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6.7
Operation sequence of the burner
6.7.1
Burner start-up
0 s:
TL thermostat/pressure switch closes.
2 s:
The control box starting cycle begins. Servomotor starts:
rotate to the left by 90°, i.e. until the contact intervenes
with cam I (Fig. 25 on page 23).
26 s:
the air damper arrives to the MAX. output position.
The fan motor starts up. Start of the pre-purging phase.
57 s:
the servomotor rotates towards the right, as far as the
angle set on cam III (Fig. 25 on page 23) for MIN output.
77 s:
the air damper and the gas butterfly valve adopt the MIN
output position (with cam III)(Fig. 25 on page 23) at 20°.
92 s:
Ignition electrode strikes a spark.
The safety valve VS opens, along with the adjustment
valve VR, quick opening. The flame is ignited at a low
output level, point A.
Delivery is then progressively increased, with the valve
VR opening slowly up to MIN. output, point B.
94 s:
The spark goes out.
118 s:
The starting cycle comes to an end.
6.7.2
Operation
Burner without modulating operation kit
Once the start-up cycle is completed, the servomotor command
moves on to the TR thermostat/pressure switch that controls the
pressure or the temperature in the boiler, point C.
(The electrical control box still continues to check the presence of
the flame and the correct position of the air and gas maximum
pressure switches).
–
If the temperature or the pressure is low so the thermostat/
pressure switch TR is closed, the burner progressively in-
creases the output up to the MAX value (section C-D).
–
If subsequently the temperature or pressure increases until
TR opens, the burner progressively decreases its output to
the MIN. value (section E-F). The sequence repeats endless-
ly.
–
The burner locks out when the heat request is less than the
heat supplied by the burner at MIN. output, (section G-H).
The TL thermostat/pressure switch opens, and the servomo-
tor returns to angle 0°.
The air damper closes completely to reduce heat losses to a
minimum.
Burner with modulating operation kit
See manual enclosed with the adjuster.
6.7.3
Ignition failure
If the burner does not fire, it goes into lockout within 3 sec. after
the gas valve opens and 108 seconds after TL closes.
6.7.4
Burner flame goes out during operation
If the flame should accidentally go out during operation, the burn-
er will lock out within 1s.
Start-up, calibration and operation of the burner
(n = seconds from instant 0)
27
GB
Standard ignition
Ignition failure
D3857
Fig. 33
D3858
Fig. 34
20040559
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