MODULE IV - Condensing boiler technology Page 28

MODULE IV Condensing boiler technology Page 28

In contrast to conventional gas heating systems condensing boiler systems work with significantly lower temperatures. As a result:

... the exhaust gas transport can not be realised using the natural gas buoyancy (also see explanations above).
... the exhaust gases are condensing and so humidity insensitive pipe materials have to be used.

Prior to their use these materials have to be examined and have to be approved with a test seal and test report by the IfBt (Institute for Construction Technique). So far the following materials fulfil those special requirements: Aluminium, polyvinylidenflorid (PVDF), polypropylene (PPS), rustproof steel, borsilicum glas and refractory/fire clay.

The following table gives an overview over the areas of use of the different materials:

Material	Temperature categories			Exhaust gas temperature limiter
Material	A < = 80°C	B < = 120°C	C < = 160°C	Exhaust gas temperature limiter
Aluminium	-	-	X	no
Polyvinylidenflorid (PVDF)	X	-	-	yes
Polypropylene (PPS)	-	X	-	yes
Rustproof steel	-	-	X	no
Borsilicum glas	-	-	X	no
Refractory/fire clay	-	-	X	no