17
The twin flue pipes can be fitted with or without additional
e
lbows and need no clamps, simply ensure that the red o-
ring is inserted in the female end of the flue pipe and push
t
he extension piece fully into the previous section of flue pipe
or elbow, check that the o-ring is not dislodged when
assembling the flue.
T
he twin flue pipes can be fitted with or without additional
e
lbows and need no clamps, simply ensure that the red o-
ring is inserted in the female end of the flue pipe and push
the extension piece fully into the previous section of flue
pipe or elbow, check that the o-ring is not dislodged when
assembling the flue (greasing the seal will aid assembly).
Twin pipe can also be converted back to Coaxial flue to
enable vertical termination with a coaxial kit by using the
pipe bridge (Twin - Coaxial Adaptor - Part No. 3318089).
When running the twin flue pipe vertically.
It is not possible to terminate concentrically horizontally.
Termination is only possible with separate air and exhaust
terminals.
When siting the twin flue pipe, the air intake and exhaust
terminals must terminate on the same wall, the centres of
the terminals must be a minimum of 280 mm apart and
the air intake
must not be sited above the exhaust
terminal (refer to Fig. 2.22). The air intake pipe can be run
horizontally, however, the terminal and the final 1 metre of
flue must be installed either horizontally or with a slight fall
away from the boiler to avoid rain ingress.
It is also strongly recommended that the air intake pipe run
be constructed of insulated pipe to prevent condense
forming on the outside of the tube.
The maximum permissible flue length for twin flue is
dependent on the type of run used.
For flue runs with the intake and exhaust pipes under the
same atmospheric conditions (T
YPE 4) the maximum
length is 40 metres
, for runs with the terminals under
different atmospheric conditions (T
YPE 5) the exhaust
terminal must extend 0.5 metres above the ridge of the
roof (this is not obligatory if the exhaust and air intake
pipes are located on the same side of the building). For
TYPE 5 also, the maximum permissible combined length is
40 metres.
The maximum length is reached by combining the total
lengths of both the air intake and exhaust pipes. Therefore
a maximum length of 40 metres for example, will allow a
flue run of 20 metres for the air intake and 20 metres for
the exhaust pipes, also for each 90
o
elbow 2.2 metres must
be subtracted from the total length and for each 45
o
elbow
1.4 metres must be subtracted from the total flue length.
Some of the acceptab
le flue configurations are detailed on
page 20.
F
or fur
ther inf
or
mation relating to flue r
uns not illustrated,
please contact the
T
echnical
Depar
tment on 0870 241
8180.
Fig. 2.18B
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