Posted By Tom Garvey,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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Should our electrical standard for industrial machinery keep current with what the rest of the world is doing? If you build machines for the global marketplace, you’d answer "do it or die.” A harmonized NFPA 79 paves the way for you to build a machine that your company can sell from Boston to Bombay. If you buy machines for your factories around the world, you’re answering, "Of course!” One standard for machine wiring makes it easy for you to write one purchasing specification. However, if you’re involved with electrical safety, the answer should be: "It depends on what the rest of the world is doing.”
My first experience with this issue came via a large machine tool from Japan. My employer spent several million dollars to purchase the machine. My co-worker and I spent several weeks pulling the factory wiring out and replacing it with listed MTW (Machine Tool Wire). Why? The type of insulation used by the manufacturer was not Type MTW. What type of insulation did the machine builder use? Unknown. There were no markings on the jacket. Did the insulation have the low flame spread; low smoke development characteristic of listed Type MTW? Unknown. Insufficient documentation was provided. The AHJ decided not to take a chance. We completely rewired the machine.
The roots of NFPA 79 stretch back to 1941. The US machine tool industry faced a formidable challenge: Produce the millions of parts needed to support the war effort. The metal working industry wrote the first standard. They wanted machines that were safer to operate. They needed machines that were more productive and required less maintenance. The electrical components needed to be high quality and very reliable.
Modern industrial machinery appears in a wide variety of forms. A recent international machine tool show in Chicago featured the products of thousands of companies from 36 nations. Their products filled 1.4 million square feet of exhibit space: equipment that utilizes the latest technology such as lasers that cut, drill and weld; sophisticated robots that weld, assemble, or transport parts. The equipment represents the broad scope of "Industrial Machinery.” Industrial machinery includes simple machines, such as a drill press. On the other end is a complex manufacturing system. Such a "machine” may be city blocks long. Examples are a paper-manufacturing machine or an automotive assembly line.
Many of the machines present at the show were not built and wired to meet NFPA 79. Instead, they were manufactured using IEC 60204 as the electrical safety standard. IEC 60204 is one of the standards of the International Electrotechnical Commission, a global organization that was founded in 1906. It prepares and publishes international standards for electrical, electronic, and related technologies. Individuals from more than 50 countries sit on its various technical committees.
One of the committees is TC-44, Safety of Machinery. The US is a major player on TC-44. The chairman is John Bloodgood of JFB Enterprises, Fond du Lac, Wisconsin. Mr. Bloodgood is an internationally recognized expert on industrial machinery and related standards. National Electrical Equipment Manufacturers Association is also represented on TC-44. Mr. David Fisher of Rockwell Automation, Milwaukee, WI is a participating member. Mr. Fisher’s expertise is industrial control systems. Both men have also served as principal members on the NFPA 79 committee for many years.
The NFPA 79 Committee is convinced of the need to harmonize NFPA 79 with comparable standards. NFPA 79 is also an international standard. Companies that both buy and build machines for the global marketplace use it. Principal members represent organizations that both buy and build for factories across the globe. The 1991, 1994, and 1997 NFPA 79 included both references to other international standards as well as technical changes that reflect harmonization with related international standards.
The Next Step
The big push for harmonization started in 1998. In March 1998, the committee prepared a statement of work. The major elements of the statement of work are:
Harmonization – Purpose
As the users and the manufacturers of industrial machines move toward a global manufacturing community, the need for a harmonized standard affecting industrial machinery becomes an economic necessity. Generally, large users and manufacturers find regulations burdensome. However, multiple regulations as well as conflicting regulations are an economic disincentive to global expansion. In order to ease the burden of differing regulation, and at the same time maintain the high standard of electrical machine safety, the NFPA 79 committee has expressed their desire, through balloted vote, to harmonize NFPA 79 with IEC-60204-1.
Importance of Issue – Harmonization
The United States industrial machine manufacturers are no longer the world leaders in producing industrial machines, nor are they the major users of industrial machines. Today’s industrial machines are very complex and expensive. As manufacturing lines become modular and transportable, industrial machines originally produced for a foreign market may quickly be transported to the domestic market. The reverse is also true. Differing electrical standards add a large cost to multinational manufacturers as they build and sometimes move manufacturing facilities.
Harmonization – Objective
This work is necessary to accomplish the goal of allowing industry to economically build one industrial machine capable of passing a detailed electrical safety inspection using either IEC 60204-1 or NFPA 79 standard.
Both the NEC Technical Correlating Committee and the NFPA Standards Council reviewed the statement of work in July of 1998. The TCC unanimously recommended the following action to the Standards Council:
"The Technical Correlating Committee agrees with the efforts of the NFPA 79 committee to harmonize the technical requirements of NFPA 79 and IEC 60204, where feasible and where in concert with the NEC and its related codes and standards.
The Technical Correlating Committee agrees with the use of the ANSI style manual relative only to those items noted in the forward of the present NFPA 79. However, use of mandatory language shall be in accordance with the NFPA style manual.
The committee can continue references to other standards as necessary, but only where those references do not conflict with our presently adopted principles, practices, product standards, and the NEC.”
The NFPA Standards Council considered and concurred with the recommendation. Since 1998, the committee has been active in creating a series of panel proposals. The committee’s objectives are fourfold.
1. Renumber NFPA 79 to follow the numbering format used by IEC-60204.
2. Harmonize the language of NFPA 79 with the IEC 60204 where the technical requirements are substantially equal. The harmonized text will follow the NFPA Style manual.
3. Add new technical requirements that reflect the current state of the industry.
4. Modify the current technical requirements where appropriate, without decreasing the intended level of safety.
The committee recognizes the critical nature of the third and fourth objectives. The impetus for change may be harmonization with international standards or current industry practice. However the substantiation must clearly document the need for the change and the impact on electrical safety. There are safety practices, such as listed insulation, that are inherent in our safety standards. This type of requirement will be maintained.
NFPA 79 is a consensus standard. The committee will meet to consider proposals in March 2001. The Report on Proposals will be published in the spring and available to interested members of the public: That’s YOU. Help keep the committee on target. Reinforce our effort to make the standard truly international. Check our work. Keep us honest. Send us your comments.
About Tom Garvey: Tom Garvey inspects for the state of Wisconsin. He represents the International Association of Electrical Inspectors on Code Making Panel-11 for the National Electrical Code. He is the IAEI representative on NFPA 79, The Electrical Standard for Industrial Machinery. The global companies that make up Wisconsin's industrial base gives Tom frequent opportunities to view a variety of attempts in harmonizing the electrical wiring of industrial machinery to the NEC market.
Posted By Ravi Ganatra,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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The requirement for sunlight resistance for conductors that are exposed to direct sunlight was added in Section 310-8 of the 1999 National Electrical Code (NEC).1 However, the implementation of this requirement has resulted in some confusion for the users of the Code. For the purpose of listing and or markings on the products, Code requirements like this are spelled out in the applicable product standards. The present requirements and the needed changes in these standards are discussed to address the confusion. Facts, opinions, and recommendations are presented here to facilitate the enforcement of this requirement.
In response to a proposal, Section 310-8 was revised for the 1999 National Electrical Code (NEC) by organizing each location type and stipulating a list of identified insulation types for each location. Additionally, a new paragraph (d), Locations Exposed to Direct Sunlight, was added to read:
(d) Locations Exposed to Direct Sunlight. Insulated conductors and cables used where exposed to direct rays of the sun shall be of a type listed or marked "sunlight resistant.”
The panel rejected the proposed exception and a public comment supporting the exception to not require "sunlight resistant” capability of insulated conductors of drip loops where they are exposed to direct rays of sun. The recommended exception was not accepted since the drip loops expose the insulation to sunlight, which can deteriorate the insulation. Thus, insulated conductors where exposed to direct rays of sun shall be listed or marked "sunlight resistant.” Figure 230.5 from the NEC Handbook, slightly modified and shown in Figure 1, provides a good example of drip loops.
Figure 1. Figure 230.5 from the NEC Handbook, slightly modified and shown in Figure 1, provides a good example of drip loops.
Since the wording of 310-8(d) states that the products shall be listed or marked sunlight resistant, the question arises as to how should an inspector (or a user) verify that the product meets this requirement? Further, since manufacturers do not (and cannot) repeat all of the mandated requirements for listing in the print legends on their products, how does one verify that a product meets this requirement? Are there any changes made in the product standards as result of the adoption of 310-8(d)? Were there requirements already in place for suitability of the products exposed to sunlight? Are there separate requirements when products are marked "sunlight resistant?” Is this difference in requirements in the product standards responsible for the confusion between "suitability” and "listing or marking” for "sunlight resistant?” These and other relevant items are discussed below to assist inspectors and users in making their decisions.
The obvious choice is to examine the product for marking. However, if the requirement is mandatory and it is included in the requirements for listing, then it may not be necessary to include it in the marking on the product. For wire and cable products, this is helpful as it keeps the length of the print legends manageable. This desire to keep the print legend short and manageable creates a potential for confusion. Thus, when there is no obvious marking on the product and there is a doubt about the compliance, the inspector or user is forced to rely upon 110-3(b) of the NEC and ask for a confirmation from the manufacturer.
Figure 2. Figure 2 describes applications of conductors where compliance with sunlight resistant requirement is required or not required in accordance with 310-8(d)
At present no changes have been made in the product standards as a result of the adoption of 310-8(d) in the 1999 NEC. Products affected by this change include thermoset and thermoplastic insulated conductors, such as Types XHHW-2, RHH, RHW-2, THW-2, THHN, THWN-2, etc., recognized in Table 310-13 of the NEC. These products are listed in accordance with product standards developed by the Underwriters Laboratories, Inc., namely UL 44, Standard for Thermoset – Insulated Wires and Cables, and UL 83, Standard for Thermoplastic – Insulated Wires and Cables. Figure 2 describes applications of conductors where compliance with sunlight resistant requirement is required or not required in accordance with 310-8(d). For an optional marking of sunlight resistant, the conductors covered by UL 44 and UL 83 are required to meet the requirements of 720-hour carbon-arc or xenon-arc exposure tests. This marking is used typically for products that are used outdoors in messenger supported applications or in conjunction with "For CT Use” marking for conductors supported by cable trays. The two markings, both being optional, were thus combined logically because cable trays are permitted to be used outdoors also and the products supported in these cable trays are then exposed to sunlight.
Figure 3. Figure 3 describes the typical applications of Type SE products.
Type SE and Type USE products are listed in accordance with UL 854, Standard for Service – Entrance Cables. Conductors (and jackets) used for these products are required to meet the requirements of 300-hour carbon-arc or xenon-arc exposure test as part of the listing for these products. Compliance with this requirement is considered not sufficient for the marking of "sunlight resistant.” The products have been treated as "suitable for exposure to sunlight.” Figure 3 describes the typical applications of Type SE products. Type SE and Type USE (along with Types RHH or RHW) can be marked sunlight resistant provided they meet the requirements of 720-hour test. Considering the requirements of UL 44 (or UL 83) and UL 854 together, the same conductor type can imply the following possibilities:
1. Conductor intended for use in raceways (or other cable constructions other than Types SE or USE) need not be subjected to either 300-hour or 720-hour test. (Thus, conductors in the drip loops of these installation methods may not meet the requirement of 310-8(d).)
2. Above conductors if supported by a messenger (used outdoors) are subjected to a 720-hour test.
3. Conductors used in Type SE (or USE) are subjected to a 300-hour test.
4. Conductors supported by a cable tray are subjected to a 720-hour test, if marked "sunlight resistant.”
The above hopefully makes it clear why Code Making Panel 6 adopted the aforementioned language for 310-8(d). It provides a consistent requirement for conductors that are exposed to sunlight. Conductors exposed to direct sunlight shall be either listed or marked sunlight resistant. Whether the requirement for listing or marking of a product as sunlight resistant is 300-hour test or 720-hour test is up to the standards development process.
To maintain the effective link between the Code and Standards development processes and to define clear performance requirements, it is the author’s opinion that one single requirement for sunlight resistant should be used in the product standards. This is consistent with requirements for other application oriented markings for wire and cable products such as, "For CT Use,” "FT 4,” "LS,” etc. Historically, for sunlight resistant capability the industry is more familiar with black color insulation on conductors and in most, if not all, cases these materials are known to exceed the requirement of 720-hour test.2 However, insulation on conductors in colors other than black require significant additions of UV stabilizers to make them suitable for the application. Since no formal data has been collected, reported, or presented, the limited field experience with colored insulation and black color insulation complying with 300-hour test requirements suggests that the colored insulation does not perform as well as the black color insulation.3 Hence, it may be desirable to select the 720-hour test as the requirement for products so that they can be considered as complying with 310-8(d).
While the standards development process resolves this issue, inspectors and users can review the following to determine compliance with 310-8(d):
• Marking on the product ("Sunlight Resistant,” or "SUNRES”). This marking is afforded to those products that comply with the requirements of 720-hour test.4
• In the absence of marking on the product, seek confirmation of listing (or compliance) from the manufacturer5
• For conductors to be installed in raceways or a part of a cable (other than Type SE and USE) assembly and exposed to sunlight when outside the raceway or cable assembly. (Need for confirmation exists whether compliance with requirements of 300-hour test or 720-hour test is acceptable.)
• For conductors and the overall cable in Types SE and USE. (No need for confirmation on Type SE or USE products, if compliance with requirements of 300-hour test is acceptable.)
• There are no changes in the sunlight resistant requirement for conductors and cables supported by the cable trays. These products are typically identified with "SUNRES” marking in conjunction with "FOR CT USE” marking.)
Given the confusion with implementation of 310-8(d) adopted in 1999 NEC, the issue is on the table for the 2002 NEC. Inspectors and users can make their contribution by submitting comments, where applicable, on various proposals that have been acted upon by CMP-6.
1 National Electrical Code® and (NEC)® are registered trademarks of The National Fire Protection Association
2 Historic experience with black color insulation is derived from the inherent UV resistant properties of the carbon black added in the insulation. In the future, this may or may not be the case for black color insulation as other pigments could be used to provide the color. In such cases, additives will have to be added to the insulation to make it sunlight resistant.
3 In Canada, the similar experience has supported a change in the product standards.
4 At present Type UF is afforded this marking when complying with the requirements of 300-hour test. However, this may change and compliance with the requirements of 720-hour test may become part of the listing requirement for Type UF products.
5 Alcan Cable has verified that insulation and jacketing materials it employs on Types XHHW-2, SE, USE-2, USE-2 or RHH or RHW-2, MC, and TC meet the requirements of 720-hour test for Sunlight Resistant marking.
Read more by Ravi Ganatra
Posted By Lori Tennant,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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The first part of this series of articles provided a general understanding of the IEC and how it operates. Often more confusing though, to a new participant in the IEC, is the overall standards making process. This article will provide information on how to process an idea from its initial conception as a proposal, through its final publication as an international standard. Although there are several procedures in the IEC process for expediting development and approval of standards, based on the needs of industry, this article will address only the principle stages involved in the preparation of an IEC standard or a revision to an existing standard.
More detailed information on the drafting of international standards is covered in the following three IEC Directives:
Part 1: Procedures for the technical work
Part 2: Methodology
Part 3: Rules for the structure and drafting of international standards
Once the process is understood, the next question is, "How do I as an electrical inspector get my ideas and proposals included in this development process?” The final part of this article will outline the many ways an individual can participate in not only the IEC but also in the US National Committee of the IEC (USNC).
What is the IEC Standards Making Process?
As previously mentioned, there are streamlined procedures in the IEC which have been introduced to allow flexibility in the standards development process in order to get technical documentation into the marketplace quicker. Typically, these procedures allow for elimination of various stages in the process depending on the consensus of the committee and the need of the industry sector involved.
Following is a table, which summarizes the full six-stage process involved in the preparation of a new IEC standard or a revision to an existing standard. A brief description of each stage, along with its approval requirements, is given following the table.
This stage is for those projects which are envisioned for the future. They are not yet at the mature stage where they may proceed to further development. They may need better definition of the project or more testing or data collection before they can enter the overall standardization process.
A proposal for new work typically comes from a specific industry through their National Committee. When submitting a NP, the proposer should make every effort to supply either a draft or outline of the proposal. They are also requested to nominate a Project Leader. The proposal is then circulated through all members of the respective Technical Committee or Subcommittee for a three-month ballot. The NP is approved if a simple majority of the P-members (Participating) vote positively and a minimum of four or 25% of the P-members agree to actively participate in the work and nominate experts.
Once a NP is approved, responsibility for development of a Working Draft (WD) is delegated to a group of experts in a Working Group (WG). In most cases, the WD is prepared by the Project Leader of the WG (also referred to as Convenor in some WGs). This stage is complete when the WG has reached consensus on the draft and it is ready for circulation to the Technical Committee or subcommittee as a Committee Draft for Comment (CD).
During this consensus-building stage, the CD is circulated to all P- and O-members of the Technical Committee or Subcommittee for comments. Once all comments have been resolved and consensus reached, the CD is ready to proceed to the next stage. Prior to being circulated as a Committee Draft for Vote (CDV); however, the draft must be in bilingual text, both English and French.
At the enquiry stage, the bilingual CDV is circulated to all members for a five month voting period. This is the last stage where technical comments can be submitted. The CDV is approved if a two-thirds majority of the P-members are in favor and not more than one quarter of the votes cast by all members are negative. After the comments are addressed and resolved by the Committee, a revised version is prepared for circulation as a Final Draft International Standard (FDIS).
At the approval stage, the FDIS is circulated to all members for a two-month voting period. At this time, members have to be very definitive in their voting; either positive, negative or abstention. Positive votes cannot include any comments. Negative votes should be accompanied by technical reasons substantiating the vote. The FDIS is approved if a two-thirds majority of the P-members are in favor and not more than one-quarter of the votes cast by all members are negative. If the FDIS is approved, it is then published. If it is not approved, it is referred back to the Technical Committee or Subcommittee for reconsideration.
This stage is the sole responsibility of the IEC Central Office. Within two months following the approval of the FDIS, they publish and circulate the International Standard.
U.S Participation in the IEC Standards Making Process
As mentioned in the previous article, full members of the IEC are National Committees. The official US member, through ANSI, is the United States National Committee of the IEC (USNC). ANSI does not develop any US positions; they only facilitate position development by establishing consensus among accredited US Technical Advisory Groups (TAGs). ANSI ensures that the TAGs follow its guiding principles of consensus, due process and openness.
Within the USNC, a TAG exists for each IEC TC or SC where the US is a P- or O- member. TAG membership is open to all "US national interested parties.” ANSI defines a US National interested party in its Rules of Procedure as, "any individual located in the United States, representing an organization, company, government agency or themselves, including US branch offices of foreign companies, that is directly or materially affected by the relevant standards activity.” The primary purpose of a TAG is the development and submission (through ANSI) of US positions on all the activities and ballots of the respective IEC committee.
Among the various responsibilities of a TAG, which are outlined in ANSI’s Rules of Procedure, is the nomination of US experts, project leaders and convenors to serve on IEC Working Groups. Each TAG will also select a Technical Advisor (TA), who serves as the chair of the group and is responsible for overall participation in the international committee’s work. Also in some cases, a TAG will appoint a Deputy Technical Advisor (DTA) to assist the TA in the everyday work of the group.
How do I participate in the IEC Standards Making Process?
The only way to influence the technical content of proposed international standards is to ensure strong US participation.
There are many areas in both the USNC and the IEC where you can participate as an electrical inspector. IAEI members can participate in the USNC by becoming a member of the TAG for the IEC committee that has the responsibility for their technical area of interest. This is easily accomplished by contacting either the TA for the TAG or the Secretary of the USNC. (This information is available on the ANSI website atwww.ansi.org) In some cases, TAGs are further broken down into WGs that correspond with the relevant IEC WGs. This also allows for further participation. There also exists the opportunity of becoming appointed as a TA or DTA of a TAG, once an opportunity comes available. IAEI does participate at the USNC management level, but an inspector’s expertise at the technical level is needed.
If you want direct involvement in the IEC standards making process, there are opportunities for participation in the IEC TCs, SCs and WGs. Since members of these committees are typically nominated and appointed by the respective TAG, it is recommended that you also actively participate in the corresponding TAG to the IEC committee of interest.
In the first two articles of this series, we’ve covered the IEC, its structure, the standards making process, and most importantly, where and how you can participate in activities that affect the electrical inspection community and the overall electrical industry.
You are probably thinking, "”Okay, I now understand the IEC, the USNC and how I can participate, but why should I?”" The final part of this series will cover the relationship of the IEC to world trade and the interaction between the IEC and the North American electrical safety system and how this impacts the inspection community.
About Lori Tennant: Lori L. Tennant is the senior standards engineer, international for Square D Company/Schneider Electric North America where she is responsible for the overall coordination of company activities related to International Standards as well as coordinating all USNC involvement. Tennant holds a bachelor of science degree in electrical engineering with a minor in biomedical engineering from Purdue University. She currently represents Square D as the alternate for the Company Member Council Executive Committee of the American National Standards Institute (ANSI); and is also a member of NEMA's International and Regional Standardization Committee as well as the Joint Task Force on Conformity Assessment. Tennant is a member of NFPA and has represented the company in the electrical inspector community through the International Association of Electrical Inspectors (IAEI).
Posted By Michael Callanan ,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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Perhaps the greatest advancement in worker safety over the past 30 years has been the development and implementation of ground-fault circuit-interrupter (GFCI) protection. Both the National Electrical Code (NEC) and the Occupational Safety and Health Administration (OSHA) have initiated requirements designed to afford a superior level of protection for both employees and the general public who may be exposed to the hazards of electricity. The purpose of this article will be to explore this development as it relates to GFCI protection for temporary wiring as required by Article 305 of the NEC and OSHA’s 1926, Subpart K, Electrical Standards.
Photo 1. Typical "Spider box" supplies GFCI protected receptacles for use on construction sites.
Both the NEC and OSHA recognize that workers performing construction, demolition and maintenance activities are especially vulnerable to the hazards of electricity. Frequently, workers have environmental and physical conditions which directly impact their ability to work safely around the hazards associated with the use of electrical tools and equipment. Essentially, the NEC developed and OSHA adopted a two-prong approach to affording protection to workers. Until recently, (1996 NEC) Article 305 and OSHA 1926.404(b) have both permitted either the use of the Assured Equipment Grounding Conductor Program (AEGCP) or the use of GFCI protection for all 125-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites. The concept of the AEGCP is that frequent and regular inspection and testing of all equipment grounding conductors, receptacles and attachment plugs, will "assure” that the continuity of the EGC is maintained and that a low-impedance grounding path will protect workers sufficiently against the hazards of electrical shock by facilitating the operation of the overcurrent device. GFCI devices, on the other hand, sense an unbalance or leakage current in the area of 4-6 mA and open the circuit in a 1/40 of a second to provide protection against electrocution.
Diagram 1. GFCI protection required for 15, 20, and 30 ampere, 125-volt receptacles on construction sites.
The 1996 NEC
Two significant changes occurred in Section 305-6, Ground-Fault Protection for Personnel, in the 1996 NEC. First, the scope of the GFCI requirements was greatly expanded by removing the limitation to construction sites only. Prior to the 1996 NEC, the GFCI requirements for 15- and 20- ampere, 125-volt receptacle outlets, only applied to personnel on construction sites. The 1996 NEC removed this limitation and expanded the scope of the provision to include all "temporary wiring installations utilized to supply temporary power to equipment used by personnel during construction, remolding, maintenance, repair, or demolition of buildings, structures, equipment or similar activities.” This was a dramatic expansion of the scope and resulted in a significant advancement for worker safety.
Diagram 2. Principles of operation of GFCI protective devices
The second significant change was the restrictions placed on the use of the AEGCP. Prior to the 1996 NEC, either the GFCI or the AEGCP could be utilized to meet the requirements of this section. In the 1996 NEC, the use of the AEGCP was strictly limited to "other receptacles not covered in (a).” This meant that, for other than industrial establishments (see exception) all 15- and 20-ampere, 125-volt, single-phase receptacle outlets had to be provided with GFCI protection.
Interestingly, CMP-3 also clarified that when providing GFCI protection, cord sets incorporating listed GFCI protection for personnel are permissible.
Diagram 3. Typical protective GFCI devices
The changes in the 1996 NEC were a great step, a leap, towards enhancing worker safety. Subsequent revisions have continued to expand the scope of the protection to include 30-ampere, 125-volt, single-phase receptacle outlets and to clarify that where GFCI protection is required, such protection is required, regardless if the receptacle exists or is considered to be part of the permanent wiring of the building. In other words, if personnel are performing any of the covered activities, (construction, demolition, maintenance, etc.), they must be provided some form of GFCI protection, regardless if the outlet exists or is part of the permanent wiring of the building.
Often this is accomplished by the use of listed cord sets which incorporate the GFCI protection into the cord set. Notice that the wording of Section 305-6(a) currently permits "cord sets or devices incorporating listed ground-fault circuit interrupter protection for personnel identified for portable use.” Two points relevant to this provision. First, note that the cord set must utilize listed GFCI protection, not that the cord set must be listed. This sentence structure is intentionally different from other NEC sections mandating similar requirements. That is because OSHA does permit employers to construct their own extension cord sets. There are several conditions that must be met but the practice is acceptable. Requiring the cord sets to be listed would severely limit this provision. Secondly, the cord sets must utilize GFCI protection which is identified for portable use. Such protection includes "open neutral” protection which enhances personnel safety where such devices are subject to the possibility of losing a neutral connection. For this reason, it is not permissible to utilize standard GFCI receptacles, intended for permanent installation only, as part of a "shop-made” cord set.
Diagram 4. GFCI tripping curves showing time and milliampere values
OSHA Construction Standards
Since the early 1970’s, OSHA Construction Electrical Standards have been driven by the NEC. Current requirements parallel the 1984 edition of the NEC. In fact, Section 1926. 404(a) Note, states, "If the electrical installation is made in accordance with the National Electrical Code ANSI/NFPA 70-1984, exclusive of Formal Interpretations and Tentative Interim Amendments, it will be deemed to be in compliance with 1926.403 through 1926.408, except for 1926.404(b)(1) and 1926.405(a)(2)(ii)(E), (F), (G), and (J).” Unfortunately, as we have just discussed, significant changes in the NEC have occurred which are not currently enforceable by OSHA. The restriction on the AEGCP for example, does not exist within the OSHA regulations. The addition of the 30-ampere, 125-volt receptacle outlet is not included as well. The scope of application for GFCI requirements for OSHA is still limited to construction sites only.
Needless to say, there exists great differences between the NEC requirements and the OSHA regulations. From an enforcement point of view and from a safety point of view this is troublesome. Section 6(b) of the OSHA Act mandates steps that must be taken before OSHA can promulgate a new rule. Logistically, OSHA is simply not capable of keeping up with the latest developments in the NEC.
This fact, however, ought not change employer strategies for protecting personnel from electrical shock. The use of GFCI protection provides a level of safety superior to that of the AEGCP and it can be implemented in an easier and more cost-efficient manner for the employer. OSHA regulations are a minimum safety standard for protecting workers. Particularly when it comes to GFCI requirements, employers should follow the provisions of Article 305 and strive to enhance personnel protection by adhering to the stronger of the two standards.
Read more by Michael Callanan
Posted By David Young,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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Every year, thousands of vehicles run into electric and communication utility poles. The consequences are obvious. There may be some things we can do to reduce the number of accidents or the severity of the accidents.
To see what I might be able to do to reduce pole/vehicle accidents, I did a study in my company to investigate the details of the pole/vehicle accidents we had in one year. I had one of my engineers visit every pole struck by a vehicle to determine the location of the pole relative to the roadway. We also studied the files to determine the conditions under which the poles were struck. The results were not surprising. Over half the accidents occurred at night. About one quarter of the poles was located within three feet of the "traveled way,” i.e., the travel lanes of the highway. Most of the poles were located on the outside of curves, at intersections and at entrances to commercial establishments.
Poles at intersections are most commonly hit during accidents with other vehicles. Poles on the outside of curves are most commonly hit by out-of-control vehicles. The drivers may have fallen asleep, been under the influence of alcohol or drugs, the visibility may have been poor, or the roads may have been slippery. Only one percent of the poles was located on straight sections of the highway.
Why are there so many poles close to the road?
In many states, utilities do not have "the right of eminent domain.” Utilities in these states must get permission from the property owners to install their poles. If the property owners do not give permission to the utility, the utility is forced to install their poles on the highway right-of-way. In many cases, the highway right-of-way is not much wider than the roadway. The result, poles are located very close to the travel lanes. I have noticed that poles located next to the travel lanes on windy roads usually have a collection of side-view-mirrors on the ground next to them.
Short of removing the poles completely, the only way to prevent pole/vehicle accidents is to put something between the travel lanes and the poles, like a guardrail. Guardrails are expensive and the accidents are not eliminated, only accidents with poles. The National Electrical Safety Code® (NESC®) in Rule 231B recommends that poles be located far enough from the travel lanes of the highways so that normal traffic on the travel lanes does not strike the poles. Our problem is not normal traffic. Placing poles further away from the travel lanes may reduce the number of accidents. In one of the accidents I investigated, the vehicle crossed a twenty-foot wide six-foot deep ditch and then traveled 140 feet across a field to hit the pole. Utilities like to build their facilities along roadways to reduce construction and maintenance costs. Wake-up strips on the edge of the travel lanes reduce accidents due to drivers falling asleep.
In my study, very few of the poles involved in accidents were located next to curbs. This is probably due to the fact that curbs are only prevalent in urban areas where the speed limit is lower and the accidents are fewer. Because visibility of poles at night may be a factor contributing to accidents, my company and the State of Maryland have both started programs of installing reflectors on poles close to highways and poles located in bad locations relative to curves.
Street light poles designed to break-away with very little force are working very well in reducing vehicle damage and human injury. Some utilities have tried special hardware to convert their utility poles into "break-away” poles. The special hardware can only be used on poles where there is no equipment installed and on tangent poles, i.e., poles located in straight sections of a line. Unfortunately straight sections of lines are usually parallel to straight sections of highways where there are very few accidents. Also, designing poles that support high voltage conductors to break-away easily may not be in the best interest of public safety.
Utility ratepayers are not willing to accept the additional expense to put all utilities underground. Electric and communication utility poles are not the problem. The problem is vehicles leaving the roadway. If utility poles were eliminated, there would still be vehicle accidents. We need to remind people to drive slower when the road conditions and visibility change, to pull over when they get sleepy, and not to drive when they have been drinking.
Read more by David Young
Posted By Michael Johnston,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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Anyone who has been involved in the electrical field for any length of time has heard the phrase, "path of least resistance,” on many occasions. From the first-year apprentice starting out in the electrical trade to the seasoned veteran of the industry with many years of experience and accomplishments, the phrase is used to describe what path electrical current will take. The phrase is stated with pride "Electricity takes the path of least resistance,” or "Current takes the path of least resistance,” and usually not much thought is given to what is really meant by that statement. This article will review some basic principles of this fundamental element and discuss how this current flow relates to electrical safety.
It is appropriate to review some basic elements of the electrical circuit. First, in order for electrical current to flow, there needs to be a complete circuit or path. Voltage (E) will push current (I) through a resistance (R). These are the basic components of Ohms law. Analogous to electrical current flow is water flowing through a water pipe. The bigger the pipe is, the less the resistance to the flow of the water through the pipe; the smaller the pipe, the more resistance to the flow of water through it. The same holds true for electrical current. Larger electrical conductors (paths) offer lower resistance to current flow. Smaller electrical conductors (paths) offer greater resistance to current flow.
Figure 1. Electricity will take any path available to try to return to the source, including through the human body.
Figure 2. Amperes operate overcurrent devices. Low impedance path means higher current flow.
Where does the current flow? Current will always try to seek out the source, be it normal current or fault current. As for taking the path of least resistance, that is partially correct. Electrical current will take any and all paths available to try to return to its source. If several paths are available for current to flow, it will divide and the resistance of each path will determine how much current will flow on each particular path.
The electrical code in Article 250 mentions several times the term "low impedance path.” As a quick overview, opposition to current flow in a DC circuit is called "resistance.” Total opposition to current flow in an AC circuit is called "impedance,” which is made up of three elements: resistance, capacitance, and inductance. When the term "low impedance path” is used in the Code, it is referring to a path for current to flow on that offers little opposition to current flow whether it is normal current or fault current; the key element is low opposition or impedance.
Figure 3. Current flowing on proper paths provided
Overcurrent devices require current (amperes) flow to operate. The higher the impedance of the path, the lower the current that will flow through the overcurrent device. The lower the impedance of the path, the greater the amount of current that will flow through the overcurrent device. Understanding these basic elements of electrical circuits helps apply some important rules in Article 250 of the NEC.
There are two conductors of a grounded system— the grounded conductor and the equipment grounding conductor—that should be discussed, and a brief story related about each. They are the grounded conductor and the equipment grounding conductor. The grounded conductor (usually a neutral) of a system has been grounded once, at the service or at the source of a separately derived system. The term "grounded” is past tense, which means that the action has already happened. The grounding of the grounded (neutral) conductor of a system is accomplished by a connection to ground through a grounding electrode conductor either at the service or at a separately derived system. The other conductor to look at is the equipment grounding conductor. The word "grounding” is present tense, which means the action is ongoing. In equipment grounding conductors, the action is ongoing through every electrical enclosure all the way to the last outlet on the branch circuit. The equipment grounding conductor puts all metal enclosures at earth potential along the way, and also provides a low impedance path for fault current to flow on if a ground fault should occur in the system. So it is important that the equipment grounding conductor of the circuit make a complete and reliable circuit back to the source. At the source or service is where the grounded (neutral) conductor and the equipment grounding conductor are required to be connected together through a main bonding jumper. The main bonding jumper is defined in the Code as the connection between the grounded conductor and the equipment grounding conductor at the service. In a separately derived system, this connection is made with a bonding jumper installed between the grounded conductor and the equipment grounding conductor. These bonding jumpers complete the fault current circuit back to the source.
The NEC, in recent cycles, has been revised to continue its migration away from the use of the grounded conductor downstream of the main bonding jumper in a service or downstream of the bonding connection at a separately derived system for grounding equipment. The reasons are elementary as stated earlier. Current, be it normal current or fault current, will take all the paths available to it to try to seek out its source. If the grounded conductor (neutral) and equipment grounding conductors are connected at points downstream of the service or separately derived system connections, such as at sub panels, there will be multiple paths available for current to try to return to the source. This can lead to current flowing on water piping systems, conduit, equipment grounding conductors, and any other electrically conductive path.
In the 1996 NEC the electric range and dryer circuits were required to include an equipment grounding conductor in addition to the insulated grounded conductor. Range and dryer circuits that were existing prior to the adoption of this rule are permitted to continue the use of the grounded or neutral conductor to ground the boxes and frames of the equipment. New installations must maintain this isolation between the grounded conductor and the equipment grounding conductor.
Figure 5. Current will seek its source. It takes any and all paths available. The amount of current flowing in each path is dependant on the impedance of that particular path
In the 1999 NEC, there was a revision to the rules covering the use of the grounded conductor for grounding purposes at a second building or structure. Section 250-32 (b)(1) requires that if an equipment grounding conductor is installed with the feeder supplying the second building or structure, that isolation between the grounded (neutral) conductor is to be maintained. There is an allowance in Section 250-32(b)(2) to utilize the grounded conductor of the feeder for grounding equipment under three specific and very restrictive conditions. First, an equipment grounding conductor is not included with the feeder supplying the building or structure. Second, there are no continuous metallic paths bonded to the grounding system in both buildings. Third, there is no ground-fault protection of equipment installed at the service. If all of these conditions are complied with, the grounded conductor must be used for grounding and be connected to the building or structure disconnecting means. The grounded conductor is also required to be connected to a grounding electrode at the building or structure and installed in accordance with Part C of Article 250. This will serve as the grounding means and as the path for normal current and also the path for fault current to clear overcurrent devices. In Section 250-32(b)(2) the Code mentions a requirement of having no continuous metallic paths bonded to the grounding system in each structure. This is encompassing of all paths, not just wires or conduits. These paths could include items such as metal water pipes, other metal piping, steel members, and paths such as the shielding on a communications cable or a coaxial cable installed between the structures. It is important to remember that current will take all the paths to seek out the source. If this connection were made and there was a ground-fault protection device at the service in accordance with Section 230-95, these connections could desensitize the GFP device and it may not operate properly when called upon to do so in ground-fault conditions because of multiple paths for current.
In summary, it is important that the basic elements of current flow be understood and thought of carefully while applying the rules of the NEC. Section 250-24(a)(5) states that a grounding connection to any grounded circuit conductor on the load side of the service disconnecting means shall not be made, unless otherwise permitted in the article. The FPN gives reference to three situations where this is acceptable, but is restrictive. Sections as reviewed in this writing are for separately derived systems in Section 250-30(b), for separate buildings or structures in Section 250-32, and for grounding equipment under the limitations of Section 250-142. Installers and inspectors should be watchful to ensure there are no neutral to ground connections on the load side of the grounding connections at the service disconnecting means or on the load side of the grounding connections for a separately derived system. In other words, isolate the neutrals and equipment grounding conductor connections. Give current (be it fault current or normal current) the low impedance path anticipated by the requirements of the NEC.
Read more by Michael Johnston
Posted By Philip Cox,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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The purpose of the National Electrical Code is stated in Section 90-1 as "…the practical safe guarding of persons and property from hazards arising from the use of electricity.” The term "practical safeguarding” is significant in that it emphasizes that Code rules are designed to provide a level of safety to both people and property that is practical in nature. While the term "practical” is not specifically defined in view of safety rules, input from both the industry and the public through the consensus form of code development helps determine what it means in different situations. Effectiveness of a safety rule in achieving its desired level of protection, the probability that a destructive incident is likely to occur, the cost associated with applying it, and the ability to enforce it are some factors that must be considered when adopting safety rules. Each element must be evaluated when making the decision as to whether or not a safety provision meets the test of "practical safeguarding” as used in 90-1. Electricity is a vital part of our daily lives. It is one of the reasons our quality of life has risen to its present level. We are very dependent upon the use of electricity in our homes and workplaces and need to learn to live and work safely with this very beneficial form of energy. While the ability to use electrical energy has made life much better for us, abuse, misuse, accidents, etc., that result in an uncontrolled release of that energy can be very destructive to people and property. There is a challenge to those in code development to provide reasonably safe living and work locations.
Diagram 1. Flash protection Section 110.16
Three proposals accepted by NEC Code Making Panel No. 1 during the panel meetings held in January 2000 can have, if they are adopted, a significant impact upon those who install and maintain electrical systems. They were influenced by incidents involving electricians being injured or killed while working on energized electrical equipment and the need to add safety provisions in the Code to protect workers. Members of the electrical industry who are involved in the installation and maintenance of electrical systems recognize that hazards exist and that safety procedures should be followed when working with those systems. These three proposals recommend changing provisions in Article 110 in the 2002 NEC to include safety measures that can provide an additional level of safety for workers. All three proposals focus on steps being taken that will allow workers to take action to better protect themselves.
The first proposal involves adding a new 110-16 to cover flash protection. The wording adopted by CMP-1 action on Proposal No. 1-235 during the meeting in January 2000, reads: "110-16. Flash Protection. Switchboards, panelboards, and motor control centers installed in other than residential occupancies shall be marked in the field to indicate the incident energy in calories per square centimeter for a worker at a distance of 457 mm (18 in).
FPN: See NFPA 70E-2000, Electrical Safety Requirements for Employee Workplaces, for calculation methods and charts related to incident energy.” (see diagram 1)
It is probably safe to say that most electricians who work either as construction electricians or in electrical maintenance have either witnessed the occurrence of an electrical fault or know of someone who was involved in one where a tool slipped or something happened to create a line-to-line or a line-to-ground fault. Many incidents occur without damage to property or injury to personnel because factors needed to cause a more severe situation did not occur at the appropriate time or in the necessary order. However, many do cause significant property damage and harm to workers. The proposed new wording will not prevent a fault from occurring, but will require information to be available that can help qualified workers protect themselves where they are required to work electrical equipment while it is energized.
Where people are required to work on switchboards, panelboards, motor control centers, etc., while the equipment is energized, measures should be taken to provide as much protection against injury for workers as practical. Provisions in existing 110-26 require a minimum amount of working space for those workers to safely perform their jobs. This rule provides for a reasonable amount of space for qualified workers to maneuver while at the face of the energized equipment. Requirement in Proposal 1-235 will add an important element. This new provision will require that the amount of incident energy available at a distance of 18 inches be marked on the equipment. Where the amount of energy is known, the qualified worker can use that information to select the proper type of protective clothing and equipment that are designed for that level of energy release. This is an important step in the advancement of safety for personnel.
Diagram 2. 110.26(C) Panic Hardware
The second set of proposals affects provisions in Article 110 associated with working space around electrical equipment, such as switchboards, panelboards, and motor control centers. These provisions have primarily focused on identifying the location and dimensions of the required space and includes rules on access and entrance to that space. Previous attempts to include specific requirements that provide for workers to exit the designated space have not been successful. While many CMP-1 members agreed with the concept of having a safe and reliable means of exiting electrical equipment rooms, the supporting documentation was not deemed strong enough to justify making such a major change. However, information has been accumulating to support the addition of rules requiring doors leading out of rooms containing certain types of electrical equipment to have simple pressure release mechanisms to permit workers to safely exit the area in an emergency situation. It may be time to give favorable consideration to the addition of this rule to provide additional safety for workers.
Proposal No. 1- 260a includes a recommendation to add new wording to 110-26(C)(2) that provides for workers to be able to readily exit the required working space around equipment rated 0-600 volts, over 1200 amperes, and more than 6 ft wide. The first paragraph in 110-26(C)(2) is proposed to read:
"(2) Large Equipment.For equipment rated 1200 amperes or more and over 1.8 m (6 ft) wide that contains overcurrent devices, switching devices, or control devices, there shall be one entrance to the required working space not less than 610 mm (24 in.) wide and 2.0 m (6 ½ ft ) high at each end of the working space. Where the entrance has a personnel door(s), the door(s) shall open in the direction of egress and be equipped with panic bars, pressure plates, or other devices that are normally latched but open under simple pressure.”
Proposal No. 1-291a is the third proposal and is a companion to Proposal 1-260a. This proposal amends 110-33 to require this same type of equipment for personnel doors used for exiting the area of electrical equipment rated over 600 volts. It will read:
"110-33. Entrance and Access to Work Space
(A) Entrance.At least one entrance not less than 610 mm (24 in.) wide and 2.0 m (6 1/2 ft) high shall be provided to give access to the working space about electric equipment. Where the entrance has a personnel door(s), the door(s) shall open in the direction of egress and be equipped with panic bars, pressure plates, or other devices that are normally latched but open under simple pressure.” (see diagram 2)
If Proposals 1-260 and 1-291a are adopted, they will add another dimension of safety for people who are required to work on energized equipment. Providing a means for workers to readily exit an area where electrical equipment is involved in a destructive release of energy is necessary. Where a worker is injured by occurrence of a fault in electrical equipment, it becomes even more important for the individual to be able to open the door by pressure alone rather than by having to twist the door knob. Panic bars and other types of equipment that provide for a door in an electrical equipment room or area to be opened outward is a positive step in addressing this safety concern.
In conclusion, a fundamental question should be asked regarding these proposals. If they are adopted, will they result in the practical safeguarding of persons? I believe that the answer is Yes.
Read more by Philip Cox
Posted By Philip Cox,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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This is the final segment in the series of articles covering a number of proposed changes for the 2002 National Electrical Code.
Article 400 – Flexible Cords and Cables
400-22. Grounded-Conductor Identification.
Proposal No. 6-192:The provisions for identifying the conductor intended for use as the grounded conductor in flexible cords have been revised by deleting the term "natural” before the word "gray.” The term "natural gray” is not a generally defined term in the industry.
Proposal 6-197:A new section has been added to require the outer covering of flexible cords and cables to be flame retardant.
Article 406 – Receptacle, Cord Connectors, and Attachment Plugs (Caps)
Proposals 2-18 and 18-70:A new article entitled "Receptacle, Cord Connectors, and Attachment Plugs (Caps)” has been added to include material covering receptacles, cord connectors and attachment plugs that was previously located in Part L of Article 410. This new article also includes material that was previously located in 210-7. A task group of CMP-18 recommended the relocation of this material as part of the overall effort to make the Code more user friendly. This is an attempt to locate rules covering this type of equipment in a common area.
Article 410 – Lighting Fixtures, Lampholders, Lamps, and Receptacles
Proposal Nos. 18-4 and 18-70:The title of Article 410 has been revised to read "Lighting Fixtures, Lampholders, and Lamps.” This proposed change was initiated by a task group of CMP-18. Material previously in Part L of Article 410 was relocated to a new Article entitled "Receptacles, Cord Connectors, and Attachment Plugs (Caps).” The result is a separation of the material previously located in Article 410. Those rules remaining in Article 410 will relate to lighting, whereas provisions in the new Article 406 will apply to receptacles, cord connectors and attachment plugs. This arrangement should make it easier to locate and use the applicable rules.
410-14(a). Connection of Lighting Fixtures.
Proposal No. 18-19:The title of 410-14 and the first sentence of 410-14(a) have been revised by deleting the wording "electric discharge.” The title of 410-14(a) is "Independent of the Outlet Box” and the first sentence of (a) is "Lighting fixtures supported independently of the outlet box shall be connected to the branch circuit through metal raceway, nonmetallic raceway, Type MC cable, Type AC cable, Type MI cables, Type NM cable, or for an individual fixture, by flexible cord as permitted in Section 410-30(b) or (c).” The deletion of "electric discharge” expands the application of this rule to include lighting fixtures other than electric discharge type.
410-16(a). Outlet Boxes.
Proposal No. 18-26:This section has been revised by deleting the wording "…weighing 50 lb (22.7 kg) or less.” from the first sentence and deleting the entire second sentence which reads "A fixture that weighs more than 50 lb (22.7 kg) shall be supported independent of the outlet box unless the outlet box is listed for the weight to be supported.” This action correlates with that taken on Proposal 9-36. Rules associated with outlet boxes fall within the jurisdiction of CMP-9 and are more appropriately located in Article 370.
Proposal No. 18-28:A new exception was added to read: "When replacing a luminaire, it shall be permitted to connect an equipment grounding conductor from the outlet in compliance with Section 250-130(c). The lighting fixture shall then be grounded in accordance with 410-18(a).” The new exception applies only where a luminaire is being replaced and the circuit supplying the fixture does not include an equipment grounding conductor. Where those conditions exist, the same rules in 250-130(c) that apply to receptacle replacement and branch circuit extension apply. Under these conditions, an equipment conductor is permitted to be run from the outlet supplying the luminaire to one of the five locations stated in 250-130(c).
Proposal No. 18-34:Existing 410-56(a) has been revised in title and text and relocated as 406-2(b). The new 406-2(b) will read: "(a) Rating. Receptacles and cord connectors shall be rated not less than 15 amperes, 125 volts, or 15 amperes, 250 volts, and shall be of a type not suitable for lampholders.”
This revised wording provides a clearer rule on the rating of cord connectors.
410-57(b). Wet Locations.
Proposal No. 18-43:Existing 410-57(b) has been revised and relocated in Article 406. New text was added as 406-8(b)(1) and text previously identified under 410-57(1) and (2) have been re-identified as (a) and (b) respectively under a new 406-8(b)(2). The wording in 406-8(b)(1) will now read: "(1) 15- and 20-ampere outdoor receptacles. 15- and 20- ampere, 125- and 250-volt receptacles installed outdoors in a wet location shall have an enclosure that is weatherproof whether or not the attachment plug cap is inserted.” The new wording in 406-8(b)(2) reads: "Other receptacles. All other receptacles installed in a wet location shall comply with (a) or (b) below:” The wording in (a) and (b) under 406-8(b)(2) is the same as found in 410-57(b)(1) and (2). This change provides clearer guidance as to the weatherproof conditions for cord cap connection to outdoor receptacle whether or not they are attended and unattended while in use. This change also provides information regarding voltage and ampere rating of the receptacles under consideration.
Article 422 – Appliances
Proposal No. 20-6:The wording "or listed instantaneous water heaters” has been added following "stamped vessel.” It will now read "Water heaters and steam boilers employing resistance-type immersion electric heating elements contained in an ASME-rated and stamped vessel or listed instantaneous water heater shall be permitted to be subdivided into circuits not exceeding 120 amperes and protected at not more than 150 amperes.” This change will permit listed instantaneous water heaters to follow the rule in this section on subdividing circuits as allowed for the other types of water heaters in ASME-rated and stamped vessels.
422-47. Water Heater Controls.
Proposal No. 20-11a:This section has been revised to read: 422-47. Water Heater Controls. All storage or instantaneous-type water heaters shall be equipped with a temperature-limiting means in addition to its control thermostat to disconnect all ungrounded conductors. Such means shall be:
(1) Installed to sense maximum water temperature; and
(2) Either a trip-free, manually reset type or type having a replacement element.
Such water heaters shall be marked to require the installation of a temperature and pressure relief valve.
Exception No. 1: Storage water heaters that are identified as being suitable for use with supply water temperature of 82 degrees C (180 degrees F) or above and a capacity of 60 kW or above.
Exception No. 2: Instantaneous-type water heaters that are identified as being suitable for such use, with a capacity of 4 L (1 gal) or less.
FPN: See ANSI Z21.22-1999/CSA 4.4-M99, Relief Valves for Hot Water Supply Systems.”"
This revised wording should more correctly state the intended rules for this section and make the intent clearer.
422-62. Appliances Consisting of Motors and Other Loads.
Proposal No. 20-18:This section was restructured and reworded to better clarify the intent of the section. The addition of the title of (A) "Nameplate Horsepower Markings” and (B) "Additional Nameplate Markings” make this section easier to follow. The new wording in 422-62(A) adds needed information for this section. The wording in 422-62 (a) and (b) in the 1999 NEC was revised and located as subsections under (B) Additional Nameplate Markings. The revised section will now read:
422-62. Appliances Consisting of Motors and Other Loads.
(A) Nameplate Horsepower Markings. Where a motor-operated appliance nameplate includes a horsepower rating, that rating shall not be less than the horsepower rating on the motor nameplate. Where an appliance consists of multiple motors, or one or more motors and other loads, the nameplate value shall not be less than the equivalent horsepower of the combined loads, calculated in accordance with Section 430-110(c)(1).
(B) Additional Nameplate Markings. Appliances,
other than those factory-equipped with cords and attachment plugs with nameplates in compliance with Section 422-60, shall be marked in accordance with (1) and (2).
(1) Marking. In addition to the marking required in Section 422-60, the marking on an appliance consisting of a motor with other load(s) or motors with or without other load(s), shall specify the minimum supply circuit conductor ampacity and the maximum rating of the circuit overcurrent protective device. This requirement shall not apply to an appliance with a nameplate in compliance with Section 422-60 where both the minimum supply circuit conductor ampacity and maximum rating of the circuit overcurrent protective device are not more than 15 amperes.
(2) Alternate Marking Method. An alternate marking method shall be permitted to specify the rating of the largest motor in volts and amperes, and the additional loads(s) in volts and amperes, or volts and watts in addition to the marking required in Section 422-60. The ampere rating of a motor 1/8 hp or less or a nonmotor load 1 ampere or less shall not be required to be marked unless such constitute the principal load.
Article 424 – Fixed Electric Space-Heating Equipment
424-44(g). Ground Fault Circuit-Interruption Protection for Heated Floors of Bathrooms, and in Hydromassage Bathtub, Spa, and Hot Tub Locations.
Proposal Nos. 20-27 and 20-28:(g) Ground-Fault Circuit-Interruption Protection for Heated Floors of Bathrooms, and in Hydromassage Bathtub, Spa, and Hot Tub Locations. Ground-fault circuit-interrupter protection for personnel shall be provided for electrically heated floors in bathrooms, and in hydromassage bathtub, spa, and hot tub locations.
This section now requires a ground-fault circuit-interrupter (GFCI) protection for personnel on all electrically heated floors in bathrooms, and in hydromassage bathtub, spa, and hot tub locations regardless of the type of flooring or heating cables.
Article 430 – Motors, Motor Circuits, and Controllers
430-32. Continuous-Duty Motors.
Proposal No. 11-31:The text of 430-34 and its FPN were relocated as 430-32(C), 430-32 was restructured, and references included within the section were revised. This change was made to locate motor overload requirements in one section. Section 430-34 appeared to be a modification of the provisions in 430-32(a) and is more appropriately located in that section.
430-34. Selection of Overload Relay (Relocated as 430-32(C).
Proposal No. 11-36:The wording "sensing element or setting of” and "sensing elements or incremental settings” has been added and the new section will now read: "Selection of Overload Relay. Where the sensing element or setting of the overload relay selected in accordance with 430-32(a)(1) and 430-32(b)(1) is not sufficient to start the motor or carry the load, higher size sensing elements or incremental settings shall be permitted to be used, provided the trip current of the overload relay does not exceed the following percentage of the motor nameplate full-load current rating.” The change should give a clearer understanding of the permitted increase in the sensing element of overload relays. This modified section has been relocated as 430-32(C).
Proposal No. 11-45:The provision under (c) Other Group Installations that reads: "(3) Each circuit breaker is one of the inverse time type and listed for group installation,” was changed to read, "(3) Each circuit breaker shall be listed and be of the inverse time type.” It was contended that performance requirements of circuit breakers in UL 489 are the same for HACR type as they are for other types.
430-53(d). Single Motor Taps.
Proposal No. 11-46:A new tap rule has been added to this section to cover conductors supplying specific manual motor controllers. It permits conductors sized at not less than 1/10 the rating of the short-circuit and ground-fault protective device on their supply side to feed listed manual motor controllers that are marked "Suitable for Tap Conductor Protection in Group Installations.” Reference was made to developments being made in UL 508.
430-62(a). Specific Load.
Proposal No. 11-48:The first paragraph in 430 was revised by deleting the wording "shown in” and adding "in accordance with Section 430-52 and” following "device” and before "Table 430-152.” This change makes it clearer that the "maximum permitted value” for the branch circuit device is required to comply with Table 430-152 as modified by 430-52. Exception No. 1 of 430-52(c) permits the value to be rounded up to the next larger size. Exception No. 2 provides for an increase in the Table 430-152 value where the device selected according to 430-52(c), Exception No. 1 is not sufficient for starting the motor.
430-62(a). Specific Load.
Proposal No. 11-50:A new exception has been added to read: "Exception No. 2: Where the feeder overcurrent protective device also provides overcurrent protection for a motor control center the provisions of 430-94 shall apply.” This change should resolve any apparent conflict with the provisions in 430-94.
430-63. Rating or Setting – Power and Light Loads.
Proposal No. 11-51:This section was revised by adding "and service” after "feeder” and by adding the wording "or a single motor comprised of a hermetic refrigerant motor-compressor, the rating permitted by Section 440-22″ following "…permitted by Section 430-52.” A new exception similar to the one added in 430-62(a) was added to read: "Exception. Where the feeder or service overcurrent protective device provides the overcurrent protection for a motor control center the provisions of 430-94 shall apply.”
Proposal No. 11-57a:A new 430-83(a)(3) was added to read: "Molded Case Switch. A molded case switch rated in amperes shall be permitted as a controller for all motors, including Design E.” This new text recognizes that molded case switches can be used as motor controllers as is similarly permitted for circuit breakers in 430-83(a)(2).
Article 500 -Hazardous (Classified) Locations, Classes I, II, and III, Divisions 1 and 2
Proposal No. 14-2a:Article 500 has been reorganized and revised to provide a more logical order, to address classification of locations and material groups, to cover equipment including protection techniques, and to provide information on equipment marking, design, and approval. Technical and editorial changes accepted in other proposals have also been included in the revised text. This change also includes a number of new definitions.
Article 527 – Temporary Wiring
Article 527. Temporary Installations.
Proposal No. 3-141:Former Article 305 entitled "Temporary Wiring,” has been renumbered as Article 527 and re-identified as "Temporary Installations.” Provisions in this article are more extensive in nature than covered by the title of Chapter 3, "Wiring Methods and Materials.” The article is more appropriately located in Chapter 5.
Article 550 – Mobile Homes, Manufactured Homes, and Mobile Home Parks
Proposal 19-37:The article was extensively rewritten to incorporate the requirements of NFPA 501 for manufactured homes. The document will become the basis for the HUD Part 3280 rules and will be the primary construction standard for manufactured housing.
Article 555 – Marinas and Boatyards
Proposal 19-135:Article 555 has been totally rewritten. It incorporates existing NEC rules and physical installation rules from NFPA 303.
Article 647 – Sensitive Electronic Equipment
Proposal No. 15-72:A new Article 647, entitled "Sensitive Electronic Equipment,” has been added and the scope covers "…commercial and industrial occupancies where the use of sensitive electronic equipment is connected to a separately derived system operating at 120 volts line-to-line and 60 volts to ground.”
Article 680 – Swimming Pools, Fountains, and Similar Installations
Proposal No. 20-30a:Article 680 was revised extensively and reorganized in a more logical manner to make it easier use. It also includes changes made through action taken on other proposals.
Article 690 – Solar Photovoltaic Systems
690-56. Identification of Power Sources.
Proposal No. 3-194:A new section was added to cover identification requirements for photovoltaic power systems supplying buildings or structures. This section specifies the location and other requirements for plaques or directories required for these systems.
Article 692 – Fuel Cell Systems
Article 692. Fuel Cell Systems.
Proposal No. 3-206:A new article has been added to cover requirements for the installation and use of fuel cells.
Article 695 – Fire Pumps
695-4(b)(1). Overcurrent Device Selection.
Proposal No. 15-88:A new sentence was added to 695-4(b)(1) to read: "An instantaneous trip circuit breaker shall be permitted to be used as the disconnecting means and overcurrent protection and shall be permitted to be set to a maximum of twenty times motor full load current.”
695-6(d). Overload Protection.
Proposal No. 15-97:A new exception was added to 695-6(d), Overload Protection, to read: "Exception: For on-site standby generator(s) which produce continuous currents in excess of 225 percent of the FLA of the fire pump motor, the conductors between the on-site generator(s) and the combination fire pump transfer switch controller or separately mounted transfer switch shall be installed in accordance with Section 695-6(b) or protected in accordance with Section 430-52.”
Article 725 – Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits
725-2. Abandoned Cable.
Proposal 16-32:A new definition of "Abandoned Cable” has been added to read: "Cable that is neither terminated at both ends, at a connector or other equipment, nor identified for future use with a tag.” This new definition provides an initial step in addressing the issue of abandoned cable in buildings. This proposed change is associated with that recommended for 725-3(b) for the removal of abandoned cable.
725-3(b). Spread of Fire or Products of Combustion.
Proposal 16-80:This section was previously 725-3(a) but has been relocated as 725-3(b) and amended to read : "(b) Spread of Fire or Products of Combustion. Section 300-21. Abandoned cables not intended for future use shall not be permitted to remain.” This new provision will require cable covered by this article to be removed if it is no longer intended to be used. This same concept has also been included in other related articles in Chapters 7 and 8.
A special thanks go to the individuals serving on NEC Code Making Panels who contributed to the development of this summary of changes by providing valuable information on action taken by the panel on which they serve. This summary of proposed Code changes includes only a limited number of proposals and actions taken by Code Making Panels. A more comprehensive coverage will be included in the Analysis of the Changes in the NEC that is scheduled to be published in September 2001. That publication is expected to include over 400 Code changes, an analysis of each, and numerous graphics representations of those changes.
Read more by Philip Cox
Posted By Philip Cox,
Wednesday, November 01, 2000
Updated: Tuesday, February 12, 2013
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The neon sign industry has come a long way since that type of lighting technology was introduced into the United States in 1923.
The first neon sign is reported to have been created in Paris, France, in 1910 by George Claude. Two custom made neon signs were brought to Los Angeles, California, from France in 1923 by Earle Anthony. Those signs were installed at Mr. Anthony’s place of business as a new form of advertising. Mr. Anthony’s use of neon lighting became popular and the neon sign industry began to develop and expand in the United States and Canada. The demand for neon lighting has fluctuated over time and is used extensively at the present time. It can be used very effectively to enhance the outline of a building, to provide information, and to create special effects. While it can be used to accomplish so many things, it needs to be installed and maintained properly in order for the installation to be safe and to perform appropriately. Inspectors and installers need to be well trained in this technology. The IAEI worked with the National Electric Sign Association (NESA), now known as the International Sign Association (ISA) and others within the industry to develop a Neon Installation Manual. That manual provided a valuable step in a much needed training program. ISA was instrumental in promoting the distribution of the Neon Installation Manual to people within the sign industry.
The Neon Installation Manual was welcomed by the industry but it became evident that many people wanted a more comprehensive book. In response to that trend, IAEI staff and others within the industry began work on a project to revise the Neon Installation Manual to meet those demands and to incorporate provisions of the 1999 NEC. As the work progressed, it became clear that a revision of the Neon Installation Manual would not accomplish the desired objectives and that another approach was needed. It was decided that the existing NIM will remain as it is and that a totally new document will be developed.
The new book will be different in design, objective, intent, and format. A working draft of the new book has been developed and includes a broad coverage of neon lighting, ranging from a brief history of the development of neon to the final end use and maintenance. The new book will be in a format designed for both classroom and personal use. The historical summary, neon theory, installation information, maintenance principles, and information on how to inspect neon installations will provide a very useful source of information. An added feature is the use of rules related to both the Canadian Electrical Code and the National Electrical Code. Users of the new book on neon will find numerous realistic and descriptive color drawings and photographs included to make the information more easily understood. In addition to the participation by several individuals in the development stage, there will be a review and comment process to allow for needed input from the industry before the book is published. A number of seminars on neon lighting have been conducted using some of the new material and the input from the participants have been very positive.
In summary, the new book is intended to provide general and detailed information for designers, contractors, installers, inspectors, and maintenance personnel. It is hoped that industry representatives will find that the material is a valuable educational resource and that it benefits from both their participation and support as was demonstrated with the earlier work.
Read more by Philip Cox
Posted By Mike McManus,
Friday, September 01, 2000
Updated: Monday, February 11, 2013
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Code Making Panel 2 recognized the need for arc-fault circuit-interrupter (AFCI) protection when it accepted proposals and accompanying substantiation for the 1999 National Electric Code. Now, as the January 1, 2002, implementation of AFCI requirements in Section 210-12 of the 1999 NEC rapidly approaches, the technology and level of protection provided by various types of AFCIs are progressing rapidly as well.
In fact, the code panel anticipated that progress, correctly believing that a delayed effective date would spur AFCI development and completion of an AFCI product standard (UL 1699). What the panel may not have anticipated was that technology would advance so quickly as to provide new protection opportunities, unforeseen in both the 1999 NEC and UL 1699.
Instead of broadly considering the problem of arc-initiated fires, the Code’s AFCI content appears to focus on single-product technology. As a result, current AFCI Code requirements, while appropriate for the technology available at the time of adoption, could result in a solution that may not provide the most comprehensive protection. In this article, the authors discuss the limitations of the technology and solutions in the current code language as well as the risks those limitations pose, especially in series arcing on the branch wiring, cords, and extension wiring. We will also describe what we believe to be the solution (the Outlet Branch Circuit AFCI) and encourage its recognition and support.
Photo 1. Lamp cord arc manifests into fire
Regardless of regulatory and technology issues, there’s no disagreement on the need for AFCI protection. It’s been clearly demonstrated in Consumer Product Safety Commission (CPSC) data, which have been widely cited in numerous Code proposals. Residential electric equipment is involved in approximately 41,000 fires each year, resulting in more than $650 million in annual property loss. That alone would justify extensive investment in AFCI technology. Add 360 fire deaths and thousands of injuries annually, and the case for AFCI protection is undeniably closed.
In searching for a comprehensive solution to the arcing problem, it’s important to understand what arcing is, the different types of arcs that occur, and how common they are in residential wiring systems.
Arcing is a luminous discharge of electricity across an insulating medium. An arc can cause a fire once the electrical energy from the arc is converted to thermal energy. The heat generated is then transferred to a combustible material that ignites.
Arcing occurs in wiring in two basic forms: parallel arcing and series arcing. Parallel arcing is an arc fault between two conductors—hot and neutral or hot and ground. An example is a metal object penetrating the insulation of a cable or cord, "”shorting”" the hot wire to the neutral or equipment grounding conductor.
Series arcing occurs on a single conductor when there is a break in the conductor and an arc is established between the conductor’s broken ends. Examples include loose terminations in a twist-on wire connector, loose device connections, and partially severed lamp cords.
There is no data indicating which type of arcing is more prevalent—nor where each is most likely to occur in a branch circuit. But what’s important is that we recognize that both arcing types contribute to the problem. Therefore, a solution should address both series and parallel arcs that occur on branch wiring, power supply cords, and extension wiring.
The current UL 1699 standard recognizes five different types of AFCI devices. By UL definition, none of these five AFCI types provides protection of the entire branch circuit, power supply cords, and extension cords connected to them. Branch Feeder AFCIs protect branch circuits—but offer only "”limited”" protection of cords. Outlet AFCIs protect only cords. Combination AFCIs come closest to providing complete protection of the branch circuit and connected cords.
However, the most advanced AFCI type didn’t exist when UL 1699 was published. It’s the Outlet Branch Circuit AFCI—an AFCI receptacle that provides series protection for the entire branch circuit including cords and extension wiring. It also provides parallel protection downstream from the point of installation, protecting the branch circuit, cords, and extension wiring, extending to, but not including powered devices. This technology is so new it has not yet been recognized by the standard.
Here are the five currently recognized AFCI types with their UL definitions:
•Branch Feeder AFCI– A device installed at the origin of a branch circuit or feeder, such as at a panelboard, to provide protection of the branch circuit wiring, feeder wiring, or both against the unwanted effects of arcing. This device also provides limited protection to branch-circuit extension wiring. It may be a circuit breaker type device or a device in its own enclosure, mounted at or near the panelboard.
•Outlet Circuit AFCI– A device installed at a branch-circuit outlet, such as an outlet box, to provide protection of cord sets and power-supply cords connected to it (when provided with receptacle outlets) against the unwanted effects of arcing. This device may provide feed-through protection of the cord sets and power-supply cords connected to downstream receptacles.
•Combination AFCI– An AFCI which complies with the requirements for both Branch Feeder and Outlet Circuit AFCIs. It is intended to protect downstream branch-circuit wiring, cord sets and power-supply cords.
•Portable AFCI– A plug-in device intended to be connected to a receptacle outlet and provided with one or more outlets. It is intended to provide protection to connected cord sets and power-supply cords against the unwanted effects of arcing.
•Cord AFCI– A plug-in device connected to a receptacle outlet to provide protection to the power-supply cord connected to it against the unwanted effects of arcing. The cord may be part of the device. The device has no additional outlets.
These definitions tell only part of the story, for they don’t reveal that Branch Feeder AFCIs essentially protect against parallel arcs only … that Combination AFCIs protect against both parallel and series arcs … and that the Outlet AFCI protects against series arcs only. However, you will find this important information in UL 1699’s test criteria.
The UL 1699 tests are summarized (Table 1) with additional test details in the following paragraphs. It’s also important to fully understand the type of arc and the level of energy present at each of the different arcing events.
The various UL test sections simulate specific types of real-world arcing. We’ve included examples to clarify the protection the various recognized products actually provide. Keep in mind that the variety and conditions for arcing vary greatly, as do the technologies available for detecting and mitigating arcs before ignition. A device may not be required to stop a specific type of arc—but that doesn’t mean that type of arc can’t cause a fire.
56.2 – Carbonized-Path Arc Ignition Test
This test simulates such real-world conditions as a screw or nail driven through the wall that initiates a series arcing condition by severing the hot conductor. This test is performed using a piece of NM-B cable with ground. As prescribed in the UL standard for sample preparation, NM-B is cut and pyrolized, simulating a severed line conductor that develops a carbon path over time. The test also calls for a piece of cotton fire indicator placed adjacent to the cut.
When power is applied to the circuit, the AFCI is supposed to clear the arcing that occurs on the sample before the cotton fire indicator ignites.
The Combination AFCI clears this event as an actual series arc. Current UL-listed Branch Feeder AFCI devices don’t—because they rely on 30mA Ground-Fault Protection for Equipment (GFPE) technology for detection and circuit deenergization. That means they require the presence of ground, with the arc being detected as leakage rather than a series arc.
Should ground wire terminations be loose or absent (as in older dwellings with two-wire branch circuits), a series arc will go undetected by a Branch Feeder AFCI until the arc propagates to a parallel arcing condition. Once this parallel arc reaches 75A, the Branch Feeder AFCI will clear it. Before that happens, there’s a significant potential for ignition of combustible materials in proximity of the fault. This condition is highly repeatable in the laboratory using the test criteria.
56.3 Carbonized Path Arc Interruption Test
This test simulates such conditions as a cord running through a doorway, with the cord having been severed or damaged by being repeatedly pinched. 56.3 is a parallel arc clearing test required of Branch Feeder and Combination AFCIs, performed on both 16AWG SPT-2 flexible cord and NM-B sheathed cable. Samples have a transverse cut made across the conductors and the insulation. Each sample is then wrapped in PVC and fiberglass tape and pyrolized using alternating cycles of high voltage. Once power is applied to the circuit, the AFCI must detect and clear the arc within eight arcing half cycles.
56.4 Carbonized Path Arc Clearing Time Test
How would Combination, Outlet, and Portable AFCIs respond to severed lamp or appliance cords; loose terminations at cord ends, devices or twist-on wire connectors; or even loose circuit breaker terminations? This test is intended to find out. A sample of pyrolized SPT-2 cord is wired into the branch circuit in series. When power is applied, a series arc crosses the sample’s carbonized path. Per the UL requirement, the sample is wired so that there are no adjacent conductors—so the arc is a true series arc, with no possibility of a subsequent parallel fault developing. The AFCI must deenergize the circuit within one second. This test is required for Combination and Outlet AFCIs but not required for Branch Feeder AFCIs.
56.5 Point Contact Test
All AFCI devices must face the point contact or "guillotine” parallel arc fault test. It simulates the severing or "shorting” of hot to neutral or hot to ground resulting from a metal object (for example, a chair leg) breaking through insulation. This test covers Branch Feeder and Combination AFCIs and includes both SPT-2 and NM-B cable. A steel blade contacts first one conductor and then the second at a "point contact,” creating a parallel arc fault. Test criteria include limiting the short circuit current to a minimum of 75 amperes rms using a prescribed length of 14 AWG NM-B. The AFCI must clear the arc fault within eight arcing half cycles.
58.1.3 Operation Inhibition Test
(Arc Generator or Opposing-Electrode Test)
The opposing-electrode test simulates loose terminations or a severed conductor as a series arcing condition. This series arc fault test is required for Outlet, Combination, Portable, and Cord AFCI products but not for Branch Feeder AFCIs. The test uses an arc generator consisting of opposing copper and carbon electrodes. The arc generator connects in series with the LINE, with various loads applied. With the electrodes touching, the circuit is closed. The electrodes are then slowly separated until arcing occurs. The AFCI must clear the arcing condition in less than a second. This test accurately reflects types of series arcing that occur in the real world, as arcing can cause fire at currents at or below 5 amperes.
UL 1699 also calls for a thorough battery of additional tests the products must pass, which simulate conditions that may cause the device to nuisance trip. Common arcs such as a light bulb failing, switches being actuated, or the plugging in of loads should not be detected by the AFCI. Nuisance tripping testing in UL 1699 is very thorough, and all manufacturers are taking additional steps to eliminate any nuisance tripping.
While the NEC mandates AFCI protection of branch circuits, it doesn’t currently address protecting the power supply or extension cords plugged into a branch circuit. Outlet Branch Circuit AFCIs provide unequivocal protection of cords plugged into the branch circuit, not simply "”limited”" protection as in the case of Branch Feeder AFCIs. This level of protection coupled with protection of the branch circuit fully addresses the problem of arcing-related fires, providing protection that consumers have a right to expect. Outlet Branch Circuit AFCIs will provide familiarity and convenience for the installers and homeowners as well. Outlet Branch Circuit AFCIs are currently undergoing extensive testing and will soon be commercially available.
Read more by Mike McManus