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November/December 2002
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 [...]
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 [...]
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 [...]
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 [...]
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 [...]
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 [...]
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 [...]
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 [...]
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 [...]
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 [...]
