The standard circuit breaker symbol for electrical circuit schematics is a rectangle (representing the breaker housing) intersected by a single line (the current path), featuring a manual trip lever indicated by a short perpendicular hash mark on the switch arm. However, the exact geometry changes depending on whether you are reading an ANSI/IEEE 315 drawing in North America or an IEC 60617 drawing internationally. Before you trace a fault or design a subpanel layout, you need to know exactly which standard your schematic follows.
The Complete Circuit Breaker Symbol Reference Table
The table below maps the most common breaker types to their respective schematic symbols. Use this as your primary bench and jobsite reference when reading single-line diagrams or control schematics.
| Breaker Type | ANSI/IEEE 315 (US / NEC Context) | IEC 60617 (International) | Practical Application & Meaning |
|---|---|---|---|
| Standard Thermal-Magnetic | Rectangle with a straight line passing through. A switch arm crosses the line with a small perpendicular tick mark (trip indicator). | A rectangle intersected by a line, with a switch arm and a small 'x' or cross inside the rectangle to denote automatic tripping. | Standard branch circuit protection (e.g., Square D QO, Eaton BR). Protects against both overloads (thermal) and short circuits (magnetic). |
| Magnetic-Only (MCP) | Same as thermal-magnetic, but the rectangle contains a sharp zigzag or coil symbol to denote magnetic trip only. | Rectangle with a coil symbol inside and the standard IEC trip cross. | Motor Circuit Protectors. Used in motor control centers (MCCs) alongside separate overload relays. Does not protect against slow overloads. |
| Ground Fault (GFCI / GFI) | Standard breaker symbol with a small sine wave or the letters 'GFI' / 'GF' appended next to the housing. | Standard IEC breaker symbol with a toroid (donut) symbol drawn around the phase and neutral lines. | Required for wet locations (kitchens, bathrooms, outdoors). Detects current imbalance (typically 4-6mA) between hot and neutral. |
| Arc Fault (AFCI) | Standard breaker symbol with a jagged arc symbol or the letters 'AF' / 'AFCI' appended. | Standard IEC breaker symbol with a specialized arc-flash graphic or 'AF' text designation. | Required for living areas and bedrooms (NEC Article 210.12). Detects high-frequency arcing signatures that standard thermal trips miss. |
Regional Standards: Which Symbol Set Applies to You?
Reading the wrong standard is the fastest way to misinterpret a control circuit. The symbol you are looking at depends entirely on the origin of the equipment and the drafting standard used by the engineer.
North America (ANSI/IEEE 315 & NEMA)
If you are working in the US or Canada, your schematics will almost universally follow ANSI/IEEE 315 and NEMA conventions. In this system, the circuit breaker symbol for an electrical circuit heavily relies on the 'tick mark' on the switch arm to denote the trip mechanism. The physical breakers you install (like a Siemens QT or Square D HOM) will be reflected in these drawings. NEC (NFPA 70) does not dictate schematic symbols directly, but it mandates the application of the devices these symbols represent.
Europe and Global (IEC 60617)
International drawings, and increasingly modern global OEM equipment, use IEC 60617. The IEC approach is more modular. Instead of drawing a completely different symbol for a breaker versus a contactor, IEC uses a base switch symbol and adds standardized function indicators (like the 'x' for automatic tripping or the toroid for ground fault). If you are troubleshooting an imported CNC machine or a European-manufactured VFD panel, expect IEC symbols.
Old UK (BS 3939) vs. Harmonized
If you are troubleshooting legacy equipment in the UK, you might encounter BS 3939 symbols. The old British standard used a distinct 'loop' on the switch arm to indicate a breaker, which looks remarkably similar to a modern disconnect switch. The UK has since harmonized with IEC 60617, but panels built before the early 2000s may still feature the legacy loop notation. When in doubt, trace the physical wire to the DIN rail to verify the component.
Rows People Get Wrong (And How to Fix Them)
Even experienced electricians and controls technicians misread specific rows in schematic tables. Here are the most common points of failure and how to interpret them safely.
A standard disconnect switch symbol looks almost identical to a breaker, minus the trip indicator. In IEEE 315, a disconnect is just a switch arm over a line. A breaker has the perpendicular tick mark. In IEC, a disconnect lacks the 'x' inside the rectangle. The Fix: Always look for the trip hash or the 'x'. If it is missing, it is a manual disconnect, meaning it will not clear a short circuit automatically.
Fuses and breakers serve similar overcurrent roles but have vastly different let-through currents and replacement procedures. In older schematics, a fuse is a rectangle with a solid block in the middle, or a squiggly line. Modern IEEE uses a rectangle with a solid central bar. The Fix: If the symbol has a moving arm (a hinge point), it is a breaker. If it is a static line or block inside a rectangle, it is a fuse.
On 30-year-old blueprints exposed to UV light or oil mist, the tiny trip indicator tick mark on a breaker symbol often fades away, making it look like a standard switch. The Fix: Never assume a faded symbol is a breaker. Look at the context: does the symbol sit on the main feeder line protecting a 40A load? A 40A manual switch is rare in that position; it is almost certainly a breaker. However, for safety, treat the physical device as a manual switch until you can read the physical label on the breaker toggle (e.g., 'HACR', 'SWD', or 'Class CTL').
Frequently Asked Questions
What is the circuit breaker symbol for electrical circuit diagrams in AutoCAD?
In AutoCAD Electrical or standard AutoCAD with electrical toolsets, the circuit breaker symbol is typically deployed as a dynamic block. For North American projects (JIC standard), the block is usually named CB_1P or CB_2P (1-pole or 2-pole) and features the IEEE 315 rectangle with the trip hash. For IEC projects, the block library will use the IEC 60617 standard, often tagged as QF (the standard IEC letter code for a circuit breaker, whereas NEMA/IEEE often uses CB or Q). Always verify your project's symbol library configuration before drafting, as mixing JIC and IEC blocks in a single schematic will cause confusion during panel building.
How do I tell a breaker symbol from a fuse symbol on a faded schematic?
When the ink is faded and the trip lever hash mark is invisible, look at the letter designation next to the symbol. In NEMA/IEEE standards, a breaker is typically labeled CB (Circuit Breaker) or Q, while a fuse is labeled F or FUS. In IEC standards, a breaker is designated by the letter Q (or QF), whereas a fuse is designated by F. If the letters are also faded, check the physical panel: if the device has a toggle handle that can be manually switched ON and OFF, it is a breaker. If it requires a puller tool or physical replacement element, it is a fuse.
Does the circuit breaker symbol change for GFCI or AFCI breakers?
Yes, but usually only by an appended text or minor graphic modifier rather than a completely new base symbol. The base thermal-magnetic breaker symbol remains the same. For a GFCI, drafters will add the text 'GFI', 'GF', or 'EPD' (Equipment Protective Device) next to the rectangle, or draw a small toroid (circle) around the phase and neutral lines passing through it. For an AFCI, the text 'AF' or 'AFCI' is added. In strict IEC drafting, a specialized arc-flash symbol (a small jagged star) may be placed inside the breaker rectangle to denote arc-fault protection. Always cross-reference the panel schedule, as the schematic symbol alone rarely specifies the exact mA trip threshold (e.g., 5mA personnel vs. 30mA equipment protection).
