Savio 20/1 MFS User Manual page 7

General information
not sense the correct velocity, the burner will shut
down.
Operating sequence on central heating mode
The function switch must be set on
The water in the main circuit is sent to the c.h. system
when the 3---way valve is in the c.h. position. In this con-
figuration, the divertor is in the upper position and the
d.h.w. heat exchanger circuit is cut out.
The appliance is controlled by an electronic thermostat;
water delivery temperature can be adjusted from 35 ° C
to 85 ° C.
When heat is requested, a command reaches the full
sequence control p.c.b.; this command starts the fan,
which switches the air pressure switch. After the air
pressure switch has been switched, the combustion
chamber is purged of any residual unburned gasses for
a few seconds. Next , the lighting cycle begins with a
spark from the ignition electrode; at the same time,
electrical power is fed to the two ON---OFF operators on
the gas valve.
If the flame detection electrode does not sense the
flame within 4 seconds from the beginning of the cycle,
the full sequence control p.c.b. interrupts the lighting
cycle, the electric spark is shut off and the power is dis-
connected from the two ON---OFF operators on the gas
valve; as a result, the burner is shut down.
At this point, the shut down warning light appears and
the reset push---button must be pressed to restart the
lighting cycle.
If the detection electrode senses flames within 4 sec-
onds from the beginning of the cycle, the full sequence
control p.c.b. interrupts the electric sparks and holds
the burner alight.
At the same time, the temperature of the heating circuit
is measured by the main circuit temperature probe and
this temperature is compared with the value set on the
c.h. temperature adjustment (
After lighting has been accomplished, the amount of
flow from the gas valve is determined by the electronic
regulation p.c.b.:
position.
).
rev. 17.09.93
--- when the temperature of the c.h. water is less than
the preset temperature by a ? t value (difference be-
tween output and input temperature) between 6 ° C
and 15 ° C, the appliance will supply heating power
which ranges from 35 to 100% of its maximum ca-
pacity;
--- when the temperature of the c.h.water is less than
the preset temperature by a ? t value which is less
than 6 ° C, the appliance will supply its minimum
heating power (35% of its maximum heating
power);
--- if the minimum power is greater than the heat
emitted from the radiators, the burner will shut
down.
Heating power can be varied from 35 to 100% of the
maximum rated power.
Operating sequence on d.h.w. mode
Whenever a d.h.w. tap is opened, the d.h.w. flow switch
on the d.h.w. system is activated and a signal is sent to
the electronic regulation p.c.b. This signal moves the
shutter on the 3---way valve and thus closes the c.h.
water circuit and opens the d.h.w. heat exchanger cir-
cuit.
The burner will operate at nominal power, or at a power
rating which keeps d.h.w. at the constant temperature
desired (as long as the demand for heating power does
not exceed the nominal power supplied by the boiler).
Thus, burner operation depends on the amount of
d.h.w. used and the temperature which has been set on
the d.h.w. temperature adjustment (
D.h.w. only operation
When the function switch is set on
adjustment system is deactivated, the 3---way valve is
no longer actuated, the shutter closes water delivery to
the c.h. circuit and opens delivery to the d.h.w. heat ex-
changer. When d.h.w. is withdrawn from the d.h.w. sys-
tem, operation of the appliance will be the same as
operation with the function switch set on
).
position, the c.h.
position.
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