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 and a suitable flexi liner
fitted.
Chimney Terminations
All chimneys should terminate above the roof 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.
Flue Draught
For correct performance of the appliance, it is
recommended that the flue pull be a minimum of 1mm
H
2
O.
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.
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.
Should this occur, a flue stabiliser must be fitted either
in the flue pipe or chimney, but in the same room as the
appliance.
Installation Instructions
3
Fig.2 Flue Layouts
