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5 AST 14 C 120/00
Reference regulations.
The fact that yield exceeds 100% derives
from the fact that the European Community
Regulations prescribe, for all boilers, to
calculate efficiency by referring to the net
calorific value, which does not consider the
condensation heat of steam; this method
allows to compare the efficiency of
condensing boilers and traditional boilers on
the same basis.
European Efficiency Directive 92/42/CEE,
enforced in Italy by Presidential Decree
660/96
With methane, the theoretical latent heat that
can be recovered is equal to 11%.
The UNI11071 (July 2003) Reference
Regulation supplies clear and detailed rules
for the installation and maintenance of a
plant interlocked to a condensation
generator or similar, with a nominal heat
input that does not exceed 35 kW.
Finally, the next publication of the CIG E01.08.929.0 Regulation project will cover the field of plants
with potentiality greater than 35 kW, covering a current Regulation “vacuum” and also making
application of condensation generators in this ambit clear.
What does the regulation say.
Definition of condensation appliance or similar (art. 3.1).
The Regulation defines condensation appliances similar to those appliances for which, when
running regularly, in all or some functioning conditions and/or installation of the plant, the
Manufacturer envisions the formation of condensation of the combustion products not only inside
the appliance but also in the combustion products evacuation in amounts such to request their
conveying and/or disposal.
Condensation discharge system (art. 5).
In all cases, the condensation appliances or similar, as previously defined, must always be
connected to a domestic waste disposal plant. It is important that the attachment of the
condensation discharge pipe is realised in a way to prevent the escape and return of the unburned
residues or emission into the environment or the drain system. To obtain this, a siphon must be
used (inside the appliance and/or interlocked to the fumes discharge system) constructed in a way
to prevent the escape of gaseous combustion products into the environment or the drain system.
Regarding the set-up, the Regulation prescribes that the condensation cannot be used by the
utility; they must have flow without leaks, must not have constrictions that prevent regular
discharge and cannot undergo the eventual freezing of the fluid (condensation).
For the regular flow, the Regulation envisions a slope or inclination of the discharge plant greater
than 3%. In all cases, stagnation of the condensation must be prevented with exception to that
present inside the discharge siphon inside the combustion products evacuation system.
N.B. The connection plant of the condensation discharge to the disposal plant of domestic waste is
not part of the gas plant (art. 5 paragraph 5.1).
-Treatment of the condensation:
The Regulation considers the noteworthy quantity of waste water produced in domestic uses (180
litres pro-capite), well-known for its high basicity, which allows to effectively dilute the acid
condensation produced by the appliances or similar and therefore, declares the possibility to
discharge the condensation into the drain system directly. This is because of the alteration of
the pH due to mixture of the domestic waste (power less than 35 kW it can be practically ignored).
