10.2 Switches, Receptacles and Industrial Control Panels

Article 404 — Switches

404.2(A) Three-Way and Four-Way Switches. Three-way and four-way switches shall be wired so that all switching is done only in the ungrounded circuit conductor. Where in metal raceways or metal-armored cables, wiring between switches and outlets shall be in accordance with 300.20(A).

404.2(B) Grounded Conductors. Switches or circuit breakers shall not disconnect the grounded conductor of a circuit, with an exception where the switch or circuit breaker simultaneously disconnects all conductors of the circuit, or where the device is arranged so the grounded conductor cannot be disconnected until all ungrounded conductors have been disconnected.

404.2(C) Switches Controlling Lighting Loads. Where switches control lighting loads supplied by a grounded general-purpose branch circuit, the grounded circuit conductor for the controlled lighting circuit shall be provided at the switch location. The grounded conductor shall be extended to any switch location as necessary and shall be connected to switching devices that require line-to-neutral voltage to operate the electronics of the switch in the absence of a connected load.

Exception: The grounded circuit conductor shall be permitted to be omitted from the switch enclosure where either of the following conditions applies:

1. Conductors for switches controlling lighting loads enter the box through a raceway that has sufficient cross-sectional area to accommodate the extension of the grounded circuit conductor of the lighting circuit to the switch location, whether or not the conductors in the raceway are required to be increased in size to comply with 300.17.
2. Cable assemblies for switches controlling lighting loads enter the box through a framing cavity that is open at the top or bottom on the same floor level, or through a wall, floor, or ceiling that is unfinished on one side.

The purpose is electronic switches, dimmers, timers, and occupancy sensors, which need a neutral to power their electronics rather than leaking current through the load.

404.4 Damp or Wet Locations. A surface-mounted switch or circuit breaker in a damp or wet location shall be enclosed in a weatherproof enclosure or cabinet complying with 312.2. A flush-mounted switch or circuit breaker in a damp or wet location shall be equipped with a weatherproof cover. Switches shall not be installed within wet locations in tub or shower spaces unless installed as part of a listed tub or shower assembly.

404.8(A) Accessibility. All switches and circuit breakers used as switches shall be located so that they may be operated from a readily accessible place. They shall be installed such that the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, is not more than 2.0 m (6 ft 7 in.) above the floor or working platform.

Three exceptions apply, covering busway installations, switches or circuit breakers installed adjacent to motors or appliances and accessible by portable means, and hookstick-operated isolating switches for over 1000 volts.

404.9(A) Faceplates. Faceplates provided for snap switches mounted in boxes and other enclosures shall be installed so as to completely cover the opening and seat against the finished surface.

404.9(B) Grounding. Snap switches, including dimmer and similar control switches, shall be connected to an equipment grounding conductor and shall provide a means to connect metal faceplates to the equipment grounding conductor, whether or not a metal faceplate is installed. Two exceptions cover replacement snap switches where no equipment grounding conductor exists in the box — provided the switch is GFCI protected or the faceplate is nonmetallic — and listed assemblies.

404.14 Rating and Use of Snap Switches. (A) AC general-use snap switches shall be used only on AC circuits, for resistive and inductive loads not exceeding the ampere rating at the voltage involved, for tungsten-filament lamp loads not exceeding the ampere rating at 120 volts, and for motor loads not exceeding 80 percent of the ampere rating at the rated voltage. (B) AC-DC general-use snap switches may be used on either AC or DC circuits with narrower limits. (E) Dimmer switches shall be used to control permanently installed incandescent luminaires unless listed for the control of other loads and installed accordingly.

404.15 Marking. Switches shall be marked with the current, voltage, and, if horsepower rated, the maximum rating for which they are designed.

Article 406 — Receptacles

406.3(A) Receptacle Rating. Receptacles shall be listed and marked with the manufacturer's name or identification and voltage and ampere ratings.

406.3(D) Isolated Ground Receptacles. Receptacles incorporating an isolated equipment grounding conductor connection intended for the reduction of electrical noise shall be identified by an orange triangle located on the face of the receptacle. Where installed in nonmetallic boxes, they shall be covered with a nonmetallic faceplate.

406.4(A) Grounding Type. Receptacles installed on 15- and 20-ampere branch circuits shall be of the grounding type, and grounding-type receptacles shall be installed only on circuits of the voltage class and current for which they are rated, with an exception for nongrounding-type replacements as permitted in 406.4(D).

406.4(B) To Be Grounded. Receptacles and cord connectors that have equipment grounding conductor contacts shall have those contacts connected to an equipment grounding conductor.

406.4(C) Methods of Grounding. The equipment grounding conductor contacts of receptacles and cord connectors shall be grounded by connection to the equipment grounding conductor of the circuit supplying the receptacle or outlet, in accordance with 250.130 and 250.146.

406.4(D) Replacements — covered in detail in section 6.4 of this guide. The pattern is that replacement triggers current GFCI, AFCI, tamper-resistant, and weather-resistant requirements.

406.5 Receptacle Mounting. Receptacles shall be mounted in boxes or assemblies designed for the purpose, and such boxes or assemblies shall be securely fastened in place unless otherwise permitted elsewhere in the Code.

• (A) Boxes That Are Set Back. Receptacles mounted in boxes that are set back from the finished surface shall be installed such that the mounting yoke or strap of the receptacle is held rigidly at the finished surface.
• (B) Boxes That Are Flush. Receptacles mounted in boxes that are flush with the finished surface or project therefrom shall be installed such that the mounting yoke or strap of the receptacle is held rigidly against the box or box cover.
• (C) Receptacles Mounted on Covers. Receptacles mounted to and supported by a cover shall be held rigidly against the cover by more than one screw or shall be a device assembly or box cover listed and identified for securing by a single screw.
• (E) Receptacles in Countertops and Similar Work Surfaces in Dwelling Units. Receptacles shall not be installed in a face-up position in or on countertop surfaces or work surfaces unless listed for countertop or work surface applications.
• (F) Receptacles in Seating Areas and Other Similar Surfaces. Shall not be installed in a face-up position unless listed for the application.

406.6 Receptacle Faceplates (Cover Plates). Receptacle faceplates shall be installed so as to completely cover the opening and seat against the mounting surface. Metal faceplates shall be of ferrous metal not less than 0.030 in. thick or nonferrous metal not less than 0.040 in. thick. 406.6(B) Grounding requires metal faceplates to be grounded.

406.9 Receptacles in Damp or Wet Locations — covered in section 6.4.

406.11 Connecting Receptacle Grounding Terminal to Box points to 250.146.

406.12 Tamper-Resistant Receptacles — covered in section 6.4.

406.15 Dimmer-Controlled Receptacles. A receptacle supplying lighting loads shall not be connected to a dimmer unless the plug/receptacle combination is a nonstandard type that is specific to the equipment identified in the applicable standard.

Article 409 — Industrial Control Panels

An industrial control panel is an assembly of two or more components consisting of power circuit components only, control circuit components only, or a combination of power and control circuit components.

409.20 Conductor — Minimum Size and Ampacity. The size of the industrial control panel supply conductor shall have an ampacity not less than 125 percent of the full-load current rating of all resistance heating loads plus 125 percent of the full-load current rating of the highest rated motor plus the sum of the full-load current ratings of all other connected motors and apparatus based on their duty cycle that may be in operation at the same time.

409.21 Overcurrent Protection. An industrial control panel shall be provided with overcurrent protection in accordance with Parts I, II, and IX of Article 240, sized in accordance with 409.21(B).

409.22 Short-Circuit Current Rating. An industrial control panel shall not be installed where the available fault current exceeds its short-circuit current rating as marked in accordance with 409.110(4).

409.30 Disconnecting Means. Where an industrial control panel has a disconnecting means, the disconnecting means shall meet the requirements of 430.109 and 430.110 where it is used as the motor disconnecting means.

409.60 Grounding. Multisection industrial control panels shall be bonded together with an equipment grounding conductor or equivalent grounding bus sized in accordance with Table 250.122.

409.110 Marking. An industrial control panel shall be marked with the following information that is plainly visible after installation:

1. Manufacturer's name, trademark, or other descriptive marking;
2. Supply voltage, number of phases, frequency, and full-load current for each incoming supply circuit;
3. Industrial control panel short-circuit current rating, based on one of: an approved method; or listing;
4. If the industrial control panel is intended as service equipment, it shall be marked to identify it as being suitable for use as service equipment;
5. Electrical wiring diagram or the identification number of a separate electrical wiring diagram or a designation referenced in a separate wiring diagram;
6. An enclosure type number shall be marked on the industrial control panel enclosure.

The short-circuit current rating is the item to remember. 409.22 makes it enforceable: if the available fault current at the installation exceeds the marked SCCR, the panel may not be installed there. That interacts directly with 110.24, which requires service equipment in other than dwelling units to be field marked with the maximum available fault current.