EN • 3
ENGLISHFRANCAISNEDERLANDSESpAñoLITALIANoDEuTSCH
662Y0000.B
FUNCTIONAL DIAGRAM (illustrations D)
1. Air
2. Gas
3. Venturi
4. Fan
5. Offset adjustment screw
6. Gas flow a adjustement screw (CO2)
7. Air - gas mixture
OPERATION
The BG 2000-S burner is fitted with a gas valve – venturi assembly,
an electronic controller, a fan, a flame holder and lighting and
ionisation electrodes.
CONTROLLING THE AIR – GAS MIXTURE (illustrations D)
As the fan sucks in air through the venturi, a drop in pressure (P1) is
produced in the neck of the venturi.The gas valve regulator then reacts
to maintain a pressure differential equal to the offset value between the
pressure at the gas valve outlet (P2) and atmospheric pressure (P3):
P2 – P3 = offset
If the air flow decreases, P1 increases; the same occurs for P2; P2
is then >P3; the regulator R is moved higher to make P2 – offset =
P3; pressure P4 falls and the valve C is turned down: the gas flow
decreases.
By careful adjustment of the offset, an air – gas pressure ratio of 1 is
obtained, regardless of the fan speed.
The pressure differential between the venturi neck and the gas valve
outlet then causes gas to be sucked through the venturi.
The gas flow adjustment screw can be used to adjust the quantity of
gas injected for a given air flow, which will set the %CO2 in the flue gas.
A given output can then be set simply by adjusting the speed of rotation
of the fan and the % CO2 to preset values.
LIGHTING AND FLAME CONTROL
The S 4565 AD 2080 control unit performs the tasks of lighting the
burner by producing a spark at the ignition electrode, and maintaining
the flame when the gas valve is opened by measuring the ionisation
current.
The lighting sequence is shown in the diagram below: When the boiler
thermostat detects a demand for heat, the fan starts; after 15 seconds
of preliminary flushing, the gas valve is opened and simultaneously
a spark is produced. If an ionisation current is detected in the first 5
seconds, combustion occurs normally until the end of the demand. If
not, the gas valve is closed and the fan stopped, the burner being in
safety mode. It must then be reset manually before lighting is attempted
again.
Ionisation
Thermostat
Fan
Gas valve opens
Spark
15s
5s
BURBER TUBE GAS (illustrations E / F / G)
The air-gas mixture leaving the gas valve - venturi assembly is forced
into the burner tube gas and combustion spreads evenly around the
burner.
BG 2000-S burners are fitted with three different types of flame holder:
two are made of stainless steel (illustration E) for outputs less than
60 kW, the others (illustrations F / G) receive metal fibre (NIT) which
distributes the flame better. It also gives longer life and considerably
lower pollution emissions.
BG 2000-S / 100
BG 2000-S / 60 / 70
G
F
BG 2000-S / 25 / 35 / 45 / 55 - (SV / 35)
E
1 7
2
5
R
3 4
6
P1
P2
P3
P4
D
