82
ting pressure value set. When the con-
necting link is inserted, both the pro-
grammed t echnical pause and the
period of operation at minimum pressu-
re in the startup phase will be cancel-
led. 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 opera-
tions described above be carried out by
authorized technical staff.
3.2
TEMPERATURE SENSOR
3.2.1
Model “BF”
The boiler is equipped with sensor for
detecting heating temperature. The sen-
sor acts as a limit stat, switching-off the
burner when the temperature measured
is higher than 85°C; the reset temperatu-
re is set at 80°C.
When sensor has trip-
ped, 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.
3.2.2
Model “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 boiler does
not work for either heating or hot water.
If the hot water probe (SS) is off, the boi-
ler works for heating only.
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 igni-
tion normally takes place within 10 seconds.
However, it is possible for ignition failures
to occur, with consequent activation of
signal indicating that the control box has
“locked out”.
–
Gas failure
: The control box runs throu-
gh the cycle normally sending electric
power to the ignition electrode. The
electrode continues 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 cau-
sed by the gas cock being closed or by
one of the valve coils having a break in
the winding, 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 ter-
minal 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
“OF” SMOKE SAFETY DEVICE
This is a safety device against possible
smoke emission into the ambience (18 fig.
3). 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 con-
stitute a danger. The intervention of the
device locks out the appliance because the
burner has not ignited. In this case, place
the rotary switch to the (
) position must
be pressed for the boiler to restart auto-
matically. Should the boiler continue to “lock
out”, it will be necessary to make a careful
check on the flue pipe, making all the neces-
sary modifications and amendments so that
it can work properly.
3.5
“BF” SMOKE PRESSURE SWITCH
The pressure switch (8 fig. 3) with fixed set-
tings 9.5-14.4 mm H
2
O is able to guaran-
tee the boiler operation even with air
intake and smoke outlet pipes at the maxi-
mum limit of the length allowed (fig. 16).
3.6
“OF” WATER PRESSURE SWITCH
The water pressure switch (15 fig. 3) is
tripped, stopping the burner, if the pres-
sure in the boiler is lower than 0.6 bar.
To restore burner functioning, restore
p r e s s u r e i n t h e s y s t e m t o a v a l u e
between 1-1.2 bar.
3.7
FLOW SWITCH WATER
In model
“OF”
the flow switch (8 fig. 5) is
tripped, stopping the burner, when no
water is detected in the hot water cir-
cuit. In model
“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 restore burner func-
tioning, check system pressure and the
functioning of the pump and the flow
switch.
3.8
HEAD AVAILABLE
TO SYSTEM
Residual head for the heating system is
shown as a function of rate of flow in the
graph in fig. 17.
TABLE 3
Temperature (°C)
Resistance (
Ω
)
20
12.090
30
8.313
40
5.828
50
4.161
60
3.021
70
2.229
80
1.669
0
200
1600
1400
1200
1000
800
600
400
PORTATA (l/h)
PREV
ALENZA RESIDU
A (mbar)
500
400
100
200
300
30
25
Fig. 17
FLOW RATE (l/h)
RESIDU
AL
HEAD
(mbar)
Fig. 16
