81
K800000000SE 023942A0 080914
ANNEX C
Flue gas analysis according to Italian Law No. 10/1991 and subsequent modifications
and supplements, Legislative Decree 192/2005 and the UNI 10389-1 standard
Preamble
It is Seitron's intention, by means of this compact guide, to provide boiler installers/service technicians with a
quick and easy way to understand whether a boiler conforms to the requirements of Italian Law no. 10 dated
January 1991, and subsequent modifications and supplements, and Legislative Decree 192/2005.
The contents of this guide have been extremely simplified whereby they are not to be deemed at all
comprehensive of the complex phenomenon of combustion.
Flue Gas Analysis: theory
During the combustion process taking place in a boiler, part of the heat evolved by the burner is transferred to the
water or air to be heated. The quantity of heat available at the burner is called the input rating (Pf) and is usually
declared by the boiler manufacturer. Part of this energy, known as the useful output (Pu), is used by the boiler.
The remainder is lost to the flue gas in the stack and is known as Stack loss (Qs).
Thus we can say that:
Pf=Pu+Qs
THE THERMAL EFFICIENCY OF COMBUSTION is given by:
ŋ=100-Qs
According to the Italian Legislative Decree 192/2005 the MINIMUM thermal efficiency ŋ should respect the values
below:
For hot water generators:
For hot air generators:
Period of installation
Minimum efficiency %
Minimum with Pn < 35 kW
Before 29/10/1993
83 + 2 * log Pn - 6
around 80 %
After 29/10/1993
84 + 2 * log Pn - 3
around 83 %
Period of installation
Minimum efficiency %
Minimum with Pn < 35 kW
Before 29/10/1993
84 + 2 * log Pn - 2
around 85 %
From 29/10/1993 to 31/12/1997
84 + 2 * log Pn
around 87 %
From 01/01/1998 to 07/10/2005
Standard boilers
84 + 2 * log Pn
Low temperature boilers
87.5 + 1.5 * log Pn
Condensing boilers
91 + 1 * log Pn
around 87 %
around 90 %
around 92.5 %
After 08/10/2005
Condensing boilers
90 + 2 * log Pn - 1
Other boilers
88 + 2 * log Pn - 1
around 92 %
around 90 %
