Features; Electronic Ignition - Sime RS Mk.II Instructions Pour L'utilisateur

3

FEATURES

3. 1

ELECTRONIC IGNITION

"RS Mk.II" boilers have automatic igni-
tion (with no pilot light), so they have an
SM 191. 1 electronic control and pro-
tection device with a built-in transfor-
mer (fig. 15).
Ignition and flame detection are con-
trolled by two sensors at the ends of
the burner.
Ignition takes place directly in the bur-
ner; the utmost safety is guaranteed,
with tripping times of within 2 seconds
in the event that the flame accidentally
goes out or there is no gas supply.
3. 1 . 1 Functioning cycle
Before turning on the boiler use a volt
meter to check that the terminal
board has been wired up correctly,
complying with the phase and neutral
positions shown in the diagram.
Press the switch on the control panel.
At this point the boiler will start up,
sending a current discharge through
the SM191. 1 programmer to the igni-
tion electrode while opening the gas
valve. Burner ignition normally takes 1
to 2 seconds. In the event that ignition
fails, the boiler shutdown signal will be
triggered. Let us sum up how this can
happen:
– No gas supply
The boiler performs the cycle nor-
mally, sending voltage to the ignition
electrode, which continues
discharge for a maximum of 8
seconds. If the burner is not ignited,
the boiler shuts down.
This may occur the first time the boi-
ler is started up or when it has been
inactive for some time and there is
air in the pipes. It may be caused by
failure to open the gas valve due to
an interruption in the electrical coil.
– Ignition electrode fails to
discharge
The gas valve to the burner normally
opens; if this does not occur within 8
seconds the boiler will shut down.
This may be the result of an inter-
ruption in the electrode cable, or the
cable may not be properly fastened
to terminal 10; or the boiler's tran-
sformer may have been burnt out.
– The flame is not detected
The electrode continues to dischar-
ge even though the burner is
2
4
SECONDA
ELETTROVALVOLA
GAS
PRESSOSTATO GAS
KEY
1 SM 191. 1 device
2 Interference filter
already ignited. After about 8
seconds the discharge will stop and
the burner will be shut down, while
the device's shutdown indicator light
to
will come on.
This occurs if phase and neutral
have not be connected properly on
the terminal board.
The detection electrode cable may
be interrupted or the electrode itself
may be grounded; the electrode may
be worn and require replacement.
NOTE: if the device shuts down, press
the illuminated pushbutton only after
waiting at least 20 seconds from
when the indicator light came on, or
the device will not be released.
3. 1 .2 Ionisation circuit
The ionisation circuit may be controlled
using a micro-ammeter with a dial or,
better yet, a digital reading, with a
scale of 0 to 50 µ .
The micro-ammeter's terminals must
be wired up to the detection electrode
3
BOBINA
VALVOLA GAS
3 Ignition electrode
4 Detection electrode
cable in series. During regular opera-
tion the reading fluctuates around
6÷ 12 µ .
The minimum ionisation current at
which the device may be shut down is
around 1 µ .
If this occurs, check that there is pro-
per electrical contact and check the
end of the electrode and its ceramic
guard for wear.
3.2 STEP CONTROL
THERMOSTAT
"RS Mk.II" boilers have a control ther-
mostat with dual contacts with diffe-
rentiated calibration which permit a
reduction in power before the burner
goes out completely through the coil
assembly (fig. 22) mounted on the
gas valve control.
This step modulation system offers
the following advantages:
– Higher overall boiler yield.
– Limitation of temperature increases
in the cast iron body (thermal iner-
tia) to within acceptable values
when the burner goes out.
1
Fig. 15
67