Switches + Receptacles Types Reference

Why this matters

Wrong device for application = code violation OR safety hazard. Customer with a 15A outlet on a 20A circuit, no GFCI in the bathroom, OR a single-pole switch where 3-way needed - gets it wrong, calls back, loses trust. The right device every time = solid work. This is the field card.

Switch types

Single-pole: one switch controls one light. Most common. Two brass terminals, both the same, so line and load can land on either, plus a green ground screw. Toggle is marked ON/OFF, because a single-pole switch has a fixed off position. Two same-colored screws plus ON/OFF on the handle is how you tell it from a 3-way across the room.

Three-way: two switches control one light (top + bottom of stairs). 3 screws (1 common dark, 2 travelers brass). NO on/off marking.

Four-way: middle switch in 3-or-more-location control. Between two 3-way switches. 4 screws.

Double-pole: 240V circuit; 2 hot wires switched simultaneously. 4 screw terminals.

Dimmer: switches AND varies brightness. Incandescent + LED-compatible dimmers differ.

Motion sensor: PIR sensor + switch; lights on with motion.

Smart switch (Wi-Fi, Z-Wave, Zigbee): home automation; some need neutral, some don't.

Pilot light switch: indicator lamp shows when switched on (basement, exterior).

Timer switch: digital countdown OR programmable; bath fan + outdoor lights.

Receptacle types

15A standard duplex (NEMA 5-15R): most common residential outlet. 120V, 15A.

20A duplex (NEMA 5-20R): one slot perpendicular (T-shaped). Required where a single receptacle sits alone on an individual 20A branch circuit. A duplex counts as two receptacles, so a 15A duplex is permitted on a 20A circuit. See the mistakes section.

240V outlets:

• 30A dryer (NEMA 14-30R): four-prong
• 50A range (NEMA 14-50R): four-prong, used for ranges + EV chargers
• 30A older dryer (NEMA 10-30R): three-prong; no separate ground (legacy)
• 50A older range (NEMA 10-50R): three-prong; legacy

GFCI (Ground-Fault Circuit Interrupter): trips on imbalance to earth. Required: kitchen counter, bath, garage, outdoor, basement, laundry. NEC 210.8.

AFCI (Arc-Fault Circuit Interrupter): trips on series + parallel arc faults. Required: most habitable rooms. NEC 210.12.

Dual-function (CAFCI + GFCI): combination protection.

USB-integrated receptacle: built-in USB ports. Limited charging speed (typically 2.1A per port).

Tamper-resistant (TR): child-safety shutters; REQUIRED on all new residential receptacles per NEC 406.12.

Weather-resistant (WR): outdoor-rated for damp/wet locations.

In-use weatherproof cover: required outdoor with continuously-plugged cord.

Receptacle ratings

Switch wiring basics

Single-pole: line in (black) to one terminal, load out (black) to other. Neutral straight through (white passes; not switched). Ground to green screw.

3-way (with 14/3 cable): dark screw = common (line OR load); 2 brass screws = travelers. Red + black wires of 14/3 are travelers; white usually neutral except in switch-loop scenarios.

Switch loop (older wiring): only 14/2 (no neutral); requires re-marking. New code requires neutral at switch box.

GFCI installation

At outlet (typical kitchen): wired LINE in (incoming power) + LOAD out (downstream outlets). Downstream outlets all GFCI-protected.

At breaker: whole circuit GFCI-protected from panel.

Self-test feature (post-2015): GFCI tests itself every few seconds; lights status LED.

AFCI installation

At breaker (most common): AFCI breaker replaces standard.

Combination AFCI/GFCI breaker covers both.

Common AFCI nuisance trips: motor brushes (vacuum, hair dryer); cheap LED drivers; cordless tool chargers. Resolve by replacing the noisy device OR upgrade to a less-sensitive AFCI breaker.

Locations where GFCI required (residential)

• All kitchen counter outlets
• Bath outlets
• Garage outlets
• Outdoor outlets
• Pool / spa area
• Basement (unfinished + finished both)
• Crawl space
• Laundry
• Wet bar
• Boathouse / dock
• Within 6 ft of any sink

Locations where AFCI required (residential)

• Most habitable rooms (bedroom, living, dining, family, hallway)
• Recreation room, library, sunroom
• Closets, dens

Common device mistakes

15A on a 20A circuit, and people get this backwards in both directions. NEC 210.21(B) runs the other way from how it is usually repeated: where a 20A circuit serves two or more receptacles, 15A devices are permitted, which is why nearly every 20A kitchen circuit in the country is populated with 15A duplexes. What is not permitted is a single receptacle, one contact device alone on the yoke, on an individual branch circuit rated above it. A duplex is two receptacles, not one, so it does not trip that rule. Missing tamper-resistant (TR) on new install. No GFCI in required location. AFCI omitted from required circuit. Pigtail neutral wire to old GFCI line side (wires backstabbed; failed). Wire-nut splice in shallow box (overfill). Decora device in narrow plate (won't fit). Smart switch without neutral wire (won't function).

Spec-grade vs commercial-grade

Residential / contractor grade: the builder-box device. Thin contact metal, backstab holes, plastic strap. Fine for a bedroom lamp circuit, first thing to fail in a garage.

Spec grade: heavier contacts, better grip retention, steel strap, side screws that will take real torque.

Commercial / hospital grade: highest grip retention and impact rating. Hospital grade carries a green dot and is required where the code calls for it, not just where somebody wants a better device.

For pro service work: spec-grade minimum; commercial for high-use locations.

Color coding

White: standard interior, neutral.

Almond: matches older trim.

Ivory: matches older trim variant.

Black: commercial / industrial.

Gray: commercial / utility.

Dimmer compatibility

Incandescent: any dimmer works.

Halogen: dimmable.

LED: requires LED-rated dimmer; some bulbs don't dim smoothly.

CFL: most don't dim; some "dimmable" CFL work poorly.

Fluorescent tube: needs special dimmer + dimmable ballast.

Smart bulbs (Hue, LIFX): do NOT use dimmer; smart-bulb has own dimming.

Receptacle install workflow

1. Confirm power off + verify dead with multimeter
2. Remove old device + photo wiring
3. Strip new wire (typical 1/2" - 5/8" exposed)
4. Side-screw termination (don't backstab); torque to the value marked on the device or in its instructions, commonly around 16 in-lb on a residential device, using a calibrated driver
5. Pigtail multiple wires + use wire nut + 6" pigtail to device
6. Push device into box without binding wire
7. Mount + plate
8. Power on + test (voltage tester at all 3 outlets if duplex)

Code compliance check

• TR on all residential receptacles (NEC 406.12)
• GFCI in required locations (NEC 210.8)
• AFCI on required circuits (NEC 210.12)
• Kitchen-counter spacing: no point along the counter wall line more than 24 in from a receptacle, which works out to 4 ft between devices. NEC 210.52(C) has been reworked across recent editions, so check the one your AHJ adopted before laying out a kitchen.
• 6-foot rule (within 6 ft from any point on a wall), NEC 210.52(A)

References

• NEC Article 210 (Branch Circuits)
• NEC 406 (Receptacles + Cord Connectors)
• NEC 404 (Switches)
• UL 498 (Attachment Plugs + Receptacles)
• UL 943 (Ground-Fault Circuit Interrupters)
• Manuall internal: Wire Termination Types, Breaker + Panel Reference