Temperature Sensor; Operating Cycle - Sime FORMAT.zip 4 25 OF Manual Del Instalacion

90 seconds, which occurs both at
system cold starting and at subse-
quent re-ignitions.
The aim is to overcome the problem of
repeated ignitions and turning off with
very short time intervals between.
This could occur in particular in systems
presenting high head losses.
At each restart after the period of slow
ignition, the boiler will set itself for about
1 minute at the minimum modulation
pressure, and will then move to the hea-
ting pressure value set.
When the connecting link is inserted,
both the programmed technical pause
and the period of operation at minimum
pressure in the startup phase will be
cancelled.
In this case, the times elapsing between
turning off and subsequent re-ignition will
depend on a temperature difference of
5°C detected by the C.H. sensor (SM).
ATTENTION:
It is essential that the operations descri-
bed above be carried out by authorized
technical staff.
3.2 TEMPERATURE
SENSOR
3.2. 1 Model "25 BF"
The boiler is equipped with sensor for detec-
ting heating temperature.
The sensor acts as a limit stat, switching-off
the burner when the temperature measu-
red is higher than 85°C; the reset tempe-
rature is set at 80°C.
When sensor has tripped, the boiler will
not function for either service.
Table 3 shows the resistance values (Ω)
that are obtained on the sensor as the
temperature varies.
TABLE 3
Temperature (°C) Resistance (Ω)
20 12.090
30 8.313
40 5.828
50 4. 1 61
60 3.021
70 2.229
80 1.669
3.2.2 Model "25 OF"
Table 3 gives resistance values (Ω) obtai-
ned with the heating and hot water probes
when the temperature changes.
If the heating probe (SM) is off, the boi-
ler does not work for either heating or
hot water. If the hot water probe (SS) is
off, the boiler works for either heating
or hot water but does not modulate in
D.H.W. mode.
3.3 ELECTRONIC IGNITION
Ignition and flame detection is controlled by
an electrode located on the burner. These
guarantee maximum safety with interven-
tion times, for accidental switching off or
gas failure, of within one second.
3.3. 1

Operating cycle

Rotate the rotary switch to summer or win-
ter, the red led should light up.
Burner ignition normally takes place within
10 seconds. However, it is possible for igni-
tion failures to occur, with consequent acti-
vation of signal indicating that the control
box has "locked out".
– Gas failure
The control box runs through the cycle
normally sending electric power to the
ignition electrode. The electrode conti-
nues spark discharge for a maximum of
10 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 gas cock being closed or by one of
the valve coils having a break in the win-
ding, so that the valve cannot open.
– Ignition electrode fails to spark
In the boiler, only the gas to the burner is
seen to open. After 10 sec. the control
box "locks out".
This may be due to a break in the wire of
the electrode or to the wire not properly
fastened to the electric terminal of the
ignition transformer.
The electrode is earthed or very worm
and needs to be substituted.The control
box is defective.
When there is a sudden voltage failure, the
burner shuts out immediately; when power
supply returns, the boiler will start up again
automatically.
3.4 "25 OF" SMOKE
SAFETY DEVICE
It is a safety measure against the outflow of
PRESSOSTATO
SMOKE
PRESSURE
SWITCH
smoke into the environment due to ineffi-
ciency or a partial clogging up of the flue (18
fig. 3).
It acts by blocking the gas valve when the
release of smoke into the environment is
continuous and in such a quantity as to be
dangerous. To restart the boiler, and reacti-
vate the button of the thermostat.
If the blockage occurs repeatedly a thorou-
gh control of the flue will be necessary,
making all the modifications and taking all
the precautions necessary in order for it to
be efficient.
3.5 "25 BF" SMOKE
PRESSURE SWITCH (fig. 16)
The pressure switch with fixed settings 9.5-
14.4 mm H O is able to guarantee the boi-
2
ler operation even with air intake and smoke
outlet pipes at the maximum limit of the
length allowed.
The value of the signal to the pressure swit-
ch is measured by means of an instrument
connected as shown in fig. 16.
3.6 "25 OF" WATER
PRESSURE SWITCH
The water pressure switch (15 fig. 3) is
tripped, stopping the burner, if the pressu-
re in the boiler is lower than 0.6 bar.
To restore burner functioning, restore
pressure in the system to a value between
1-1.2 bar.
3.7 FLOW SWITCH WATER
In model "25 OF" the flow switch (8 fig. 5)
is tripped, stopping the burner, when no
water is detected in the hot water circuit.
In model "25 BF", on the other hand, it is
tripped and stops the burner when it
does not detect water in the primary cir-
cuit (> 400 l/h).
To res t ore burner functioning, check
system pressure and the functioning of the
pump and the flow switch.
ROOM SEALED
CAMERA STAGNA
FAN
VENTILATORE
(--)
(+)
IT
ES
PT
GB
GR
RO
RUS
Fig. 16
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