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© Baxi Heating UK Ltd 2011
8.0 Flue Options
Vertical
Flues
(ii)
(i)
The total equivalent length for this example is
= 6.5 metres.
1m extension
135°bend
91.5°bend
1m
0.25m
0.5m
5
2
2
5.0m
0.5m
1.0m
AIR DUCT
N
o
of
fittings/pipes
Sub total
Equivalent
Length Value
Equivalent Length Air Duct = 6.5m
1m extension
135°bend
91.5°bend
1m
0.25m
0.5m
5
2
2
5.0m
0.5m
1.0m
FLUE DUCT
N
o
of
fittings/pipes
Sub total
Equivalent
Length Value
Equivalent Length Flue Duct = 6.5m
(ii)
(i)
C
Roof
Terminal
A
B
This bend is equivalent to
1 metre
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
8.2 Twin & 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
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 (i) to (ii) as
shown.
Vertical
Flues
(Twin Pipe)
(ii)
(i)
1m Min to
15m Max
120mm Min
apart
Y
1m Min
to
15m Max
600mm Min
apart
Mini Terminal
on Air Duct
(sited in loft)
T
Q
IMPORTANT: All flue systems must be securely
supported at least once every metre. Suitable pipe
supports are available as accessories.