Operation Sequence Of The Burner; Burner Start-Up; Operation; Burner Flame Goes Out During Operation - Riello 20074125 Installation, Use And Maintenance Instructions

6.8

Operation sequence of the burner

6.8.1

Burner start-up

T0 0s TL thermostat/pressure switch closure.
T1 06 Fan motor start. Servomotor starts:
rotates 90° towards the right, i.e. until the inter-
vention of the contact on the cam 4)
T2 38s The air damper is positioned to MAX output.
T2 38s Pre-purging phase with air delivery
of the MAX output. Duration 32 seconds.
T3 70s The servomotor rotates left up to the angle
set on the cam 2).
T4 102s The air damper and the gas butterfly valve
set to MIN output (with cam 2).
T5 103s Ignition electrode strikes a spark.
T6 109s The VS safety valve and the VR adjustment
valve open (rapid opening).
The flame is ignited at a low output level,
point A (Fig. 36). There follows a progressive
increase of the input, slow opening of the valve,
up to the MIN output, point B (Fig. 36).
T7 112s The spark goes out.
T8 133s The starting cycle of the electrical
equipment ends.
6.8.2

Operation

Burner without the RWF ... output power regulator
Once the starting 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 (Fig. 36).
(The electrical control box continues to check the presence of the
flame and the correct position of the air and gas maximum pres-
sure 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° limited by the contact of the cam 2).
The air damper closes completely to reduce heat losses to a
minimum.
For every change of output, the servomotor will automatically
change the gas output (butterfly valve), the air output (fan damp-
er) and the air pressure.
Burner with the RWF ... output power regulator
See manual enclosed with the adjuster.
6.8.3

Burner flame goes out during operation

If the flame should accidentally go out during operation, the burner
will lock out within 1s.
20079034
Start-up, calibration and operation of the burner
(n° = seconds from instant 0)
6.8.4

Ignition failure

If the burner does not fire (Fig. 37), it goes into lockout within 3
sec. after the gas valve opens and 122 seconds after the control
device TL closes.
6.8.5

Control box reset

To carry out the control box reset, proceed as follows:
➤ Press the reset button 2) (Fig. 6 on page 15).
34 GB
Normal ignition
Ignition failure
20078983
Fig. 36
20078986
Fig. 37