Reading drawings · Lesson 2 of 7

Symbols: IEC and ANSI/NEMA

Symbols are the alphabet of drawings. There are two schools: IEC (European, and most of our region) and ANSI/NEMA (American, which you will meet on American machines). In this lesson you will see both side by side, review them with cards, and practise until you can recognise any symbol at a glance.

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1Two schools, same meaning

	IEC 60617	ANSI / NEMA
Drawing direction	Vertical current paths, top to bottom	Ladder: horizontal rungs, left to right
NO contact	A slanted line	Two parallel lines -\| \|-
Coil	A rectangle	A circle with the device name inside
Device name	-K1, -S1 and -F2	CR1, PB1, OL and M
Where you meet it	European machines, Siemens, Schneider, ABB, most projects in our region	American machines, Allen-Bradley, older drawings

The golden rule: a drawing is always drawn with the power off and no buttons pressed (normal state). NO means open in that state, and NC means closed. When the coil is energised, all its contacts change over.

2Symbol cards

Each card shows the symbol in both schools. Think first about what it is, then flip the card.

19 symbols

3Things that confuse people

NO and NC in NEMA: the same two lines; the difference is the diagonal line. If it has a diagonal line across it, it is NC.
Push button or contact? In IEC the push button is the same contact with an actuator [ joined by a dashed line (mechanical link). Without the actuator it is a relay contact.
The overload has two symbols: the thermal element in the power circuit, on the phases, and the 95-96 contact in the control circuit. Both are the same device, -F2.
Timers: the parachute shape on a contact means its action is delayed. Check in the catalogue whether it is on-delay or off-delay.
Lamps: in NEMA, R red usually means "running" and G green "stopped". In IEC 60204, green means "running/safe" and red "danger/emergency". Check the legend page.

From the field: an American filling machine arrived with a European panel that had been modified. You will find half the drawings in NEMA and half in IEC. Do not get confused: read the name and the terminals, and the shape confirms it.

4Exercise: match the symbol

Sometimes you will see a symbol and choose its name; sometimes you will see an IEC symbol and choose the same one in NEMA, or the other way round.

Match the symbol

?Lesson quiz

Get at least 5 of 6 right to complete the lesson.

Symbols follow IEC 60617 and ANSI/NEMA (IEEE 315 / NFPA 79); device tags follow IEC 81346. Every company draws a little differently: the legend page at the front of the drawing set is the reference. Your progress is saved on this device only.
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