GFCI Outlet Symbol
Definition: The GFCI Outlet symbol represents a Ground Fault Circuit Interrupter receptacle — a mains-voltage outlet with built-in current-sensing electronics that trips within 25 milliseconds whenever the difference between Hot and Neutral currents exceeds approximately 5 mA, as required by NFPA 70 (NEC) Article 210.8 and UL 943 in North America.
Also known as: GFI outlet, ground fault outlet, ground fault receptacle, RCD outlet, safety outlet, GFCI receptacle.
What the GFCI Outlet symbol means
The GFCI Outlet symbol denotes a special electrical receptacle that provides personnel protection against electric shock by continuously monitoring the current flowing out on the Hot conductor (pin: Hot) and returning on the Neutral conductor (pin: Neutral). When those two currents differ by more than ~5 mA — indicating current is leaking through a person or fault path — the internal relay trips and de-energises the outlet in under 25 ms, well within the threshold for ventricular fibrillation.
In wiring diagrams the GFCI Outlet symbol differs from a standard duplex outlet by the addition of TEST and RESET button indicators on the face plate, and it carries a three-terminal connection: Hot (line-side hot), Neutral (line-side neutral), and Ground (equipment-ground conductor). Downstream LOAD terminals (when present) allow a single GFCI device to protect multiple ordinary outlets on the same branch circuit.
How to identify the GFCI Outlet symbol
The GFCI Outlet symbol is drawn as a rectangle or stylised outlet face containing two parallel vertical slots (Hot and Neutral openings) plus a rounded ground slot below them, and is distinguished by two small rectangles labelled TEST and RESET on the face. In schematic form it may appear as a standard outlet symbol with the letters 'GFI' or 'GFCI' annotated alongside. The three connection points — Hot (top), Neutral (bottom), and Ground (left side) — are explicitly labelled in block-diagram representations.
Function in a circuit
A GFCI outlet continuously compares the current in the Hot and Neutral conductors using a differential current transformer. Under normal operation these currents are equal. If a ground fault occurs — for example, a person contacting a live conductor — the fault current returns via an unintended path, creating an imbalance. The internal comparator detects this imbalance and triggers a solenoid that mechanically opens both the Hot and Neutral contacts simultaneously, removing power from the outlet. The RESET button re-latches the contacts after the fault is cleared; the TEST button injects a deliberate imbalance to verify the mechanism functions.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60755 defines requirements for residual-current devices (RCDs), the IEC equivalent of GFCIs. IEC 60617 does not prescribe a unique schematic symbol for a GFCI outlet specifically; the outlet is drawn as a socket-outlet symbol (IEC 60617 database reference S00319) with a supplementary annotation indicating RCD or RCCB protection. |
|---|---|
| ANSI/IEEE 315 | ANSI/NFPA 70 (NEC) Article 210.8 mandates GFCI protection locations; UL 943 defines the product standard (Class A: 5 mA trip). In ANSI wiring diagrams the GFCI outlet is drawn as a standard duplex outlet rectangle with 'GFCI' labelled and TEST/RESET buttons shown on the symbol face. |
| Key difference | IEC countries use the term RCD (residual-current device) or RCCB and depict it as a circuit-breaker block with a ground-fault coil; ANSI/North American practice uses the GFCI label on the outlet face symbol. The trip threshold is identical (IEC Class A = 30 mA for general use; NEC/UL 943 Class A = 5 mA for personnel protection). |
Terminals / pins
| Pin | Name |
|---|---|
| hot | Hot |
| neutral | Neutral |
| ground | Ground |
Typical values
Trip threshold: 5 mA (UL 943 Class A, personnel protection); trip time: ≤25 ms at 264% of rated current. Voltage ratings: 120 V AC (North America standard), 125 V AC (rated), 15 A or 20 A current ratings. Ground conductor: bare or green, minimum 14 AWG for 15 A circuits.
Where the GFCI Outlet symbol is used
- Bathrooms — NEC Article 210.8 requires GFCI protection for all 120 V receptacles within 1.8 m (6 ft) of a water source
- Kitchens — countertop receptacles within 1.8 m of a kitchen sink must be GFCI-protected per NEC 210.8(A)(6)
- Garages and unfinished basements — all 120/240 V receptacles require GFCI protection per NEC 210.8(A)(2)
- Outdoor outlets — any outdoor receptacle on grade level accessible to the public must be GFCI-protected
- Crawl spaces and boathouses — areas subject to dampness require GFCI outlets to prevent electrocution from standing water
- Pool and spa equipment — all receptacles within 6 m (20 ft) of a pool or spa require GFCI protection per NEC 680
- Construction sites — temporary power receptacles on job sites must be GFCI-protected per OSHA 29 CFR 1926.404(b)(1)
Example
In a bathroom lighting and outlet circuit, a single 15 A GFCI outlet is installed at the first receptacle from the panel. Its LINE terminals receive Hot and Neutral from the branch circuit breaker; its LOAD terminals feed two standard duplex outlets downstream. A wiring diagram shows the GFCI symbol (with TEST/RESET buttons) connected via its Hot pin to the circuit hot, Neutral pin to neutral, and Ground pin to the ground bar, protecting all three outlets against ground faults without requiring individual GFCI devices at each location.
Key facts
- A GFCI outlet (Ground Fault Circuit Interrupter outlet) trips within 25 milliseconds when it detects a current imbalance of 5 mA or more between the Hot and Neutral conductors, per UL 943 Class A and NFPA 70 NEC Article 210.8.
- The GFCI outlet symbol has three electrical connections: Hot (line-side hot conductor), Neutral (line-side neutral conductor), and Ground (equipment-ground conductor).
- GFCI protection is required by NEC in bathrooms, kitchens, garages, outdoor locations, crawl spaces, unfinished basements, boathouses, pool areas, and construction sites.
- A single GFCI outlet can protect downstream standard outlets by connecting subsequent outlets to the GFCI LOAD terminals, eliminating the need for individual GFCI devices at each location.
- The IEC equivalent of a GFCI is an RCD (Residual Current Device) or RCCB; IEC Class A RCDs trip at 30 mA for general domestic use, whereas UL 943 Class A GFCIs trip at the stricter 5 mA threshold for personnel protection.
- GFCI outlets are available in 15 A and 20 A ratings for 120 V circuits; the 20 A version has a T-shaped neutral slot and is required for kitchen countertop circuits.
- The TEST button on a GFCI outlet creates a deliberate 5 mA imbalance to verify the device will trip; monthly testing is recommended by NFPA and UL.
Diagrams that use this symbol
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Frequently asked questions
What does the GFCI outlet symbol look like in a wiring diagram?
The GFCI outlet symbol is drawn as a rectangular outlet face with two vertical slots (Hot and Neutral) and a rounded ground slot, plus two small rectangles labelled TEST and RESET. In schematic block diagrams it appears as a standard outlet rectangle annotated with 'GFCI' or 'GFI', with three labelled connection points: Hot, Neutral, and Ground.
What does GFCI stand for and what does the GFCI outlet symbol mean?
GFCI stands for Ground Fault Circuit Interrupter. The GFCI outlet symbol represents a safety receptacle that monitors current balance between Hot and Neutral conductors and disconnects power within 25 ms if a fault current of 5 mA or more is detected, protecting persons from lethal electric shock per UL 943 and NEC Article 210.8.
What is the difference between a GFCI outlet and a regular outlet symbol?
A regular duplex outlet symbol is a simple rectangle with two slot pairs. The GFCI outlet symbol adds TEST and RESET button indicators on the face and, in detailed schematics, shows separate LINE and LOAD terminal pairs, indicating the device's ability to protect downstream outlets on the same circuit.
What are the pins on a GFCI outlet symbol?
The GFCI outlet symbol has three primary pins: Hot (the line-side hot conductor, typically black wire), Neutral (the line-side neutral conductor, typically white wire), and Ground (the equipment-grounding conductor, typically green or bare copper). Full GFCI devices also have LOAD-side Hot and Neutral terminals for downstream circuit protection.
What standard defines the GFCI outlet?
In North America, GFCI outlets are defined by UL 943 (Standard for Ground-Fault Circuit-Interrupters) and mandated by NFPA 70 (National Electrical Code) Article 210.8. The IEC equivalent standard is IEC 60755, which defines residual-current devices (RCDs), and IEC 61008/61009 for RCCBs and RCBOs.
Where is GFCI protection required by code?
NEC Article 210.8 requires GFCI-protected outlets in bathrooms, kitchens (within 1.8 m of a sink), garages, outdoor locations, crawl spaces, unfinished basements, boathouses, swimming pool and spa areas (NEC 680), and temporary construction site power. Most jurisdictions adopt NEC requirements either directly or in amended form.
What is the trip threshold of a GFCI outlet?
A Class A GFCI outlet (UL 943) trips at a fault current of 5 mA (0.005 A) with a response time of 25 milliseconds or less. This threshold is chosen to be below the 10–20 mA let-go threshold for most adults and well below the 75–400 mA ventricular fibrillation threshold.
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