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STARTING UP AND REGULATION WITH METHA-
NE GAS
1) If not already done at the moment of connecting the burner to
the gas pipeline, it is indispensable to carry out a purge of the air
contained in the pipeline. As a precaution, special care should be
taken and doors and windows should be opened. Open the pipe
union on the pipeline situated near the burner and then open
a little the gas cut-off cock (or cocks). When the characteristic
odour of gas can be smelled, close the cut-off cock. Wait until
the gas present in the room has dispersed, and then reconnect
the burner to the gas pipeline. Subsequently, re-open the gas
cut-off cock.
2) Check that there is water in the boiler and that the system’s
gate valves are open.
3) Check, with absolute certainty that the discharge of combustion
products can take place freely (boiler and chimney lock-gates
should be open).
4) Make sure that the voltage of the electric line to which the burner
is to be connected, corresponds to that required by the burner
and that the electrical connections (motor or principle line) have
been prepared to match the voltage rating available. Also check
that all the electrical connections carried out on the spot are in
accordance with our electric wiring diagram.
5) Make sure that the combustion head is long enough to enter
the furnace to the extent specified by the boiler manufacturer.
6) Remove the protection cover from the disk carrying the air and
gas flow regulator screws and slacken the screws that block
the regulator screws.
7) Check that the air regulator device on the combustion head is in
correct position for the fuel throughput required (the air passage
between the diffusor disk and the head must be small for low
throughput and relatively wide when throughput is higher). See
“Combustion head airflow regulation” heading.
8) Fit a pressure gauge with suitable full scale (where the pressure
level envisaged allows, a liquid manometer is preferable; do not
use pointer gauges for low pressures) to the pressure outlet
port on the gas pressurestat.
9) Open, as far as considered necessary, the flow regulator
incorporated in the pilot flame valve(s). Also check that the
combustion airflow control shutter is sufficiently open; if neces
-
sary, alter the position by acting on the regulator screws on the
regulator disk.
10) With the burner panel switch on “O” and the master switch in
‘make’, that the fan motor rotates in the correct direction. If
necessary, reverse two phases of the motor power supply line
to change the direction.
11) Now switch the panel switch to “I” and turn the modulation
switches to MIN (minimum) and MAN (manual). With the
control system receiving electrical power, the programmer
will cause the burner to start up as described under the
foregoing heading “Description of natural gas operation”.
During pre-purge time, check for operation of the air pressu-
restat, the contacts of which should change from a pressure-
zero ‘make’ to a pressure-positive ‘make’. In the event that the
pressure is sufficient and the pressurestat fails to respond,
neither the ignition transformer nor the pilot flame gas valves
will operate so the burner will shut down in lockout.
Note that lockouts during this first ignition sequence should be
considered normal since the fuel supply line will still contain air
which must be purged before a stable flame can be obtained.
Press the “reset” button to re-start.
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 in-
dispensable 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 pos-
sible 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 -). The
minimum cell current value, to ensure the correct operation of
the control box, is shiwn on the wirung diagram.
12) As soon as the burner is ignited at low flame (main flame valve
open and modulator on minimum) make a visual inspection
of the strength and appearance of the flame, making any
corrections required (adjust the gas or air regulator screws on
the modulating disk). The next step is to take a meter reading
of the volume of gas put through the burner (see the “Meter
Reading” section). If necessary, a further correction in the
gas flow may be made as described above. Once fuel and
air flow are satisfactorily regulated, a check must be made on
combustion characteristics, using the appropriate instruments.
If the air/gas ratio is correct the level of carbon dioxide (CO2)
per unit of fuel put through should be approximately - in the
case of natural gas - 8% at minimum burner output, rising to
an optimum 10% at maximum output. We recommend that
the value of 10% should not be exceeded, as operation in too
limited an excess of air can give rise to unacceptable carbon
monoxide (CO) levels (due to variations in atmospheric pres-
sure, or dust deposits in the air lines). It is essential to verify,
using the appropriate instrument, that the percentage of CO
in flue gases does not exceed the maximum permissible level
of 0,1%.
Summary of Contents for GI MIST 1000 DSPNM-D
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