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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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Behind the Meter Cover

Posted By Joseph Wages, Jr., Tuesday, January 01, 2013
Updated: Friday, December 14, 2012

Think you might know what lurks behind the meter cover? Chances are you will think twice after reading this article!

Electrical Metering Devices

Meter enclosures are part of every electrical system. But how often do you look inside the enclosure after it has been installed and energized? A utility provider provides electricity to a customer in order to make a profit. Typically, this is accomplished by metering the electrical system at the point of connection. Electronic receiver/transmitter (ERT) meters are becoming more of the norm in today’s electrical metering systems. They provide many benefits to the electric utility provider and to the customer. But, this could allow for many unforeseen problems as well.

Photo 1. A 400-ampere, single-phase meter enclosure located at the front entrance of a church and preschool. Men, women, and children visiting this location walk by this meter enclosure on a daily basis. What’s located behind the cover could prove deadly! And chances are it will not be discovered until there is a problem.

Photo 1. A 400-ampere, single-phase meter enclosure located at the front entrance of a church and preschool. Men, women, and children visiting this location walk by this meter enclosure on a daily basis. What’s located behind the cover could prove deadly! And chances are it will not be discovered until there is a problem.

The Good Ole Days and the Standard Electrical Meter

For many years the measurement of electricity went relatively unchanged. These metering devices worked adequately for the utility provider to accomplish the goal of registering electrical usage so that a utility bill could be generated. The customer received the monthly statement and would pay his or her bill.

In the event the customer fell in arrears and did not pay the monthly bills, a customer service representative would visit the location and disconnect the power. To accomplish this, the meter seal would be cut, the electric meter removed and booted off, and then reinserted into the meter base. The cover is then reinstalled and re-sealed until a time in which the customer pays the outstanding bill and any reconnection charges. In the event of tampering, the meter would either be removed and a blank inserted or the service conductors cut and disconnected at the weatherhead or utility pole.

Photo 2. Within the meter enclosure unknown to daily passersby are several potential dangers as can be seen, such as corrosion, effects of overheating to busbars and conductors, insulation failure as well as conductor damage.

Photo 2. Within the meter enclosure unknown to daily passersby are several potential dangers as can be seen, such as corrosion, effects of overheating to busbars and conductors, insulation failure as well as conductor damage.

When the service is ready to be reconnected, the customer service representative then returns to the property, cuts the meter seal, removes the meter, removes the boots and reinserts the meter. The cover is then installed and another seal applied. This returns electricity to the customer and usage is recorded for the next monthly billing cycle.

During this entire process there were several opportunities for the utility representative to notice and report any problems developing within the meter enclosure. Upon discovery, action could be taken to alleviate potential problems before they happened. Technology has changed the way that utilities gather billing information and even the disconnection of delinquent accounts. This has in turn made it even more imperative that electrical work within the meter enclosure be installed in a code-compliant fashion.

A statement must be mentioned concerning safety regarding this issue. Unbelievably, some customers take it upon themselves to reconnect their electricity without the approval of the serving utility. This has resulted in additional fees being accessed by utility and the electrical meter being removed or the conductors disconnected at the weatherhead or utility pole. This illegal activity can result in electrical accidents up to and including death. Qualified personnel are necessary to reconnect these services to assure the safety of the electrical system. Never attempt to reconnect your electrical service! Contact your friendly utility provider for help with this situation.

Photo 3. The interior of this meter enclosure depicts damage due to overheating and corrosion. Remember, none of this damage is visible from the outside of the meter enclosure.

Photo 3. The interior of this meter enclosure depicts damage due to overheating and corrosion. Remember, none of this damage is visible from the outside of the meter enclosure.


The ERT Meter

An electronic receiver/transmitter meter (ERT meter) is used in a network meter reading environment. It can be retrofitted into existing meter enclosures and is available in single- phase and three-phase models. The meter uses electronic modules to communicate power consumption and power quality to the utility provider. The meter also allows two-way communications from the utility provider to the customer. This allows the utility provider the opportunity to be aware of outages that occur and to respond much more quickly.

The use of ERT meters saves the utility provider from physically visiting the meter location on a monthly basis. The ERT meters have a low-powered radio device that permits them to be read from a distance. This allows meter readings to be collected electronically with a mobile data collector (usually a laptop computer) or with a handheld receiver. Technicians are able to download the readings for multiple meters at one time rather than walking from house to house to look at each individual meter.

In some cases, the utility can also disconnect and reconnect the customer remotely. This can be for nonpayment of their monthly bill or to head off high demand issues on the utility system. This can be handy during high usage periods where the provider needs to disconnect loads within structures to prevent brownouts or blackouts from affecting the system. Many household devices are being produced with communication features that communicate with the electronic meters. Utilities can disconnect AC units briefly to prevent issues on the system from occurring. Most generally the customer is unaware that this has even taken place. Some consumers have expressed concerns regarding this issue as it applies to privacy. Many customers enjoy the features of ERT meters. This technology allows the customer to monitor their electrical usage. This has also allowed the customer to change some of their usage patterns in order to save money on their electrical bills by using electricity in the off-peak periods.

As you can see, the use of this technology removes the "hands on, eyes in the field” that may have visited the enclosure and discovered a problem. This can result in minor situations arising that develop into major issues. These issues can be lessened by proper equipment installation and inspection.

Photo 4. Conductor damage due to insulation failure that is not detectable from the exterior of the meter enclosure.

Photo 4. Conductor damage due to insulation failure that is not detectable from the exterior of the meter enclosure.


Preventing These Problems Begins with You

The first line of defense in addressing this issue starts with the electrical contractor. The contractor must make sure that all material used for the installation is listed and labeled as per requirements found in NEC 110.3(B). Proper application of NEC requirements will help ensure a safe and compliant installation. NEC Article 110 covers the requirements for electrical installations. Requirements found within this article include working clearances, interrupting rating, mechanical execution of work, mounting and cooling of equipment, illumination, electrical connections, arc-flash, and field marking. There are other requirements that are useful and required throughout the NEC as well.

Care must be taken to follow the manufacturer’s installation instructions. Special care must be taken to use anti-oxidant compounds as required by the NEC and the manufacturer. These requirements are found in NEC 110.14. Conductors should be stripped and prepared properly so as to not damage the conductor. Specialized tools are necessary to assure that the specific torque requirements are followed for the lugs and conductors. Informative Annex I includes recommended tightening torque values to be used in the absence of the manufacturer’s recommended torque values. These values are taken from UL Standard 486A-B.

The next line of defense lies with the electrical inspector. The inspector needs to assure the customer and utility provider that the electrical contractor has followed the guidelines for properly installing the metering equipment. A good understanding of the NEC and any additional electrical requirements required by the utility provider are necessary. Some of these requirements have been previously discussed. Additionally, the inspector needs to make sure that proper grounding and bonding has been accomplished. Grounding and bonding requirements can be found in NEC Article 250. Also, remember that the insulated fitting required at NEC 300.4(G) is required due to conductor size, not conduit type. Bushings are required for various conduit types throughout the NEC such as at 344.46 for rigid metal conduit. There have been many instances where the electrical installation has been turned down by an inspector due to a missing conduit bushing or insulated fitting.

Photo 5. For years a standard 2s meter was adequate for the needs of the utility company. Today’s technological advances have spurred changes within the utility industry in order to compete and reduce operation costs. Electronic radio transmission (ERT) meters may be able to control some electrical devices within the structure through the electrical utility to prevent system problems. These include the refrigerator, the air conditioner or some other high usage item. Privacy issues have been expressed by some people.

Photo 5. For years a standard 2s meter was adequate for the needs of the utility company. Today’s technological advances have spurred changes within the utility industry in order to compete and reduce operation costs. Electronic radio transmission (ERT) meters may be able to control some electrical devices within the structure through the electrical utility to prevent system problems. These include the refrigerator, the air conditioner or some other high usage item. Privacy issues have been expressed by some people.


Arc Flash and Available Fault Current, a Deadly Combination

New to the 2011 NEC are 110.16 and 110.24 which deal with arc-flash and available fault current markings and requirements. Section 110.16 states that the marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment. This includes meter socket enclosures as well as switchboards, panelboards, industrial control panels and other motor control centers. These requirements do not apply to dwelling units.

Service equipment must be marked with the maximum available fault current per NEC 110.24. This Code requirement further states that the field marking shall be legible and include the date that the fault-current calculation was performed. It must also be sufficiently durable to withstand the environment in which it has been installed. Modifications require that this calculation be verified and recalculated as necessary to ensure the service ratings are sufficient for the maximum available fault current at the line terminals of the equipment. An exception exists for industrial installations where conditions of maintenance and supervision ensure that only qualified persons service the equipment. Again, as previously stated these requirements do not apply to dwelling units.

These requirements help to ensure that whoever works on this equipment in the future is aware of the potential available fault current. This also brings up an interesting question. Who is responsible to adjust the modification markings to the existing equipment as per the requirements found within 110.24? Suppose the providing utility changes out the transformer to the building. Suppose the impedance is different from the existing transformer to the newly installed transformer. Who makes the changes to the marking at the service equipment? Is the building owner aware that these changes have been made and what effect it has on the available fault current to his equipment? Does the utility provider even know that this requirement is found within the NEC? How does this information get upgraded on the electrical equipment?

Photo 6. This electrical service location has a meter blank installed and the meter retired or taken out of service. This could be due to non-payment for services, tampering or because the electrical equipment is no longer in service.

Photo 6. This electrical service location has a meter blank installed and the meter retired or taken out of service. This could be due to non-payment for services, tampering or because the electrical equipment is no longer in service.


Most utilities work under the guidelines of the National Electrical Safety Code (NESC). During a power outage at 2:00 A.M. in the pouring rain and lightning, who will make these adjustments in the field? Is there communication between the utility provider and the customer concerning these changes? What happens when the utility changes the substation feeder to this area of town from one substation to another? There are different characteristics present in both substations that will affect the calculations towards what is marked on the service equipment. These are just a few questions and situations that could arise and affect the accuracy of the field markings for these installations.

Interestingly, during the 2011 NEC Report on Proposals (ROP) and Report on Comments (ROC) meetings these situations were vigorously debated and discussed. The inclusion of the date of when the calculation was conducted was agreed upon and included so that the future electrical contractor would be aware of when the calculation was conducted. Under no circumstances should the electrical contractor rely on a marking on the equipment to determine the level of personal protective equipment (PPE) required. Changes to the system may have taken place after the date the calculation was performed, changing the available fault current at the terminals of the equipment.

Technology Always Has its Ups and Downs

In conclusion, a properly installed and inspected electrical service should provide years of service to the customer. If the customer increases the electrical load by adding new electrical appliances, the service size may need to be re-evaluated. There are many existing older homes and commercial locations with electrical services that were acceptable at the time they were built. Over the years with the addition of new electrical appliances, these services may no longer be adequate for their situation. An electrical contractor should review these services and determine if modifications are needed.

Believe it or not, there are still several locations within utility territories that have only 120-volt services. Usually these are only 60-amp services. This service was all that was necessary to provide electricity to the few devices available at that time. Technology has brought us many new items to add comfort and convenience to our daily life. Many homeowners are shocked when they purchase a new air conditioner or electric dryer to find out that they will need to modify their electrical service to utilize the equipment. Many tend to be elderly and on a fixed income.

Field markings are crucial to the safety of the equipment, the electrician and the electrical inspector. All attempts should be made by the utility and the customer to maintain the accuracy of these markings. Doing so may mean the difference between life and death!

And remember to consult the utility provider and to secure the required permits from the authority having jurisdiction (AHJ) before beginning the electrical upgrade. The utility provider may need to re-evaluate transformer sizes and make adjustments to their system due to your planned modification. What worked for the utility years ago may need modification today.


Joseph Wages, Jr., is the education, codes and standards coordinator for IAEI. He represents IAEI as an alternate on NFPA CMP-3. He also serves on the UL Electrical Council and on several Technical Standard Panels. He is an ICC certified building official and holds certifications as building plans examiner, building inspector, chief building code analyst and one and two family dwelling inspector. He is also an IAEI certified electrical inspector for one- and two-family dwellings. Wages served on the State of Arkansas Apprenticeship Coordinating Steering Committee for four years. He was chief electrical inspector of Siloam Springs, Arkansas, for 15 years. He served as secretary/treasurer and education chairman for IAEI Arkansas Chapter since 2008 and as president for two years. He is a graduate of both the University of Arkansas/Fort Smith and the Northwest Technical Institute ACEF Apprenticeship Program. He has taught apprentices for the ACEF and classes for the Arkansas Chapter.

Tags:  Featured  January-February 2013 

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IAEI West Virginia: Getting Back to the Grass Roots of Safety

Posted By Thomas A. Domitrovich, Friday, December 21, 2012
New electrical contractors enter our markets every year; these individuals perform work that electrical inspectors ultimately review. Involvement in activities in which these individuals participate, using the opportunities to educate, is getting to the grassroots of electrical safety. The IAEI West Virginia recognized an opportunity to be a leader in safety through involvement with the Skills-USA program in their state. Jack Jamison and a host of other key individuals worked hard to create a program that would challenge and educate the best of the best in West Virginia. Jack and his supporters successfully set the bar for the quality of electrical contractor that our markets demand. This team was working directly with students and their educators and helped to shape the mindset of the type of entry level contractor our industries need. This was an opportunity to drive the importance of workmanship and code-compliance that these individuals will take with them into the field.


Figure 1. Volunteers who served as judges

Figure 1. Volunteers who served as judges

SkillsUSA Overview

Photo 1. Students Take Written Exam. Each student was required to take a written exam before demonstrating their hands-on skills.

Photo 1. Students Take Written Exam. Each student was required to take a written exam before demonstrating their hands-on skills.

SkillsUSA is a national organization for students in trade, industrial, technical and health occupations education (www.SKillsUSA.org). This organization sponsors a SkillsUSA Championship annual event that recognizes achievements of career and technical education students. The program is commendable in that it encourages students to strive for excellence and take pride in their chosen occupations. In addition, it engages the educators of our future trade professionals to help them tweak their programs to better prepare their students for employment. Each technical school in West Virginia had an opportunity to participate. Those that participated sent their best student for the categories in which they have interest. West Virginia sent 21 students for the Residential Wiring challenge and 9 students for the Industrial Motor Controls competition. These events occur all over the United States.

The contests for the students are designed to test the skills needed for a successful entry-level individual in their occupational field. They are created and planned by technical committees made up of representatives of labor and management. Safety practices and procedures represent a portion of the contestant’s score that judges give to each student for both a written exam and practical hands on installation skills.

SkillsUSA touches on a wide array of occupations. IAEI West Virginia sponsored the residential wiring and industrial motor controls portions of this event. The purpose of the industrial motor controls program is to evaluate each contestant’s preparation for employment and to recognize outstanding students for excellence and professionalism in the field of industrial motor controls. The SkillsUSA industrial motor controls contest is defined by manufacturer and customer specifications, industry practice, federal regulations and industry standards such as theNational Electrical Code(NEC). The contest is divided into three parts: written, oral interview, and a series of testing stations. The program is designed to demonstrate knowledge of manufacturer and consumer specifications, industry practices, federal regulations and industry standards as well as the ability to apply this knowledge and manual proficiency in applying and installing electrical wiring methods and equipment.

Photo 2. Students Arrive Prepared. Each student that participated in the Residential Wiring or Motor Control portions of the program had a cubicle with a desk where they arranged their tools. Safety was a key aspect and each student was reviewed for clothing which included eye protection, hard hats and proper clothing.

Photo 2. Students Arrive Prepared. Each student that participated in the Residential Wiring or Motor Control portions of the program had a cubicle with a desk where they arranged their tools. Safety was a key aspect and each student was reviewed for clothing which included eye protection, hard hats and proper clothing.

The purpose of the residential wiring section is to evaluate each contestant’s preparation for employment and to recognize outstanding students for excellence and professionalism in the field of residential wiring. The contest assesses the ability of the student to perform jobs or skills selected from a list of competencies as determined by the SkillsUSA Championship technical committee. There is a written knowledge exam and a skills performance contest. The skills portion of the contest includes a series of workstations that have information and instruction sheets for wiring a residence or completing a light commercial installation. West Virginia focused on a residential installation.

The winners of this year’s program will represent West Virginia at the national competition in Kansas City, Missouri.

IAEI West Virginia Involvement

Jack Jamison, secretary for IAEI West Virginia, Jim Williams and Paul Linger teamed up to spearhead this event. These individuals had a long row to hoe, so to speak, in pulling together the resources to make this event happen. Their first order of business was to get the volunteers needed. Together, with the help of these other key individuals, they made this program quite a success. Volunteers received the support of their organizations to support this event (see figure 1).

Photo 3. Judges. After the students completed the practical installation portion of testing, volunteer judges reviewed and scored each student’s work. Scott Jolliff reviews the Gold Medalist’s work.

Photo 3. Judges. After the students completed the practical installation portion of testing, volunteer judges reviewed and scored each student’s work. Scott Jolliff reviews the Gold Medalist’s work.

The electrical program was started from scratch for the state of West Virginia. Jack and his team were faced with organizing volunteers to judge, managing logistical activities as well as creating the entire electrical program for both residential and motor controls. Efforts included development of exam materials, both written and practical installation plans, not to mention the product and equipment that was needed to implement the hands-on portion of the program. This team flexed their resources to assemble the product and resources needed to make this event happen. Local distributors, contractors and manufacturers played key roles in ensuring that the equipment they needed was delivered and in place. Key contributors for the event included:

  • Eaton Corporation
  • Legrand Pass & Seymour
  • Allen-Bradley
  • Hubbell
  • Leviton
  • Miller Engineering
  • Lowe’s
  • State Electric Supply company
  • West Virginia Electric Supply Company
  • The Hite Company
  • CED Mosebach Electric Supply Company

 

The Program

Photo 4. Learning Opportunity. Jack Jamison and other volunteers ensured this was more than a contest — it was a learning opportunity. Students would suffer the loss of points but in the end it is all about learning.

Photo 4. Learning Opportunity. Jack Jamison and other volunteers ensured this was more than a contest — it was a learning opportunity. Students would suffer the loss of points but in the end it is all about learning.

On March 26that 8:00 a.m., twenty-one residential wiring students secondary and post secondary and nine industrial motor control students sat at their desks to take a written exam (see photo 1). They had one hour to complete the written portion of the exam and then six hours to work on their practical installation skills through hands-on installation (see photo 2).

For the written exam portion of the challenge, the students sat at a desk to read and answer 34 multiple choice questions. Questions 1 through 30 directly pertained to theNational Electrical Code(NEC). Students were presented with problems that required them to reference theNECfor articles and sections to help choose the answer that best answered the question. For the Residential Wiring participants, everything from the 6-foot rule to box-fill calculations was covered. The last four questions focused directly on the hands-on portion of the challenge — the students had to draw the diagram that they would soon be building in their lab area.

Photo 5. Residential Gold Medal. Jack Jamison proudly shakes the hand of the Gold Medalist for the residential wiring section of SkillsUSA WV.

Photo 5. Residential Gold Medal. Jack Jamison proudly shakes the hand of the Gold Medalist for the residential wiring section of SkillsUSA WV.

Jack Jamison and his team of industry professionals made sure that the participating students were challenged but most importantly learned something (see photo 3). It was quite clear, once the hands-on portion of the program began, who was prepared and who was not for this competition. Because of the competitive environment, Jack and his team had no knowledge of who the students were, what their names were, or what schools they represented. In addition, helping students who stumbled during their tasks had to be compensated for through point deductions. When a student did ask for help, the advice and education they received were well worth the point penalties — the room was packed with industry experience. Passing on knowledge to those who will be entering into our markets, wiring our homes and/or commercial and industrial facilities, does a lot for safety.

The Challenge to Other Chapters

Getting involved with events like this and our newest electrical contractors just may open your eyes to how important it is that we as an industry get even more involved with students of electricity. IAEI and other trade organizations such as the International Brotherhood of Electrical Workers (IBEW) and the Independent Electrical Contractors Association (IEC) and others have great programs to cultivate and grow the knowledge of new and seasoned professionals in our markets. The involvement of these young individuals is a must. West Virginia IAEI demonstrated how this organization can get involved and has plotted a course for the future through this past program. Raising the awareness of IAEI educational programs to these individuals just entering our markets is a good opportunity to educate on safety and to grow membership.

Photo 6. Motor Control Gold Medal. Paul Linger and Jim Williams proudly present the Gold Medalist for the motor control section of SkillsUSA WV.

Photo 6. Motor Control Gold Medal. Paul Linger and Jim Williams proudly present the Gold Medalist for the motor control section of SkillsUSA WV.

It takes leadership to rally the troops, set the direction, and impact a life or possibly more by getting involved with the future of our industry. This involvement and leadership builds the brand of both organization and the individual — it helps to drive membership of the right demographics. Involvement of the young budding professional entering the market is what most nonprofit organizations lack. This is key membership that drives the future of the organization. These students appreciate the types of opportunities presented by the SkillsUSA program — it gives them an opportunity to demonstrate their abilities and to build their resumes as they enter the job market. These students could be our future electrical inspectors, future chapter presidents, treasurers and secretaries who will make our chapters function and thrive. I am proud to be a IAEI West Virginia member and was even more so during this event. These types of events occur in many chapters and more than likely never get mention or recognition. Those chapters should be commended for their efforts and others should be encouraged to get yet more involved. Together we can make a difference.

As always, keep safety at the top of your list and ensure you and those around you live to see another day. If you have any tips or ideas you would like to share, please feel free to send them to me at thomasadomitrovich@eaton.com. I look forward to your input to these articles and guidance for future articles.


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Tags:  July-August 2011  Safety in Our States 

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Relevance

Posted By David Clements, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Due to new technology, social networking and competition, individuals have many options as to where and from whom they can obtain information. Consequently, associations, the traditional suppliers of industry information, are facing intense pressures. Gone are the days when members would automatically renew their memberships. IAEI is no different and we face many of the same challenges.

In order to grow our membership, we need the assistance of all members; this includes our chapters, divisions and individuals. I’ve announced a new membership drive campaign in which, for new members only, we are offering 18 months of membership for the same price as a 12-month membership (that’s six months of free membership). This is a limited time offer that expires on December 31. You can make a difference by sharing this offer with your friends in the industry who have not yet discovered IAEI.*

I recently read the book, Race for Relevance, 5 Radical Changes for Associations by Harrison Coerver and Mary Byers, which outlines what an association needs to do in order to stay relevant. Interestingly enough, we are running the race for relevance in the right direction. We will never cross the finish line as it will continue to move in a forward direction; however, we can do things to ensure we stay current and remain competitive in today’s market.

So let me touch briefly on things we have been doing to remain relevant.

• We are fulfilling our obligation to our mem-bers, to the electrical industry and to the general public to participate in code devel-opment, to provide premier education and to support the inspection process.

• We are developing a five-year strategic plan for the association, which includes strength-ening our business practices, community involvements, and member educationpractices.

• We are forging partnerships with other organizations within the industry. The most recent agreement is with ICC(International Code Council).

• Following our mission statement of promoting advocacy, IAEI has joined the Electrical Code Coalition in taking the position on early adoption of the NEC without amend-ments. This position is under great pressure from certain in-dustry associations, but the Coalition feels that both the industry and the public need a fair picture of the necessity of early adoption without amendments.

• IAEI has created a new Department of Advertising and Marketing and has commissioned the new director to create and implement a robust marketing plan for IAEI publica-tions, membership, training, and meetings.

• IAEI is enlarging its publication formats to include newer and more relevant platforms. We believe that all members will be excited and pleased with this forward move.

• IAEI will be ramping up its use of social media (Facebook, Twitter and LinkedIn) to market and promote the associa-tion. I encourage you to use these tools. I am now tweeting multiple times a week. You’ll find me @DavidEClements.

• IAEI will be optimizing the development of the board’s insight into current technologies, broader target audience, and industry diversifications.

• Members will find easier password access to their IAEI ac-count information on the website which will interact seam-lessly with the IAEI store and IAEI magazine.

Although IAEI faces the same challenges as all associations, we are up the task. We are ready and willing to embrace our industry as it evolves and to make the necessary changes. As we continue to run the race for relevance, we will not forget to provide the services and products that our members deserve.

David Clements is CEO/Executive Director of IAEI

* If you need more information about this offer, visit our website or call Annette Thomas, director of membership and customer service.

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Tags:  Editorial  November-December 2012 

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Selection of conductors – do we have a problem with this?

Posted By Ark Tsisserev, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Apparently, we do. However, there is no reason to generalize this problem. Although there might be problems (or rather challenges) for the code users in understanding of some requirements related to the selection of conductors, I’ll concentrate on two specific issues that have apparently become a source of confusion:

1. Introduction of Rule 4-006 into the CE Code; and

2. Recent UL/ULC Public Notice release 12PN-51.

So, let’s concentrate on each of these subjects separately.

Our first issue is introduction of Rule 4-006 into the CE Code. Why now?

In order to clearly follow the sequence of events, we need to "unearth” a few relevant bits of history. A number of years ago, the NEC/CEC Ampacity Task Force had been established.

This Task Force was charged with the responsibility to conduct a thorough review of the ampacity values of the NEC Tables 310.16 and 310.17 and the CEC Tables 1–4, and to harmonize these values in both Codes. The reason for such assignment was based on a need to re-calculate the ampacities used in both Codes in accordance with the objective scientific formula and to facilitate necessary changes to both Codes that would prevent excess of the maximum allowable operating temperature at any connected termination. There are many pieces of electrical equipment (fused switches, circuit breakers, panelboards, etc.) that have been tested, marked (and certified to the harmonized bi-national: UL/CSA) product standards based on the maximum permitted operating temperature at 75⁰C.

This fact has been captured by the NEC for quite some time. Article 110.14(C) of the NEC mandates temperature limitations at such termination and requires use of conductors being sized on the ampacity values in 75⁰C column of Tables 310.16 and 310.17.

Until 2012 edition of the CE Code, there was no similar requirement in the CEC, as the previous values of ampacity tables of the CEC were more conservative than in the NEC, and no temperature imitation at conductors terminations were deemed to be necessary. Therefore, users of the CE Code have been routinely selecting conductor sizes based on 90⁰C column from Tables 1–4 for termination on the equipment that is marked for the temperature restrictions up to 75⁰C.

However, after the assignment—to correlate ampacity values had been completed by the NEC/CEC Ampacity Task Force, all values of the NEC Table 310.15(B)(16) [formerly Table 310.16] and 310.15(B)(17) [formerly Table 310.17], and the CEC Tables 1–4 have been harmonized.

The result of such harmonization is seen in both Codes. The 2011 edition of the NEC and 2012 edition of the CEC have absolutely identical ampacity values in these respective tables. If we now compare the ampacities values between 2009 and 2012 editions of the CEC, we’ll see that in the latest edition of the CE Code these ampacities (particularly in 90⁰C column of Tables 1– 4) have been significantly raised.

It is obvious now that the restrictions mandated by Article 110.14(C) of the NEC have to be reflected in the CEC—to prevent unsafe operating temperatures at the point of termination of the conductors to the equipment that is marked with the temperature limitation.

New Rule 4-006 of the CE Code states this requirement as follows:

"4-006 Temperature limitations

(see Appendix B)

"(1) Where equipment is marked with a maximum conductor termination temperature, the maximum allowable ampacity of the conductor shall be based on the corresponding temperature column from Table 1, 2, 3, or 4.

"(2) Where equipment is not marked with a maximum conductor termination temperature, 90 °C shall be used by default.”

Appendix B Note on this Rule provides additional clarification on this requirement:

"Appendix B Note on Rule 4-006

"The intent of this Rule is to correlate the temperature rating of conductors where the ampacity is selected from Tables 1 to 4 with the lowest temperature rating of electrical equipment or any wire connector (terminal connector, lug, etc.). It is intended by this Rule that the ampacity of conductors be selected from the temperature column in Table 1, 2, 3, or 4 that corresponds to the temperature rating marked on the electrical equipment. As an example, where a conductor is terminated on a breaker with a 75 °C rating, the maximum conductor ampacity would be based on the 75 °C column of the Tables. It should be noted that the temperature rating of a wire connector (terminal connector, lug, etc.) that is connected to the equipment may be higher than that of the equipment itself; it is the equipment rating that determines the conductor size, not the lug.”

So, based on the requirement of Rule 4-006 and on the clarification Note on this Rule, it appears to be clear that the conductor ampacity should be selected from the temperature column that is consistent with the maximum allowable operating temperature of equipment to which that conductor is intended to be terminated.

But, what if a RW90 conductor is readily available and is intended to be used by a contractor? Could we use the ampacity value from the 90⁰C column and apply some de-rating factors of Tables 5A–5C? From the discussions on this issue between the designers, electrical contractors and regulators, it appears that there is some confusion in relation to this particular point.

Nobody would argue that a typical RW90 conductor could not be selected, but the ampacity of this conductor would now have to be selected from 75⁰C column of Tables 1–4 of the CE Code.

So, why can’t we select ampacity for a RW90 conductor from the 90⁰C column of a respective ampacity Table and to apply one of the correction factors of Tables 5A–5C?

Correction factors of Table 5A, 5B, and 5C are intended only for the allowable ampacity values obtained from Table 1, 2, 3, and 4.

It should be noted that for equipment with a conductor termination rating of 75⁰C, Rule 4-006 requires the allowable ampacities to be "based” (i.e., to be obtained) on the 75⁰C column of Table 1, 2, 3, or 4. The Rule does not permit basing the allowable ampacity on any other value than the value obtained from the 75⁰C column for equipment with a required conductor termination rating of 75⁰C.

The rationale for Rule 4-006 was to recognize how the equipment was tested during the certification process.

If we’ll review the CSA standards C22.2 No 4 Enclosed and Dead-Front Switches; C22.2 No 5 Molded-Case Circuit Breakers; Molded-Case Switches and Circuit-Breaker Enclosures; C22.2 No 29 Panelboards and enclosed panelboards and C22.2 No 244 Switchboards, we’ll find that all these standards require the conductor used during the temperature testing to be based on a 75⁰C ampacity.

The maximum allowable operating temperature of any circuit should be always limited to the lowest permissible value of such temperature for any component of the circuit.

In a practical sense, a conductor ampacity is the operating temperature for a conductor that is fully loaded to the applicable values in Tables 1, 2, 3, and 4, and this ampacity would be equal to the temperature rating of the conductor.

For example, if 4X350 kcmil copper conductors rated at 75 degrees C are installed in four raceways at an ambient temperature of 30⁰C and loaded to 1200 A, the operating temperature of these conductors would be 75⁰C. If we would select the 90⁰C rated conductor for the same example, the operating temperature of the conductor would be also 75⁰C.

If, in another example, 3X#3 RW90 conductors in a raceway are loaded to 115 A in accordance with Table 2 of the CEC, then such conductor loading would result in a conductor operating temperature of 90⁰C.

When the number of #3 RW90 conductors is increased (let say to eight conductors), Table 5C would require a correction factor of 0.7. In this case, 115 A x 0.7 = 80.5 A. Therefore, each of these 8X#3 RW90 conductors loaded to 80.5 A will again operate at the temperature of 90⁰C.

To limit the operating temperature of the conductor to 75⁰C (the maximum allowable temperature rating of the equipment) the ampacity would need to be selected from the 75⁰C column, and then the correction factor of Table 5C should be applied to the selected ampacity. In the example of 8x#3 RW90 conductors in the raceway (from the 75⁰C column of Table 2 and from Table 5C) 100 A x 0.7 = 70 Amp. Therefore, each of these 8X#3 RW90 conductors loaded to 70 Amp will again operate at the temperature of 75⁰C.

The main issue here is the effect that the operating temperature of the conductor has on the equipment to which this conductor is connected. The conductor can handle the ampacity, but the equipment was not tested with terminations above 75⁰C.

If, in addition to the discussion above, the selected 3X#3AWG RW90 conductors are terminated at the equipment rated at 75⁰C, and these conductors are operating in the ambient temperature exceeding 30⁰C, then the appropriate de-rating factor of Table 5A should be applied to the ampacity already selected from the 75⁰C column. If, for example, the ambient temperature is 40⁰C, then 100 A ampacity must be multiplied by the correction factor 0.91 from Table 5A, as the actual conductor used in this example is RW90 (and not RW75). Therefore, each of these 3X#3 RW90 conductors would be now loaded to 100 A x 0.91 = 91 A, and these RW90 conductors will again operate at the temperature of 75⁰C.

And, of course, regardless what correction factors are used for the selected ampacities, the resulting (decreased) ampacity of conductor should be checked for compliance with Rule 8-104 to ensure that it is not less than 125% of the calculated load.

Let’s now discuss the second issue – Recent UL/ULC Public Notice release 12PN-51.

UL and ULC have recently published the following notice. (However, from the perspective of application of this notice for the Canadian electrical industry, the discussion is limited only to the ULC portion of this notice).

"UL and ULC announce important changes to certification programs (Release 12PN-51)

"UL has recently conducted research on a wide array of current products and systems originally certified under UL 2196, Tests for Fire Resistive Cables and ULC-S139, Standard Method of Fire Test for Evaluation of Integrity of Electrical Cables and determined that they no longer consistently achieve a two-hour fire-resistive rating when subjected to the standard Fire Endurance Test of UL2196 or

ULC-S139. "Consequently, UL and ULC will not be able to offer certification to the currently existing program related to these standards.

"As a result, manufacturers are no longer authorized to place the UL mark or ULC mark on the following products:

"UL Classified Fire Resistive Cable (FHJR)

"ULC Listed Fire Resistant Cable (FHJRC)

"UL Listed cable with "-CI” suffix (Circuit Integrity)

"Furthermore, UL has removed from its certification directory all Electrical Circuit Protective Systems constructed with Fire Resistive Cable (FHIT).”

This notice has created a significant adverse impact on all electrical safety stakeholders, and particularly on the manufacturers of wiring products and on the electrical designers, and has become a subject of confusion in the electrical industry.

It appears from the early UL generic letter to the manufacturers of wiring products that UL (and in Canada – ULC) has published the attached public notice based on concerns that certain wiring products (which in addition to being designed, constructed, tested and certified to the applicable CSA Part II standards), are designated as "fire resistive cables” after being tested to the ULC standard S139, may, in fact, no longer conform to the ULC S139 circuit integrity test.

Apparently, some of such cables have failed the ULC S139 test, when they are installed in a metal conduit with the interior wall constructed with zinc coating, as at high temperatures a zinc coating may interact with copper conductors creating a brass alloy that melts at a lower temperature than copper conductors, thus impacting on the circuit integrity.

If the specific technical concern identified above is accurate (i.e., if it is limited to the melting of alloy inside the rigid metal conduit), the ULC following statement "manufacturers are no longer authorized to place the ULC mark on the following products: ULC Listed Fire Resistant Cable (FHJRC),” made in the referenced "Public Notice release” appears to be highly questionable, as the compliance with the circuit integrity test method described in the ULC S139 does not apparently require a certification monogram (in addition to the monogram signifying compliance of a cable with the applicable CSA safety product standard).

It is interesting to note that in accordance with Clause 6.1A of ULC S139 – the product shall be marked with the circuit integrity rating only, and not with the additional certification monogram. The ULC Notice indicating "ULC will not be able to offer certification to the currently existing program related to these standards” also appears to be questionable, as Clause 3.2.1 of the ULC S139 states the following: "Cables shall be installed in raceways or supports as permitted for that cable type by the Canadian Electrical Code.”

Based on this provision of Clause 3.2.1 of the ULC S139, each particular test assembly in accordance with this standard must reflect condition of use of a specific type of cable under relevant installation requirements of the CE Code. This means that if an armoured cable is being tested for circuit integrity in accordance with the ULC S139, such cable would not be tested in a raceway, as armoured cable is not intended by Table 19 of the CE Code to be used in raceway. Accordingly, if a typical communication, community antenna or Class 2 circuit cable would be subjected to the test in accordance with ULC S139, such test assembly would not have to include a raceway, as in accordance with the CE Code, communication, community antenna or Class 2 circuit cables are not specifically required to be installed in raceways. These examples clearly indicate that the technical concerns which prompted the ULC to publish the referenced notice would not be warranted for all test methods of the ULC S139, and that suspension of the certification of the circuit integrity tests to absolutely all types of test assemblies which are set up in accordance with Clause 3.2.1 of the ULC S139 to comply with the conductors installation requirements of the CE Code, is not necessarily warranted.

One of the main concerns with this ULC Public Notice relates to the fact that the compliance with the test methods for circuit integrity of conductors in accordance with the ULC standard S139 is mandated by the National Building Code of Canada (NBCC) and by the ULC standard S524 "Installation of fire alarm systems,” and both these documents are legally adopted for a regulatory purpose in the respective Canadian jurisdictions.

From a practical view point, the ULC Public Notice will leave the electrical industry practitioners with no other option, except for resorting to means for fire protection of conductors (required by the NBCC to be protected against exposure to fire) by encasing conduits containing such conductors in at least 100 mm of concrete.

This Public Notice appears to disregard the fact that a typical MI cable designed and constructed to very stringent requirements of the CSA standard C22.2 No.124 (which also incorporates provisions for fire rating) would not be allowed to be used for the purpose of complying with the NBCC 1 h or 2 h fire rating requirements, as Clause 6.7 of this CSA standard states the following

"6.7 Fire rating

"Cables marked in accordance with Clause 5.3 shall comply with the requirements of ULC-S139.”

It should be noted that the ULC is aware of the industry concerns, and hopefully this matter will be resolved, when this article is published.
 
Meanwhile, as usual, the electrical inspection authorities should be consulted on all applicable aspects related to the issues discussed in this article.
 

Read more by Ark Tsisserev

Tags:  Canadian Perspective  November-December 2012 

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The Slash-Rated Breaker and Shared Neutral Applications

Posted By Thomas A. Domitrovich, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012
Think back one or maybe more years ago when you had to assemble that latest purchase in front of the Christmas tree; picture the moment, if ever, you decided to open the assembly instructions and read them. It could have been before you got started — as you were drinking your coffee looking at the box and all of the parts. Or perhaps it was half way through when you couldn’t figure out how two parts went together. If you’re anything like me, it was when you were all done and you had a handful of parts left over. When it comes to electrical products, no matter how simple or how many times you’ve installed them, reading the labels on the products and the instructions can go a long way for electrical safety. Familiarity can indeed breed contempt in this arena. Today we’ll focus on slash-rated and non-slash-rated breakers and their applications.
 
This is an important topic as code requirements have driven more use of handle ties. Two 1-pole circuit breakers can be tied together with an approved handle tie but close attention to the markings and listing of the products is important to ensure they are not applied outside of their rating. Observing labels and understanding what they mean is an important first step.
 
Photo 1. 1-pole thermal magnetic circuit breakers rated 120/240V
Photo 1. 1-pole thermal magnetic circuit breakers rated 120/240V

Slash Ratings
The UL white book, in the "Marking and Application Guide – Molded Case Circuit Breakers,” which is available at www.ul.com/whitebook helps us understand the markings of circuit breakers. The General section, Item 3 entitled "Voltage Rating” illustrates that all breakers are required to be marked with their voltage rating. This marking is important to the proper application of these products, to ensure they are not applied at a voltage outside of their rating. All UL 489 Molded Case Circuit Breakers are marked with a voltage rating chosen from the following:

DC Voltage Ratings:
60, 125, 125/250, 160, 250, 500 and 600 volts

AC Voltage Ratings:
120, 127, 120/240, 240, 277, 347, 480Y/277, 480, 600Y/347 and 600 volts
 
Photo 2. Two 1-pole breakers and an approved handle tie before assembly
Photo 2. Two 1-pole breakers and an approved handle tie before assembly


This reference identifies the existence of breakers that can be designated with a single voltage rating or a slant (or slash) voltage rating. A circuit breaker that carries a single voltage rating is intended for use in circuits where the circuit voltage and the voltage to ground do not exceed the voltage rating of the breaker. A slash-rated breaker, such as 120/240 V, is intended to be used in circuits where the circuit voltage does not exceed the higher of the two voltages and the voltage to ground does not exceed the lower of the two voltages. This reference notes the following when it comes to a slash-rated breaker:
 
"Two-pole independent-trip breakers and single-pole breakers with handle ties that are rated 120/240 V ac have been investigated for use in line-to-line single-phase circuits or line-to-line branch circuits connected to 3-phase, 4-wire systems, provided the systems have a grounded neutral and the voltage to ground does not exceed 120 V.”
 
A peek into UL 489 provides an understanding of what extra testing and requirements a slash-rated breaker must endure to qualify for this slash rating. Section 6.1.5 entitled "Operating Mechanism” includes Section 6.1.5.3 stating the following:
 
"6.1.5.3 Single-pole circuit breakers rated at 120/240 V ac or 125/250 V dc shall have provision for the use of handle ties. Handle ties, when installed, shall:
a) Operate both circuit breakers when either circuit breaker handle is manually operated;
b) Not be readily removable; and
c) Not obscure the ampere marking on either circuit breaker.”
 
These important physical requirements/qualities of an approved handle tie illustrate what an approved handle tie means physically for a circuit breaker. Section 7 of this same UL standard covers the performance based testing for breakers with the handle tie in place. Section 7.1.1.12 is specific for single-pole breakers rated 120/240 V. I’ll note here that most single-pole breakers that we encounter on residential systems, as depicted in figure 1, are slash-rated in this manner. This permits the use of approved handle ties in the field in cases where a contractor decides to "share the neutral,” a practice some electrical contractors employ to reduce the amount of wire required for home run circuits. Section 7.1.1.12 identifies the testing that must be performed on these single-pole slash-rated breakers as follows:
"7.1.1.12 If a single-pole circuit breaker is rated at 120/240 V ac or 125/250 V dc, see 6.1.5.3, two such circuit breakers shall be tested together in the intended manner as a 2-pole independent-trip circuit breaker in the overload, endurance, interrupting, and dielectric voltage-withstand test described below. Two such ‘pairs’ of circuit breakers constitute a set.”

When two 1-pole breakers are combined via an approved handle tie, they must both be slash-rated breakers. This ensures that proper testing has been performed on the "pair” of breakers for their application. Even if applied on only single-phase circuits, as is the case of shared neutral applications, this "pair” of breakers may be called upon to interrupt a line-to-line fault, a condition for which they have not been tested if they are rated 120 V only. The above introduces the term independent-trip which operates such that any single breaker in the pair of combined breakers may trip without causing the trip of the other breaker(s). This can be the result of applying an approved handle tie to two 1-pole breakers. Handle ties have become more popular these days due to recent National Electrical Code (NEC) changes.
 
Photo 3. Applying the handle tie to two 1-pole breakers. Note that the ampere rating on the handle will be visible after the application of the handle tie.
Photo 3. Applying the handle tie to two 1-pole breakers. Note that the ampere rating on the handle will be visible after the application of the handle tie.

Shared Neutral Applications
The shared neutral application is familiar to many electrical contractors as sharing the neutral on the home run circuit from the breaker to first outlet can be one way of reducing material costs. Those applications where you would have pulled two 2-conductor (+ ground) wires instead are pulled with a single 3-conductor (+ ground) wire. Section 210.4 of the NEC addresses multiwire branch circuits noting that these circuits are those where all conductors originate from the same panelboard or similar distribution equipment.

An approved handle tie applied to two single-pole breakers for such applications as shared neutral installations ensures the installation meets the requirement of section 210.4(B), "Disconnecting Means,” of NEC 2011 which states:
 
"(B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.”
 
Section 210.4(B) does not require the breaker to disconnect all ungrounded conductors in the case of a trip. A breaker that operates such that only that pole which experienced the overcurrent trips while the other doesn’t is termed as an independent trip type of device. This section, rather, requires that when you turn the breaker to the off position all poles are turned to the off position. It is important to note that the construction of the breaker and the position to which the handle moves in the tripped state plays an important role on whether or not the breakers are independent trip. Some breakers trip to center. Applying an approved handle tie to two of these breakers may result in independent trip functionality as without an internal link between the two breakers, a single handle itself tripping to center may not pull the handle of the second breaker to the off position. The functionality of tripping both or all poles due to one single-pole seeing a fault, if present, is a common trip type of two pole device. Due to the internal linkages on these devices they are manufactured to ship as a two pole device. The manufacturer’s literature will indicate how the device operates, independent or common trip.

Applying the Approved Handle Tie
Care must be taken when applying an approved handle tie to two single-pole breakers in the field. As stated earlier, the practice of doing this was made easy due to the fact that most single-pole breakers you work with in residential systems are slash-rated. Sometimes the fact that most are slash-rated can lead toward a violation due to not reading the labels and checking. I guess this is a good example of the age old phrase "familiarity breeds contempt.” Before you apply an approved handle tie, you must verify that the breaker carries the slash-rating for the application and ensure that the handle tie is approved for use on that breaker. The manufacturer’s literature can be helpful and the label check is even easier. Looking for the slash-rating is a great first step for success.
 
There are single-pole breakers on the market that are not slash-rated. The ground-fault circuit interrupter (GFCI) and arc-fault circuit interrupter (AFCI) breakers are two examples. GFCI breakers provide a technical reason why the use of single-pole breakers in a shared neutral application, with an approved handle tie, is problematic. This is due to the fact that the breakers need all of the current that goes out on the hot to come back on the neutral. These devices act to trip the circuit if the current going out on the black wire (hot) does not equal the current that comes back on the white wire (neutral). Sharing the neutral with two GFCI breakers with this construction will result in instant tripping the moment a load on either breaker is energized.
 
Single-pole AFCI breakers on the market today, to the author’s knowledge, also carry a single voltage rating of 120 volts. Applying two 120V rated (NOT 120/240V) single-pole AFCI devices with an approved handle tie to serve shared neutral loads would be applying these devices outside of their rating. The bottom line for applying an approved handle tie to any pair of 1-pole breakers is to check the label for the slash rating. Slash-rated breakers are available, even for GFCI and AFCI circuits.
 
Photo 4. Final assembled 2-pole breaker with handle tie applied and approved
Photo 4. Final assembled 2-pole breaker with handle tie applied and approved

National Electrical Code Requirements
The NEC is not silent when it comes to handle ties and their application as discussed above. The various sections in the NEC that address this topic can stand for a little improvement but the requirements that align with the UL standards are there. Let’s explore this topic with respect to the NEC and I trust you’ll see what I mean.
The key sections in NEC 2011that are important for this discussion include the following:

Article 210 Branch Circuits
210.4 Multiwire Branch Circuits
210.4(B) Disconnecting Means

Article 240 Overcurrent Protection
240.15 Ungrounded Conductors
240.15(B)(1) Multiwire branch circuits
240.85 Application

Our first stop is going to be in Section 240.85, Application. This section is within Part VII of Article 240 which focuses on circuit breaker overcurrent protection. The language in this section mirrors that which is in the Marking and Application Guide for Molded Case Circuit Breakers found in the 2012 version of the UL White Book which was previously referenced in this article. Section 240.85 states the following:
 
"A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker’s voltage rating. A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1φ–3φ to indicate such suitability.
 
"A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker’s voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker’s voltage rating.”
 
This section provides guidance to help with the proper application of the product within its rating. It offers a simple check to ensure that you don’t exceed the rating of the device — measure the voltage between any two conductors. Let’s use a shared neutral application for this discussion (figure 1). Figure 1 illustrates the terminations in a shared neutral application where two 1-pole breakers have had an approved handle tie applied in the field. Measuring the voltage between any two conductors yields a maximum voltage potential reading of 240V between H1 & H2. If both or any single 1-pole breakers were rated only 120V, a violation of section 240.85 would result.
 
Section 240.15(B) is another area of the NEC that provides guidance for the application of handle ties. 240.15(B)(1) language is not specific on the voltage rating requirements of the two 1-pole breakers being handle tied. This section simply permits an approved handle tie to be applied in the field. 240.15(B)(2) does specify the voltage rating of the breakers handle tied for line-to-line connected loads. It is possible for one to mistakenly assume that two 1-pole breakers rated 120V may be handle tied as long as they are supplying single-phase line-to-neutral loads based on the words in these two sections. This would be in error, though, as other sections of the Code and UL requirements mentioned above help us to understand the proper application of these devices.
 
Section 240.15 has seen considerable changes over the years. Previous editions of the NEC, going at least back to the 1987 version of the Code, saw this "Ungrounded Conductors” section as 240-20. 240-20(B) in NEC 1987 read as follows:
 
"(B) Circuit Breaker as Overcurrent Device. Circuit breakers shall open all ungrounded conductors of the circuit.”

This had one exception:
 
"Exception: Individual single-pole circuit breakers shall be acceptable as the protection for each ungrounded conductor of 3-wire direct-current or single-phase circuits, or for each ungrounded conductor of lighting or appliance branch circuits connected to 4-wire, 3-phase systems or 5-wire, 2-phase systems, provided such lighting or appliance circuits are supplied from a system having a grounded neutral and no conductor in such circuits operates at a voltage greater than permitted in Section 210-6.”
 
This verbiage was in place, for the most part, at least as far back as NEC 1962. This section saw considerable changes in NEC 1993, NEC 1996, NEC 2005 and NEC 2011. It was in NEC 2008 that the section went from 240.20 to 240.15.
 
NEC 1990 introduced section 240.83(e), Voltage Marking. This section stated the following: "Circuit breakers shall be marked with a voltage rating no less than the nominal system voltage that is indicative of their capability to interrupt fault currents between phases or phase to ground.” This section also included a Fine Print Note (FPN) as follows:
"A circuit breaker with a straight voltage marking, e.g., 480V, may be applied in neutral grounded systems or grounded wye or grounded and ungrounded delta systems. Circuit breakers with slash voltage markings, e.g., 480Y/277V, 120/240, may be applied only in grounded neutral systems.”
 
This section ultimately ended up being split between 240.83(e) and a new 240.85, Application, section which was added in NEC 1996. This section has seen some changes since to better clarify the proper application of a circuit breaker.
 
This review illustrates an important aspect of the NEC — in some cases, many different sections of the Code work together to ensure a safe installation. When you think you have found the answer to your question quite easily, look a little harder; you just may learn something more.
 
Figure 1. Shared neutral termination on two 1-pole breakers with handle tie. The voltage between any two conductors cannot exceed the rating of the breaker (240.85).
Figure 1. Shared neutral termination on two 1-pole breakers with handle tie. The voltage between any two conductors cannot exceed the rating of the breaker (240.85).

Summary for Safety
We’ve talked a lot so far about ratings, UL requirements for single-pole and two-pole devices and the NEC. Let’s provide a quick overview via the following bulleted items:
 
  • A circuit breaker that carries a single voltage (120V) rating is intended for use in circuits where the circuit voltage and the voltage to ground do not exceed the voltage rating of the breaker. You cannot apply an approved handle tie to these breakers.
  • A slash-rated breaker, such as 120/240, is intended to be used in circuits where the circuit voltage does not exceed the higher of the two voltages and the voltage to ground does not exceed the lower of the two voltages. Single-pole breakers with slash ratings can have approved handle ties applied for shared neutral applications.
  • GFCI single-pole devices only rated 120V cannot have an approved handle tie applied. This not only is a UL violation but also results in instant tripping of the device. For those shared neutral applications, 2-pole 120/240V rated GFCI breakers are available.
  • AFCI single-pole devices rated 120V cannot have an approved handle tie applied. This is a violation of the UL listing and for those shared neutral applications 2-pole 120/240V rated AFCI breakers are available. Should a 1-pole AFCI carry a 120/240V rating, an approved handle tie may be applied for shared neutral situations.
 
The bottom line in the application of an approved handle tie is to read the labels and the manufacturer’s instructions to ensure you are not applying the product outside of its rating.
 
As always, keep safety at the top of your list and ensure you and those around you live to see another day.

Read more by Thomas A. Domitrovich

Tags:  November-December 2012  Safety in Our States 

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UL Certifies First Stand-Alone Replacement LED Tube

Posted By Underwriters Laboratories, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Question 

Does UL List (certify) stand-alone LED (light emitting diode) tubes for direct replacement of fluorescent tubes in fluorescent luminaires? 

Answer

Yes, recently UL has certified (Listed) the first stand-alone LED tube for direct replacement of a fluorescent tube in a fluorescent luminaire. The replacement tubes operate in the existing ballast circuit present in the fluorescent luminaire. They have been evaluated to operate in the ballast circuit so that the LED tube does not adversely affect the ballast operation in the luminaire. These LED tubes are certified (Listed) under the product category Lamps, Self-ballasted, Light-emitting-diode Type (OOLV), located on page 279 of the 2012 UL White Book and will bear a UL Listing Mark and also identify  the type of fluorescent tube it is intended to replace, e.g. 40W/48T12/RS.

These certified (Listed) replacement LED tubes differ from what UL has certified up until this point in that LED tube retrofits and conversions involved modifying an already Listed luminaire by replacing the ballast with a driver or removing the ballast and direct wiring the branch circuit to the lamp holders in the luminaire. These types of LED retrofit and conversion kits are certified under either of the product categories Light-emitting-diode Retrofit Luminaire Conversion Kits (IFAR) or Light-emitting-diode Retrofit Luminaire Conversion Kits for Commercial Refrigerators and Freezers (IFAS) located on page 180 in the 2012 UL White Book or Luminaire Conversions, Retrofit (IEUQ), located on page 173 in the 2012 UL White Book. For these categories, one of the major subassemblies will bear the UL Classification Mark and verbiage identifying that it is a Classified kit for use in specific luminaires.

You can also view the UL Guide Information and certifications online at www.ul.com/database and enter any of the category codes OOLV, IFAR, IFAS or IEUQ at the category code search field.


Question

AFCI Troubleshooting, Online Training at UL Knowledge Services

Answer

UL Knowledge Services (formerly UL University) is offering a free 2-hour online training class that was developed by NEMA (National Electrical Manufacturers Association) and the arc-fault circuit interrupter (AFCI) manufacturers themselves.

This FREE two-hour course will help electrical system installers complete the trouble-free installation of arc-fault circuit-interrupter (AFCI) circuit breakers. It also describes what they should do in the unlikely event that unwanted tripping should occur. Proper installation will result in fewer electrical fires started as a result of low level arcing, contributing to greater safety for those who live in the homes that have AFCI circuit breakers installed in them. It will also reduce call-backs, resulting in more satisfied homeowners.

This course is intended for anyone who installs electrical systems in residences, whether they are single, multifamily or apartment buildings—in other words, anywhere the use of AFCI circuit breakers are required by the National Electrical Code.

Some of the topics covered are:

  • Product knowledge 
  • Code requirements 
  • Wire routing and installation 
  • How to install an AFCI circuit breaker 
  • How to install wiring devices and hard wired equipment 
  • Perform a final system test 
  • How to troubleshoot 
  • Installing AFCIs in existing homes 
  • Success stories and additional resources 

Go to www.ulknowledgeservices.com, select United States as your location and search for "AFCI Basics” register and take the free course.

Tags:  November-December 2012  UL Question Corner 

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Are Type AC and Type MC cables considered pre-wired raceways?

Posted By Joseph Wages, Jr., Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Question

Is the definition of a raceway applicable to Type AC cable and Type MC cable since these wiring methods are factory assembled with insulated conductors? Are Type AC cables and Type MC cables considered pre-wired raceways? KJ

Answer

This is an interesting question, and I appreciate an opportunity to address it. Let’s begin by looking at a few definitions. I am referencing the 2011 NEC for this information. A raceway is defined in Article 100 as an "enclosed channel of metal or nonmetallic material designed expressly for holding wires, cables, or busbars, with additional functions as permitted in the Code. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways and busways.”

In Article 320, Type AC cable is defined as "a fabricated assembly of insulated conductors in a flexible interlocked metallic armor.” Looking closer at 320.100, it further states that "Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.”

Article 330 defines Type MC (metal clad) cable as "a factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking metal tape, or a smooth or corrugated metallic sheath.”

Article 300 will give us further guidance concerning a raceway as 300.18 tells us that "raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors.” This section further goes on to state that "prewired raceway assemblies shall be permitted only where specifically permitted in this Code for the applicable wiring method.”

I could not locate a definition for prewired raceway assemblies and feel that it does not apply to AC or MC cable. Article 354 covers Nonmetallic Underground Conduit with Conductors. This is known as Type NUCC. The definition states that this is "a factory assembly of conductors or cables inside a nonmetallic, smooth wall conduit with a circular cross section.” This item may fall under the nonexistent definition of a prewired factory assembly.

In conclusion, a raceway must be installed as a complete system before the routing or installation of conductors, which also provides for the removal of conductors. Cables are prewired assemblies whereby conductors cannot be installed or removed. Type AC cables and MC cables are not considered pre-wired raceways. They are fabricated assemblies of insulated conductors in a flexible metallic enclosure, interlocking metal tape, or a smooth or corrugated metallic sheath. —Joseph Wages, Jr. IAEI Alternate Rep CMP-3

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Are there any practical guidelines available to installers and the enforement community with regards to continuous loads?

Posted By Keith Lofland, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Question

A continuous load is defined as "a load where the maximum current is expected to continue for 3 hours or more.” Are there any practical guidelines available to installers and the enforcement community to apply this definition?

Answer

As stated in the question, NEC Article 100 defines a continuous load as "a load where the maximum current is expected to continue for 3 hours or more.” In some cases, the NEC tells us when certain loads are continuous. For example, 422.13 demands that a water heater with "a capacity of 450 L (120 gal) or less be considered continuous loads for purposes of sizing branch circuits.” Most commercial lighting and electric signs [600.5(B)] are considered continuous loads. Unfortunately, the Code does not always spell out clearly when to consider a load as a continuous load for calculation purposes.

This is an AHJ call. Generally, dwelling loads are not considered to be continuous. For example, a table lamp may be left on for 3-hours or more, but that is a very small percentage of the ampacity of the circuit so we would not consider the circuit to be continuously loaded. On the other hand, parking lot lights or public hallway lighting would be a continuous load because the entire circuit would be loaded for 3-hours or more.

The definition of continuous load first appeared in the 1965 NEC. The original proposal called for a continuous load to be "four hours or more.” Subsequent action by CMP-6 on the wire tables in Article 310 settled the time element to three hours or more. This code detective could not find anything in the 1965 NEC substantiation that concluded anything "magical” about the 3-hour time frame, but this was the time frame that was eventually settled upon to define a continuous load. —Keith Lofland, IAEI Director of Education

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Canadian Electrical Code Appendix B

Posted By Leslie Stoch, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Many of the Canadian Electrical Code rules display a note, "See Appendix B.” Appendix B provides important information on interpreting and applying the rules. To be sure you’re on the right track it’s always a good idea to find out what Appendix B has to say. This article reviews a sample of excerpts from this valuable information source.

Rule 10-700 defines an in-situ grounding electrode as a part of the existing infrastructure, buried a minimum 600 mm below grade and having a surface area equivalent to a manufactured grounding electrode (two rod electrodes or a plate electrode).

Appendix B provides a list of acceptable in-situ grounding electrodes such as three metres of metal water piping, concrete reinforcing rods and iron pilings. It also provides a cautionary note – metal treated with a non-conducting corrosion protection does not satisfy the requirements for an in-situ grounding electrode.

Rule 12-120(4) now requires that the internal conductors of long vertical runs of armoured or sheathed cable must be supported at intervals not exceeding the distances specified in Table 21. Alternative methods of support include a 90-degree bend or several bends totaling 90 degrees at intervals not exceeding the Table 21 intervals, a horizontal run not shorter than the vertical run or a cable designed for vertical runs.

Appendix B explains that a horizontal run that equals or exceeds the vertical length or incorporates a 90-degree bend or several bends equal to 90 degrees reduces the strain on the conductor terminations.

Rule 12-902 permits pulling armoured cables into raceways with a number of conditions.

Appendix B warns that armoured cables may be damaged when pulled into conduit or tubing. Calculations and specifications are required to determine maximum cable lengths. Cable manufacturers should also be consulted for minimum bending radii.

Rules 12-1104, 1154 and 1508 refer to temperature limitations for PVC conduit, duct and tubing and specify that PVC must not be subjected to temperatures in excess of 75°C. However, 90°C rated conductors may be installed at their assigned ampacity ratings.

Appendix B explains that continuously loaded 90°C conductors under conditions of 50% fill and 30°C ambient do not result in temperatures above 75°C. Conductors with insulation temperature ratings above 90°C are also acceptable as long as their ampacities are derated to 90°C.

Rule 12-714 requires that mineral insulated box connectors must be used for mineral insulated cables.

Appendix B explains that mineral insulated cables may have copper, aluminum or stainless steel sheaths. Therefore box connectors must be suitable for use with each sheath material.

Rule 12-012 requires that allowance must be made for expansion and contraction of PVC conduit due to changes in temperature by using approved expansion joints.

Appendix B identifies the PVC coefficient of expansion as .0520 and provides a sample calculation. For a 20-metre run of rigid PVC conduit where temperatures range from minus 40 C to plus 30 C, the change in conduit length is 20 x (40 + 30) x .0520 = 73 mm.

Rule 14-510 specifies that manually operated general-use switches must be approved and marked for each purpose.

Appendix B the required switch markings as follows:

"T” – A switch for control of tungsten AC or DC filament lamps up to 125 volts
"L” – An AC/DC switch for control of AC lamps up to 125 volts
"AC, frequency or phase markings” – A general-use switch for use only on AC circuits

Rules 18-108 and 18-154 specify that cable seals must be provided where cables enter an explosion-proof or flame-proof enclosure or where first terminating in a Zone 1 explosive gas atmosphere.

Appendix B explains that cables are not tested for their ability to withstand an internal explosion and therefore must be sealed. Seals are also necessary to prevent passage through the cables of gases, vapours or flames.

I hope I have convinced you that Appendix B holds a wealth of invaluable information. Spending a few moments to find out what it has to say can provide big dividends.

As with earlier articles, you should always consult with the electrical inspection authority in each province or territory for a more precise interpretation of any of the above.

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Grain Elevator Safety

Posted By Thomas A. Domitrovich, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

What’s tall, holds some dusty stuff, and at times can go boom? You guessed it, grain elevators. This just may be a topic you don’t hear discussed very often, yet there are statistics associated with these structures that may surprise you. Headlines such as "Three More Victims Found after Explosion at Kansas Grain Facility . . .” or "2 Hurt in Grain Elevator Explosion in Tracy, Minn. . .” are very concerning and found all too often. A simple Google search for "grain elevator explosion” brings to light the urgency of safety in these types of facilities. Grain elevators have been around for quite some time and will be around for years to come as they are critical not only to many farmers across this country but also to this country’s economy. The statistics and news reports tell us we need to be concerned about grain elevator safety, which deserves your attention and your efforts when it comes to preventing what is happening across the United States — explosions that claim millions of dollars in property and many lives.

Photo 1. Grain elevators enable the handling of loose grain in large volumes.

Photo 1. Grain elevators enable the handling of loose grain in large volumes.

Background

Grain elevators have been around for a very long time; they were invented in Buffalo in the 1842 /1843 time frame to eliminate the need to bag and handle grain. They enabled the handling of loose grain in large volumes. A grain elevator includes a complex of facilities focused on handling grain. That would include offices, weigh-bridges, storage facilities and more. The United States Department of Labor’s Occupational Safety & Health Administration (OSHA) describes grain handling facilities as those "that may receive, handle, store, process and ship bulk raw agricultural commodities such as (but not limited to) corn, wheat, oats, barley, sunflower seeds, and soybeans. Grain handling facilities include grain elevators, feed mills, flour mills, rice mills, dust pelletizing plants, dry corn mills, facilities with soybean flaking operations, and facilities with dry grinding operations of soycake” (http://www.osha.gov/SLTC/grainhandling/index.html). When it comes to safety concerns, any business that has a grain elevator on-site that is utilized for the storage, transport and/or processing of a raw agricultural commodity is a prime target. As an example, these may also include breweries where malt and other ingredients are stored.

These facilities usually employ a bucket elevator or a pneumatic conveyor to take grain from a lower level to a higher level ultimately deposited in a silo or other similar storage facility. They come in all shapes and sizes from smaller grain elevators found on a farm to large grain elevators run by companies that focus only on this aspect of the grain trade. These larger grain elevator complexes are the beginning of a journey for the grain they hold, which finds its way to grain wholesalers, exporters and local users, being emptied out of the silos or bins by gravity into railroad cars, barges or other movers like trucks. This is a very efficient way to handle massive amounts of grain and beats the backbreaking job of handling bags or sacks of the stuff. It’s a process that is critical to our U.S. economy.

The statistics around grain elevators and dust explosions, in general, command our attention. Over the ten-year period reported in table 1 coming out of a Kansas State University study, there were 16 deaths, 126 injuries and $162.8 million in damage due to "dust” explosions. Grain elevator explosions are specifically called out in this report showing 51 explosions over this ten-year period from 1996 through 2005. More recent statistics are available from OSHA and show that over a more recent ten-year period, 2001 through 2011, there have been 83 explosions 59 injuries and 13 deaths.

Table 1. U. S. Agricultural Dust Explosion Statistics

Table 1. U. S. Agricultural Dust Explosion Statistics

The above statistics cover explosions, but the hazards in these grain handling facilities are many. Having grown up in a steel mill town [Aliquippa] in the Pittsburgh, Pennsylvania, area, I can remember sitting around the table listening to my father talk about the dangers that he witnessed in the steel mill and the lives that were lost. Mills, grain elevators and similar types of facilities have certain things in common; there are high areas, gratings, many rotating machines and ultimately many locations where life and limb are at risk. Workers can be exposed to a wide variety of life-threatening hazards in these facilities. Some examples include, but are not limited to, fires and explosions from grain dust accumulation, suffocation from engulfment and entrapment in grain bins, falls from heights, crushing injuries and amputations from grain-handling equipment. Suffocation is the leading cause of death in grain bins. This typically occurs when a worker enters a filled bin and walks/works on the grain without fall protection. A person can be engulfed and trapped when caught in flowing grain. Bridged grain and vertical piles of stored grain can also engulf a worker who enters a bin. Contrary to what you may think, only a few seconds pass before you realize you are entrapped and engulfed by flowing grain, leaving you helpless to free yourself. Suffocation shortly follows as a result of being buried alive in the grain.

Table 2. Grain Elevator Explosions

Table 2. Grain Elevator Explosions

The bottom line is that the handling and transporting of grain creates many hazards in addition to the hazard of the dust created by the process. Unlike the other hazards, the dust problem is one that can become a ticking bomb. Dust is typically very fine and gets just about everywhere. This dust can become an important piece of the recipe for an explosion. The elements of a dust explosion include fuel, oxygen, containment/enclosure and an ignition source. The dust generated at these grain elevator environments is the fuel.

Dust as a Fuel

Any Boy Scout or Girl Scout can tell you how to start a fire — it doesn’t include grabbing the largest available log and holding a match to it. No, quite the opposite; you gather smaller materials (kindling) and ignite those first. In general, the hazard increases as particle sizes decrease. The surface area to mass ratio of the dust particle is a key criterion with combustible dust. The ability of a particular dust to explode is determined by its concentration in air and is influenced by factors such as chemical composition and particle size. In the January/February 2010 issue of IAEI magazine, the inaugural printing of the "Safety in Our States” column included a discussion specifically on how an electrical fire starts. The basic principles discussed there apply here as well. It was shared in that article that "When it comes to ignition, for a solid to burn, it must be volatilized. For ignition to occur, the material first must be capable of propagating self-sustained combustion. The warming, the heat, causes chemical bonds to break and the material to be decomposed into volatile substances which either ignites in the presence of a pilot or it auto ignites.” In that article, I focused on the burning of building materials; here we are talking about materials of much smaller size which increases the overall ignitible surface area. Dust particles, from a size perspective, are smaller than 0.42 mm (420 microns). For comparison sake, granules are in the 0.42 mm to 2 mm size and pellets are larger than 2 mm in diameter. The size of dust is important as there are code requirements that reference dust particle sizes. Article 500 of the NEC, Hazardous (Classified) Locations, Classes I, II, and III, Divisions 1 and 2, during the 2011 code cycle, introduced a definition for combustible dust as "Any finely divided solid material that is 420 microns (.017 in.) or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air.” Proposal 14-9 of the 2011 cycle Report on Proposals (ROP), which is available at www.nfpa.org/70, was accepted to add this definition. This proposal was submitted by the American Chemistry Council (ACC) to retain the reference to dust size which was recently removed from other documents. This same definition made it into Article 506, as well.

Photo 2. The dust generated at these grain elevator environments is the fuel.

Photo 2. The dust generated at these grain elevator environments is the fuel.

Dust clouds present a very nice recipe for ignition as there is plenty of oxygen and surface area for ignition; but in addition to dust clouds, the presence of layered dust is also a significant safety concern. Dust can settle on horizontal and vertical surfaces, and to some extent, it can also settle on ceilings. This settled dust, depending upon the surface on which it has settled, has an opportunity to dry out, resulting in the lowering of its ignition temperature. This layered dust has been identified to be the source of damaging secondary explosions. Secondary explosions, in many cases, have been much more devastating than the initial explosion which may have resulted from ignition of airborne dust. It very well may have been a small explosion whose resulting pressure waves caused the structural vibrations that were enough to dislodge layered dust which, in turn, became fuel for yet another explosion. This secondary explosion will typically be much larger and result in a chain effect of more explosions, dislodging even more dust carrying the explosions well beyond an isolated location to quite possibly the entire facility.

Ignition Sources

I guess it would be accurate to say you can’t have an explosion without an ignition source. Ignition sources can come in different forms including thermal, mechanical or electrical energy. Welding, cutting operations, matches, lighters, cigarettes and even space heaters are all examples of ignition sources that have been identified in fire investigations as the cause of dust explosions. The source, though, doesn’t necessarily have to be some external activity to the process. The equipment itself can lead to ignition through friction, misaligned belts or pulleys, metallic buckets striking leg casings and slippage of belts and more; these are all sources of ignition. The point here is that you don’t need a flame to create a dust explosion. Over one-half of the dust explosions in Germany in 2005 were from non-flame sources. Common sources of ignition include:

  • electrostatic discharge
  • friction
  • arcing from machinery or other equipment
  • hot surfaces, including, e.g., overheated bearings
  • fire

It is, however, often difficult to determine the exact source of ignition post-explosion. Static charges can occur by friction at the surfaces of particles as they move against one another and build up to levels leading to a sudden discharge to earth. The use of electric power has also been identified. Sparks from the normal operation of switches, contacts, rotating machinery, and fuses can generate sufficient energy to ignite dust clouds. I have read of various incidents that involved electricity, including one where a light bulb with a faulty extension cord was being used to illuminate a bucket elevator boot pit and caused an explosion. The heat generated by arcing and sparking or even glowing contacts can generate the energy needed to ignite dust.

Photo 3. Sparks from the normal operation of switches, contacts, rotating machinery, and fuses can generate sufficient energy to ignite dust clouds.

Photo 3. Sparks from the normal operation of switches, contacts, rotating machinery, and fuses can generate sufficient energy to ignite dust clouds.

The recipe for disaster also includes the presence of oxygen and the containment/enclosure. The influence that oxygen has on fire is quite obvious and it is hard to reduce its presence. The amount of oxygen in air is more than adequate to support grain dust explosions. Falling or airborne dust acts to "mix” the dust particles with air. It is very desirable to minimize this mixing activity for obvious reasons. Combining an oxygen rich mixture of dust particles and a contained area with an ignition source provides the explosion with the right recipe for devastating energy.

The Safety Plan and Operating Procedures

I have two words when it comes to your safety plan — "Coin Up!” For those military personnel out there, you probably know what I’m talking about. Your safety plan is a critical part of your business and when challenged with the words "Coin Up” you should be able to produce it.

For those who may not be familiar, a challenge coin is something the military uses to enhance morale and remind Brothers in Arms of their commitment to each other. The origin of the challenge coin dates back to the Second World War where it was first used by the Office of Strategic Services personnel who were deployed in enemy held France. The coins back then were a local coin used to prove your identity. They were your bona fides that you had to produce during a meeting to help verify who you said you were. These coins may have been standard coins for the area, but they were unique in specific aspects such as the type, date, and a few other unique features of the coin. These details would be examined by each party, and they prevented infiltration into the meeting by spies. Today these coins represent each military individual’s commitment to his or her unit. Other organizations have produced these coins to raise awareness and to build bonds for many different reasons. The tradition of a challenge is the most common way to ensure that members are carrying the unit’s coin. The challenge begins when a challenger draws the coin and slaps it on the table or bar. Those being challenged must immediately produce their coins. Anyone failing to do so must buy a round of drinks for the challenger and for everyone else who has his or her challenge coin. However, if those being challenged produce their own coins, the challenger has to buy the round of drinks for the group. There are many different rules around the challenge but suffice it to say, for the purposes of this discussion, "Coin Up” is a challenge to produce your safety plan.

Photo 4. Combining an oxygen rich mixture of dust particles and a contained area with an ignition source provides the explosion with the right recipe for devastating energy.

Photo 4. Combining an oxygen rich mixture of dust particles and a contained area with an ignition source provides the explosion with the right recipe for devastating energy.

The following is by no means everything you need to include in your safety plan and procedures but are some highlights. Most of these were taken from NFPA 654, "Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids.” The referential documents offered as part of this article should be reviewed and understood and should ultimately influence the content of your safety plan and operating procedures.

Emergency Action Plan (EAP): Include your procedures for reporting of emergencies and evacuations. Include critical operations as well. Your employees need to understand how to assist in orderly evacuations. The EAP should be reviewed with all new hires, when their responsibilities change, and when the EAP changes. Include the EAP in your training. Make sure that you identify and follow applicable federal, state and local laws and regulations.

Grain Handling Requirements: You need at least two emergency escape routes from certain locations. Reference OSHA 1910.272(O)(1) and (2) for the requirements of these escape routes.

Safety Training: Make sure your training is job specific and some may say annually; but more frequent sessions are advisable. It’s important to ensure your employees can identify the hazard and understand how to prevent problems. Dust accumulation is a problem in these facilities. Ignition sources should be understood and identifiable. Those who have to access or enter bins must understand engulfment and mechanical hazards. Make sure they know their entry and rescue procedures.

Housekeeping: As discussed above, layered dust presents opportunities for subsequent explosions after the initial event. Your plans must include proper house cleaning which should call for the immediate cleaning when dust layers are noted to be 1/32-inch of thickness or more over a surface area of at least 5% of the floor area of the facility or the room. This thickness may change based on the type of dust as well. Make sure that there are no surfaces that are hard to get to and clean. Dust will continue to collect in these areas without your knowledge. Only use vacuum cleaners that are approved for dust collection.

Electrical Equipment: The use of appropriate electrical equipment for the environment and the proper wiring methods are very important to safety in these locations. Equipment bonding is very important. Some electrical equipment can become warm or hot. Motors, transformers, lights and other types of equipment not only offer surfaces for dust to rest but also act to dry that dust, again providing the perfect recipe for disaster.

Dust Control: In addition to housekeeping, there are ways to minimize the escape of dust from the process equipment. Ventilation systems should be considered as well as dust filters and collection systems. Minimize or eliminate activities that generate dust clouds, especially if ignition sources are present. As noted above, the ability to identify these dust cloud generating processes and ignition sources is critical.

Inspection: Inspect areas routinely. Make sure you have access to all areas and that there are no hidden surfaces that can accumulate dust.

Ignition Source Control: The ability to identify ignition sources should lead you to be able to limit these sources in your facility. Proper machine maintenance can help here as degrading machines may offer opportunities for friction and sparks to be generated. Heated surfaces and other sources of heat or sparks should be addressed.

Vehicles and Tools: The vehicles and tools on the job site should receive critical review. Maintenance of the vehicles, tools and equipment used in these dust areas is important to eliminate ignition sources and dust cloud generation.

Closing Remarks

Grain elevators are target rich environments when it comes to safety concerns. There are many tools available today to help ensure these facilities operate in a safe manner. We need to read, understand and "Coin Up” when it comes to our safety plans. Grain elevator explosions don’t have to occur. I hope this article stimulates the discussions that need to occur in various publications and educational forums to drive a downward trend in the statistics around grain elevator explosions.

Remember, keep safety at the top of your list and ensure you and those around you live to see another day.


Related Codes and Standards

 

Related NFPA Standards:

 

 

NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities

 

 

NFPA 68, Guide for Venting of Deflagrations

 

 

NFPA 69, Standard on Explosion Prevention Systems

 

 

NFPA 70, National Electrical Code®

 

 

NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Noncombustible Particulate Solids

 

 

NFPA 120, Standard for Fire Prevention and Control in Metal/Nonmetal Mining and Metal Mineral Processing Facilities

 

 

NFPA 432, Code for the Storage of Organic Peroxide Formulations

 

 

NFPA 480, Standard for the Storage, Handling, and Processing of Magnesium Solids and Powders

 

 

NFPA 481, Standard for the Production, Processing, Handling, and Storage of Titanium

 

 

NFPA 482, Standard for the Production, Processing, Handling, and Storage of Zirconium

 

 

NFPA 484, Standard for Combustible Metals, Metal Powders, and Metal Dusts

 

 

NFPA 485, Standard for the Storage, Handling, Processing, and Use of Lithium Metal

 

 

NFPA 495, Explosive Materials Code

 

 

NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas

 

 

NFPA 505, Fire Safety Standard for Powered Industrial Trucks Including Type Designations, Areas of Use, Conversions, Maintenance, and Operation

 

 

NFPA 560, Standard for the Storage, Handling, and Use of Ethylene Oxide for Sterilization and Fumigation

 

 

NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids

 

 

NFPA 655, Standard for Prevention of Sulfur Fires and Explosions

 

 

NFPA 664, Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities

 

 

NFPA 1124, Code for the Manufacture, Transportation, Storage, and Retail Sales of Fireworks and Pyrotechnic Articles

 

 

NFPA 1125, Code for the Manufacture of Model Rocket and High Power Rocket Motors

 

 


Related ASTM Standards:

 

 

E789-95 Standard Test Method for Dust Explosions in a 1.2-Litre Closed Cylindrical Vessel

 

 

E1226-00e1 Standard Test Method for Pressure and Rate of Pressure Rise for Combustible Dusts

 

 

E1491-97 Standard Test Method for Minimum Autoignition Temperature of Dust Clouds

 

 

E1515-03a Standard Test Method for Minimum Explosible Concentration of Combustible Dusts

 

 

E2021-01 Standard Test Method for Hot- Surface Ignition Temperature of Dust Layers

 

 


Related OSHA standards found in 29 CFR:

 

 

1910.22 - General Requirements: Housekeeping

 

 

1910.38 - Emergency Action Plans

 

 

1910.94 - Ventilation

 

 

1910.107 - Spray Finishing Using Flammable and Combustible Materials

 

 

1910.146 - Permit-Required Confined Spaces (references combustible dust)

 

 

1910.178 - Powered Industrial Trucks

 

 

1910.269 - Electrical Power Generation, Transmission and Distribution (coal handling)

 

 

1910.272 - Grain Handling Facilities

 

 

1910.307 - Hazardous (classified) Locations (for electrical equipment)

 

 

1910.1200 - Hazard Communication

 


Read more by Thomas A. Domitrovich

Tags:  Featured  November-December 2012 

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