NEC 250.110 to 250.119 for the Journeyman Exam: Which Equipment Must Be Grounded and How to Identify the Grounding Conductor

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Before you size the ground

Table 250.122 sizes the equipment grounding conductor, and 250.118 lists what can serve as one. First find out whether the equipment has to be grounded at all, and how the grounding conductor is marked so nobody takes it for a circuit conductor.

Why grounding equipment matters

If a hot conductor touches a metal enclosure, the equipment grounding conductor is part of the low-impedance path that carries the fault current back to the source, so the breaker or fuse can trip. Without one, the exposed metal can stay energized and become a shock hazard.

Fixed equipment: 250.110

Exposed metal parts of fixed equipment that are likely to become energized are grounded when any one of these applies:

Condition	Example
Within 8 ft vertically or 5 ft horizontally of ground or grounded metal objects, where the exposed metal parts are subject to contact by persons	A metal light pole base next to a sidewalk
In a wet or damp location and not isolated	A unit heater in a car wash
In electrical contact with metal	An enclosure bolted to steel framing
In a hazardous (classified) location	Equipment in a paint spray area
Supplied by a wiring method that provides an equipment grounding conductor, such as metal raceway or cable with a ground	Anything fed by EMT or by cable with an equipment ground
Operating with any terminal at more than 150 V to ground	A 277 V luminaire

The section lists exceptions, such as certain enclosures for switches or breakers that are accessible only to qualified persons. Don’t assume an exception applies just because the equipment looks similar.

Fixed equipment grounded regardless of voltage: 250.112

250.112 says certain fixed equipment has to be grounded no matter the voltage, subject to the exceptions in that section. The list covers switchboard frames, motor frames, motor controller enclosures, elevator and crane equipment, electrical equipment in commercial garages and theaters (with some exceptions), electric signs, motion picture projection equipment, luminaires as Article 410 requires, and motor-operated water pumps, including submersible pumps. Mark 250.112 in your NEC. If a question names a motor frame, a switchboard or a sign, that’s where you look.

Cord-and-plug-connected equipment: 250.114

The exposed metal parts of cord-and-plug-connected equipment are grounded in these cases:

• In hazardous (classified) locations.
• When operated at more than 150 V to ground, with listed exceptions.
• In residential occupancies, for items such as refrigerators, freezers, air conditioners, clothes washers and dryers, dishwashers, sump pumps, aquarium equipment, and portable handheld motor-operated tools such as drills, saws and sanders.
• In other than residential occupancies, for a similar list plus cord-and-plug-connected appliances used in damp or wet locations or by persons standing on the ground or on metal floors. The section names other cases too.

Double insulation. Listed tools and appliances protected by a system of double insulation, or its equivalent, do not have to be grounded under the 250.114 exception. That exception does not reach the hazardous (classified) location requirement. Look for the double-insulation marking. A two-prong plug alone does not show that the equipment qualifies.

Identifying the equipment grounding conductor: 250.119

• Normal marking. An insulated or covered equipment grounding conductor has a continuous green outer finish, or green with one or more yellow stripes. It can also be bare.
• Reserved color. Conductors with green insulation, or green with yellow stripes, are not used as ungrounded or grounded circuit conductors.
• 4 AWG and larger. An insulated conductor 4 AWG or larger can be permanently identified as an equipment grounding conductor at each end and at every point where it is accessible. The marking has to encircle the conductor. You can strip the insulation from the entire exposed length, color the insulation green at the termination, or mark it with green tape or green adhesive labels at the termination.
• Multiconductor cable. Where the conditions of maintenance and supervision ensure that only qualified persons service the installation, one or more insulated conductors in a multiconductor cable can be reidentified at each end and every accessible point, by the same methods.
• Flexible cord. In a flexible cord, the equipment grounding conductor is identified as green or green with yellow stripes.

Exam trap. A single 2 AWG black conductor can be reidentified as the equipment grounding conductor with green tape at each end. A single insulated 6 AWG black conductor cannot be reidentified under the 4 AWG and larger rule. The separate allowance for conductors in a multiconductor cable applies only under the maintenance and supervision conditions in 250.119.

Worked example: a rooftop unit and a shop drill

You’re checking the grounding on a rooftop unit fed through EMT from a 480Y/277 V system.

1. Ground required? Yes, assuming the unit is fed straight from the 480Y/277 V system with no transformer in between. Each phase is 277 V to ground, above 150 V, and it is fed through EMT. Don’t go by the 480 V label alone.
2. Equipment grounding conductor: properly installed EMT, with suitable fittings and continuity, can serve as one under 250.118. If a wire-type equipment grounding conductor is also run, size it from Table 250.122; the EMT still has to stay continuous.
3. Using a 4 AWG black spare conductor as the ground: allowed if it is reidentified green at both ends and at every accessible point, such as each pull box.

Now take a carpenter’s listed, double-insulated drill with a two-prong plug, used in an ordinary work area of the same building, not a hazardous (classified) location.

1. Ground required? No. A listed double-insulated tool falls under the 250.114 exception. That exception does not cover equipment in hazardous (classified) locations.

Four quick questions

1. Smallest single insulated conductor that may be reidentified as an equipment grounding conductor? 4 AWG.
2. A fixed metal enclosure that could become energized is 7 ft above a concrete floor and subject to contact by persons. Ground required? Yes. It meets the 8 ft vertical condition in 250.110.
3. A listed double-insulated sander with a two-prong plug. Ground required? No.
4. Can a green conductor be used as a neutral? No. Green and green with yellow stripes are reserved for equipment grounding.

FAQ

Sources checked October 2026

• PSI Candidate Information Bulletin, Texas electrician examinations (updated September 15, 2026): https://test-takers.psiexams.com/api/content/bulletin/1682
• NFPA 70, National Electrical Code, 2026 Edition, Article 250