Burner Operation; Oil Pressure Switch - Riello RL 28/M Electrical Installation, Use And Maintenance Instructions

(A)
D2884
12

BURNER OPERATION

BURNER STARTING - See figure (A)
Control circuit closes, the motor starts.
The pump 3) sucks the fuel from the tank through the pip-
ing 1) and the filter 2) and pumps it under pressure to de-
livery. The piston 4) rises and the fuel returns to the tank
through the piping 5) - 7). The screw 6) closes the by-
pass heading towards suction and the de-energized so-
lenoid valves 8) - 15) - 16) close the passage to the noz-
zle.
Servomotor starts: 90° rotation to right, until contact is
made on red cam.
The air damper is positioned on MAX. output.
Pre-purge stage with air delivery at MAX. output.
Servomotor rotates to left until contact is made on orange
cam.
Air damper and pressure regulator are positioned on MIN
output.
Ignition electrode spark.
Solenoid valves 8) - 15) - 16) open; the fuel passes
through the piping 9) and filter 10), finally it enters the
nozzle.
A part of the fuel is then sprayed out through the nozzle,
igniting when it comes into contact with the spark: flame
at a low output level, point A; the rest of the fuel passes
through piping 11) at the pressure adjusted by the regu-
lator 12), then, through piping 7), it goes back into the
tank.
The spark goes out.
The starting cycle ends.
STEADY STATE OPERATION
At the end of the starting cycle, the servo-motor control
then passes to load control for boiler pressure or temper-
ature.
• If the temperature or pressure is low, the burner pro-
gressively increases output up to MAX.
• If subsequently the temperature or pressure is high,
the burner progressively decreases output down to
MIN.
• The burner shuts down when demand for heat is less
than the heat supplied by the burner in the MIN output.
Load control opens. The servomotor returns to the 0°
angle limited by contact with blue cam. The air damper
closes completely to reduce thermal dispersion to a
minimum.
Every time output is changed, the servomotor automati-
cally modifies oil delivery (pressure regulator) and air
delivery (fan air damper).
FIRING FAILURE
If the burner does not fire, it goes into lock-out within 5 s
of the opening of the fuel oil valve.
FIRING FAILURE
If the flame should go out for accidental reasons during
operation, the burner will lock out in 1 s.

OIL PRESSURE SWITCH

The oil pressure switch 25)(A) page 4 and 14)(A) page
12 is factory set to 43.5 PSI (3 bar). If the gas oil pres-
sure reaches this value in the return piping, the pressure
switch stops the burner. Burner starts again automati-
cally if the pressure goes down under 43.5 PSI (3 bar)
after burner shut down. If a loop circuit with Px pressure
feeds the burner, the pressure switch should be
adjusted to Px + 43.5 PSI.