English
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.3 Chimney stack - Fig. 7 / 11
The flue must be fitted at the top with a device called a chimney stack,
designed to aid dispersion of the products of combustion in the
atmosphere.
The chimney stack must comply with the following requirements:
-
it must have an internal section and shape the same as the flue;
-
it must have a useful outlet section of not less than twice that of the
flue;
-
the part of the flue that emerges from the roof or remains in contact
with the outside (e.g. in the case of an open loft), must be covered with
brick or tile elements and well insulated. It must be built in such a way
as to prevent the penetration of rain, snow and foreign matter into the
flue and to ensure that in the event of winds from all directions and
angle, discharge of the combustion products is assured (chimney stack
with down-draught cowl);
-
any buildings or other obstacles that are higher than the chimney stack
must not be too close to the actual stack Fig.8, Fig.9;
-
the chimney stack must be positioned in such a way as to ensure
adequate dispersion and dilution of the products of combustion and
outside the reflux area. The size and shape of this area differ according
to the angle of inclination of the roof and it is therefore necessary to
adopt the minimum heights shown in Fig.10,11;
Example: Check the slope of the roof (column
α
), and the anticipated
distance of the chimney stack from the axis of the ridge (column A); if
the distance is greater than “A” the height of the chimney stack may be
read in (column H); if the distance is less than “A” the chimney stack
must rise above the ridge by 0.5 metres.
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