Condensing boiler technology is a modern environment protecting technology which is becoming more and more important and popular in the sanitary, heating and air-conditioning sector. For this reason, service technicians have to have a good knowledge of this new technology. The present Module IV "Condensing boiler technology" addresses especially those service technicians who already have a basic knowledge of the subject. A particular emphasis has been put on demonstrating the service technicians as to how they can best explain the particularities of the technology to interested customers. In addition, various exercises and learning objectives are provided with which one can test his/her knowledge of the most important aspects of condensing boiler technology.