16
Ferroli F 24 B
1
Restrictor
For boiler operation, the restrictor supplied with the unit must be mounted following the instructions
below.
Determine the correct size of flue restrictor required. Before inserting the flue gas duct in the boiler,
check that the restrictor fitted is correct and that it is correctly positioned (see fig. 9).
Fig. 9
Choice of restrictor:
• With 2 pipe system:
- Calculate the total flow resistance of the
air and flue pipes in metres (cap. 3.04.2)
- utilise the table shown below to choose
the more suitable restrictor for the flow
resistance calculated
RESTRICTOR FOR TWO PIPE SYSTEM
Total flow resistance
of flue system
Use
restrictor
size
minimum
maximum
mm
0 m
20 m
43
20 m
55 m
No restrictor
RESTRICTOR FOR CONCENTRIC SYSTEM
Flue lenght up to:
Use
restrictor
size
Concentric
60 / 100
1 bend + 1 meter
43 mm
1 bend + 3 meters No restrictor
Concentric
80 / 125
1 bend + 5 meters
43 mm
1 bend + 12 meters No restrictor
N.B.: the diameter of the hole is
stamped on the restrictor
• With concentric systems:
- Choose correct restrictor from table
below.