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TENANCE
At the end of the heating season, it is good practice to clean the gas and light oil filters, the combustion head (disk,
insulators, nozzles), the combustion air passages and the photoelectric cell (UV). It is advisable to use wooden or
plastic instruments to clean the nozzle passages. Nozzle should be replaced after 12 months’ use.
UV CELL
If flame detection is carried out with the UV cell, the following should be taken into consideration. Even the slightest
greasiness will compromise the passage of the ultraviolet rays through the UV photoelectric cell bulb, thus preventing
the sensitive internal element from receiving the quantity of radiation necessary for it to function properly.
Should the bulb be fouled by light oil, fuel oil, etc., it is indispensable to clean it thoroughly.
It should be pointed out that even by simply touching the bulb with the fingers, it is possible to leave a slight greasiness
which could compromise the working of the UV photoelectric cell. The UV cell does not “see” daylight or light from an
ordinary lamp. It is possible to verify its sensibility with a flame (or cigarette lighter or a candle) or with the electric spark
that occurs between electrodes in an ordinary ignition transformer.
To ensure that the UV cell works properly, its current value should be sufficiently stable so as not to fall below the
minimum value required for the specific control box. It may be necessary to search experimentally for the best position
by sliding (axial or rotation movement) the body that contains the photoelectric cell in respect to the fastening clamp.
An inspection can be carried out by inserting a microammeter, with an adequate scale, in series to one of the two UV
photoelectric cell connection wires. It is obviously necessary to respect the polarity (+ e -).
AIR PRESSURE SWITCH
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 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 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.
GAS PRESSURE SWITCH
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 measures a
pressure below that at which is has been set.
The minimum and maximum 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 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.
