Ferroli F 24 B Instructions For Installation, Use And Maintenance Manual page 16

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).
N.B.: the diameter of the hole is
stamped on the restrictor
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
minimum maximum
0 m 20 m
20 m 55 m
16
1
Use
restrictor
size
mm
43
No restrictor
Ferroli F 24 B
• With concentric systems:
- Choose correct restrictor from table
below.
RESTRICTOR FOR CONCENTRIC SYSTEM
Flue lenght up to:
1 bend + 1 meter
Concentric
60 / 100
1 bend + 3 meters No restrictor
1 bend + 5 meters
Concentric
80 / 125
1 bend + 12 meters No restrictor
Fig. 9
Use
restrictor
size
43 mm
43 mm