NEC Chapter 2: Wiring and protection

08/14/2013


Identifying grounded conductors 

For insulated grounded conductors of 6 AWG or less, the conductor must be manufactured to meet the identification requirements. Namely, it must have a continuous white or gray outer finish or three white stripes along the entire length of the conductor. There are other options for mineral-insulated (MI) cable, photovoltaic (PV) power systems, fixture wires, and aerial cable.

  1. MI due to nature of construction requires re-identification at terminals
  2. Single-conductor, sunlight-resistant outdoor cable for PV systems allows distinctive white markings at terminations (690.31)
  3. Fixture wire allows ridges for the grounded conductor among other color options detailed in 400.22
  4. Aerial cable may be identified by a ridge on cable. 

Conductors larger than 6 AWG also require white or gray outer finish or three white stripes along the entire length of the conductor, but there is an option to re-identify the conductor by wrapping the cable with white or gray at termination points. Paint, tape, or shrink tube are good options. Just be sure the identification completely circles the conductor.

Where grounded conductors of two different systems are in the same raceway or enclosure, they must be identified differently from each other (200.6 D). Identification requirements are the same as explained above, plus there is an option to have a colored stripe other than green running along the insulation. Color code labels are required at junction boxes and at termination equipment. An example color code table:

Alternate uses for conductors

Conductors for systems greater than 50 V, identified by the manufacturer with white or gray, may be used for alternate purposes under the following conditions:

  • Conductors within a cable assembly that are not switched. Supply to the switch is allowed but return from switch is not.
  • Flexible cords as permitted in 400.22. 

Figure 4: This is a switched receptacle for a chain-hung fixture. The white conductor in NM cable has been re-identified with red tape and is connected to a hot conductor. Courtesy: CH2M HillWhere the grounded conductor is repurposed, it must be identified by encircling the conductor with a color other than white, gray, or green. Red tape is commonly used and paint is listed as an option; red shrink tube is a cleaner installation and it doesn’t fall off. The white conductor can only be used as the ”energized” leg to the switch. Troubleshooting the circuit and finding potential to ground on the white conductor clues the technician that this is a switch leg. Another advantage is that you end up with standard color coding at the device. This helps avoid confusion as to the purpose of the white conductor at the switch because it is energized under operating conditions. This practice is going to be less common because the 2011 NEC now requires that the grounded conductor also be carried to the switch and standard nonmetallic cable assemblies have only one neutral. 404.2 C is outside the scope of this article (see Figure 4). 

This receptacle is switched and common nonmetallic cable was used for a switch leg. Red tape was used to re-identify the ungrounded conductor. At the switch, while the circuit is energized, voltage can be found on the white repurposed wire.



Pete , United States, 08/21/13 12:12 PM:

Great Article, I've tried to explain same, hundreds of times, this distills it very well.
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Hannover Messe 2016: Taking hold of the future - Partner Country status spotlights U.S. manufacturing; Honoring manufacturing excellence: The 2015 Product of the Year Winners
Inside IIoT: How technology, strategy can improve your operation; Dry media or web scrubber?; Six steps to design a PM program
World-class manufacturing: A recipe for success: Finding the right mix for a salad dressing line; 2015 Salary Survey: Manufacturing slump dims enthusiasm
Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Warehouse winter comfort: The HTHV solution; Cooling with natural gas; Plastics industry booming
Managing automation upgrades, retrofits; Making technical, business sense; Ensuring network cyber security
Designing generator systems; Using online commissioning tools; Selective coordination best practices

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
click me