iii Preface Modern Refrigeration and Air Conditioning is the stan- dard for a new generation of learner. This classic is an excellent blend of theory, skill development, and service techniques to help you learn how to install and service refrigeration and HVAC systems. Modern Refrigeration and Air Conditioning delivers comprehensive and au- thoritative content on the basic and advanced principles of refrigeration and air conditioning, provides excellent instruction and training in the skills and techniques essen- tial for servicing and troubleshooting, and emphasizes career opportunities, workplace skills, and safety. The content in Modern Refrigeration and Air Conditioning is correlated to the curriculum guides and competencies used for HVAC Excellence and PAHRA program accreditation. The accreditation curriculum dovetails with entry-level and professional certification exam requirements. Thus, Modern Refrigeration and Air Conditioning is a valuable resource as you begin your journey toward entry-level certification, employment, professional certification, and career advancement. Modern Refrigeration and Air Conditioning has been carefully designed and crafted to make your learning experience effective and efficient. Concepts are explained clearly and simply, with text narrative supported by numerous engaging and attractive illustrations. The for- mat of each chapter helps you quickly master HVACR con- cepts and topics. In the coming years, the number of new positions in the HVACR industry combined with open positions due to retirements is expected to be significantly greater than the number of new employees entering the field. This will create a shortage of trained workers and a surplus of employment opportunities. You are entering the HVACR field at an ideal time, and Modern Refrigeration and Air Conditioning will be a fantastic resource for you as you build your career!