When reading or drawing electrical chart symbols, your first and most critical decision is the governing standard. If you are working on North American industrial panels or NEMA-rated hardware, you must use ANSI/IEEE 315. If you are designing for international markets, European installations, or modern IEC-rated PLC panels (like Siemens or Schneider), you must use IEC 60617. Mixing these two standards on a single schematic is a primary cause of miswired control panels and failed safety inspections.
How to Read This Reference Chart
This reference is structured to help you instantly resolve symbol conflicts. The ANSI/IEEE 315 column applies to US/Canadian installations, legacy NEMA panels, and most North American EDA software defaults (like older Altium libraries). The IEC 60617 column applies to global projects, IEC hardware, and modern PLC programming environments like TIA Portal or CODESYS.
Quick-Jump Index: Use these anchor points to find the most frequently queried components in the master table below:
- Passive Components: Resistors, Capacitors, Inductors
- Control Elements: Relay Coils, Contactors, Timers
- Contacts & Switches: NO/NC Contacts, Pushbuttons, Limit Switches
- Power & Ground: Transformers, Earth Ground, Chassis Ground
Master Reference Table: Essential Electrical Chart Symbols
The following data is sourced directly from the IEEE 315 standard specification and the IEC 60617 database. For a practical breakdown of how these translate to physical wiring, refer to the All About Circuits reference textbook.
| Component (Quick-Jump) | ANSI/IEEE 315 (US/NEMA) | IEC 60617 (Global/PLC) | Common Confusion to Avoid |
|---|---|---|---|
| Resistor | Zigzag line | Empty rectangle | IEC rectangles can look like fuses if not labeled with an 'R' designator. |
| Capacitor | Two parallel lines (one curved if polarized) | Two parallel lines (one curved if polarized) | Identical in both. Polarity curve always faces the negative/ground side. |
| Inductor / Coil | Three or four continuous loops | Three or four continuous loops (often with a solid core line) | Adding a solid line under the loops denotes an iron core in both standards. |
| Relay Coil | Circle, or rectangle with diagonal lines | Rectangle with parentheses: ( ) or just || |
Do not use the ANSI circle for IEC drawings; IEC reserves circles for motors and rotating machines. |
| NO Contact | Gap with an angled, hinged line | Gap with a straight, hinged line or forward slash / |
IEC uses the slash / for NO, and a slash with a cross X for NC. |
| NC Contact | Overlapping lines with an angled cross | Gap with a backward slash and cross \ or overlapping lines |
Ensure the 'cross' is clearly visible; a faint cross makes an NC look like an NO. |
| Earth Ground | Three decreasing horizontal lines | Circle with three internal lines, or the standard three decreasing lines | Chassis ground (U-shape with lines) is distinct from earth ground in both. |
| Transformer | Two sets of coil loops separated by a core line | Two overlapping circles or two rectangles | IEC overlapping circles are heavily used in single-line power diagrams. |
Decision Tree: Which Symbol Variant Should You Draw?
Do not leave your symbol choice to personal preference. Use this decision path to terminate on the exact standard and library you must select in your CAD software (e.g., AutoCAD Electrical, EPLAN, KiCad).
| IF your project meets this condition... | AND the hardware is... | THEN your concrete pick is: |
|---|---|---|
| Panel will be installed in the US/Canada and inspected under NEC/CEC | NEMA-rated contactors, Allen-Bradley PLCs, US-spec breakers | ANSI/IEEE 315 / NEMA Library. (Select 'JIC' standard in AutoCAD Electrical). |
| Panel is for export to the EU, UK, or AU, or follows CE/UKCA marking | IEC-rated hardware (Schneider TeSys, ABB, Siemens SIRIUS) | IEC 60617 Library. (Select 'IEC' standard in EPLAN or AutoCAD). |
| Drawing a low-voltage DC PCB or embedded microcontroller schematic | SMD components, ESP32 modules, op-amps, logic ICs | IEEE 315. (This is the hardcoded default for KiCad 8, Altium, and Eagle EDA tools). |
Modifiers and State Indicators: When Base Symbols Change
A base symbol only tells you what a component is. Modifiers tell you how it behaves. In schematic drafting, these graphical 'deratings' or modifiers alter the base value to indicate time delays, mechanical linkages, or thermal protections. Here is how modifiers modify the base symbol:
- Thermal Overload (Derating Modifier): A standard IEC contactor symbol is modified by adding a small box with a diagonal line or a 'thermal' tick mark on the power poles. This tells the wireman that the physical device includes a bimetallic trip unit, requiring the heater element to be sized to the motor's FLA (Full Load Amps).
- Time Delay (State Modifier): A standard NO contact is modified by adding a small 'pneumatic' arc or a clock symbol. An arc pointing away from the contact gap indicates an 'On-Delay' (timer closes after energization). An arc pointing toward the gap indicates an 'Off-Delay'.
- Mechanical Linkage: A dashed line connecting two separate relay contacts indicates they are physically ganged on the same armature. If you omit this dashed line, a panel builder might wire them as two separate relays, causing a catastrophic logic fault.
- Current Direction / Polarity: A single arrowhead next to a diode or polarized capacitor modifies the base symbol to enforce installation direction. Reversing a polarized capacitor in a 48V DC solar inverter circuit will result in immediate dielectric failure and venting.
What the Standard Tables Cannot Tell You
While ANSI and IEC tables standardize the graphical language, they have strict limitations. Relying solely on symbol tables will leave blind spots in your design documentation. Here is what the standards cannot tell you:
- Physical Proximity and Wire Routing: A schematic shows electrical logic, not physical layout. Two contacts drawn side-by-side on a schematic might be located on opposite ends of a 4-foot-long control panel. You must cross-reference the schematic with a 2D/3D panel layout drawing to determine actual wire lengths and routing paths.
- Proprietary VFD and Drive Blocks: Variable Frequency Drives (VFDs) and soft starters do not have universally standardized internal schematic symbols. Manufacturers like Yaskawa or Danfoss use proprietary black-box rectangles with custom terminal designators (e.g.,
+DC,-DC,SC,SP). You must defer to the specific manufacturer's installation manual for these terminal mappings. - Ampacity and Wire Sizing: A symbol for a circuit breaker does not dictate the wire gauge. A 20A breaker symbol looks identical whether it is protecting a 12 AWG branch circuit or a 10 AWG feeder. The wire size, insulation type (THHN vs. XHHW), and ambient temperature derating must be specified in the Bill of Materials (BOM) or the wire schedule table, not inferred from the symbol.
