IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, JANUARY/FEBRUARY 1973 Each year the National Fire Protection Association (NFPA) publishes a report of its estimates of United States fires and fire losses classified in several ways [1]. Table II shows the NFPA estimates of United States fire losses in 1971 classified by type of occupancy. From this, it is evident that residential fires are a cause of consider able property loss and that an investment in corrective measures might very well produce a monetary savings that would be greater than the cost of the correction. Table III shows the number of building fires and losses for all causes and for electrical causes only. Approximately 16 percent of all building fires are a result of electrical esses, and about 12 percent of all building fire losses are a result of electrical causes. Table IV shows that over 11000 people lost their lives in fires during 1971. The author has no knowledge of the number of lives lost in electrical fires, but a reasonable estimate is that the number is as great as the number of lives lost in accidental electrocutions. CONCLUSIONS Advances in the field of safety for the use of electric power have been made by many organizations actively engaged in the production, distribution, and utilization of electric power. These advances usually become a matter of record as requirements in the National Electrical Code. Whenever the state of the art permits the introduction of improved wiring methods, materials, or equipment into the electrical system for the purpose of enhancing safety, the National Electrical Code considers the suggested inprovement. If the estimated improvement in safety is balanced with the effect on the utility, cost, and availability to the consumer of electric power, the National Electrical Code will usually require use of the suggested improvement. The introduction of the new idea into the system is usually done on a gradual basis in order to learn in a controlled manner the various advantages and disadvantages of the suggested improvements. The GFCI is now being tested for many applications, and as field experience is accumulated, there may be many revisions in the recommended uses of the GFCI. It is always desirable to search for ways to provide greater safety. In the interest of determining the most effective means of increasing the protection to persons around the home from the hazards of electricity, a study was made of the effectiveness of the various systeins of protection available. On the basis of the known field experience of the GFCI and the analysis presented in this paper of the effectiveness of the GFCI in comparison with other methods of protection against shock hazard, GFCI protection for all receptacle outlets for cord-connected appliances in homes would seem to provide an appreciable improvement in protection against shock hazard and also a decrease in the number of fires in homes from electrical causes. APPENDIX DEFINITIONS Shielding: Shielding is the use of conductive material that is grounded and that encloses all live parts including the supply cord of the electrical equipment in such a way that total immersion of the equipment in a conductive liquid will not produce a shock hazard. This system assumes all the benefits of grounding plus the additional protection of the shielding. Grounding: Grounding, is the connection to earth by a low-impedance conductor of all exposed conductive parts of the electrical equipment. Double Insulation: Double insulation is a system of insulation by which accessible conductive parts are separated from live parts by both functional and supplementary insulation. In this study, it applies only to appliances but not to the power supply cord. Cutter-Isolated Appliance: A cutter-isolated appliance would be constructed with the cutter (or other working component) so isolated from the body of the tool or appliance that the user would not be in electrical contact SMOOT: GFCI 61 with the cutter of the appliance during use. The appliance (2) V. A. Stegenga, "Safety Regulations with regard to portable may have a metallic enclosure. This would enable the cutter of an appliance, such as a hedge clipper or a drill, to contact a live wire without establishing continuity be tween the operator and the live wire. The analysis involves consideration of this feature applied to a conventionally insulated, ungrounded construction. Ground Fault Circuit Interrupter (GFCI): The GFCI is installed in the panelboard in series with all branch circuits supplying receptacle outlets rated 20 A or less in and around the home. The GFCI does not provide protection for permanently installed equipment (including ranges, clothes dryers, etc.) or for branch circuits supplying lighting outlets only. The sensor (differential transformer) of the GFCI encompasses the three supply conductors (two ungrounded and one grounded) supplying the receptacle branch circuits. REFERENCES [1] "Fires and fire losses class fed, 1971," Fire J., vol. 66, no. 5, Sept. 1972. electric tools and other hand-held electrical equipment in the Netherlands," AIEE Conf. Paper CP61-439. Arnold W. Smoot (M'40-SM'32) received the B.S. degree in electrical engineering from the University of Maryland, College Park, in 1933. He joined Underwriters' Laboratories, Inc., in 1937 as an Assistant Electrical Engineer.. During World War II he served in the United States Navy, primarily as Instructor in the Massachusetts Institute of Technology Radar School. He returned to Underwriters' Laboratories and resumed his duties in the Electrical Department. Much of this time he was the head of the radio and television section. He is currently Research Engineer at Underwriters' Laboratories, Melville, NY, where he is responsible for research activities in hazard analysis and evaluation of methods of improving safety. Mr. Smoot is a member of Tau Beta Pi and Phi Kappa Phi and a member of the Technical Subcommittee on Swimming Pools, National Electrical Code. 70-24 1971 NATIONAL ELECTRICAL CODE (210-6(d) continued) not exceed 3 percent to the farthest outlet for power, heating, lighting. or combinations thereof. Providing further that the maximum total voltage drop for feeders and branch circuits should not exceed 5 percent over all. | 210-7. Grounding-Type Receptacles and Protection. Receptacles and cord connectors equipped with grounding contacts shall have those contacts effectively grounded. The branch circuit or branch-circuit raceway shall include or provide a grounding conductor to which the grounding contacts of the receptacle or cord connector shall be connected. Acceptable grounding means are outlined in Section 250-91(b). Exception: For extensions only in existing installations which do not have a grounding conductor in the branch circuit, the grounding conductor of a grounding-type receptacle outlet may be grounded to a grounded cold water pipe near the equipment. All 15- and 20-ampere receptacle outlets on single-phase circuits for construction sites shall have approved ground-fault circuit protection for personnel. This requirement shall become effective on January 1. 1974. 210-8. Heavy-Duty Lampholders. Heavy-duty lampholders referred to in this Article shall include lamphoiders rated at not less than 750 watts. Exception: Admedium lampholders rated at 660 waits shall be considered to be heavy-duty types. B. Specific Requirements. 210-19. Conductors. Circuit conductors shall conform to the following: (a) Ampacity. Shall have an ampacity of not less than the rating of the branch circuit and not less than the maximum load to be served. (b) Minimum Size. Shall not be smaller than No. 8 for ranges of 8 kW or more rating, nor smaller than No. 14 for other loads. (c) Exceptions: Exception No. 1: Range Loads. See Note 5 of Table 220-5. Where the maximum demand of a range of 83⁄44 kW or more rating is computed according to Column A of Table 220-5, the neutral conductor of a 3-wire branch circuit supplying a household electric range, a wall minu malınınd aaabina unit mau he smaller than 1975 National Electrical Code grounding-type receptacle shall be permitted to be grounded to a grounded cold water pipe near the equipment. (d) Replacements. Grounding-type receptacles shall be used as replacements for existing nongrounding types and shall be connected to a grounding conductor installed in accordance with (c) above. Exception: If it is impractical to reach a source of ground, a nongrounding-type receptacle shall be used. (e) Portable Equipment. The installation of grounding-type receptacles shall not be used as a requirement that all portable equipment be of the grounded type. See Section 250-45 for type of portable equipment to be grounded. (f) Noninterchangeable Types. Receptacles connected to circuits having different voltages, frequencies, or types of current (ac or de) on the same premises shall be of such design that the attachment plugs used on these circuits are not interchangeable. 210-8. Ground-Fault Circuit Protection. (a) Residential Occupancies. For residential occupancies all 120volt, single-phase. 15- and 20-ampere receptacle outlets installed outdoors and in bathrooms shall have ground-fault circuit protection for personnel. Such ground-fault circuit protection may be provided for other circuits, locations. and occupancies, and where used, will provide additional protection against line-to-ground shock hazard. See Section 215-9 for feeder protection. (b) Construction Sites. All 120-volt single phase 15 and 20 ampere receptacle outlets which are not a part of the permanent wiring of the building or structure, shall have ground fault circuit interrupters for personnel protection. Exception: Receptacles on a portable generator rated not more than 5 kW, where the circuit conductors of the generator are insulated from earth and the generator frame is insulated from earth and all grounded surfaces. 210-9. Circuits Derived from Autotransformers. not be supplied by autotranstormers. Branch circuits shall Exception No. 1: Where the system supplied has a grounded conductor that is electrically connected to a grounded conductor of the system supplying the autotransformer. Exception No. 2: An autotransformer used to extend or add an individual branch circuit in an existing installation for an equipment load without the connection to a similar identified grounded conductor when transforming from a nominal 208 volts to a numinal 240-volt supply or similarly from 240 volts to 208 volts. An autotransformer is a transformer in which a part of the winding is common to both primary and secondary circuits. [From the Federal Register, vol. 40, No. 67-Monday, Apr. 7, 1975] DEPARTMENT OF LABOR Occupational Safety and Health Administration [29 CFR Parts 1910, 1926] [Docket No. S-102] GROUND-FAULT CIRCUIT PROTECTION REVOCATION OF STANDARD Pursuant to section 6(b) of the Williams-Steiger Occupational Safety and Health Act of 1970 (84 Stat. 1593, (29 U.S.C. 655)) (hereinafter called the Act), section 107 of the Contract Work Hours and Safety Standards Act (83 Stat. 96, (40 U.S.C. 333)), Secretary of Labor's Order No. 12-71 (36 FR $754), and 39 CFR Part 1911, it is proposed to amend 29 CFR 1910.309 and 29 CFR 1926.400 by revoking the requirement of ground fault circuit protection for personnel on construction sites. L Background. In accordance with section 6(a) of the Act (84 Stat. 1593, (29 U.S.C. 655(a))), the 1971 National Electrical Code (hereinafter called NEC), (NFPA 70-1971, ANSI C1-1971) has been adopted as a national consensus standard in §§ 1910.309 and 1926.400. Section 210-7 of the NEC contains the following provision: "All 15 and 20-ampere receptacle outlets on single-phase circuits for construction sites shall have approved ground-fault circuit protection for personnel. This requirement shall become effective on January 1, 1974." On November 8, 1973, the Advisory Committee on Construction Safety and Health recommended to the Assistant Secretary of Labor for Occupational Safety and Health the suspension of the January 1, 1974, effective date of section 210-7 of the NEC pending further study. Additionally, on November 19, 1973, the National Constructors Association petitioned the Assistant Secretary to postpone the effective date of the regulation. On December 4, 1973, notice was published in the Federal Register (38 FR 33397) amending §§ 1910.309 and 1926.400, by adding paragraph (3) to § 1910.309 and paragraph (h) to §1926.400, to suspend the January 1, 1974, effective date pending reconsideration of the requirement. In order to obtain the information necessary for a reconsideration of the requirement, a notice of public hearing was published in the Federal Register on December 10, 1973 (38 FR 33983), and the issues subject to comment were dated on December 26, 1973 (38 FR 35235). A public hearing was held on February 26, 1974. After evaluating the comments received in response to the Federal Register notices and the evidence submitted at the hearing, an advance notice of proposed rulemaking was published in the Federal Register (39 FR 20499). This action was taken on the assumption that there was a need for ground-fault circuit interrupters (GFCI's) when an employee used electricity in any wet, damp, or conductive location. After evaluating all the comments and evidence received in response to the Federal Register notices, a first draft of a proposed ground-fault circuit protection standard was prepared and submitted to the Advisory Committee on Construction Safety and Health at its October 30, 1974, meeting. This draft would have required ground-fault circuit interrupters for all 120-volt receptacle ontlets on the temporary wiring of construction sites, which were used by employees. Additional evidence was submitted at this meeting, and a motion was passed to continue to hold the ground-fault circuit protection standard in abeyance. until an unbiased, independent study was conducted on the need and efficacy of GFCI's. II. Issues. The entire record submitted has raised a number of issues relating to the standard. The major issues are discussed separately as follows: (a) Nuisance tripping. One issue about the requirement for ground-fault circuit interrupters was that these devices were subject to nuisance tripping. Nuisance tripping occurred, it was claimed, when the GFCI's would often trip open the circuit. Some commenters claimed that there were instances of |