This publication is the concluding text in a four-part curriculum for air conditioning and refrigeration. Materials in Book 4 are designed to complement theoretical and functional elements in Books 1-3. Instructional materials in this publication are written in terms of student performance using measurable objectives. The course includes six units. Each unit contains some or all of the basic components of a unit of instruction: performance objectives, suggested activities for teachers, information sheets, assignment sheets, job sheets, transparency masters, tests, and answers to the tests. Units are liberally illustrated and are planned for more than one lesson or class period of instruction. Information for the teacher includes an instructional/occupational analysis of air conditioning and refrigeration, a list of tools and equipment needed, and a list of references. Topics covered by the six units are the following: gas furnaces, electrical heating systems, residential cooling systems, heat pump systems, balance points, and hydronics. (KC)