6.1 Switches, Receptacles & Light Fixtures (0501)

Switch Ratings and Types (NEC Article 404)

Switches are rated by current, voltage, and the type of load they can control. 404.14 sets what each class of general-use snap switch may control:

Two traps live in this section. First, the tungsten "T" marking belongs to the AC-DC switch — an AC-only snap switch already handles tungsten loads to its rating at 120 V without a T mark. Second, an AC-only switch must not be used on a DC circuit, because it relies on the AC current zero-crossing to extinguish the arc. A switch must always have a current rating not less than the load it controls and a voltage rating not less than the circuit voltage.

Knife Switches (404.2)

The knife-switch rules live in 404.6, not 404.2. 404.6(A) requires single-throw knife switches to be placed so that gravity will not tend to close them; a switch approved for use in the inverted position must have a locking device that holds the blades open. 404.6(B) permits double-throw knife switches to be mounted with the throw either vertical or horizontal, and requires a locking device where the throw is vertical. 404.6(C) requires single-throw knife switches, molded-case switches, and switches with butt contacts to be connected so the blade is de-energized when the switch is in the open position — the connection that keeps a lineman from finding a live blade behind an "off" handle.

Receptacle Ratings and Configurations (NEC Article 406)

A receptacle is a contact device installed at an outlet for connection of an attachment plug. NEC 406.3 sets receptacle ratings and configurations. Receptacles shall not be connected to a circuit of higher voltage or current than their rating.

Common NEMA Configurations (non-locking)

Receptacle Types and Required Locations

• 406.4(A) Grounding type — receptacles installed on 15 A and 20 A branch circuits shall be the grounding type.
• 406.12 Tamper-resistant — listed tamper-resistant receptacles are required for 125 V and 250 V, 15 A and 20 A receptacles in dwelling units, guest rooms and guest suites of hotels and motels, child care facilities, preschools and elementary education facilities, medical and dental offices and outpatient facilities, assembly occupancy gaming areas, dormitory units, and the other occupancies listed there. This is a commercial-inspector item as much as a residential one.
• 406.9(B) Weather-resistant and covers — receptacles in wet locations must be listed weather-resistant, and 15 A and 20 A receptacles in wet locations require an in-use (extra-duty) cover that remains weatherproof with an attachment plug inserted. In damp locations the cover need only be weatherproof when the plug is removed.
• 406.4(D) Non-grounding replacement — where a grounding means does not exist, a non-grounding-type receptacle may be replaced with another non-grounding receptacle, or with a GFCI-type receptacle marked "No Equipment Ground."
• 406.5 Mounting — receptacles must be mounted in identified boxes or assemblies. Where the box is set back from a noncombustible surface (permitted by 314.20 up to 1/4 in.), the receptacle must be installed so the mounting yoke is held rigidly at the finished surface, and receptacle faceplates must completely cover the opening (406.6).
• Combination devices — a switch-and-receptacle device on one strap must satisfy Article 404 for the switch portion and Article 406 for the receptacle portion, including the TR, WR, and GFCI requirements for its location. For box-fill purposes the whole strap is still one yoke — worth two conductor allowances under 314.16(B)(4).

Luminaires and Light Fixtures (NEC Article 410)

A luminaire is a complete lighting unit consisting of a light source and parts to position, protect, and connect it.

• 410.10 Damp, wet, or corrosive locations — luminaires shall be identified for the location. A luminaire in a wet location shall be listed for wet locations; chain-mounted luminaires in damp locations shall have the chain grounded.
• 410.11 Luminaires near combustible material — luminaires must be constructed, installed, or equipped with shades or guards so that combustible material is not subjected to temperatures in excess of 90 °C (194 °F).
• 410.16 Luminaires in clothes closets — the storage space is defined dimensionally, and only listed luminaire types are permitted, with specific clearances from the storage space.
• 410.30 and 410.36 Supports — luminaires and lampholders must be securely supported. A luminaire installed in a suspended (dropped) ceiling must be securely fastened to the ceiling framing member by mechanical means such as bolts, screws, or rivets, and listed clips identified for that ceiling framing member are permitted; the framing members themselves must be securely fastened to each other and to the building structure. A luminaire weighing more than 50 lb (23 kg) must be supported independently of the outlet box unless the box is listed and marked for that weight (314.27(A)(2)).
• 410.62 Cord-connected luminaires — where a luminaire is cord-connected, the cord must be a listed flexible cord (not fixture wire), and the specific conditions in 410.62(C) apply to cord-connected lampholders and to luminaires supplied by a cord and plug.

Fixture Wires (Article 402)

Fixture wire (Article 402) is permitted only inside luminaires and similar equipment and for connecting luminaires to their branch-circuit conductors — it is not a branch-circuit wiring method (402.11). Common types include TF, TFF, TFN, TFFN, SF, SFF, and PF. Allowable ampacity comes from Table 402.5 (not Table 402.3, which lists types and insulations):

402.6 makes 18 AWG the minimum fixture-wire size, and 240.5(B)(2) sets the branch-circuit ratings that a given fixture wire may be tapped from, including run-length limits for 18 AWG and 16 AWG.