The use of the infrared thermography techniques is progressively showing as an important tool in the research of very different thermal applications, in this case air conditioning systems. The Instituto de Ingeniería Energética de la Universidad Politécnica de Valencia has developed a Joule Project, financed by the European Community for the Study and Characterization of propane heat pumps, adapted to the use in the South European countries. The
substitution of the fluorocarboned refrigerants by natural fluids as propane is the main objective of this project. With the study, important efficiency improvements have been obtained, in relation with the use of the classical refrigerants, for both summer and winter conditions. The use of the thermography in this project has been quite useful in the achievement of several important tasks as the study of the compressor start up process, as it is
described in the paper.