Minimum and maximum flue heights
Internal:
600mm above the apex is the minimum height above the building if
within 1.5 metres of the surface,
see drawings Figure 1 & 2
.
Maximum height is no more than 25 metres, if this exceeded please
consult BMM Heaters or consideration should be given for a fan
assisted
flue.
External:
Minimum flue height is 1 metre above appliance roof.
Maximum height is no more than 25 metres, if this exceeded please
consult BMM Heaters or consideration should be given for a fan
assisted
flue.
Flue terminal
A flue terminal (must be approved) needs to provide an extraction effect under
virtually all wind conditions, the free area of outlet openings should be at least
twice the nominal area of the flue. Outlet openings should be provided preferably
all round, or at least on opposite sides.
It is important for the terminal of an individual open flue system to be located so
that it is not likely to be subjected to wind pressures which could restrict or reverse
the flow of combustion products through the flue.
The ideal position is above the highest point on the roof. It is absolutely essential
that the terminal is positioned outside the building so that it is freely exposed to
any wind and is not shielded by any roof structure or object to such a degree that
they create undesirable pressure regions around the terminal.
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