Potterton Performa 30 HE Installation & Service Instructions Manual page 19

Vertical
Flues
(Twin Pipe)
Y
X
Vertical
Flues
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 2009
Roof
Terminal
Y
C
B
This bend is equivalent to
1 metre
8.0 Flue Options
8.2 Twin & Vertical Flue Systems
1. Maximum permissible equivalent flue lengths are:-
Vertical Concentric
Vertical Twin Pipe
* Both the air and flue duct can be up to 12 metres
long each.
2. 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
91.5° bend
The elbow supplied with the standard horizontal flue is
not included in any equivalent length calculations
NOTE: Flue length is measured from point X to Y
as shown.
IMPORTANT: All flue systems must be securely
supported at least once every metre. Suitable pipe
supports are available as accessories.
The total equivalent
length for this example is
Equivalent
Length Value
1m extension 1m
135°bend 0.25m
91.5°bend
0.5m
Equivalent Length Air Duct = 6.5m
Equivalent
Length Value
1m extension 1m
135°bend
0.25m
91.5°bend 0.5m
Equivalent Length Flue Duct = 6.5m
3m
12m*
0.5 metres
1.0 metres
0.25 metres
0.50 metres
= 6.5 metres.
AIR DUCT
N o of Sub total
fittings/pipes
5 5.0m
2 0.5m
2 1.0m
FLUE DUCT
N o of Sub total
fittings/pipes
5 5.0m
2 0.5m
2 1.0m
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