Subpanel Symbol
Definition: The Subpanel symbol represents a secondary electrical distribution panel — also called a sub-distribution board or load centre — fed from a main service panel via a feeder circuit, used in wiring diagrams to show a branch distribution point that supplies breakers for circuits in a specific area of a building, per ANSI/NFPA 70 (NEC) and IEC 60364 conventions.
Also known as: sub-distribution board, secondary panel, load centre, breaker box, distribution panel.
What the Subpanel symbol means
A subpanel symbol denotes a subordinate electrical distribution enclosure that receives power from a main panel through a dedicated two-pole breaker (feeder breaker) and then distributes that power to multiple individual branch circuits. The symbol typically shows two incoming line conductors (L1 and L2) and a neutral bus, indicating that the subpanel operates at the same system voltage as the main panel.
Subpanels are used to extend electrical distribution to remote locations — a detached garage, a workshop, an additional floor, or a large appliance bank — without running individual circuits all the way back to the main service entrance. The subpanel symbol in a wiring diagram signals that all branch circuits drawn emerging from it share a common feeder overcurrent protection device located at the main panel.
How to identify the Subpanel symbol
The subpanel symbol is drawn as a rectangular enclosure box, typically wider than it is tall, with two incoming feeder conductors entering from the top (labelled L1 and L2) and a neutral conductor entering at the centre top or descending from a centre neutral bus. Inside the rectangle, vertical lines or short stubs represent individual branch circuit breakers. This distinguishes it visually from a single-breaker symbol (which shows only one device) and from the main panel symbol (which typically includes the service entrance conductors and meter).
Function and usage boundary
A subpanel functions as a local distribution hub that accepts a high-current feeder — typically 60 A, 100 A, or 200 A — from the main panel and subdivides it into lower-current branch circuits through individual overcurrent protection devices (breakers). It provides a local disconnect location, simplifies wiring runs in large or multi-building installations, and allows independent isolation of a zone without affecting the rest of the building's circuits.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60364-5-52 and IEC 61439-3 govern low-voltage distribution boards; the schematic symbol for a distribution board in IEC practice uses a rectangle with incoming and outgoing conductors and does not prescribe a unique single glyph — functional block notation is standard. |
|---|---|
| ANSI/IEEE 315 | ANSI/NFPA 70 (National Electrical Code) defines subpanel installation requirements; IEEE 315 / ANSI Y32.2 does not assign a unique standardised glyph specifically for subpanels — wiring diagrams use a labelled rectangle block convention widely adopted in North American electrical drafting. |
| Key difference | IEC documentation refers to 'distribution boards' (DB) and uses IEC 61439-3 consumer units notation; ANSI/NEC documentation uses 'panelboard' or 'loadcenter'. Both use a rectangular block in schematic diagrams, so the visual difference is labelling and context rather than glyph shape. |
The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.
Logical terminals
| Logical ID | Editor terminal name |
|---|---|
| l1 | L1 |
| l2 | L2 |
| neutral | Neutral |
Where the Subpanel symbol is used
- Detached garages and outbuildings fed from a residential main panel
- Workshop or machine shop areas requiring multiple 20 A and 30 A circuits
- Additional floors of a multi-storey building served by a single main service entrance
- Commercial office suites within a larger building receiving a tenant feeder
- Outdoor equipment pads (HVAC, irrigation pumps) needing local branch circuit distribution
- Home additions where running individual circuits to the main panel is impractical
- Industrial machine cells requiring a local panel with lockable main disconnect
Key facts
- A subpanel (sub-distribution board) is a secondary electrical panel fed by a feeder circuit from the main service panel, used to distribute power to branch circuits in a remote area of a building.
- The subpanel symbol in wiring diagrams shows a rectangular enclosure with two line conductors (L1, L2) entering at the top and a neutral bus, representing 120/240 V single-phase distribution in North American practice.
- The feeder breaker protecting a subpanel is located in the main panel, not in the subpanel itself; the subpanel's main breaker (if present) serves as a local disconnect.
- Per NFPA 70 (NEC) Article 225 and 230, the feeder conductors must be sized to carry the calculated load of all branch circuits in the subpanel, with the feeder breaker sized accordingly.
- IEC 60364-5-52 and IEC 61439-3 govern equivalent distribution boards in international practice; the functional block symbol is a labelled rectangle in both IEC and ANSI schematic conventions.
- Subpanels have their own neutral bar and ground bar which must be bonded together only in the main panel, not in the subpanel, per NEC 250.24(A)(5) to prevent objectionable neutral current on grounding conductors.
- Common subpanel sizes in North America: 60 A (6–12 spaces), 100 A (12–24 spaces), 200 A (24–42 spaces); IEC equivalent consumer units are rated 63 A or 100 A with 6–24 module DIN-rail spaces.
Frequently asked questions
What does the subpanel symbol mean in a wiring diagram?
The subpanel symbol represents a secondary electrical distribution panel fed from the main service panel via a feeder circuit. It shows where power is subdivided into multiple branch circuits for a specific zone or outbuilding. The symbol is drawn as a labelled rectangle with L1 and L2 feeder conductors entering at the top and individual breaker stubs shown inside.
What does the subpanel symbol look like?
The subpanel symbol appears as a rectangle (wider than tall) with two line conductors entering at the top labelled L1 and L2, and a neutral conductor at the centre. Short vertical stubs or lines inside the rectangle represent individual branch circuit breakers. It differs from the main panel by having no meter symbol and showing only feeder inputs rather than service entrance conductors.
What is the difference between a main panel and a subpanel symbol?
The main panel symbol includes the service entrance conductors and sometimes a meter, representing the point where utility power enters the building. The subpanel symbol shows only feeder conductors entering from another panel, indicating it is a downstream distribution point. Both use rectangular block notation in wiring diagrams, but context, labels, and feeder origin differentiate them.
What standard defines the subpanel symbol?
In North America, subpanel installation is governed by ANSI/NFPA 70 (NEC); the schematic symbol is a labelled rectangle per IEEE 315 / ANSI Y32.2 block notation. Internationally, IEC 60364-5-52 and IEC 61439-3 govern distribution boards; both standards use a rectangular block in functional wiring diagrams without a unique single glyph.
How many circuits can a subpanel supply?
A subpanel can supply as many branch circuits as it has breaker spaces. Common North American subpanels provide 6, 12, 24, or 42 spaces. The total load of all branch circuits must not exceed the feeder breaker rating (typically 60 A, 100 A, or 200 A) that protects the subpanel feeder in the main panel.
Why is the neutral and ground bonded in the main panel but not in the subpanel?
NEC 250.24(A)(5) requires the neutral-to-ground bond only at the main service panel (the first means of disconnect from the utility). In a subpanel, the neutral bar and ground bar must remain separated to prevent neutral current from flowing on equipment grounding conductors, which would create a shock hazard and nuisance tripping of GFCI devices.
What are the pin/terminal labels on the subpanel symbol?
The subpanel symbol has three primary terminals: L1 (Line 1, one hot conductor of the feeder), L2 (Line 2, the second hot conductor), and Neutral (the grounded conductor of the feeder). Individual branch circuits inside the panel connect to L1, L2, and Neutral as appropriate for 120 V or 240 V loads.
Related symbols
- Circuit Breaker symbol
- Light Fixture symbol
- Main Panel symbol
- Outlet symbol
- Switch (3-Way) symbol
- Switch (SPST) symbol
Physical breadboard, PCB, and panel mapping
No universal physical profile is published for this symbol yet. Create a versioned custom part from the exact manufacturer dimensions and terminal map before fabrication.
Place the Subpanel symbol directly on a wiring diagram or schematic in the free online editor — no download required.