Specifications

Detailed recommendations for fluing are given in the
current Building Regulations J/1/2/3.
The following notes are intended to give a general
guidance:-
The cross sectional area of the flue serving the appliance
must not be less than the area of the flue outlet of the
appliance and be at least 4.5m high.
The flue pipe to be used must not be less than 102mm
internal diameter. Flue pipes and fittings should be
constructed from one of the following materials:-
a) Mild Steel with a wall thickness of 3mm minimum.
b) Stainless Steel to BS.1449. Part 2.
c) Cast Iron to BS.41.
d) Mild Steel, acid resistant vitreous enamel lined to BS.1344.
Part 2
Chimneys
Chimneys should be built of masonry or be assembled
from factory-made insulated components.
Masonry chimneys may be built of any masonry material,
with a lining, of if flue blocks., without a lining.
The chimney lining should be 125mm minimum diameter
and be formed of moisture and acid resistant liners to
BS.1181 with rebated or socketed joints uppermost.
Alternatively, linings may be imperforate clay flue pipes as
described in BS.65 or flue blocks to BS.1289 and installed
to BS.6461.
A 125mm minimum diameter factory-made, insulated
chimney, complying to BS. 4543 may be fitted and
installed to BS.7566.
Use of older existing chimneys
Older chimneys must be swept thoroughly, and a suitable
flexi liner fitted.
Chimney Terminations
All chimneys should terminate above the highest roof ridge
level in accordance with current Building Regulations and
statutory requirements as outlined in BS.6461 Part 1 and
BS.7566 Parts 1 to 4.
However well-designed, constructed and positioned, the
satisfactory performance of a flue can be adversely
affected by the down-draught caused by adjacent tall
buildings and trees or even nearby hills. These deflect the
wind creating a zone of high pressure over the terminal
causing it to blow directly down the chimney flue.
A suitable anti-downdraught terminal such as the Marcone
will usually effectively combat low pressure down-blow but
no known cowl is likely to prevent down-draught due to a
high pressure zone.
Chimney Cleaning
Ensure there are accessible airtight flue cleaning doors in
order to obtain cleaning access to the complete chimney.
Providing the appliance is operating correctly, an annual
chimney flue clean will suffice, but if in doubt, arrange for a
half yearly clean, preferably at the beginning/end of the
central heating season.
Flue Draught
For correct performance of the appliance, it is
recommended that the flue pull be a minimum of 1mm
H
2
O.
High Chimney Draughts
A well sealed, tall exposed chimney on a hill, is an
instance where generated draughts could be excessive
and must be controlled.
Installation Instructions
3
Fig.2 Flue Layouts
FLUE SYSTEM - See Fig.2