Heating engineer
20
3
Table 3.7
C33 type maximum allowed length with 80/125 roof
coaxial terminal and Ø 80 ducts
Indicative maximum lengths (m)
Air pipe
Flue gas exhaust pipe
G30
8
8
G45
3
3
G60
-
-
G100
-
-
Table 3.8
C33 type maximum allowed length with 100/150 roof
coaxial terminal
Indicative maximum lengths (m)
Air pipe
Flue gas exhaust pipe
Ø 80
Ø 100
Ø 80
Ø 100
G30
11
30
11
30
G45
7
26
7
26
G60
4
17
4
17
G100
1
8
1
8
Table 3.9
C33 type maximum allowed length with 130/210 roof
coaxial terminal
Indicative maximum lengths (m)
Air pipe
Flue gas exhaust pipe
Ø 80
Ø 110
Ø 130
Ø 80
Ø 110
Ø 130
G30
13
30
30
13
30
30
G45
9
30
30
9
30
30
G60
5
30
30
5
30
30
G100
2
22
30
2
22
30
3.3.3.6
C53 type installation with separate ducts
Figure 3.6
C53 type installation with separate ducts
Table 3.10
C53 type maximum allowed length with separate
ducts
Indicative maximum lengths (m)
Air pipe
Flue gas exhaust pipe
Ø 80
Ø 100
Ø 110
G30
1
19
30
30
G45
1
13
30
30
G60
1
9
30
30
G100
1
5
24
30
3.3.4
Sizing and installing combustion air/
exhaust fumes ducts
In order to dimension the duct system, the total pressure
drop of the system must be calculated.
The total allowed pressure drop in the flue gas exhaust
system depends on the unit model (Table 3.11
p. 20).
The pressure drops of the flue and air pipes available as
Robur optional are shown in Table 3.12
Table 3.13
p. 21 shows the pressure drops for Ø 100 flue
and air pipes in aluminium, available on the market.
The pressure drops of the coaxial pipes available as Robur
optional are shown in Table 3.14
Resistance from the separate terminals are negligible
since they are very low.
When designing, it must be checked that the total pres-
sure drop of the piping system is lower than the maximum
pressure drop allowed for the unit (Table 3.11
p. 20). An
example of how to calculate pressure drops is given in
Paragraph 3.3.5
The maximum lengths of air and flue gas exhaust pipes,
depending on the type of installation, are shown in tables
under the installation type figures, described in Paragraph
3.3.3
The above lengths are intended to be approxi-
mate values for standard installations where the
air and flue gas exhaust ducts follow linear paths
as shown in the respective figures. Otherwise, you
must proceed with the calculation of the pressure
drop (Paragraph 3.3.5
p. 22): installation will be
permitted if the total pressure drop is lower than
the maximum admissible pressure drop (Table
p. 20).
The Ø 80, 110 and 130 pipes available as Robur op-
tional are made of stainless steel, while the Ø 100
adapters available as Robur optional are made of
aluminium.
Table 3.11
Data for the calculation of the air/fumes system with pipes found on the market
G30
G45
G60
G100
Installation data
Flue temperature
Nominal heat input G20
°C
85,0
95,0
85,0
Fumes flow rate
Nominal heat input G20
kg/h
51
76
102
155
CO
2
percentage in fumes
Nominal heat input G20
%
8,8
9,1
8,9
9,5
Flue gas exhaust
residual head
Pa
65
100
120
200
