Thermasis ASTRA, Installation And User Manual

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5.4. Chimney stack
The chimney stack is a device fitted on the top of
the chimney that is designed to aid dispersion of
the products of combustion in the atmosphere.
Chimney stack must comply with the following
requirements:
•
it must have an internal section and shape the
same as the flue (A);
•
it must have a useful outlet section (B) of not
less than twice that of the flue (A);
•
the part of the chimney that emerges from
the roof or remains in contact with the outside
(e.g. in the case of a flat roof), must be
covered with brick or tile elements and in any
case 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).