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Start-up, calibration and operation of the burner
5
5.6
Operation sequence of the burner
Burner start-up
• 0s:
TL closed.
• 0s:
TL thermostat/pressure switch closes.
• 2s:
The control box starting cycle begins. Servomotor
starts: rotate to the left by 90°, i.e. until the contact
intervenes with cam I (Fig. 7).
• 26s:
The air damper arrives to the MAX. output position.
The fan motor starts up.
Start of the pre-purging phase.
• 57s:
the servomotor rotates towards the right, as far as the
angle set on cam III (Fig. 7) for the MIN output.
• 77s:
The air damper and the gas butterfly valve adopt the
MIN output position (with cam III) (Fig. 7) at 65°.
• 92s:
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.
• 94s:
The spark goes out.
• 118s: The starting cycle comes to an end.
STANDARD IGNITION
Steady state operation
Burner without themodulating 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
increases 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 end-
lessly.
6463
• 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.
Ignition failure
If the burner does not switch on, there is a lockout within 3s of
the electrical supply reaching the gas valve.
It may be that the gas does not arrive at the combustion head
within the safety time of 3s.
In this case increase gas ignition delivery.
The arrival of the gas at the pipe coupling is shown on the
pressure gauge of Fig. 36.
5.7
Burner flame goes out during operation
D3857
If the flame should accidentally go out during operation, the
Fig. 33
burner will lock out within 1s.
5.8
Stopping of the burner
The burner can be stopped by:
intervening on the disconnecting switch of the electrical sup-
ply line, located on the boiler panel;
removing the hood and working on the "AUT/MAN" switch of
Fig. 27.
22
GB
D3858
Fig. 34
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