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DESCRIPTION OF OPERATION WITH GAS (METHANE) (see BT 8710/1)
The burner command and control (cycle relay) equipment is turned on by means of the switch on the control
panel ( I).
Control box
Safety
and relative
delay
programmer
in seconds
LFL 1.333
3
Cycle relay
When the thermostats (pressure switches for steam boilers) are closed, the cycle relay equipment carries out the
ignition program, and starts the fan and pump motors to carry out the pre-ventilation phase.
The pressure of the air supplied by the fan must be high enough to activate the relative pressure switch, otherwise
the unit shuts down "cut-out". During "pre-ventilation" the air lock is switched to the 2
regulating servomotor (pre-ventilation with air open – see BT 8653/1).
Subsequently, the air regulation servomotor moves the air lock to the set position for the 1
the ignition, followed by opening of the 1st (pilot) flame valve and the safety flame. The valve for the first flame has
a built-in flow regulator that allows the gas delivery for starting to be regulated. The safety valve is activated and
deactivated at the same time as the valve for the first flame. As a result the flame, detected by the flame detection
device (UV photocell) allows the ignition phase to proceed and be completed when ignition is deactivated.
The unit activates the air regulation servomotor, which moves the air lock to the set position (see BT 8653/1) for
nd
the 2
flame. As the air regulation servomotor turns, a special cam closes a microswitch, that delivers power to
the solenoid valve of the 2
does not open the air lock of the 2
If there is no flame, the unit shuts down as a result of a "safety cut-out".
The valves close immediately in the event of a "safety cut-out".
LAYOUT (GAS PART)
Anti-vibration
union
Ball
Filter
Gas pressure
cock
reducer or
stabiliser
D = Distance between pressure stabiliser and valves, approx 1.5 ÷ 2 m.
Control box Specifications
Preventilation /
air lock open time
in seconds
31,5
nd
flame, which opens gradually. Therefore, it is clear that if the air regulation servomotor
nd
flame, the gas valve of the 2
Leak detector (where fitted)
valves and relative pressure switch
Minimum
Pressure
Switch
Pair of flanges
Preignition
Postignition
in seconds
in seconds
6
nd
flame will not be opened either.
Maximum
Pressure
Switch
Safety
Two-position opening
Valve
valve
with flow regulators
for the 1
st
17
Time between 1st flame
& 2nd flame
in seconds
3
12
nd
flame position by the air
st
flame. It then activates
Air pressure
switch
Air lock
Air lock
and 2
flame
nd
control electric motor
BT 8710/1
Combustion
head
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