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IAEI News provides educational forums, updates on electrical codes and reports of innovative research to facilitate the development and enforcement of practices designed to drive efficiency and compliance with the highest standards of product development and safety—for the public as well as for electrical personnel. The magazine reaches authorities with power of product specification, approval and acceptance. Published six times a year by the International Association of Electrical Inspectors.

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The Cost of Losing an Arm

Posted By David Young, Friday, January 01, 1999
Updated: Monday, August 27, 2012

Tom had flash burns to his face. Fortunately, he had been wearing safety glasses. What was left of his right arm had to be amputated above the elbow. He was in the hospital for almost four months. The medical care and physical therapy would continue for years.

Tom said that he and two experienced linemen were called out on trouble at two o’clock in the morning. A relatively new housing development was completely out of telephone service. Upon arrival at the development, they found a water company crew up to their waists in a water main break. The break was at the entrance to the long drive leading back to the development. The water company excavation was next to the trench line where the telephone company’s three hundred pair cable entered the development. The water company crew indicated it might be twelve hours before they would be done with their repair. Tom’s foreman assumed that the water main break or the repair excavation damaged the telephone cable. Since the nearest termination pedestal on the development side of the break was almost five hundred feet away, the decision was made to cut the telephone cable on the development side of the water problem and splice in a new cable around the water problem to the source terminal pole on the other side.

The foreman attached the transmitter of a cable tracer to the telephone cable at the development side pedestal. With a sensor to pick up the signal, Tom marked the location of the cable on the ground.

The telephone company maps showed the telephone cable had been installed in joint trench with the electric and cable TV cables. Since the NESC® in Rule 353D requires the power company high voltage cables to be installed at a minimum depth of 30 inches, the backhoe operator carefully dug down about 24 inches. So as not to damage the other cables, Tom and the backhoe operator dug the next 6 inches by hand. They found three jacketed cables: one about 0.9 inches in diameter and two cables about 1.3 inches in diameter. The cables were only a few inches apart. One of the larger cables was clearly marked with a lightning bolt and wording that indicated that it was a power cable. The NESC® in Rule 350G requires all direct buried communication cables and jacketed supply cables installed after January 1, 1996 to be marked with an identification symbol at spacing not more than 40 inches. The symbol for power cables is a lightning bolt. The symbol for communication cables is a telephone hand set. The marking is only required on one side of the cable.

Since one of the two large cables was marked and the cable TV cable is usually smaller than the telephone cable, the unmarked large cable was assumed to be the telephone cable. Since the transmitter of the cable tracer was still attached to the telephone cable at the pedestal, they tried to confirm their assumption. Because the cables were so close together, the sensor could not confirm their assumption. Tom was directed to cut the unmarked large cable . . .

Fortunately for Tom, his partners knew CPR and a paramedic team was only a few minutes away.

Photo 1

Photo 1

The investigation found that the two large cables were both power cables energized at 7200 Volts. The marking on the cable Tom cut was on the underside. The fault current that vaporized Tom’s cable cutter was about 9,000 Amps. The smaller cable was the cable TV cable. It was marked with a blue stripe facing to the side. The telephone cable they were looking for was next to the cable TV cable in undisturbed soil. It was only marked with the manufacturer’s name.

The NESC® in Rule 352 requires a horizontal minimum separation of 12 inches between direct buried supply and communication cables to permit access to and maintenance of either facility. The cables involved in the accident had been installed in "Random Separation.” "Random Separation,” supply and communication cables buried together at the same depth with no deliberate separation, is allowed by the NESC® in Rule 354 but only where the applicable requirements of Rule 354D are met and all parties are in agreement. The joint trench agreement between the telephone and power company did not mention "Random Separation.” The two companies’ construction standards only showed the NESC® 12-inch minimum. The work orders that directed the crews to install the cables spoke only of joint trench. Obviously, the crews who installed the cables were in agreement. But were the companies in agreement? The cable tracer equipment could not distinguish between cables installed so close together. The NESC® in Rule 423E requires positive identification before cutting into a cable. Did the people responsible for purchasing the tracer equipment know about the "random separation”? Had the crews been properly trained as to the hazards of random separation? Were the companies in agreement?

Photo 2

Photo 2

Even when the cable is marked, it’s a 50/50 chance that the marking faces down. If companies are going to do "Random Separation” to reduce trench expense, the employees must be properly trained and have the proper tools to deal with cables in close proximity.

Tom took the power company to court and Tom won. OSHA fined the telephone company. How much money did the companies really save going with "Random Separation”? [See photo 1]

Test yourself:Which of the four cables is the three hundred pair telephone cable? [See photo 2]

From left to right, the first cable is a cable TV cable (diameter 0.93″). The second cable is a 25kV class high-voltage cable (diameter 1.26″). The third cable is a 15kV class high-voltage cable (diameter 1.10″”). The fourth cable is a 300 pair telephone cable (diameter 1.30”).


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Tags:  January-February 1999  Other Code 

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A Closer Look: Looking at Article 240 Through the 1999 NEC

Posted By John E. Brezan, Friday, January 01, 1999
Updated: Monday, August 27, 2012

For those of us who have been using the NEC for a number of years, when looking at the 1999 edition, we see a whole new document. This will be a cycle of relearning what we already know. Along with the changes is the relocation of a lot of existing information. It would be impossible to explain all of the rework and changes in Article 240 in just one short article. It is my recommendation that you check the IAEI News for a seminar in your area and attend it.

But let us browse through Article 240, examining the highlights briefly:

Section 240-3(d) Small Conductors is a relocation from the bottom of Table 310-16. There is not anything new here; it was felt that the rule would be better served if this information were located in the Overcurrent Protection Article and that it would, possibly, be easier to find.

Section 240-3(e) Tap Conductors now have a definition of their own as used in 240. In the past there were major abuse and misuse of the rules for a tap conductor and there was not a clear statement as to what a tap conductor is. Hopefully the definition will clear up any questions as to what is a tap conductor.

Section 240-6(c) Restricted Access Adjustable-Trip Circuit Breakers now defines what "”restricted”" means and what has to be done to comply with the rules of installation. There are three ways to restrict access and at least one of the three must be met.

Section 240-21 Location in Circuit has undergone some major rewrite that did not cause any code requirement changes but it will make life a lot easier when applying the rules. There is now a separation of taps to feeders from the requirement for transformer secondaries.

Section 240-21(a) has been divided into two parts: (a) Branch-Circuit Conductors specifies that for this tap one must comply with Section 210-19. The new (b) Feeder Taps lets one know that he is now in the rules for feeder taps. The wording in the 10 ft. tap rule was changed from "”the line side of the tap conductor shall not exceed 1,000 percent of the tap conductor’s ampacity”" to "”shall not exceed 10 times the ampacity of the tap conductor.”" This change was made simply to make the understanding of the math easier. If this still confuses some people you could always do the math both ways. The greatest change was really the rearrangement so that all of the 10 ft. rules are in one location and all of the 25 ft. rules are in another location and so on, you get the idea.

Under Section 240-21(b)(5) Outside Taps of Unlimited Length did not see any significant changes here. Perhaps the most significant event here is something that did not happen. There were a number of proposals and comments for the rule to allow termination in up to six disconnects instead of one. The main argument here was that it is felt, by the proposers and commenters, the number of disconnects should follow the same rules as Service Equipment. The panel felt that they should not be treated the same because of the differences between the two and that there would be less overloading of the tap conductors if limited to one disconnect rather than a maximum of six. I think this one will be back.

There is an interesting clarification to Section 240-21(g) Conductors from Generator Terminals that now spells out that the conductors are not protected from short-circuit or ground-fault under the specifications of 445-4. The conductor sizing has changed and the wording in 445-5 provides for additional language for the sizing of these conductors to afford them the protection needed.

These are some of the changes and relocation of information in 240, but there are some major changes that I did not even mention. I hope you found this to be of interest and may have even picked up some new information that will be of help to you in this new code cycle. I hope that I have an opportunity to present some more of Article 240 in the future such as the new Part H and the rewrite of Part I. Please do not feel as though you have to wait for me, let one of the IAEI Seminars introduce you to these exciting changes. Check your magazine for dates and places, and check with your local chapter.


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Tags:  Closer Look  January-February 1999 

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Which GTO cable types may be used in electric signs?

Posted By Underwriters Laboratories , Friday, January 01, 1999
Updated: Monday, August 27, 2012

Question: GTO cable

Which GTO cable types may be used in electric signs? I am especially interested in the cable that looks like a coaxial cable.

Answer

The following GTO cable types may be used in electric signs (UXYT), and in field-installed skeleton tubing (UZBL):

GTO Cable (general information)

— GTO cable is listed under UL’s category Gas Tube Sign and Ignition Cable (ZJQX) in the General Information Directory (white book) and Electrical Construction Equipment Directory (green book). UL listed GTO cable is available in three voltage ratings, 5 kV, 10 kV, and 15 kV, which correspond to the UL designations GTO-5, GTO-10 and GTO-15, respectively. The voltage rating and corresponding designation are marked on the cable.

GTO cable used in electric signs is rated for a maximum service temperature of 60°C, unless marked otherwise. The construction of GTO cable consists of a single stranded conductor of a size ranging from No. 18-10 AWG, which is also marked on the cable. The insulation consists of a single layer, with or without an outer jacket.

GTO Cable With Braided Shield —

The GTO cable construction that resembles a coaxial cable includes a braided shield over the high voltage insulation and has an outer polymeric jacket over the shield. This cable construction is UL listed and has been evaluated for the same applications as GTO cable.

GTO Cable Used With GTO Cable

Sleeving — For UL Listed Signs (UXYT), listed GTO cable may be used only within the sign or other electrical enclosure, or installed using one of the wiring methods specified in UL 48, Standard for Electric Signs. In place of the specified wiring methods, exposed lengths of GTO cable used in dry and damp locations may be provided with UL Listed GTO Cable Sleeving (UYMR, Sign Accessories). GTO cable used with Listed GTO Cable Sleeving has not been evaluated by UL for use in wet locations or where concealed within a wall or attic, or above a suspended ceiling.

GTO Cable With Integral Sleeve —

Listed GTO cable marked "LISTED WITH INTEGRAL SLEEVE” is similar to GTO cable, except the insulation is thicker for the integral sleeve cable. GTO cable with integral sleeve is intended to be used in the same manner as GTO cable with Listed GTO Cable Sleeving. Supplemental cable sleeving is not required for integral sleeve GTO cable.

GTO Cable Used in Field-Installed

Skeleton Tubing – When used in fieldinstalled skeleton tubing, GTO cable must be installed in accordance with Part B of Article 600 of the NEC®. UL listed field-assembled systems, intended for permanent installation in accordance with Article 600, are covered under the category Field Assembled Skeletal Neon and Outline Lighting Systems (UZBL).


Question: Daisy-chaining outlet strips

I have been told that "daisy-chaining” outlet strips may present a potential fire and/or electrical hazard. I want to use two listed strips, each with integral 10A overcurrent protection, connected in series, to provide power to several pieces of computer equipment on adjacent desks. The total connected load would be less than 10A. Would you comment on whether (or why) this may be a fire hazard or dangerous practice, if all other requirements of the NEC® are followed? What other applications for extension cords might create a safety concern?

Answer

Extension cords (cord sets) and outlet strips (relocatable power taps) are not intended to be used as a substitute for fixed wiring in a structure. They provide power to portable appliances, such as personal computers and peripherals. Relocatable power taps are considered extensions of the branch circuit. Therefore, they are intended to plug directly into a branch-circuit outlet, not another relocatable power tap or an extension cord. Extension cords are intended to extend the power supply cord of electrical equipment, and should be marked with a current rating sufficient for the load of the connected equipment.

Use of these devices in series has not been evaluated by UL. Potential overheating can be one concern with a series arrangement. Other considerations in a seriesconnected arrangement include the reaction between overcurrent protective devices on relocatable power taps, increased voltage drop, potential tripping hazards, and an increased likelihood that additional available outlets may lead to an overload.

Extension cords attached to building surfaces with staples or other connectors may be subject to weathering, damage from the staples, mechanical abuse, strain or repeated flexing. In some cases, they may be placed under carpet, through holes in walls, floors, or ceilings: or through openings in partitions with sharp edges. These are conditions that can result in damage to the insulation or conductors, and increase the likelihood of an electric shock or fire. In these situations, the extension cords are a substitute for fixed wiring in a structure, which is prohibited by Section 400-8 of the NEC®.

While the NEC® doesn’t specifically reference series-connection of relocatable power taps or extension cords, this arrangement is prohibited by the Uniform Fire Code (UFC), Section 8508.3, and the 2000 International Fire Code (IFC)-Final Draft, Section 605.4.2. These Codes indicate that power taps are required to be directly connected to a permanently installed receptacle. Regarding extension cords, the UFC and IFC Final Draft each require that extension cords be plugged directly into an approved receptacle, power tap or multiplug adapter.


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Tags:  January-February 1999  UL Question Corner 

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IAEI Chapters Promoting Good Education

Posted By Philip Cox, Friday, January 01, 1999
Updated: Monday, August 27, 2012

Two major purposes of the IAEI is to promote the uniform understanding and application of the NEC and other electrical codes and to collect and disseminate information relative to the safe use of electricity. In trying to achieve these objectives or goals, the IAEI focuses on education for both its members and the electrical industry in general. This is a great challenge. The IAEI staff and other contributors work hard to develop and produce educational material of a quality that can be readily used as learning tools for self motivated people who learn well through their own study and for others who prefer the classroom setting. With every educational product developed, ongoing review of the material is made to see where improvements can be made to help users get more out of the material. Good education and the continual improvement of both knowledge and skills can have a positive effect on electrical safety. Knowledge and skill will not on their own make electrical installations better or the use of electrical systems safer. However, when a person has achieved those and works hard to properly apply them, the end result will be very beneficial.

IAEI sections, chapters, and divisions provide excellent opportunities for electrical training through the many conferences and training programs they conduct. These programs can complement the work done by the IAEI international office. In fact, some work closely with the IAEI international office in conducting either IO developed seminar programs or jointly developed educational programs. Coordinated joint effort involving chapters and the IO can work well in most cases and can be beneficial to IAEI members. Several chapters have effective education programs and, in addition to providing training, attract a number of new members. They do it through dedication to promoting good education and through well-organized and effectively run chapter programs. It takes strong and dedicated leaders in those chapters to do the job they do and they don’t hesitate to make the effort. All IAEI sections, chapters, and divisions working hard and achieving success are to be commended.

It is appropriate to single out one chapter that has consistently reached a high level of achievement. That chapter has shown support for the international office, used IAEI developed training materials, and has worked as a partner in promoting the IAEI education program. I doubt that anyone is surprised to learn that the Wisconsin Chapter has once again set the pace and provided a good example for other chapters. Wisconsin Chapter members have set their sights high for 1999. A number of seminars on the Analysis of the 1999 National Electrical Code® have been scheduled within the state of Wisconsin during the first part of 1999. As of the date of this writing, over 1,000 people have preregistered for those seminars. Those seminars will be conducted using the IAEI material and qualified chapter members will conduct the training. Chapter members have conducted training programs within the state of Wisconsin for several years in a row. Not many chapters can attract the number of people that the Wisconsin Chapter does, but the potential is there for reaching many people who need to get more involved and become more familiar with electrical safety.


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Tags:  Editorial  January-February 1999 

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