17
Ignition and detection electrodes
17.1
Function
Three electrodes are fitted near the front part of the
burner. The ignition sparks take place between the me-
tallic edges of the ignition electrodes over the central
ramp of the burner during the ignition sequence.
The third electrode is the detection electrode and it de-
tects the presence of the flame.
Fig. 1 shows the electrodes configuration on the mo-
dels M90E.24S, M90E.28S.
Fig. 2 shows the electrodes configuration on the model
M90E.32S.
Ignition
Female
Fig. 1
Detection
Male
Female
Fig. 2
Detection
Male
Ignition
17.2
Checks
Check the position of the electrode edges
n
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1
Remove all the case panels, the sealed chamber
lid and the combustion chamber lid.
2
Check for the correct distance between the me-
tallic edges of the ignition electrodes (see Fig. 3).
Ignition
Fig. 3
3
Check the integrity of the detection electrode and
ensure that its metallic edge is correctly placed
over the ramp of the burner.
Check the connection wires.
n
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1
Remove all the case panels, the sealed chamber
lid and the combustion chamber lid.
2
Check for the integrity of the insulation of wires
which connect the electrodes to the ignition de-
vice.
17.3
Removal
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1
Remove all the case panels, the sealed chamber
lid and the combustion chamber lid.
2
Disconnect the electrode wires from the full se-
quence ignition device.
3
Remove the burner by unscrewing the four
screws placed at the right and left sides of the
burner.
3b
For model M90E.28S and M90E.32S remove also
the plate C (see Fig. 2 on page 35).
Unscrew the screws A (Fig. 4) which hold the
4
electrodes to the burner.
Two screws are used on the models M90E.24S,
M90E.28S
Three screws, one for each electrode, are used
on the model M90E.32S.
4 mm
33