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7.4. BOILER STACK CONNECTION
The design of a flue pipe and its connection to the boiler should conform to the
requirements of current national regulations in a country of destination (e.g., Minis-
ter of Infrastructure Regulation concerning technical conditions that should be met
by buildings and their setting, of 12 April 2002,
Journal
of Laws No. 75, item 690).
The boiler should be directly connected to the stack with a smoke connection
in form of a steel pipe (of a thermal resistance of >400 °C) of a diameter allowing
its tight connection to the flue outlet and insertion into the flue pipe. A connection
between the flue and the stack must be tightly sealed (e.g., with high tempera-
ture silicone, ceramic sealant, etc.). The pipe should slope up slightly towards the
stack (at least 5°).
Dimensioning and selection of the flue pipe and the connector should be
performed by a designer holding necessary licences, and the stack system
should be constructed by a qualified person in accordance with current spe-
cific regulations in a country of destination.
The stack height and cross-section, as well as the precision of its dimensioning
have a significant effect on a correct boiler operation, therefore they should ensure
maintaining of the required size of the flue pipe (see Table 3, Table 4). A too small
pipe may also cause or facilitate formation of soot deposited in the boiler convec-
tion ducts.
When it is not possible to ensure recommended chimney parameters and
there are problems with the flue pipe manifested as incorrect work of the boiler, a
flue gas exhaust fan or a cowl with an integrated fan can be installed, supporting
and stabilising the flow.
It is important for the stack to start at the boiler room floor level, to provide for
flue gas return. It is also important to provide a clean out hatch with a tight closing
system in the bottom part of the stack.
To prevent a reverse flow in the flue pipe it should reach at least 0.6 m above
a roof ridge. Stack usefulness (patency) should be checked and confirmed by a
licensed chimney sweep at least once a year.
NOTE:
When the flow in the stack is too strong, it will suck excessive amounts of
air from outside to the furnace, increasing heat losses, increasing amounts
of dusts blown out of ashes. In such case it is recommended for the installer
to install a flue gas damper and clean out hatches on a duct connecting the
flue with the stack. The flue gas damper can reduce the too strong flue gas
flow. The device for the flue gas flow control is not provided with the boiler.
The flue pipe to which the central heating boiler will be connected must meet
requirements of current specific regulations of a country of destination (e.g., PN-
89/B-10425 Smoke, fumes and ventilation ducts, made of bricks. Technical re-
quirements and acceptance tests; Minister of Infrastructure Regulation concerning
