Baxi Duo-tec Combi HE a Range Installation And Servicing Instructions page 22

Vertical
Flues
Y
X
IMPORTANT: All flue systems must be securely
supported at least once every metre. Suitable pipe
supports are available as accessories.
Y
X
Vertical Flues
(Twin Pipe)
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 45° bend
A
X
22
© Baxi Heating UK Ltd 2012
For terminal position
see literature
provided with kit
1m Min to
15m Max
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
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 telescopic
flue kit is not included in any equivalent length calculations
NOTE: Flue length is measured from point X to Y as
Y
shown.
Mini Terminal
600mm Min
on Air Duct
apart
(sited in loft)
T
1m Min
to
15m Max
Length Value
1m extension
135°bend
91.5°bend
Length Value
1m extension
135°bend
91.5°bend
(60/100) (80/125)
10 metres 20 metres
15 metres
0.5 metres
1.0 metres
0.25 metres
0.50 metres
Q
The total equivalent length for
this example is = 6.5 metres.
AIR DUCT
Equivalent
N of
o
fittings/pipes
1m 5
0.25m 2
0.5m 2
Equivalent Length Air Duct = 6.5m
FLUE DUCT
Equivalent
N of
o
fittings/pipes
5
1m
2
0.25m
2
0.5m
Equivalent Length Flue Duct = 6.5m
Sub total
5.0m
0.5m
1.0m
Sub total
5.0m
0.5m
1.0m