Understanding the Wiring Diagram Legend: A Comprehensive Guide

When it comes to implementing a reliable wiring design for any electrical system, wiring diagram legends are crucial. Wiring diagrams are standardized guides that illustrate the schematic representation of an electrical system and emphasize the internals of the wiring system. Legends are the symbols used in wiring diagrams that explain the function of each component. Any reading of the wiring diagram must start with understanding the wiring diagram legend.

Wiring diagram legends include various essential components such as schematic symbols, labels, current flow lines/arrows, terminal marks, etc. But deciphering these components can seem overwhelming at first. In this guide, we walk you through one of the most common wiring diagram legends, the American National Standard Institute (ANSI) diagram, and provide simple instructions on how to read and interpret it.

Interpreting the Components of the Wiring Diagram Legend

To properly read a wiring diagram, you must be familiar with the different components of the diagram and their meanings. ANSI wiring diagram legends have several common components including:

Schematic symbols

Labels

Current Flow lines/arrows

Terminal marks

Schematic Symbols

Schematic symbols are the most important part of a wiring diagram, because they show the physical configuration of all the wiring devices connected in a circuit. In an ANSI wiring diagram, there could be anywhere between 200-300 schematic symbols representing various components. However, there are nine key schematic symbols all engineers must be familiar with:

Ion	Symbol	Description
Inductor	L	A coil of wire that has a magnetic field when exposed to an alternating current.
Capacitor	C	An electrical medium that collects and stores electrical charge.
Transformer	T	A device that transfers power from one circuit to another through electromagnetic induction.
Diode	D	A two-terminal semiconductor device that allows current to move only in one direction.
Resistor	R	A device used to reduce or control the flow of electricity.

Labels

Connected to the components are the labels which provide clear descriptions of the components involved in the circuit. Each label should describe a specific component or a joint connection. In the wiring diagram, a label should contain information like the name of the component, its type or class, etc. Reports and datasheets may also be referenced in order to fully describe the component.

Current Flow Lines or Arrows

Current flow lines or arrows illustrate the current path and particular direction within the circuit. The arrows generally point away from the power source to the other components in the circuit. On a wiring diagram, these arrows follow the wire pattern around the circuit.

Terminal Marks

Terminal marks are labels for terminals and electrical connections. Generally, a terminal mark will contain information about its connected component, such as which wire goes to which wire number. Terminal marks must be strictly followed and must correspond to wiring diagrams in order for the system to work correctly.

By understanding each component of an ANSI wiring diagram legend and how they are connected, you can confidently develop and implement a reliable wiring design for an electrical system. Plus, when troubleshooting, being able to interpret the wiring diagram legend can make your job a lot easier!

Electrical Schematic Symbols Names And Identifications