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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
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