Service manual

Service manual E000129004
4
Chapter 2: Checks, servicing and
replacement of components
2.1. Fan, gas valve and venturi assembly
The function of the fan is to force the mixture of air and
gas into the burner.
The flow rate of the air-gas mixture and consequently the
input power of the boiler is proportional to the speed of
the fan that is controlled by the electronic control p.c.b.
The venturi assembly A placed on the inlet port of the fan
allows the mixing of gas and air in the right proportion.
The gas-air ratio can be adjusted by the venturi screw B
(fig 8).
Fig 8
F Removal of the assembly
Warning: isolate the boiler from the mains
electricity supply before removing any covering or
component.
1 Remove the cover (section 1.4.
2 Close the gas inlet valve.
3 Lower the control panel (section 1.7).
4 Disconnect the wirings from the fan C and gas valve D
(fig 9).
5 Unscrew the Allen key screws E and separate the gas
connection F from the gas valve.
6 Unscrew the Allen key screws G and the bracket H.
Fig 9
7 Remove the fan with the venturi assembly and the gas
valve.
8 To separate the fan from the venturi assembly and gas
valve unscrew the screws I (fig 10).
9 To separate the gas valve from the venturi assembly
unscrew the screws J.
10 Re-assemble the parts following the removal
procedures in the reverse order.
Replacing the parts replace also the gaskets that ensure
the gas circuit tightness.
If the venturi assembly has been replaced, before to start
the boiler ensure that the venturi screw B (Fig. 8) is
completely tighten (clockwise) than carry out a complete
adjustment as explained in the installation manual.
Warning: After cleaning or replacement as detailed
above refer to section Combustion adjustment check in
the chapter Commissioning of the installation instructions
manual.
Fig. 10