How to Use the Color Code Colors are used throughout Heating and Cooling Essentials to indicate different states of gases and liquids in refrigeration systems. Various equipment components and materials are also identified with color. The following key shows what each color represents. States of Liquids or Gases High-pressure Liquid Low-pressure Liquid High-pressure Gas Water Water Vapor Copper Tubing Wood, Building Partitions Evaporators and Condensers Fuses and Other Electrical Components Airflow Flow, Other Fluids Iron, Steel, Other Metals Refrigerant Oil Motors and Compressors Metering Devices, Valves, Thermostats Low-pressure Gas Components and Materials Other Special features, materials, or components not otherwise coded. Note: In some schematic representations, additional colors may be used to aid understanding. They will be identified in a key accompanying the illustration. Using This Textbook ix Copyright Goodheart-Willcox Co., Inc.