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15) Then turn off the switch to ignite the burner. When the burner is lit, with the second flame, immediately check the
gas supply, first visually and then by reading the meter. Depending on these checks, gas delivery can be adjusted,
if necessary, to the value required in each specific case (boiler power), remembering that methane develops 8550
kcal/m
3
. With the burner on at the 2
nd
flame, check the gas delivery by calculating the difference in two readings
taken exactly one minute apart. Multiply this value by sixty to obtain the delivery in 60 minutes, i.e. one hour. The
delivery measured is taken as the actual value if the meter measures a pressure of less than 400 mm H
2
O,
otherwise the value calculated must be multiplied by the correction coefficient (see the chapter “Reading the
meter”). Then, multiply the hourly delivery (m
3
/h) by the heating power of the gas, thereby obtaining the power
delivered in kcal/h. This value must be equal to, or very close to that required by the boiler (lower heating power for
methane = 8550 kcal/m
3
). Adjust the flow regulator for the 2nd flame to suit each specific case. To avoid possible
damage to the boiler, do not keep the burner operating if the flow exceeds the maximum allowed. The burner
should therefore be stopped immediately after the two meter readings are taken.
16) Use suitable instruments to check that combustion occurs correctly (CO
2
= 8 - 10% for methane / CO max. 0.1%).
To optimise combustion and for good flame stability (no flicker), the combustion head regulator may have to be
adjusted (see the chapter “Regulating the air to the combustion head”). Normally the air gap between the disc and
the head must be reduced when working with a reduced fuel delivery. The gap must be opened proportionally when
the burner is working with at higher fuel delivery.
When the flame disc is adjusted, normally it is also necessary
to correct the position of the air shutter of the first and second flames, then, check that ignition occurs correctly.
17) The air pressure switch is used to put the unit on safety (cut-out) if the air pressure is not at the required level.
The pressure switch must therefore be adjusted to cut-in, closing the contacts (which must be closed during
operation), when the air pressure in the burner reaches a sufficient level. The pressure switch connection circuit
provides for automatic control, therefore the contact must be able to remain closed when at rest (fan stopped and
lack of air pressure in the burner) to actually enable this condition, otherwise the command and control unit will not
be activated (the burner will stay off). If a contact required to remain closed during the working cycle is not closed,
the unit will only complete part of its cycle and then shut down “cut-out” without activating the ignition transformer or
the gas valves. To check that the air pressure switch is working properly, increase the setting with the burner on first
flame only, until the switch cuts in, which must result in immediate burner shut down “cut-out”. Reset the burner by
pressing the special pushbutton and bring the setting on the pressure switch to a sufficient value for detecting the
air pressure present during the pre-ventilation phase.
18) The gas pressure pressure switches (minimum and maximum) are used to prevent the burner from working
when the gas pressure is outside the required limits. According to the specific function of the pressure switches, it
is clear that the the minimum pressure control switch must have its contact closed when it detects a pressure
above its setting. The maximum pressure switch must have its contact closed when it detects a pressure below its
setting. The maximum and minimum gas pressure switches must therefore be set at the time of burner testing,
according to the pressure measured in each case. The pressure switches are electrically connected in series so
that when the gas pressure switches intervene (when the circuit opens) the unit is not turned on. Intervention (i.e.
opening of a circuit) of any pressure switch when the burner is working (flame lit), causes the burner to stop
immediately. When testing the burner, it is essential to check that the pressure switches are working properly.
Pressure switch intervention (opening of the circuit), which must shut down the burner, is checked by operating the
respective regulation devices.
1
9) Safety checks Check the efficiency of the UV photocell flame detector.
At least one minute after ignition, remove the photocell from its seat. When the UV photocell is removed from its
seat it can no longer “see” the ultraviolet radiation emitted by the flame, therefore the relative relay is de-activated.
The burner immediately shuts down “cut-out”. Even slight oiliness greatly affects the passage of UV rays to the bulb
in the UV photocell, preventing the sensitive internal element from receiving the amount of radiation required for
the unit to work properly. If the bulb becomes fouled by gas oil, fuel oil, etc., it must be cleaned properly. Even
touching the bulb with a finger can leave enough oiliness to affect UV photocell operation. The UV cell does not
“see” daylight or light from a normal lamp. Its sensitivity can be checked with a flame (lighter, candle) or an electric
spark between the electrodes of an ordinary ignition transformer.
To ensure that the unit works properly, the current on the UV cell must be sufficiently stable and must not fall below
the minimum value required for the specific unit. This value is given in the wiring diagram. The best position may
have to be found by experimenting, by sliding (axial movement or rotation) the body containing the photocell on the
clamping bracket. The unit can be checked by connecting a micro-ammeter, with a suitable scale, in series with
one of the two UV photocell cables. Obviously the polarity must be respected (+ and -). The unit can only be reset
manually by pressing the special pushbutton (reset). The cut-out efficiency check must be carried out at least
twice. Check the efficiency of boiler thermostats or pressure switches (their intervention must shut down the burner).
Check the efficiency of air and gas pressure switches.
