Features - Sime RS Mk.II Serie Instrucciones Para El Instalador Y El Usuario

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FEATURES

3. 1 ELECTRONIC
IGNITION
"RS Mk.II" boilers have automatic ignition
(with no pilot light), so they have an SM
191. 1 electronic control and protection devi-
ce with a built-in transformer (fig. 15).
Ignition and flame detection are controlled
by two sensors at the ends of the burner.
Ignition takes place directly in the burner;
the utmost safety is guaranteed, with trip-
ping 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 ignition electrode while
opening the gas valve.
When the gas pressure is insufficient, the
pressure switch does not enable the start-
up cycle and the insufficient gas pressure
warning signal is enabled. 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:
– Air in the gas pipes
The boiler performs the cycle normally,
sending voltage to the ignition electrode,
which continues to discharge for a maxi-
mum of 8 seconds. If the burner is not
ignited, the boiler shuts down.
This may occur the first time the boiler 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 interruption
in the electrode cable, or the cable may
not be properly fastened to terminal 10;
or the boiler's transformer may have
been burnt out.
– The flame is not detected
The electrode continues to discharge
even though the burner is already ignited.
After about 8 seconds the discharge will
2
4
SECONDA SECOND
ELETTROVALVOLA GAS SOLENOID
GAS
VALVE
GAS PRESSSURE SWITCH
PRESSOSTATO GAS
KEY
1 SM 191. 1 device
2 Interference filter
stop and the burner will be shut down,
while the device's shutdown indicator
light 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 indica-
tor 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 cable in
series. During regular operation the rea-
ding fluctuates around 6÷ 12 µ . The mini-
mum ionisation current at which the device
may be shut down is around 1 µ .
If this occurs, check that there is proper
electrical contact and check the end of the
electrode and its ceramic guard for wear.
1
3
COIL
BOBINA
GAS VALVE
VALVOLA GAS
3 Ignition electrode
4 Detection electrode
3.2 STEP CONTROL
THERMOSTAT
"RS Mk.II" boilers have a control thermo-
stat with dual contacts with differentiated
calibration which permit a reduction in
power before the burner goes out comple-
tely through the coil assembly (fig. 22)
mounted on the gas valve control.
This step modulation system offers the fol-
lowing advantages:
– Higher overall boiler yield.
– Limitation of temperature increases in
the cast iron body (thermal inertia) to
within acceptable values when the bur-
ner goes out.
3.3 OPPOSED
INSTALLATION
OF TWO BOILERS
On request, accessories may be supplied to
permit opposed installation of two boilers so
as to reduce overall dimensions and permit
easy connection with the flue by allowing
flue gases to be evacuated through a single
duct (fig. 16-17).
Table 2 shows the dimensions of the two
combined boilers and stack diameter.
Fig. 15
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