24
GB
Continuous modulation functioning
It is the functioning that is obtained by sending an appropriate signal to the air damper servo-control, therefore
the power issued by the burner can assume any intermediate value between a pre-fixed minimum and maximum.
The continuous modulation is requested when the boiler water temperature or steam pressure variation must
be contained within the narrow range.From the diagram it can be seen that the shutdown, pre-ventilation, flame
formation and passage maximum power stages are the same described in the previous paragraph.The effective
flame modulation is obtained by giving the system the following equipment, supplied in kits on request:
- LANDIS boiler probe for temperature or pressure;
- regulator, LANDIS RWF 40 with casing for bracket-mounting;
- regulator field adapter, controlled by the boiler probe and with calibration suitable for the scale of the same pro-
be.
corresponding to start-up flow rate (with gas flow always closed).
c) Formation sequence of the start-up flame: the coils relative to the gas solenoid valves are excited and the gas
regulator is partially open in relation to the start-up air pressure.
d) Passage sequence to the main flame or second stage: the servo-control activates the opening of the air (up to
maximum flow rate calibration) whose increase in pressure causes the gradual increase of the gas flow rate.
e) Passage sequence from maximum flow rate to first stage: on command of the boiler thermostat/pressure switch
(regulator), the servo-control determines the closure of the air.The consequent pressure decrease at the burner
head leads to progressive partialisation of the gas until reaching minimum flow rate.The burner repeats the pas-
sage from the first to the second stage, from the second to the first or stops completely always in relation to the
command given by the boiler regulator to the servo-control.
start-up min.
30%
air
gas
1s max
functioning
time
