Vertical
Flues
(Twin Pipe)
Y
X
Vertical
Flues
Y
X
8.0Flue Options
8.2Twin & Vertical Flue Systems
1.Maximum permissible equivalent flue lengths are:-
| (60/100) | (80/125) |
Vertical Concentric | 10 metres | 20 metres |
Vertical Twin Pipe | 15 metres |
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2.Any additional “in line” bends in the flue system must be taken into consideration.
Their equivalent lengths are:- Concentric Pipes:
135° bend | 0.5 metres |
93° bend | 1.0 metres |
Twin Flue Pipe |
|
135° bend | 0.25 metres |
91.5° bend | 0.50 metres |
The elbow supplied with the standard horizontal telescopic flue kit is not included in any equivalent length calculations
NOTE: Flue length is measured from point X to Y as shown.
Total Equivalent Length =
A+B+C+1x90°Bend
All vertical and angled runs must be included, measured from the boiler adaptor (point X) to the joint with the flue terminal (point Y). One 91.5° bend or two 135° bends can be included without reduction of the flue length.
If further elbows are required the flue length must be reduced by the following amounts:-
Roof
Terminal
The total equivalent length for this example is
1 metre for each 91.5° bend
Y
= 6.5 metres.
0.5 metre for each 135° bend
C
B
This bend is equivalent to 1 metre
A
X
20© Baxi Heating UK Ltd 2008
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| AIR DUCT |
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| Equivalent | No of | Sub total |
| Length Value | fittings/pipes |
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1m extension | 1m | 5 | 5.0m |
135°bend | 0.25m | 2 | 0.5m |
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91.5°bend | 0.5m | 2 | 1.0m |
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| Equivalent Length Air Duct = 6.5m | ||
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| FLUE DUCT |
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| Equivalent | No of | Sub total |
| Length Value | fittings/pipes |
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1m extension | 1m | 5 | 5.0m |
135°bend | 0.25m | 2 | 0.5m |
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91.5°bend | 0.5m | 2 | 1.0m |
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| Equivalent Length Flue Duct = 6.5m | ||
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