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November-December 2002
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November-December 2002 CoverNovember-December 2002

TABLE OF CONTENTS

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Features

Nonincendive Equipment for Use in Hazardous (Classified) Locations

by Nicholas Ludlam

What is nonincendive equipment? Section 500.7(F) of the National Electrical Code explains that it is a protection technique for equipment installed in Class I, Division 2, hazardous (classified) locations. With the advent of more stringent environmental regulations, intentional release of flammable materials is greatly restricted and, with the resulting changes in containment techniques, many areas that previously were classified as Division 1 (continuously flammable) have been reclassified as Division 2 (infrequently within the flammable range). Read more

The Danger of Voltage Gradients in the Aquatics Environment

by Bob Herzig

Hidden beneath the glamour and excitement of an aquatics complex is a detailed and essential safety system. This frequently misunderstood network is the swimming pool bonding grid. Article 680 of NEC 2002 covers this system and was revised in this latest edition. Several sections changed paragraph numbers and other information was reformatted to provide clearer interpretation of this section. Section 680.26, Bonding, was formerly 680.22 in NEC 1999. The intent of this section still remains to provide an equipotential plane in the aquatics environment for safety. Read more

Understanding the Zone Area Classification Method in the NEC

by Edward M. Briesch

The division classification method has been used in the United States since being incorporated into NEC 1920 to cover electrical and electronic equipment and wiring in extra-hazardous areas where fire or explosion hazards may exist from flammable and combustible liquids, vapors, or gases. The use of the term extra-hazardous locations implied that an electrical installation was already a hazardous installation but where used in areas, rooms, or compartments with some chemicals, it was more hazardous than usual. In NEC 1931, the term classifications was added to the NEC along with Class I, Class II, and III. The term extra-hazardous has been dropped from the NEC. These areas are now called hazardous (classified) locations which differentiates the hazardous chemical areas with electrical equipment from hazardous health areas. Read more

Installation of Intrinsically Safe and Nonincendive Systems

by Benjamin P. Schaefer

With technology rapidly advancing, new developments in sensing and process control have increased the number of products using intrinsically safe or nonincendive circuits as their protection technique for hazardous (classified) locations as defined in Articles 500 through 505 of the 2002 National Electrical Code ANSI/NFPA 70 (NEC)1. With lower installation and maintenance costs, these protection techniques have found increased favor in applications traditionally requiring explosionproof devices. Though these concepts have been in use in industry for many years, some confusion still exists in regards to the installation of these devices. Following the proper installation requirements is important to the overall safety of intrinsically safe and nonincendive circuits. Read more

Isolated Power Systems

by Michael Johnston

Generally, electrical systems used in power distribution systems for premises wiring are required to be grounded. The NEC includes rules that often make this determination. Some electrical systems are required to be grounded, while other systems are permitted to operate ungrounded (see 250.20 and 250.21). Then there are those systems that are not permitted to be grounded (see 250.22). One such ungrounded electrical system is the isolated power system utilized in health care facilities. This article focuses on some key installation requirements for these systems, and also takes a look at inspections of these ungrounded electrical systems. Read more

Area Classification for Class I Locations

by Donny Cook

Area classification, for locations where combustible materials (flammable gases or vapors, flammable liquids, or combustible liquids) are processed or handled, is the analysis of a space to determine the likelihood of an ignitible mixture of flammable materials and oxygen. If the analysis determines that ignitible concentrations are or may be present in the air in quantities sufficient to produce explosive or ignitible mixtures, this will limit the electrical equipment that is permitted to be used in that space. If the ignitible mixture exists, the NEC provides special requirements for electrical wiring and equipment to minimize the likelihood that the electrical system will become an ignition source in the space. Read more

Comparison of Division and Zone Systems

by Paul Babiarz

There are two significant changes that electrical inspectors must be cognizant of with the new zone classification system. First, all zone-rated equipment can be used in Division 2, which is 90 percent of classified areas. Second, zone-rated products will have different markings and labels. Before getting into the details of these requirements, it may be useful to examine the background of these Code changes. This paper will briefly describe the explosion-protective techniques and sort out the differences for electrical inspectors in equipment and installations. Read more


Intrinsic Safety

by Paul Babiarz

Intrinsic safety is the method of protection for control and instrumentation circuits where the nominal voltage is 24 VDC or less and the current is normally less than 100 mA. The concept of intrinsic safety is to limit the voltage and current so that there is never a spark with enough energy to create an explosion. Intrinsic safety when properly used removes the ignition from the explosion triangle. Read more

Departments

Editorial

A Look at Resolutions, again!

by James W. Carpenter

As the year 2002 draws to a close and the new year comes before we know it, we traditionally reflect on what the past year has brought and what we expect for the next. Many of us make new year’s resolutions with good intentions of keeping them and making changes in our lives or work. I wonder what new year’s resolutions you will be making? May I suggest a few? What about resolving to gain more knowledge to help you in your job? The IAEI has many excellent educational programs to help you with this resolution. The Analysis of the Changes, 2002 NEC, is a thorough presentation of the many important changes in the NEC. Read more

Canadian Code

The Canadian Electrical Code – More Changes

by Leslie Stoch

This article covers some changes in the rules for installing wiring and cables provided in the new 2002 edition of the Canadian Electrical Code. In earlier versions of the code, Rule 4-004(1)(d) and (2)(d) allowed the use of IEEE Standard, Power Cable Ampacity Tables IEEE 835 with the alternative of using the Appendix D underground ampacity tables to size underground cables. Read more

Other Code

NESC Substation Grounding – Part 2

by David Young

The almost two hundred pages and ninety five equations of IEEE Standard 80-2000 provide a well explained procedure for the design of safe and practical grounding systems for electric substations. There are two objectives of a safe grounding system as detailed in Clause 4.1: "To provide means to carry electric currents into the earth under normal and fault conditions without exceeding any operating and equipment limits or adversely affecting continuity of service,” and "To assure that a person in the vicinity of grounded facilities is not exposed to the danger of critical electric shock” under normal and fault conditions. Read more


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