Electrical engineers and designers generally follow accepted standards for the basic electrical and electronic symbols. These electrical symbols can be classified as those used on connection and interconnection diagrams and those used on elementary or schematic diagrams.

Connection and interconnection symbols represent complete electrical devices such as switch outlets, receptacle outlets, lighting fixtures or luminaires, and auxiliary systems. These symbols take the form of relatively simple geometric shapes modified with lines and letters inside or outside of them. The intent was to create a kind of technical shorhand that could be easily learned.

They were kept simple to reduce the time and expense of preparing drawings, particularly those used in the field for installation of common off-the-shelf electrical components.

Figure below includes a selection of electrical connection and interconnection symbols recommended by the American National Standards Institute (ANSI) for use on architectural drawings. These symbols, or modified versions of them, are widely used on electrical drawings in North America. Appendix A also includes a page of these symbols.

CAD electrical drafting software has eliminated the chore of reproducing these symbols. The software contains a library of symbols that can be accessed from a menu, downloaded, and dragged into position on the face of the screen as needed.

The basic symbols can be modified to fulfill special requirements or identify devices not listed in the standard symbol list. In the past, symbols were usually drawn by the drafts person tracing around the inside of geometric cutouts in templates made of sheet plastic.

As with line conventions, the motivation for using standardized symbols is to eliminate the time involved in trying to interpret drawings that include unfamiliar proprietary symbols. It is important that the symbols be easily recognized by all parties involved in an electrical project, from the designer to the electricians doing the work.

As a result, the chances of making costly mistakes in interpretation are lessened. Moreover, large architectural and consulting engineering firms with national and international clients approve of symbol standardization because of the many people of different backgrounds, languages, and cultures who could be using the drawings. This is especially true of large-scale new construction projects such as hospitals, power stations, and industrial plants involving many different contractors.

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