Technical data

11
STRATA2
example 2
A single Strata 2-120 boiler is to be installed with a
room sealed flue using separate air and flue gas tubes
of DN100.
The flue gas tube takes a part horizontal, part vertical
internal route to a roof termination. The air tube takes a
similar route. Flue gas route vertical section = 3m,
horizontal section = 2m. System includes 2 x 90º bends.
Resistance of flue gas tube =
5 x 1m lengths DN100 tube @ 7.0Pa = 35
2 x DN100 90º bends @ 7.0Pa = 14
1 x open termination @ 7.0Pa = 7
Flue gas tube resistance = 56Pa.
Take into account 3m of vertical tube will generate 10Pa.
Therefore operating resistance of flue gas tube = 56 – 10
= 46Pa.
Now calculate air tube resistance which must be
added to flue gas tube operating resistance to obtain
final resistance.
Air tube length = 6.5m (no consideration is given
to whether vertical or horizontal). System includes
2 x 90º bends.
Resistance of air tube =
6.5 x 1m lengths DN100 tube @ 4.0Pa = 26
2 x DN100 90º bends @ 4.0Pa = 8
1 x DN100 termination with rain cap @ 8.0Pa = 8
Air tube resistance = 42
Total operating resistance = 56 + 42 = 98Pa
conclusion: Final operating resistance is less than
100Pa, therefore no alternative design is required as flue
system has no effect on boiler output.
example 3
A single Strata 2-120 is to be installed using 100/150
concentric flue components. The flue route is all
horizontal, to a horizontal wall termination
Length of flue = 4m
System includes 1 x 90º bend + 2 x 45º bends.
Resistance =
4 x 1m lengths 100/150 concentric tube @ 12Pa = 48
1 x 100/150 90º concentric bends @ 12Pa = 12
2 x 100/150 45º concentric bends @ 6Pa = 12
1 x 100/100 to 100/150 concentric adaptor @ 2Pa = 2
1 x 100/150 concentric terminal @ 15Pa = 15
Total resistance = 89Pa.
conclusion: Total flue system resistance is less than
100Pa, therefore no alternative design is required as flue
system has no effect on boiler output.
examples of calculating flue pressure loss
Flue System Resistance - Pa
120
118
116
114
112
110
108
106
104
102
100
98
96
94
92
0 50 100 150 200 250 300 350 400 450
Boiler Output kW at: Flow 50°C Return 30°C
effect of
flue system resistance
on boiler output