21
8.0 Flue Options
© Baxi Heating UK Ltd 2014
Vertical
Flues
Vertical Flues
(Twin Pipe)
(ii)
(i)
(ii)
(i)
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.
1m extension
45°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
45°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
660mm
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 45° 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° elbow
0.5 metre for each 45° elbow
The total equivalent length for
this example is = 6.5 metres.
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)
Q
T
IMPORTANT:
All flue systems must be securely
supported at least once every metre. Suitable pipe
supports are available as accessories.
