Riello RS 70 VA Installation, Use And Maintenance Instructions page 22

D521
(A)
(B)
(C)
(D)
1)
2)
19
3 - AIR PRESSURE SWITCH (A)
The air pressure switch can be connected in dif-
ferential mode, see 1)(A), i.e. it is under pres-
sure either by the depression or pressure
generated by the fan.
Air pressure switch connected as in 2)(A):
Adjust the air pressure switch after having per-
formed all other burner adjustments with the air
pressure switch set to the start of the scale (A).
With the burner operating at MIN output,
increase adjustment pressure by slowly turning
the relative knob clockwise until the burner locks
out.
Then turn the knob anticlockwise by about 20%
of the set point and repeat burner start-up to
ensure it is correct.
If the burner locks out again, turn the knob anti-
clockwise a little bit more.
D794
4 - MINIMUM GAS PRESSURE SWITCH (B)
Adjust the minimum gas pressure switch after
having performed all the other burner adjust-
ments with the pressure switch set at the start of
the scale (B).
With the burner operating at MAX output,
increase adjustment pressure by slowly turning
the relative knob clockwise until the burner locks
out.
Then turn the knob anticlockwise by 0,2 kPa
(2 mbar) and repeat burner start-up to ensure it
is uniform.
If the burner locks out again, turn the knob anti-
clockwise again by 0,1 kPa (1 mbar).
D3855
5 - MAXIMUM GAS PRESSURE SWITCH (C)
Adjust the maximum gas pressure switch after
having performed all the other burner adjust-
ments with the maximum gas pressure switch
set at the end of the scale (C).
With the burner operating at maximum output,
lower adjustment pressure by slowly turning
the relative knob anticlockwise until the burner
locks out.
Now turn the knob clockwise by 0,2 kPa
(2 mbar) and repeat the start-up of the burner.
If the burner locks out again, turn the knob
clockwise again by 0,1 kPa (1 mbar).
1 kPa = 10 mbar
D3856
WARNING
FLAME PRESENCE CHECK (C)
The burner is fitted with an ionisation system
which ensures that a flame is present. The mini-
mum current for control box operation is 4 µA.
The burner provides a much higher current, so
that controls are not normally required. How-
ever, if it is necessary to measure the ionisation
current, disconnect the plug-socket (see con-
nector CN1 and CN2 on the wiring diagram
Sheet 3) on the ionisation probe cable and
insert a direct current microammeter with a base
scale of 100 µA. Carefully check polarities!
As the normal flame variations produce ionisa-
tion current values that are sometimes unstable,
you are advised to always maintain a current of
at least 20 µA while making the calibrations.
NOTE: reaching the maximum output, the flame
root tends to increase and the ionisation current
consequently decreases. In relation to this, the
high output measurements are very important.
S8990