Chapter 4 Requirements

Figure 01

Note: This article is based on the 2020 NEC.

How well you implement Chapter 4 Equipment for General Use requirements directly affects how well you implement Article 250.

Chapter 4 Equipment for General Use helps you apply Article 250 to installations involving general equipment. Five articles are of particular interest:

• Article 404—Switches. The requirements apply to switches of all types such as snap switches, dimmer switches, circuit breakers, fused and non-fused disconnects, and automatic timer switches.
• Article 406—Receptacles and Attachment Plugs (Caps). This article covers the rating, type, and installation of receptacles and attachment plugs (cord caps).
• Article 408—Switchboards and Panelboards. The requirements apply to switchboards, panelboards, and distribution boards that supply lighting and power circuits.
• Article 410—Luminaires, Lampholders, and Lamps. Because of the many types and applications of luminaires this article is fairly extensive.
• Article 440—Air-Conditioning and Refrigeration Equipment. Article 440 applies to electrically driven air-conditioning and refrigeration equipment with a hermetic compressor motor.
  

Article 404 Switches
The metal mounting yokes for switches, dimmers, and control switches must connect to an equipment grounding conductor. Metal faceplates must be bonded to the equipment grounding conductor [404.9(B)].

Snap switches, dimmers, control switches, and metal faceplates are considered connected to an equipment grounding conductor using either of the following methods:

(1) Metal Boxes. The switch is mounted with metal screws to a metal box or a metal cover that is connected to an equipment grounding conductor per 250.148.

Direct metal-to-metal contact between the device yoke of a switch and the box is not required. The switch is connected to the effective ground-fault current path when the yoke is mounted with metal screws to a metal box. Figure 01

(2) Nonmetallic Boxes. The grounding terminal of the switch yoke must connect to the circuit equipment grounding conductor.

Ex 1: Where no means exists within the box for bonding to an equipment grounding conductor, or if the wiring method at the existing switch does not contain an equipment grounding conductor, a switch without such a connection to the equipment grounding conductor is permitted for replacement purposes only. A switch installed under this exception must have a faceplate that is nonmetallic with nonmetallic screws, or the replacement switch must be GFCI protected.

Ex 2: Listed assemblies are not required to be bonded to an equipment grounding conductor if all four conditions in Exception No 2 are met. For example, the device has a nonmetallic yoke.

Ex 3: An equipment grounding conductor is not required for bonding a snap switch with an integral nonmetallic enclosure complying with 300.15(E).

Metal enclosures for switches and circuit breakers must be connected to an equipment grounding conductor of a type recognized in 250.118 [250.4(A)(3)]. Where nonmetallic enclosures are used with metal raceways or metal-armored cables, they must comply with 314.3 Ex 1 or Ex 2 [404.12].

Article 406 Receptacles and Attachment Plugs (Caps)
Receptacles of the isolated equipment grounding conductor type must be identified by an orange triangle marking on the face of the receptacle [406.3(D)].

Isolated ground receptacles must have the grounding contact of the receptacle connected to an insulated equipment grounding conductor installed with the circuit conductors, per 250.146(D) [406.3(D)(1)].

Receptacles installed on 15A and 20A branch circuits must be of the grounding type, except as permitted for 2-wire receptacle replacements as permitted in 406.4(D)(2) [406.4(A)].

The equipment grounding conductor contacts of receptacles and cord connectors must be connected to the equipment grounding conductor of the circuit supplying the receptacle or cord connector [406.4(C)].

The branch-circuit wiring method must include or provide an equipment grounding conductor to which the equipment grounding conductor contacts of the receptacle or cord connector are connected. See 250.118 for acceptable types of equipment grounding conductors..

If the receptacle to be replaced is in a location that requires an AFCI- and/or GFCI-type receptacle, the replacement receptacle must be installed at a readily accessible location [406.4(D)].

If an equipment grounding conductor exists in an outlet box, each replacement receptacle must be of the grounding type and the receptacle’s grounding terminal must be connected to the circuit equipment grounding conductor per 406.4(C) [406.4(D)(1)].

If an equipment grounding conductor does not exist in the outlet box, a replacement receptacle can be a [406.4(D)(2)].:
(a) Nongrounding-type receptacle.
(b) GFCI-type receptacle if the receptacle or the cover plate is marked “No Equipment Ground.” An equipment grounding conductor is not required from the GFCI-type receptacle to any receptacle outlets downstream.
(c) GFCI-protected grounding-type receptacle if the receptacle or the cover plate is marked “GFCI Protected” and “No Equipment Ground.” An equipment grounding conductor is not required from the GFCI-protected grounding-type receptacle to any receptacle outlets downstream.

GFCI protection functions properly on a 2-wire circuit without an equipment grounding conductor because the circuit’s equipment grounding conductor serves no role in the operation of a GFCI device.

Metal faceplates for receptacles must be connected to the circuit equipment grounding conductor [406.6(B)]. The grounding terminal of receptacles must be connected to an equipment grounding conductor per 250.146 [406.11].

Article 408 Switchboards and panelboards
Metal cabinets containing panelboards must be connected to an equipment grounding conductor of a type recognized in 250.118 [215.6 and 250.4(A)(3)]. Where a panelboard cabinet contains equipment grounding conductors of the wire type, a terminal bar for them must be installed and bonded to the metal cabinet [408.40].

Equipment grounding conductors cannot terminate on the neutral terminal bar except as permitted by 250.142(A) for services and separately derived systems.

Many panelboards are rated for use as service disconnects, which means they are supplied with a main bonding jumper [250.28]. This screw or strap is not permitted to be installed except when the panelboard is used for a service disconnect [250.24(A)(5)] or a separately derived system [250.30(A)(1)].

Article 410 Luminaires, Lampholders, and Lamps
Because of the many types and applications of luminaires, manufacturers’ instructions are very important and helpful for proper installation. UL produces a pamphlet called the Luminaire Marking Guide, which provides information for properly installing common types of incandescent, fluorescent, and high-intensity discharge (HID) luminaires.

Metal poles used for the support of luminaires must be connected to an equipment grounding conductor of a type recognized in 250.118 [250.4(A)(5)]. Because the contact resistance of an electrode to the Earth is so high, very little fault current returns to the power supply if the Earth is the only fault current return path. As a result, the circuit overcurrent protective device will not open and clear the ground fault, and the metal pole will become and remain energized by the circuit voltage.

Luminaires and lighting equipment must be connected to the circuit equipment grounding conductor as required in Article 250 and Part V of this article [410.40].

410.44 Equipment Grounding Conductor
The metal parts of luminaires must be connected to an equipment grounding conductor of a type recognized in 250.118 [410.44].

Ex 1: Replacement luminaires may connect an equipment grounding conductor in the same manner as replacement receptacles in compliance with 250.130(C). The luminaire must then comply with 410.42.

Ex 2: Where no equipment grounding conductor exists at the outlet, replacement luminaires that are GFCI protected or do not have exposed conductive parts are not required to be connected to an equipment grounding conductor.

Luminaires with exposed metal parts must be provided with a means for connecting an equipment grounding conductor [410.46]. Lighting equipment identified for horticultural use must be connected to the circuit equipment grounding conductor as required in Article 250 and Part V of this article [410.182].

Article 440 Air-Conditioning and Refrigeration Equipment

Where air-conditioning or refrigeration equipment is installed on a roof and connected with a metallic raceway, an equipment grounding conductor of the wire type must be installed within the outdoor portion of the metallic raceway systems that use compression-type fittings [440.9].

When the wiring method for rooftop units is not a threaded type system, you cannot rely on the raceway to serve as the equipment grounding conductor as permitted by 250.118 and must install an appropriately sized wire-type equipment grounding conductor instead.

Metal raceway systems with compression fittings could be subjected to movement and physical damage from roof activities such as snow removal or a roof repair/replacement. The installation of a wire-type equipment grounding conductor provides reassurance of the effective ground fault current path in case of a ground fault at the air conditioning or refrigeration equipment.

Error prevention
If you meticulously apply the Chapter 4 requirements pertaining to the general equipment you are installing, one result is you move that entire installation toward conformance with the grounding and bonding requirements of Article 250.

A good way to prevent errors is to consider each metal object and review how it connects to the equipment grounding conductor (or not). For example, all of your switches have metal faceplates. If those switches are mounted in nonmetallic boxes, you need to ensure the grounding terminal of each switch yoke connects to the equipment grounding conductor.

If the drawings inadvertently leave out one or more of the requirements we have just discussed, this type of review should catch the omissions.