©
EUROHEAT
DISTRIBUTORS (H.B.S) LTD. March 2006
Technical Guide IN1087 Edition C
15
Installation Notes
Assuming that the flue maintains much of its heat and density difference with the surrounding air, the
taller the flue the greater the potential performance, because the column of hot “light” air is matched
with a similar sized column of “heavy” air.
So far we have only considered flues as vertical tubes, but the reality is that of necessity many have
several changes of direction. Making the flue gases change direction requires “effort” and so slows the
flow; gases flowing horizontally have no incentive and rely on any existing vertical flow for momentum,
and again waste considerable potential performance. Ironically the smaller the diameter of the flue
and the faster the flue gases are travelling the more significantly the flue is affected by changes of
direction, but this has to be weighed against the heat losses from the larger diameters.
A complex flue may look impressive but its
performance will be disappointing. It will not give the
performance of the taller vertical illustration but that
of the shorter vertical illustration. Install changes of
direction only when there is no alternative.
Always try to leave the stove with the minimum horizontal length. If it is practicable to use a top
mounted flue this is ideal, as is the use of back mounted Tee branch where any debri will collect
in the unused branch and can be emptied by removing the end cap. Do not leave the stove with a
bend or elbow because deposits will collect and restrict the flue at this point. Do not leave the stove
with a horizontal run or the stove will be almost impossible to light. The performance of any flue will
deteriorate as deposits coat the surface and accumulate at any change of direction. All flues should
be regularly inspected not only for cleaning but to ascertain its condition because like everything it
will eventually need replacement.
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