Caleffi handbook In this second manual I have rearranged and updated the text of my working files relating to heating circuits and heat emitters. In the section covering the circuits I felt it was desirable to highlight the numerical examples so that notes and observations of general interest could be drawn from them. I have chosen to avoid hypothetical situations and to base my book on actual systems which are suitable for demonstrating the essential technical aspects relating to the choice and design of the circuits. I have given a number of examples of a theoretical nature in order to show how the parameters involved interact. To know how to assess the true “significance” of these factors makes it possible to develop an analytical attitude towards the simplified hypotheses and approximations which are adopted. In addition examples have been included to demonstrate the use of the proposed practical procedures within the scope of the individual items. With procedures of this type it has been possible to significantly reduce the effort required for theoretical calculations. In the second section of the manual I have examined the heat emitters, analysing them from the following points of view: 1. structural and performance characteristics 2. heat output provided under various operating conditions 3. commissioning and maintenance requirements. This has been achieved by analysing the main factors governing the choice of type and size, position and maintenance of the emitters. I should like to thank Paolo Barcellini of Caleffi and my friends in the STC office, Umberto Bianchini and Roger Brescianini for the invaluable assistance they have given me. I should also like to thank the Caleffi company who provided me with everything I needed to complete this manual and have it printed. Mario Doninelli