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Common Electrical Symbols Chart

How the most common schematic and one-line symbols are drawn and what they stand for, following IEEE 315 practice, with notes on the IEC forms you may also see.

Ref EL-0060IEEE 315

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Electrical drawings use graphic symbols instead of pictures of parts. IEEE 315 (also published as ANSI Y32.2) is the main US standard for these symbols. Drawings from Europe and many machine builders use IEC 60617 symbols, which differ for some devices. Every drawing set should have a legend; the legend governs over any chart.

How to read it

Find the shape on the drawing and match it below. Letters next to a symbol identify the device (M for motor starter coil, CR for control relay, PB for pushbutton). Contacts with the same letters as a coil are operated by that coil. Contacts are always drawn in their de-energized, at-rest state.

Chart

Device	How it is drawn	Notes
Ground (earth)	Vertical line ending in three horizontal lines, getting shorter	Chassis ground may be drawn with angled lines instead
Resistor	Zigzag line	IEC: small rectangle
Capacitor	Two short parallel lines; one may be curved	Curved plate marks the negative side on polarized types
Inductor or coil winding	Series of loops or bumps
Transformer	Two windings side by side, often with lines between for an iron core	Dots mark polarity
Fuse	Rectangle with a line through it, or an S-shaped curve
Circuit breaker	Curved arc over a break in the line, or a square box on one-lines	Check the legend on one-line drawings
Normally open contact	Two short parallel vertical lines	Closes when the device operates
Normally closed contact	Two parallel lines with a diagonal slash	Opens when the device operates
Relay or starter coil	Circle with letters inside	Letters match the contacts it operates
Pushbutton	Bar above two terminals: NO bar sits above the gap, NC bar touches below
Motor	Circle with M or MOT	On one-lines, often with horsepower
Pilot light	Circle with letter for color (R, G, A) or radiating lines
Battery	Pairs of long and short parallel lines	Long line is positive
Conductors crossing, not connected	Lines cross with no dot	Older drawings use a small hump
Conductors connected	Dot at the junction

Key points

Ladder diagrams show control circuits as rungs between two vertical power rails. Read each rung left to right.
One-line (single-line) diagrams show power distribution with one line standing for all phase conductors.
Wire numbers on a schematic match the labels in the panel; use them to trace circuits.

Common mistakes

Reading a normally closed contact as open because the device is energized in the field. The drawing shows the at-rest state.
Assuming a US symbol where the drawing uses IEC symbols, or the reverse.
Ignoring the drawing legend, which may define special symbols.

Governing standards: IEEE 315 (graphic symbols for electrical and electronics diagrams, ANSI Y32.2); IEC 60617 for IEC symbols; NFPA 79 for industrial machinery drawings.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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