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A Closer Look: Article 695, Fire Pumps

Posted By Robert Duncan, Monday, March 01, 1999
Updated: Monday, August 27, 2012

Article 695 first appeared in the 1996 National Electrical Code, it covers the electrical construction and installation portion for Fire Pumps. The performance, maintenance and testing requirements are in NFPA 20.

The committee received 23 proposals during the proposal stage and received 34 public comments during the comment period.

In Article 695 portions are marked with a superscript "”x”" which means it is extracted material from NFPA 20, Standard for the Installation of Centrifugal Fire Pumps. This reflects the work of both CMP 15 and NFPA 20 which has been supported by a joint task group of members of both committees which has been very helpful in providing a good working arrangement with both groups.

The following are some of the significant changes that appear in Article 695 of the 1999 NEC.

Section 695-3 has probably had the most significant changes. The power sources for Electric Motor-Driver Fire Pumps must be reliable and capable of carrying the sum of the locked-rotor current of the hre pump motor (s) and the pressure monitor pump motor(s) and the full-load current of any hre pump accessory equipment when connected to this power sources. Power sources may be one of three types.

  1. A separate utility service.
  2. On-site power production facility.3. Multiple Sources, which are a combination of a generator, Separate service or feeder source, when approved by the authority having iurisdiction.

Section 695-3(b)(2) was added to the 1999 NEC to cover independent feeders serving multiple buildings. This section requires the supply conductors to comply with Section 695-4(b).

Section 695-6 was revised to eliminate some exceptions and to clarify the requirements. 695-6~ address the conductor sizing is based on 125 percent of the fire pump motor and 100 percent of any associated fire pump accessory equipment and not based on the locked rotor current of the fire pump.

Section 695-6(e) now permits the use of Flexible nonmetallic conduct Type LFNC-B as a wiring method for pumps.

Section 695-6(fl reflects that the UL listing requires that no other loads, other than the fire pump motor are to be connected to the fire pump power transfer switch.

Section 695-7 was added to clarify that voltage drop is from the power source and not the power wiring.

Section 695-10 requires the Fire Pump Controller, Transfer Switches and Motors are required to be listed for fire pump service. This requirement has been in NFPA 20 and is not included in Article 695. UL currently has companies that have their equipment listed.


About Robert Duncan: Robert C. (Bob) Duncan, IAEI Representative CMP-15, has been a member of CMP-15 since 1987. Member NFPA 20, Fire Pumps Member NFPA 96, Ventilation Control and Fire Protection of Commercial Cooking Operations. Member ASME A17.1 Safety Code for Elevators and Escalators, Electrical Committee Member NFPA, Past IAEI Chairman Southern Section, Florida Chapter and Central Florida Division.

Tags:  Closer Look  March-April 1999 

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Changes in the Canadian Electrical Code (1998): Sections 18 and 20

Posted By Leslie Stoch, Monday, March 01, 1999
Updated: Monday, August 27, 2012

Sections 18 and 20 of the Canadian Electrical Code define hazardous locations and specify the types of electrical equipment and wiring methods acceptable in areas where flammable or explosive materials are handled, stored or produced. In such areas, the risk of a fire or explosion may exist due to the presence of flammable gases or vapours. The electrical code provides requirements for protection in hazardous locations, from electrical ignition sources, due to the effects of electrical arcing or heating.

Sections 18 and 20 have always seemed rather complicated to the average person. Now they may seem even more so, since we have just inherited two different methods for classifying Class I hazardous locations and methods of protection for each. As you begin to peruse the 1998 Canadian Electrical Code, Sections 18 and 20, you will notice some major changes. Class I locations are now defined as "explosive gas atmospheres,” which contain "a mixture with air, under atmospheric conditions, of flammable substances in the form of gas, vapour or mist–”. In other words, if a flammable or explosive gas, vapour or mist can occur, the area must be classified.

You will also discover that the two-division system has been replaced by three zones. At the beginning, I should point out that both systems result in a safe installation when equipment and wiring are correctly installed. In this article, let’s review the differences and similarities between the old system of classification and the new.

In the 1994 CEC version, Class I hazardous locations had two divisions:

Division 1– where flammable gases or vapours exist:

  • Continuously, intermittently or periodically
  • Due to repair, maintenance or leakage
  • Due to breakdown or faulty operation

Division 2– where flammable gases or vapours:

  • Are in closed systems or containers
  • Where prevented by positive mechanical ventilation
  • Next to a Division 1 location, with positive air pressure

In the 1998 CEC, the 1994 requirements have been moved to Appendix J, and the earlier requirements have been replaced by the new IEC system in Sections 18 and 20.

In the new 1998 CEC, Class I hazardous locations are divided into three zones in accordance with the European IEC classification system, which recognizes a higher hazard level than we are accustomed to in North America:

Zone 0– where an explosive gas atmosphere exists continually or for long periods. It is estimated that such locations are found in only 1% of hazardous location installations. Under our Division system, Zone 0 would have fallen within Division 1, but with no special recognition of a higher hazard level.

Zone 1- where an explosive gas atmosphere:

  • Is likely to occur in normal operation
  • May exist due to repair, maintenance or leakage
  • Is next to a Zone 1 location

Zone 2– where an explosive gas atmosphere:

  • Is unlikely, but may occur for a short time
  • Flammable materials may be handled, stored, used or contained in a closed system
  • Next to a Zone 1 location with positive air pressure

You may have noticed that the definitions for Zones 1 and 2 are almost identical to our old Divisions 1 and 2. The big change is Zone 0, which is intended to contain the most hazardous conditions.

In the 1998 CEC, the Scope paragraph of Section 18 prescribes application of the new zone classification system as follows:

  • The Division system of classification may still be used for additions, modifications and renovations to existing facilities
  • Appendix J requirements are to be followed when classifications are made in accordance with the Division system
  • Class I, Zone 2 electrical equipment may also be installed in a Class I, Division 2 hazardous location

Eventually, you may find that the provincial and territorial electrical code authorities may still decide to amend the application of the new system of classification.

Where the old system required the use of explosion-proof electrical equipment, the new system permits a wider assortment of equipment types, all of which can satisfy code requirements when correctly applied.

Zone ILocations – may have equipment of the following types:

  • Class I, Division 1
  • Intrinsically safe – creates insufficient energy to ignite a fire or explosion
  • Flameproof – similar to explosion-proof
  • Increased safety – a method of ensuring connections don’t come loose, causing sparking or overheating
  • Oil-immersed
  • Pressurized – using a protective gas
  • Sand-filled
  • Encapsulated – arcing contacts are enclosed within a com pound

Zone 2locations – may have equipment of the following types:

  • Class I, Division 1 or 2
  • Intrinsically safe
  • Equipment permitted in Zone 1
  • Non-sparking
  • Nonincendive – a form of intrinsic safety, but only incapable of causing an ignition under normal conditions
  • No-arcing, sparking or heat- producing

In some cases, electrical equipment may use more than one of the above protection methods.

You may also have noted that wiring methods for Zones 1 and 2 are quite similar to Divisions 1 and 2, except that:

  • Non-tapered threads are acceptable, but in some atmospheric groups, must have at least eight engaged threads
  • Adaptors must be used where wiring systems and equipment have different threadforms
  • Some equipment has factory- made seals and does not require field-installed seals

Only intrinsically safe electrical equipment marked ExI or Exia is permitted in Zone 0. Intrinsically safe circuits are usually instrument wiring to sensors in the Zone 0 hazardous locations. An example of a Zone 0 location is within the nozzle boot of a gasoline dispenser.

Intrinsically safe electrical equipment does not require a flame-proof enclosure, field-installed sealing or any other protection method. However, field-installed seals are required at:

  • The point where conduit leaves a Zone 0 location
  • The first termination after a cable enters the Zone 0 location.

All flammable gases and vapours are grouped according to their common explosive characteristics. Under the North American system, four levels are used – A, B, C and D. The IEC system uses three levels – IIA, IIB and IIC. Both designation systems are found in the 1998 CEC. In the IEC system, electrical equipment temperature codes are reduced from fourteen to six.

As in past articles, your local inspection authority should be consulted for a precise interpretation of any of the above in each province or territory as applicable.


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Tags:  Canadian Code  March-April 1999 

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An Inspector’s Most Common Hazardous Conditions

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

I spend a lot of time inspecting electric supply facilities for hazardous conditions and violations of the National Electrical Safety Code® (NESC®). Even when I’m on vacation, I don’t stop inspecting. I’ve shared the "problems” with my wife so often that now she points them out to me. I’ve driven all over the United States and find that no matter where I go, the hazards are out there, particularly in non-utility owned supply facilities.

The most common hazard I see with substations is access by non-qualified persons. A substation (electric supply station) by definition is an area within which electric supply equipment is located and the interior of which is only accessible to qualified persons. Qualified persons are people having adequate knowledge of the installation, construction and operation of apparatus and the hazards involved. The clearance requirements of the NESC inside a substation are not as stringent as the clearance requirements for electrical facilities located in areas accessible to the general public because the substation is not accessible to the general public. When we allow the general public (non-qualified persons) in substations, we are asking for trouble.

How do we keep non-qualified people out?

Photo 1. When the grade is raised next to a fence, the fence height must be adjusted

Photo 1. When the grade is raised next to a fence, the fence height must be adjusted

1. The surrounding fence must be at least 7-foot tall (Rule 110A1). Because chain link fences are so easy to climb, particularly by children, it is my opinion that a chain link fence without barbed wire is not an effective barrier. When the grade is raised next to a fence, the fence height must be adjusted. (See photo 1)

Remove Aids to Climbing:

If a parking lot is adjacent to a substation, appropriate barriers should be used to prevent vehicle parking and dumpsters up against the fence.

2. The fence and gates must extend to the ground. The roadway under gates must be reconditioned after heavy use. If the roadway under gates is subject to washout, the roadway should be paved. (See photo 2:)

Photo 2. The roadway under gates must be reconditioned after heavy use. If the roadway under gates is subject to washout, the roadway should be paved

Photo 2. The roadway under gates must be reconditioned after heavy use. If the roadway under gates is subject to washout, the roadway should be paved

3. Warn the public of the hazards inside the substation with appropriate WARNING signs in compliance with ANSI® standard Z535 at least at each entrance and on each side (Rule 110A1). ANSI Z535 recommends that the signs shall be so placed to alert the viewer in sufficient time to take appropriate action to avoid harm.

Photo 3. The second most common substation hazard is lack of grounding

Photo 3. The second most common substation hazard is lack of grounding

4. Do not store materials within a substation even if such materials are stored well away from energized conductors and equipment (Rule 110B2). The storage of materials within a substation invites non-qualified personnel like material delivery personnel and thieves.

The second most common substation hazard is lack of grounding. (See photo 3)

Photo 4.

Photo 4.

The metal fence surrounding the substation and all non-current-carrying metals parts within the substation must be electrically bonded together and effectively grounded (Rule 123A). The grounding methods must be in compliance with Section 9 of the NESC. The grounding must be designed to limit tough, step and transferred voltages in accordance with industry practice. IEEE standard 80 is one source that may be utilized to provide guidance in meeting these requirements. To meet these requirements, usually a ground grid must be installed under the substation with grounding conductors bonding the fence and non-current-carrying parts to the grid.

The most common hazard I see with overhead lines is inadequate ground clearance or clearance to other structures, particularly signs.

Photo 5.

Photo 5.

Most overhead hazards are created by people who change the environment around the supply facilities, not by the people who originally constructed the facilities. For example, an overhead high voltage line was constructed to serve a large industrial company. The property between the utility service point and the customer’s substation was designated "employee parking.” The line was designed to meet the vertical clearance requirements of the NESC as stated in Rule 232 for an area accessible to truck traffic. Five years later, the management of the company decided to make the employee parking lot into a raw material storage area complete with a crane to move the materials. The use of the land under the overhead line was changed. The line should have been moved. (See Photo 4 & 5)

If you have general questions about the NESC, please call me at 302-454-4910 or e-mail me at dave.young@conectiv.com.

National Electrical Safety Code, NESC and IEEE are registered trademarks of the Institute of Electrical and Electronics Engineers. ANSI® is a registered trademark of the American National Standards Institute. ANSI Z535 is a publication of the National Electrical Manufacturers Association (NEMA).


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Tags:  March-April 1999  Other Code 

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I recently encountered a lightning protection system on a water treatment plant that was certified by UL. What is a “Letter of Findings”?

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

Question: Letter of findings

I recently encountered a lightning protection system on a water treatment plant that was certified by UL with what was referred to as a ‘Letter of Findings.’ The only type of lightning protection certification I’m familiar with is the UL Master Label. What is a ‘Letter of Findings,’ and what other types of certifications currently are available for lightning protection systems?

Answer

A Letter of Findings is one of the three basic types of certifications that Underwriters Laboratories Inc. provides for lightning protection systems. The others are the more recognized Master Label and Reconditioned Master Label certifications. Below is a description of each of these programs.

Master Label — The Master Label is a Listing Mark that covers a lightning protection system installed in accordance with UL 96A, Installation Requirements for Lightning Protection Systems. With any certification based on UL 96A, there are limitations regarding the types of buildings that may qualify for the protection system. Buildings that do not qualify for a Master Label include those that handle, process or store flammable or explosive materials and structures with incomplete lightning protection systems. A partially protected structure may include a church where only the steeple is protected or a school where only the chimney is protected. Other examples of partial protection include a series of interconnected buildings where only one building is protected and the others are not, or interconnected buildings where both buildings have systems, but only one system complies with the current Standard UL 96A.

Reconditioned Master Label – The Reconditioned Master Label is a Listing Mark that covers a lightning protection system that has been refurbished or expanded to comply with UL 96A. This type of certification is identical in scope with the Master Label, except that it applies only to refurbished systems.

Letters of Findings – UL’s Letters of Findings indicate that an isolated roof section or an entire building complies with either UL 96A, NFPA 780 or Army Material Command (AMC) Regulation 385-100. The requirement regarding the size of an isolated roof section states that firewalls or similar means of building separation must isolate the protected roof section from other sections of the roof.

The lightning protection system must also be complete within itself (i.e., have the proper number of down conductors and air terminals for its size, etc.).

The following Standards include the noted limitations:

UL 96A, Installation Requirements for Lightning Protection Systems – This Standard does not cover buildings that store or handle explosive materials, flammable liquids, or flammable gases. NFPA 780, Lightning Protection Code – This standard does not cover buildings that house explosive materials.

AMC-R 385-100, Safety Manual — This standard does not include limitations.


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Tags:  March-April 1999  UL Question Corner 

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Electrical Inspector Certification Program in the United States

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

Certification is an important step in the progression of becoming a truly professional, highly trained and skilled electrical inspector. The Canadian Section of the IAEI promotes an inspector certification program in Canada and operates separately from its counterpart in the United States. An article on the Canadian Electrical Inspector Certification Program is scheduled for a later date.

The IAEI participates in an electrical inspector certification program along with the Building Officials & Code Administrators International (BOCA). Several states also participate in the program. BOCA and the state of New Jersey had major roles in the development and implementation of the program. The Educational Testing Service of New Jersey worked with the sponsoring organizations in providing professional services in both development and administration. The Chauncey Group International presently serves as the administrator for the program. Other inspector certification programs also exist. The International Conference of Building Officials (ICBO) and the Southern Building Code Congress International (SBCCI) each have an inspector certification program. The IAEI and ICBO have a memorandum of understanding to recognize one another’s certification.

IAEI Bylaws include provisions that contain the basic framework for establishing and maintaining an inspector certification program. They are: "The IAEI is to establish an electrical inspector certification program designed to meet all IAEI program objectives and, if deemed necessary, to participate with other national, regional, state or provincial authorities, agencies or groups in established and recognized certification programs. The IAEI program is to have inspector certification modules consisting of not less than: (1) Electrical Inspector, General; (2) Electrical Inspector, One- and Two-Family; and (3) Electrical Inspector, Plan Review.” In following this provision of the IAEI Bylaws, the IAEI actively works within the established program to assist in providing the necessary administrative and technical support to help make the existing program meet its objectives.

One objective that the IAEI has not achieved is the implementation of a recertification program to help those who hold inspector certificates maintain an acceptable level of continued training. The provisions authorizing a recertification program are already in the IAEI Bylaws and plans are to take steps necessary to have the program operational by the end of the year. It is important for this service to be offered to members and others who hold certification issued by the IAEI. The IAEI education committee is scheduled to meet within a few months and one major item on the agenda is to provide recommendations on how to best implement the program. Additional provisions or guidelines need to be developed before the recertification program can be fully functional. In addition to meeting the need of IAEI certificate holders, it is important that the program implemented will also be recognized by other organizations which have recertification programs.

While the existing program used by the IAEI effectively tests a person’s knowledge of the Code, recommendations are coming from within the electrical industry to develop a more comprehensive inspector certification program. Concern expressed by industry is that one who has no experience in electrical construction can become certified through existing programs simply by learning Code rules well enough to pass the examination. The complaint is that knowing what the Code rules are does not necessarily mean that the individual either understands the significance of the rules or knows how to apply them. It is stressed that an electrical inspector must not only know electrical code rules, but he or she must also understand electricity and electrical systems in order to know how to evaluate what they see in an actual installation in the field and know how and when to properly apply Code rules. The issues raised by members of the electrical industry will need to be addressed in the near future.


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Tags:  Editorial  March-April 1999 

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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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Grounding & Bonding

Posted By Leslie Stoch, Sunday, November 01, 1998
Updated: Friday, August 24, 2012

The Canadian Electrical Code has a long and precise definition for grounding as: "a permanent and continuous conducting path to the earth with sufficient ampacity to carry any fault current liable to be imposed upon it, and of sufficiently low impedance to limit the voltage rise above ground and to facilitate the operation of the protective devices in the circuit.” When we talk about grounding, we are usually thinking about electrical systems.

The code has an equally precise, but not as lengthy definition for bonding as: "a low impedance path obtained by permanently joining all non-current-carrying metal parts to assure electrical continuity and having the capacity to conduct safely any current likely to be imposed upon it. When we talk about bonding, we are usually thinking about metallic items such as equipment enclosures.

The rules for grounding and bonding are designed to protect people and property against the dangers of electrical shocks and electrically caused fires by:

  • Limiting electrical circuit voltages
  • Minimizing differences in potential between metal objects such as equipment enclosures and other grounded metal.
  • Making sure that fuses and breakers trip promptly when they should
  • Reducing voltage surges caused by lightning or other causes.

The code specifies that alternating current systems must be connected to ground for voltages up to 150 phase to ground or if the system carries a neutral.

The code also provides a number of exceptions where it would be more hazardous or impractical to operate with a grounded electrical system.

One such exception is electrical arc furnaces. It would be easy to see why a grounded system would be impracticable and maybe even hazardous, since the return currents might find many paths back to its source.

Another exception would be isolated circuits such as wiring to the underwater speakers in a swimming pool. If these circuits were to be grounded, under fault conditions, there could be a higher possibility of current flow in the water, which could be very hazardous to swimmers.

A third exception to the rule is an electric crane running across a hazardous area containing combustible fibres. It would be easy to see why it is advisable to eliminate some of the arcing and sparking risks so as to minimize the possibility of fire.

The code has some very specific requirements for grounding an electrical system. The system must be connected to ground once at the owner’s main substation or by the electrical utility and once again in the owner’s main service. The code prohibits any connections to ground once past the owner’s main electrical service.

This requirement has two main purposes:

  • To maintain control of return currents by ensuring that they flow only on the insulated neutral conductor and not select random paths back to their source; and
  • To ensure that the ground fault protection in switchboards will operate accurately and when it should.

The code is also very specific about bonding. It specifies that except for double insulated devices, metallic electrical equipment enclosures and raceways must be bonded to each other and to ground by a number of acceptable means such as bonding wires, busbars, metallic cable sheaths or metallic raceways.

The code prohibits using the identified circuit conductor (neutral) as the means of bonding electrical enclosures. Once again, there are several valid reasons:

  • To maintain control of return currents as above; and
  • To avoid grounding the electrical system past the main service, which the code prohibits; and
  • To avoid the possibility that equipment enclosures could become live should the identified conductor (neutral) become accidentally disconnected.

The code goes to great lengths to ensure that all related metal objects remain at ground potential and do not develop differences in potential to each other. For these reasons, it specifies that in addition to the above, we must also bond to ground all of the following with a building:

  • Metal water piping when not used for grounding the electrical system
  • Metal gas piping
  • Metal waste piping
  • Metal supports for computer room floors

In dairy barns and other agricultural buildings where small differences in potential can have harmful effects upon animals (tingle voltages), all metal is bonded together, including all water piping, stanchions, water bowls, vacuum lines an even the floors where cattle are milked.

Another area where very small potential differences can be dangerous to people is that area in or around swimming pools. Section 68 of the code includes some very precise requirements for bonding all of the metal objects in the vicinity of a pool, in particular when electrical equipment is used within three metres of the pool.

As in previous articles, you should seek the advice of your local inspection authorities for an exact interpretation of any of the above as they apply in each province or territory.

Some Special Requirements

Several months ago in two previous articles, we covered some of the standard grounding and bond fundamentals contained in the Canadian Electrical Code. Now let’s look at some less usual or more interesting code requirements covering some special circumstances. It’s unlikely that all of our readers will have had an opportunity to employ all of the following.

One excellent example is Rule 18-132(2), which deals with bonding electrical equipment in Class I, Division 1 hazardous locations. Such locations contain dangerous concentrations of flammable gases or vapours which may ignite or explode on occurrence of a spark due to any cause including a loose bonding connection.

You may not be aware that Rule 18-132(2) has some exceptional bonding rules for electrical circuits, not only within the hazardous location, but also within the non-hazardous location from which the hazardous location circuit is supplied. (See Sketch A). This rule refers us to Rule 10-606(1)(a), (c) and (d), and Rule 10-60(2) (Means of Assuring Continuity at Service Equipment).

In simpler terms this combination of CEC rules tells us that circuit bonding in Class I, Division 1 hazardous locations and the rest of each circuit originating outside the hazardous location, must satisfy the special CEC conditions normally reserved for bonding on the supply side of customer main services.

As a direct result, electrical circuits in Class I, Division 1 hazardous locations and all the way back to their points of supply are restricted to the following methods of bonding and bonding connections:

  • Bonding conductors
  • Threaded couplings and bosses
  • Grounding bushings and bonding jumpers
  • Standard locknuts and bushings are insufficient and you will notice that EMT connections are not anywhere included in this list.

I have always interpreted the above rules as applying to only a complete circuit from its source (such as a distribution panelboard or motor control centre) in a non-hazardous location to electrical equipment in a hazardous location. But do these rules also affect the feeders upstream from these sources and perhaps back to the main substation? I hope someone can enlighten me. The code is not very specific on that point and I’m afraid you’ll have to discuss that issue with your local inspector for the best interpretation.

Livestock buildings and facilities also necessitate special grounding and bonding practices. CEC Rule 10-402(4) specifies that livestock waterers must be bonded with minimum #6 AWG copper conductors. Also, Rule 10-406(5) requires that all metal such as water pipes, vacuum lines, water bowls and stanchions must be bonded with #6AWG copper conductors.

For what reasons do we need these heavy wire sizes and special precautions? Tingle voltages (between electrical objects and the floor or between metal objects) in livestock buildings or other areas may originate from electrical ground faults in farm buildings or neutral potentials from primary electrical distribution systems. Cattle are extremely sensitive to very small voltages and will refuse to drink if tingle voltages are present in water bowls. They may also withhold milk during milking. Both of these actions along with their general unease in the presence of tingle voltages may lead to deterioration in health and a loss of production.

For these reasons and for safety reasons the CEC has created some special grounding and bonding requirements in livestock areas where these conditions may exist. To supplement the effectiveness of these rules, a device sometimes called tingle voltage filter is also available.

I am sure you already know that Rule 10-204 specifies that AC services, when required to be grounded, must only be grounded once at the customer’s main electrical service and once again back at the transformer supplying the service. Rule 10-204(1)(d) also prohibits any grounding or bonding connections to the system neutral downstream from the main service.

This sub-rule has two important purposes. It is designed to prevent grounding and bonding conductors, metal piping, ducts, cable sheaths or building structures from becoming parallel paths for unbalanced neutral currents. It also ensures that electrical system ground fault protection will operate effectively to eliminate dangerous and destructive arcing ground faults when called upon.

If that be the case, how do we treat an emergency standby generator which must have its neutral interconnected with the building system neutral? If the generator neutral is interconnected with its case inside the machine, there is no choice but to provide multi-pole switching to disconnect the generator neutral simultaneously with the phase conductors. If the neutral is isolated from the case and if not separately grounded, the neutral does not require disconnection from the electrical system neutral, but a separate grounding conductor must be installed to the generator case.

As with past articles, please consult your local electrical inspector in each province or territory for an exact interpretation of the above as applicable.


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Tags:  Canadian Code  November-December 1998 

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