Potterton Promax 12 SL Installation And Service Instructions Manual page 21

Vertical Flue System
Examples (Twin Pipe)
Y
X
Vertical Flue
System Examples
Y
X
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:-
1 metre for each 91.5° bend
0.5 metre for each 135° bend
A
X
© Baxi Heating UK Ltd 2007
Roof
Terminal
Y
C
B
This bend is equivalent to
1 metre
8.0 Flue Options
8.2 Twin & Vertical Flue Systems
Concentric
The maximum equivalent lengths are 4m (vertical). Their
lengths exclude the standard elbow and terminal assembly
(vertical).
Twin Flue
The total maximum equivalent flue length is 150m.
NOTE: Each 1m of flue duct should be calculated as 2m.
Any additional "in line" bends in the flue system must be
taken into consideration. Their equivalent lengths are:
Concentric Pipes: 135° bend
93° bend
Twin Flue Pipe: 135° bend (air duct)
135° bend (flue duct)
90° bend (air duct)
90° bend (flue duct)
The total equivalent length for this example is
17.2 + 34.4 = 51.6 metres.
Equivalent
Length Value
1m extension
1m
135°bend 1.3m
91.5°bend
4.8m
Equivalent Length Air Duct = 17.2m
Equivalent
Length Value
1m extension 2m
135°bend
2.6m
91.5°bend
9.6m
Equivalent Length Flue Duct = 34.4m
0.5 m
1.0 m
1.3 m
2.6 m
4.8 m
9.6 m
AIR DUCT
N o of Sub total
fittings/pipes
5 5.0m
2 2.6m
2 9.6m
FLUE DUCT
N o of Sub total
fittings/pipes
5 10.0m
2 5.2m
2 19.2m
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