Heating engineer
32
3
Table 3.9
C33 type maximum allowed length with 130/210 roof
coaxial terminal
Indicative maximum lengths (m)
Next-G
Air pipe
Flue gas exhaust pipe
Ø 80
Ø 110
Ø 130
Ø 80
Ø 110
Ø 130
G 20 EC
30
30
30
30
30
30
G 30, G 30 EC
29
30
30
29
30
30
G 35 EC
20
30
30
20
30
30
G 45, G 45 EC
16
30
30
16
30
30
G 60, G 60 EC
12
30
30
12
30
30
G 75 EC
7
30
30
7
30
30
G 90, G 90 EC
7
30
30
7
30
30
3.3.3.6
C53 type installation with separate ducts
Figure 3.6
C53 type installation with Ø 80 separate ducts
Table 3.10
C53 type maximum allowed length with separate
ducts
Indicative maximum lengths (m)
Next-G
Air pipe
Flue gas exhaust pipe
Ø 80
Ø 100
Ø 110
G 20 EC
1
30
30
30
G 30, G 30 EC
1
30
30
30
G 35 EC
1
30
30
30
G 45, G 45 EC
1
29
30
30
G 60, G 60 EC
1
23
30
30
G 75 EC
1
14
30
30
G 90, G 90 EC
1
15
30
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. 32).
The pressure drops of the flue and air pipes available as
Robur optional are shown in Table 3.12
Table 3.13
p. 33 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 residual
head of the appliance (Table 3.11
p. 32). 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 approximate
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. 34): installation will be per-
mitted if the total pressure drop is lower than the
residual head of the appliance (Table 3.11
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
G 20 EC
G 30
G 35 EC
G 45
G 60
G 75 EC
G 90
Installation data
Flue temperature
Nominal heat
input
G20
°C
82,0
75,0
85,0
100,0
79,0
99,0
82,0
Fumes flow rate
Nominal heat
input
G20
kg/h
33
49
60
74
98
127
151
CO
2
percentage in fumes
Nominal heat
input
G20
%
9,3
9,5
9,2
9,0
9,2
9,3
Flue gas exhaust
residual head
Pa
65
80
100
130
150
200
