Description of functioning
t e c h n i c a l
15
3.1.3.- Gas Circuit
Characteristics of the gas components:
Gas valve:
(Part number FCB1130)
This is one of the most important components of the boiler. It
regulates output power, gas consumption, combustion, mo-
dulation
.
The SIT-845 SIGMA valve is equipped with two on/off safety
valves powered by the
PCB
at 230V AC, plus a
modulating
valve also powered by th
e PCB
in
DC ensuring continuous
modulation.
The valve has two
test nipples
(A)
is the inlet supply pressure
(B)
Is the outlet pressure from the modulating section of the valve
(Burner pressure can also be tested at the inlet pipe to
the burner)
Spark generator
A
B
This component
has 2 functions the 1st is to create a
high tension voltage at the spark electrodes. The unit also
provides a connection for the 230v ac from the PCB to
the twin gas valve solenoids (EV1 +EV2)
(Part number MCB3055)
Gas pressure
modulation
:
This is a progressive modulation type boiler, i.e. it automatically adjusts its gas con-
sumption to the USER’s needs at all times.
When the boiler needs to heat water at maximum power, there is maximum gas pres-
sure to the burner and, inversely, when modulation is at a minimum it uses minimum
power and the pressure to the burner is also minimum.
The gas pressure to the burner
varies
according to the gas
type (propane/ natural)
FCB1130
14
