8.1 Flexible Cords, Fixture Wires, Switches, Receptacles & Panelboards (Articles 400-408)
Key Takeaways
- Flexible cords may not substitute for fixed wiring, run through walls, ceilings, floors, doorways, or windows, or be concealed behind building surfaces or above suspended ceilings (NEC 400.12).
- An AC general-use snap switch may control a motor load of no more than 80 percent of its ampere rating (NEC 404.14(A)(3)).
- A grounded conductor must be provided at switch locations controlling lighting in bathrooms, hallways, stairways, and habitable rooms or occupiable spaces, with limited exceptions (NEC 404.2(C)).
- A nongrounding receptacle with no grounding means may be replaced with a GFCI receptacle marked 'No Equipment Ground' (NEC 406.4(D)(2)).
- Every panelboard circuit must be legibly identified by its clear, evident, and specific purpose, and not by transient conditions such as a tenant's name (NEC 408.4(A)).
Last updated: September 2026
Why this section matters
The PSI outline gives Articles 400 through 427 and 455 through 480 about three questions. They are mostly one-step lookups, so knowing where each rule lives is worth quick points.
Flexible cords and cables (Article 400)
Uses permitted (400.10(A)) include:
- pendants and wiring of luminaires;
- connection of portable luminaires, portable and mobile signs, or appliances;
- elevator cables and wiring of cranes and hoists;
- connection of utilization equipment to make frequent interchange easier;
- preventing the transmission of noise or vibration;
- appliances fastened in place but designed to be removed for maintenance and repair (the appliance must be identified for cord connection);
- connecting moving parts;
- temporary wiring as Article 590 allows.
Uses not permitted (400.12):
- as a substitute for the fixed wiring of a structure;
- run through holes in walls, structural ceilings, suspended or dropped ceilings, or floors;
- run through doorways, windows, or similar openings;
- attached to building surfaces (limited tension take-up exceptions);
- concealed by walls, floors, or ceilings, or located above suspended or dropped ceilings;
- installed in raceways, except as the Code permits;
- where subject to physical damage.
Ampacity and protection:
- Cord ampacity comes from Table 400.5(A)(1). Column A applies when three conductors are current-carrying and Column B when two are.
- Washington requires Column A for pendant boxes and luminaire cord drops (WAC 296-46B-314, -410).
- Cords are protected per 240.5.
- In a cord, the equipment grounding conductor is identified green or green with yellow stripes (400.23), and the grounded conductor per 400.22.
- Strain must be relieved so pull is not transmitted to joints or terminals (400.14).
Fixture wires (Article 402)
- Minimum size 18 AWG (402.6).
- Fixture wires are not branch-circuit conductors (402.11), except as Class 1 circuit conductors under Article 725.
- Ampacity (Table 402.5): 18 AWG = 6 A, 16 AWG = 8 A, 14 AWG = 17 A, 12 AWG = 23 A, 10 AWG = 28 A.
- Tap rules (240.5(B)(2)): on a 20 A circuit, 18 AWG fixture wire is limited to 50 ft of run and 16 AWG to 100 ft; 14 AWG and larger are permitted. On a 30 A circuit, 14 AWG and larger. On 40 A and 50 A circuits, 12 AWG and larger.
Switches (Article 404)
| Rule | 2020 NEC |
|---|---|
| Three-way and four-way switches are wired so all switching is in the ungrounded conductor | 404.2(A) |
| A grounded conductor must be installed at switch locations controlling lighting loads supplied by grounded general-purpose circuits serving bathrooms, hallways, stairways, and habitable rooms or occupiable spaces. Exceptions include raceway systems with room to add one later, and accessible framing cavities. | 404.2(C) |
| Switches may not disconnect the grounded conductor of a circuit, except where all circuit conductors open simultaneously or as otherwise allowed | 404.2(B) |
| Switches in damp or wet locations must be in weatherproof enclosures. Switches may not be installed within tub or shower spaces unless part of a listed tub or shower assembly. | 404.4 |
| Accessibility: the center of the grip of the operating handle, in its highest position, no more than 6 ft 7 in. above the floor or platform | 404.8(A) |
| Where the voltage between adjacent devices in a box exceeds 300 V, identified barriers must be installed between them (for example, a 277 V switch next to a 120 V switch on another phase) | 404.8(B) |
| Snap switches, dimmers, and similar controls must be connected to an EGC and provide a way to ground metal faceplates | 404.9(B) |
Switch ratings (404.14):
- AC general-use snap switches may control resistive and inductive loads up to their ampere rating, tungsten-filament lamp loads up to their rating at 120 V, and motor loads up to 80 percent of their ampere rating.
- AC-DC general-use snap switches may control resistive loads up to their rating, inductive loads up to 50 percent of their rating, and tungsten lamp loads only if T-rated.
- Dimmers may control only permanently installed incandescent luminaires unless listed for other loads.
Receptacles (Article 406)
Replacement rules (406.4(D)) come up often on exams:
- Where a grounding means exists in the box, the replacement must be a grounding-type receptacle connected to it.
- Where no grounding means exists, the choices are:
- a nongrounding receptacle;
- a GFCI receptacle marked "No Equipment Ground";
- a grounding-type receptacle supplied through a GFCI, marked "GFCI Protected" and "No Equipment Ground." An EGC may not be connected from the GFCI-type receptacle to any outlet supplied from it.
- Where the NEC now requires GFCI protection at that location, the replacement must be GFCI protected.
- Where the NEC now requires AFCI protection, the replacement must be a listed outlet branch-circuit AFCI receptacle, a receptacle protected by one upstream, or a receptacle on a combination AFCI breaker.
- Tamper-resistant and weather-resistant types are required on replacement wherever the NEC now requires them.
Other receptacle rules:
- Receptacles may not be installed face-up in countertops or work surfaces unless listed as countertop or work-surface assemblies (406.5(E), (F)).
- Metal faceplates must be at least 0.030 in. (ferrous) or 0.040 in. (nonferrous) thick (406.6).
- Receptacles controlled by an automatic control device, such as an energy management system, must be marked with the controlled-receptacle symbol (406.3(E)).
- A receptacle may not be dimmer-controlled unless it is part of a listed dimmer-receptacle combination (406.15).
Switchboards, switchgear, and panelboards (Article 408)
| Rule | 2020 NEC |
|---|---|
| Circuit directory: every circuit and circuit modification must be legibly identified by its clear, evident, and specific purpose, and not described by transient conditions of occupancy (such as "John's office"). Spares are described accordingly. | 408.4(A) |
| Source of supply: in other than one- or two-family dwellings, every panelboard or switchboard supplied by a feeder must be marked with where its power originates | 408.4(B) |
| High-leg (orange) conductor lands on the B phase | 408.3(E)(1) |
| Each panelboard must be protected by an overcurrent device rated no higher than the panelboard, located within or on the supply side of it | 408.36 |
| Panelboards in damp or wet locations need weatherproof enclosures (Washington: never in clothes closets, toilet rooms, or shower rooms, WAC 296-46B-408) | 408.37 |
| Panelboards must be mounted in cabinets, cutout boxes, or enclosures designed for them | 408.38 |
| The EGC terminal bar is bonded to the cabinet. EGCs connect to the grounded (neutral) bar only where 250.24(A)(5) or 250.142 allows (at the service or a separately derived system). | 408.40 |
| Each grounded conductor lands on its own terminal, not shared with another conductor (parallel conductors on terminals identified for them excepted) | 408.41 |
| A panelboard must have physical means to prevent installing more overcurrent devices than it is designed, rated, and listed for | 408.54 |
Why 408.41 matters: if two neutrals share one terminal, removing one neutral to work on its circuit can loosen the other and open a live multiwire neutral. That can put series voltage across loads on the other circuit, as described for multiwire circuits in Section 5.1.
Test Your Knowledge
An AC general-use snap switch is rated 20 amperes, 120/277 volts AC. What is the largest motor load it may control under NEC 404.14(A)?
A
B
C
D
Test Your Knowledge
An electrician replaces a two-prong receptacle in a 1950s house. The box has no equipment grounding conductor or other grounding means. Which replacement does NEC 406.4(D)(2) allow?
A
B
C
D
Test Your Knowledge
Which panelboard directory entry meets NEC 408.4(A)?
A
B
C
D