opens inthe2ndflame position
(pre-ventilation with air open). Subsequently, the air shutter returns to the 1st flame position for ignition.
This“pre-washing”caseswhenelectrovalveno.1closes(openintherestposition)andthisinterruptsthefreedischarge
of oil towards the cistern. When electrovalve no. 1 closes, an increase in pressure in the delivery pipes follows.
Whenthe light oil pressure reaches7 bar,themechanical valve which canbefound in the atomizerunitopens allowing
oil to reach the 1st flame nozzle and come out of it into the combustion chamber finely atomized. The pressure
stabilises at about 10 bar because the 1st flame pressure regulator has been set at this value. As soon as atomized
oilcomesoutofthenozzle, it is ignited by the spark betweenelectrodeswhichhasbeenpresentsince the motor started
up. If the flame appears regularly, the programmer passes over the “shut down”position and inserts the motor which
activates the combustion air shutter and puts it in the 2nd flame position.
While this is happening, an adjustable cam activated by the same motor, closes the electrical contact which takes
voltage to electrovalve no. 2 which intercepts the flow of oil through the 1st flame pressure regulator. The 1st flame
pressure regulator is excluded in this way and the pressure increase until it reaches the value at which the pressure
regulator incorporated in the pump has been set (16 bar). The 16 bar pressure also acts on the mechanical valve
which,uptoapressurevalueof13bar, prevents the fuel from flowing to the second nozzle. Thisvalveisopenedinthis
waybythe pressure, and thesecondnozzle also starts operating. The 16bar, pressurenowacts on the two nozzles.
When the unit is working at a pressure of 16 bar, it is operating at maximum capacity.
Note: From the above outline it is evident that the choice of nozzles with respect to the desired total
burneroutput(2nozzlesin operation) should be madetakingintoaccountthedeliveryratescorrespondingtothe
lightoil16bar, operating pressure. It should benoted,however, that when the burner operates onlywiththe1st
flame,the delivery rate of thefirst nozzle corresponds to thevalues given in the10bar,pressuretable because
thepressureregulatorforthe1stflameissetatthisvalue. Obviously, it is possible to changetheratiobetween
the1st and 2nd flame withinawide range by replacingthenozzles. However,it should be rememberedthatfor
efficientoperations the fuel supply for the 1stflame should not beless than theminimum burner output (shown
onthe name-plate) for eachspecificmodel. A smaller output couldmake ignition difficult, andcombustion with
the1stflame only might not be satisfactory. Fromthemomentthe flame appears in thecombustionchamber,
theburneriscontrolled and monitored by the photoresistant cellandthermostats,theprogrammer continues its
cycle and disconnects the ignition transformer; consequently the burner is “on”and operating at full rating. If
theprogrammeisinterrupted (voltage failure, manualoperation,thermostattripping,etc.)duringthepre-washing
phase, the programmer will return to its original position and automatically repeat the whole burner start-up
cycle. When the temperature or pressure reaches the value preset on the thermostat or operating pressure
switch, its tripping will cause the burner to stop. The burner will resume its operation automatically when the
temperature or pressure value falls by the required amount. In case of flame failure during operations, the
photoresistant cell will trip immediately (1 second) and stop current to the relay which then opens and conse-
quentlydisconnects the washing electrovalve. Thisinturn rapidly discharges theexisting pressure and thejet
ofatomizedoiliscutoffbytheautomaticclosureof the atomizing unit valve as soon as the pressure drops below
7bar. In this case,thestart-upcycleisrepeatedautomaticallyandiftheflameignitesnormallyagain,theburner
will also resume its normal operations. If there is a poor flame or no flame at all, the unit goes automatically to
“shut down”.
