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PRACTIKA 28-33
USE AND INSTALLATION MANUAL
Chapter 4
page 21
Installing a “Practika”
Technical dept. - All rights reserved - Reproduction prohibited
above any structure adjacent to the chimney itself (including the ridge of the roof) at least 8 metres
away.
The flue pipe must have a diameter of no less than the boiler union;
for flue pipes with a
square or rectangular cross-section, the internal cross-section must be increased by 10% compared
to the boiler union.
We recommend calculating the flue cross-section from the following report to guarantee adequate
draught:
S
= K x P/√H
S
ensuing section in cm
2
K
reduction coefficient: 0.04 for wood and pellet
P
boiler output in kcal/h
H
height of the chimney in metres, measured from the flame axis to the outlet of the chimney into
the atmosphere. When sizing the flue pipe, please take into account the actual height of the
chimney in metres, measured from the flame axis t the top, decreased by:
0.50 m for every change in direction of the union duct between the boiler and the flue pipe
1.00 m for every metre of horizontal development of the union itself.
We recommend the sole use of outlet ducts which are suitable for the
type of fuel used. The supplier will not be held in any contractual and
non-contractual way liable for damage caused by installation and
usage errors and in any case due to failure to observe the instructions
provided by the manufacturer of the appliance.
The products of combustion of the boiler cannot be discharged in
collective flue ducts.
The correct installation of the flue duct is necessary to encourage the
normal flow of smoke from the combustion chamber to the outside in
the event of an electrical power failure.
Remember that a draught of 25-30 Pa must be guaranteed.
Below are the main characteristic traits of the flue duct according to the provisions of
standards UNI 7129 and UNI 10683:
The smoke outlet must be equipped with inspection valves;
The minimum height of the pipe directly connected to the smoke outlet of the boiler must be
between 2÷3 m;
If the presence of a horizontal section is necessary, we recommend that the same is of a maximum
length of 1.5 m and with a slope gradient of 3÷5% to encourage the smoke to flow away;
Use of a wind-proof and rain-proof terminal
to avoid changing the slight overpressure inside
the flue pipe (we recommend you end the flue pipe with a horizontal section);
The outlet ducting must be made with suitable materials which can withstand the products of
combustion and any condensation of the same (the inspection valve can allow any condensation
that has formed to be vented);
The ducts must be built to ensure maximum seal against smoke (UNI 10683);
We recommend you insulate the duct, especially on the outside part exposed to the weather.
