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/ flue system from the top of the hearth base to the
top of the chimney terminal is 4.5m (15'). If this is not
possible then a 'spinner' type cowl, to compensate for
any potential limited up-draught, should always be
specified and specialist advice sought on the correct
type.
Under no circumstances should the stove's 150mm
(6") diameter flue be reduced in any part of the flue
system as this could cause a build-up of dangerous
carbon monoxide gas.
When your new inset stove is installed with a flexible
flue liner it should be possible to sweep the chimney
through the stove by simply removing the baffle plate
inside the 'roof' of the stove. However, if you do not
use a liner the installer should, if possible, provide an
alternative means, such as a soot door with adequate
air-tight seal, in the chimney wall to be able to clean
the whole of the chimney / flue system.
Since stoves create flue gases at a much greater
temperature than those produced by an open fire or
gas appliance it does not necessarily follow that your
chimney will function adequately (or safely) when
your new stove is installed. The best way to ensure
that you have a fully functioning flue system is to fit
an approved flexible multi fuel flue liner.
Alpha strongly recommend fitting a chimney liner for
the following reasons:
• A flue liner is a major 'quantifiable' component in
a total and fully functioning flue system. As such it
will provide a consistent flue draught from the stove
through to the chimney terminal and when back-filled
with vermiculite will deliver much needed insulation
to keep flue gases as hot as possible which will help
minimise the amount of smoke produced. It will also
improve the stove's operation with greater control
over the fuel burn rate and improve environmental
and fuel efficiency.
• Your existing chimney could leak smoke, fumes and
potentially dangerous 'invisible' carbon monoxide into
other parts of the building.
• Condensation or creosote 'tar', often associated
with burning wood, could eventually seep through the
walls, particularly if they are made of old or porous
brick and / or are jointed with lime mortar, eventually
causing unsightly stains on decorative coverings.
• Stoves work best with the correct draught. Pre-1965
chimneys which have been built for open fires have
larger (and irregular shaped) voids than those best
suited for a modern stove and thus could reduce the
effectiveness of the flue draught by making the flue
too cold and difficult to warm. This is a particular
problem if the chimney breast is on an outside wall
and / or is subject to a strong prevailing wind.
• The interior surfaces of older flues could be eroded
and also have rough surfaces which could cause
resistance to the smooth flow of gases and
consequently result in poor up-draught.
• Unfortunately many houses built since 1965 with
clay or concrete chimney liners suffer from these
being poorly installed, either through being fitted the
wrong way up or not receiving an appropriate
application of mortar to make a complete seal on
each joint. Even though not particularly old, this could
still potentially cause leaking smoke and fumes or
condensation stains
Your approved installer will be able to advise you on
the suitability of your chimney after undertaking a
thorough inspection and smoke test. Any solid fuel
flexible liner which is specified should be double
skinned stainless steel, either 904L or 316Ti grade and
be CE marked and / or Hetas Approved.
The British Flue and Chimney Manufacturers
Association website, accessed through
www.feta.co.uk/bfcma, produces an authoritative and
informative download Yellow Guide to solid fuel flues
and chimneys.
The Chimney Terminal
The existing chimney pot or terminal must be suitable
for stove installation and should not restrict the smoke
and fumes from the stove. It must provide at least the
same outlet area as the flue pipe. It may be that your
existing chimney terminal has been replaced with a
ventilating terminal if the fireplace has been closed off
at some point and this will need replacing.
Your installer will be able to advise you on the correct
specification of any new cowl or terminal. Cowls have
the additional advantage of limiting rain entering the
flue system which could cause the inside of the stove
to rust when it is not being used, particularly during
the long periods outside the heating season.
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