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September-October 2002
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September-October 2002 CoverSeptember-October 2002

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Features

Supplementary Grounding Electrodes

by Michael Johnston

Electrical systems and non-current-carrying metal parts of equipment in an electrical installation generally are required to be grounded; however, alternatives are given within the NEC that relax the grounding rules for equipment. These alternatives include isolation, insulation, or guarding as methods of providing equal and effective safety measures without grounding the metal parts or equipment. It is important to meet all of the provisions of the Code when utilizing any of these alternatives. Read more

Series Combination Rating Requirements

by Tim Crnko

Series combination ratings are utilized to attempt to save money on some jobs. This article presents a simple checklist that can be completed by the contractor and/or designer when series rated combinations are proposed. The checklist is designed to be a single sheet that is double sided. The front side requires information for a specific series rated application. The backside provides an easy reference of general application information and provides the specific National Electrical Code requirements. In the plan review stage, the checklist provides the AHJ the necessary information to review series combinations in their specific application. Read more

Structured Cabling: An Essential Utility for the 21st Century

by Ian Hendler

By the early 1990s, the industry was rolling out another approach to smart homes. The technology had many names at first, but today the industry has settled on the name structured wiring. However, the standards bodies have recently given the technology the designation of structured cabling. This new cabling system was initially developed by manufacturers in the voice and data industry for commercial applications. It was subsequently reengineered and downsized for residential applications to make the technology practical, economical, and worthwhile to consumers. Read more

3rd Harmonic Blocking Filter: Is the Cure Worse Than the Disease?

by Tony Hoevenaars

It is commonly known that conventional transformers and neutral conductors can become overloaded and hot due to harmonics generated by computer equipment and other non-linear loads. Triplen current harmonics (mainly 3rd and 9th) sum arithmetically in the neutral and circulate in the primary windings of transformers. A simple and effective solution being commonly applied is to use K-rated, or more preferably, harmonic mitigating transformers and to double the ampacity of the neutral conductor. This prevents overheating without introducing negative side effects. Third harmonic blocking filters, on the other hand, reduce neutral current by preventing loads from drawing 3rd harmonic current. Read more

Update on NFPA 79, 2002

by Tom Garvey

NFPA 79, the Electrical Standard for Industrial Machinery 2002 edition, is scheduled to be published in October 2002. During this past cycle, NFPA 79 has undergone a major overhaul in an effort to harmonize requirements with those of IEC 60204. This, as you can imagine, was a major undertaking and resulted in a heavy workload. The work pioneered by the NFPA 79 technical committee has provided a benchmark for future harmonization efforts. This article will discuss the harmonization process that took place and resulting changes to the NFPA 79 standard. In addition, significant changes that occurred during the 2002 cycle will be discussed individually. Read more

AFCI Troubleshooting

by Dan Prater

Although not required by UL Standard 1699, all of the listed branch/feeder arc-fault circuit breakers currently available also provide a certain degree of ground-fault protection for electrical equipment. Read more

Departments

Editorial

"Yesterday things were different…Today, they are different again.”

by James W. Carpenter

The opening line from a southern gospel music song by the Cathedrals has special meaning for me at this point of my life. Yesterday, I was very comfortable in my position as the chief electrical engineer, state electrical inspector with the North Carolina Department of Insurance. Today, I find myself moved to another state and with a new position—CEO & Executive Director of the International Association of Electrical Inspectors. Now you may surmise from the opening of this editorial that big changes are coming as I begin this experience as your CEO, but I am not one to rush in and make a lot of changes. Read more

Canadian Code

Canadian Electrical Code Revisions: Grounding and Bonding Requirements

by Leslie Stoch

The new 19th edition of the Canadian Electrical Code has brought about some changes in the grounding and bonding rules. Not many of these are major changes. In a few instances, a change might simply be the re-arrangement of some words or the relocation of rules to more logical places in the code. In this article, we will review some of the revisions made in Sections 10, 60, and 68 as they affect grounding and bonding. Read more

UL Question Corner

Are dry type transformers with expanded metal bottoms suitable for installation on combustible floors?

by Underwriters Laboratories

Dry type transformers with expanded metal bottoms are not suitable for installation on combustible floors. They are required to be enclosed. The enclosure houses all uninsulated live parts. However, the bottom of the enclosure does not need to be provided (or may have openings) for transformers intended to be pad mounted. Read more

Other Code

NESC Substation Grounding

by David Young

I have written several times in the IAEI News about the hazards associated with substations and some of the easy ways to understand NESC requirements for substations. In my November/December 1997 article titled "A Substation is Not Just a Fence,” I discussed the fallacy of using a fence as a quick and inexpensive fix to electrical facilities with clearance problems. Read more


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