3.1
CONTROL BOX
The
“RMG”
boilers are provided with
automatic ignition (without pilot bur-
ner). They are therefore equipped with
FM 11 electronic control and protec-
tion, with a built-in transformer, located
inside the instrument panel protection
box. Ignition and flame detection is con-
trolled by two electrodes located on
the burner.
These guarantee maximum safety with
intervention times, for accidental swit-
ching off or gas failure, within 8
seconds.
3.1.1
Operating cycle
Before igniting the boiler, use a voltme-
ter to make sure that the electrical
connection to the terminal block has
been made properly, respecting the
position of live and neutral, as shown in
the diagram.
Then press the switch on the control
panel detecting voltage and lighting the
led lamp.
The boiler is now ready to start
working; a discharge current is sent to
the ignition electrode through the FM
11 programmer, and the gas valve
opens at the same time.
Burner ignition normally takes place
within 2 or 3 seconds. However, it is
possible for ignition failures to occur,
with consequent activation of signal
indicating that the equipment has
“locked out”.
Failures may be due to one of the fol-
lowing causes:
–
Gas failure
The control box runs through the
cycle normall y sending electric
power to the ignition electrode.
The electr ode continues spar k
discharge for a maximum of 8 sec.
If the burner does not ignite, the
control box “locks out”.
This may occur upon first ignition or
after long periods of boiler lay-off
when there is air in the pipes.
It may be caused by the failure of
the gas valve to open owing to a
break in the electric coil.
.
–
Ignition electrode fails to spark
In the boiler, only opening of gas to
the burner is seen to occur. After 8
sec. the control cox “locks out”.
This may be due to there being a
break in the wire of the electrode or
the wire not being properly fastened
to the terminal of the control box; or
else, the transformer has burnt out.
–
No detection of flame
The continuous spark discharge of
the electrode is noted starting from
ignition even though the burner is lit.
After 8 seconds have elapsed, the
sparks cease, the burner goes out,
and the warning lamp indicating
equipment “lock-out” lights up.
This occurs when the position of live
and neutral has not been respected
on the terminal block.
There is a break in the wire of the
sensing electrode or the electrode
itself is earthed: the electrode is
worn out and needs replacing.
The control box is falty
When there is a sudden voltage failu-
re, the burner shuts out immediately;
when power supply returns, the boiler
will start up again automatically.
3.1.2
Ionization circuit
The ionization circuit is to be checked
using a dial-type micro-ammeter, or
preferably a digital micro-ammeter
with a 0 to 50 µA scale. The micro-
ammeter terminals must be series-
connected to the wire of the sensing
electrode. Under normal operating
conditions,
the
value
oscillates
between 6 - 10 µA.
The minimum value of the ionization
current for which the equipment can
“lock out” is about 1 µA.
In this case, make sure that there is a
good electrical contact and check the
degree of wear of the end part of the
electrode and the corresponding cera-
mic protection.
3.2
REGULATION THERMOSTAT
“RMG”
boilers are equipped with a
regulating thermostat with a double
contact having differentiated setting (6
fig. 2). This makes it possible to obtain
a reduction of heat output before the
burner goes out completely, by means
of the coil assembly installed on the
gas valve regulator.
This step-modulation system affords
the following advantages:
–higher overall boiler efficiency;
–cont ainment wit hin accep t able
values of the increase in temperatu-
re that takes place in the cast-iron
body (heat inertia) when the burner
goes out.
3.3
SMOKE SAFETY DEVICE
This is a safety device against possible
smoke emission into the ambience (8
fig. 2). The safety device goes into
action by blocking operation of the gas
valve when the return of the smoke
into the ambience is continuous and in
quantities that might constitute a dan-
ger. To restart the boiler, the cover of
the thermostat must be unscrewed
and reset the underlying button. Make
sure the control panel is disconnected
before carrying out this operation.
Should the boiler continue to “lock out”,
it will be necessary to make a careful
check on the flue pipe, making all the
necessary modifications and amend-
ments so that it can work properly.
42
3
CHARACTERISTICS
Fig. 6
KEY
1
Electrode support
2
Electrode unit
3
Electrode ignition cable
4
Electrode detection cable
