HVAC schematics are diagrams describing the detailed functionality of a system. They consist of wiring diagrams for the electrical system and plumbing diagrams for air flow and refrigerant lines. Schematics use various types of symbols, lines and annotations.
The electrical portion of the schematics typically consist of a ladder, line and installation diagram. A ladder diagram displays the main power input to each device. A line diagram shows the specific control wiring to components and lower voltage circuits. An installation diagram shows the interfaces to the rest of the building, including power input, thermostat and sensors. The plumbing portion of the schematic shows the layout of the air flow ducts, air returns and refrigerant lines to the conditioning unit.