17
The flue must be sized according to the generator section and firebox power supply by qualified
personnel (see UNI 13384). For generators connected in parallel, each generator must have its
own flue.
Due to the various installation places, during normal operation, the flue section and height must
guarantee a minimum draught of - 20 Pa (±30) measured by applying a 1/4” hose connection to
the manifold located on the side of lower door inspection window and by inserting a rubber pipe
connected to a deprimometer (see fig. 6.5.1).
Should you not be able to obtain a sufficient draught, we recommend installing an electric fan for
forced draught of the flue.
6.5 Flue and draught
The flue is one of the most important elements for a correct generator operation.
In general a good draught is obtained when flue is thermally insulated, designed with a double
wall and insulated to prevent the fumes from cooling, thus maintaining the pressure difference
that allows the fumes to go up the flue to the external outlet.
We recommend using stainless steel for the parts in contact with the fumes in order to prevent
acid condensation due to the features of the used fuel. The surrounding structures may effect the
correct operation of the flue: e.g., the distance and height of nearby buildings; therefore, accor-
ding to the regulations in force, the top of the flue must exceed the ridge of the roof or of any
other building at a distance of less than 10 m by at least 1 m.
An
excessive draught
will reduce the generator efficiency: part of the combustion gas is
sucked in the flue together with the fuel particles before being fully burnt, thus increasing
fuel consumption.
A
poor draught
decreases the efficiency of the generator because it slows down the com-
bustion producing smoke return.
The flue section must have the same diameter as the fume pipe fitting, narrower sections are not
allowed. Moreover its weight must not lay on the fume pipe fitting in order to prevent collapses in
the structure of the generator.
Fig.6.5.3
shows how to install it correctly.
fig. 6.5.1
