The electrical symbols you are most likely to find on electrical construction drawings are found in below Figures
Knowing the special characteristics of these symbols will improve your ability to remember them and to interpret other symbols that are not used in these drawings.
Other symbols may also be used, provided that a suitable explanation of their meaning is included
on the drawings where the symbol is used or that a symbol legend sheet is provided. Most drawings
today are produced with computer-aided design and drafting software (a CADD program). A symbols
library is included with the CADD software. These symbols may vary slightly from one software package to another, but the experienced electrician can usually readily understand them.
Electrical plans are generally drawn to scale. However, graphic symbols indicate only the approximate locations of electrical equipment such as switches and receptacles and are not drawn to scale. Details are provided in the specifications or on the plans that will give mounting heights, dimensions above countertops, distances from doors, height above the floor, and so forth, for accurate locations of receptacles, luminaires, and other equipment.
If more than one symbol is located immediately adjacent to another, it usually means that a
multigang box for multiple wiring devices and a single cover are to be installed. For example, if three
switches are to be located in a common box and under a 3-gang cover plate, three “S” symbols will
be drawn at the location. Obviously, the electrician will need to be certain a box with adequate size is
selected to enclose the number of wires and devices required. The owner or architect will indicate in
the specifications the maximum number of wiring devices permitted in a common box. Typically, this
is three or four. Cover plates to accommodate more than four switches are often a special order item.