How will you meet new code requirements for arc reduction?: Q&A Session

Arc flash incidents occur all too often and impact many lives. To address the problem in the industry, NEC 240.87 was developed to ensure arc flash safety in the electrical industry. Three industry experts weigh in through an extensive Q & A.

By Thomas Domitrovich, Ken White, Jim Dollard April 30, 2014

Thomas Domitrovich, PE, LEED AP, Eaton, Ken White, retired, Olin Chlor-Alaki, and Jim Dollard, safety coordinator, IBEW Local 98, answered the following Webcast-viewer questions related to NEC 240.87 code requirements:

Q: To what extent are foremen/supervisors responsible for following arc-fault safety, procedure for calculating safety distance?

  • A: Jim: Everyone is responsible for safety. See NFPA 70E 2012 105.3 and 110.3.

Q: How should PPE selection be approached with respect to NFPA 70E Annex H vs. Table 130.7(C)(16)? Why do the two tables differ for the same energy levels? Should we not be using hazard/risk categories when an analysis has been performed?

  • A: Jim: Excellent question! The HRC tables and Annex H are different because doing a study and using the tables are two completely different approaches. The tables are based on empirical data from industry and the collective experience of the committee. A study is based on formulas and data gathered by the engineer. The tables are built conservatively and a study that identifies an exposure at 7.5 cal cannot be classified as an HRC 2. An understanding of the definition of "arc rating" is essential. The user must fully understand ATPV and EBT. Perhaps the 2018 edition of 70E will get that done.

Q: Can you discuss why the NFPA 70E has different methods of PPE selection and why they are different for the same incident energy? i.e. Annex H vs. Table 130.7(C)(15)(a)

  • A: Jim: Excellent question! The HRC tables and Annex H are different because doing a study and using the tables are two completely different approaches. The tables are based on empirical data from industry and the collective experience of the committee. A study is based on formulas and data gathered by the engineer. The tables are built conservatively and a study that identifies an exposure at 7.5 cal cannot be classified as an HRC 2. An understanding of the definition of "arc rating" is essential. The user must fully understand ATPV and EBT. Perhaps the 2018 edition of 70E will get that done.

Q: Have adequate and functional auto-darkening hoods been developed yet?

  • A: Jim: I am not certain about "auto-darkening," but the tint on the shields has progressed to allow more light to see the task at hand.

Q: Jim or Tom, Please explain how the NEC-2014 requirements for 1200A breakers affects existing equipment. What about overcurrent protection such as fuses?

  • A: Thomas: The National Electrical Code applies to new construction but this technology can be applied to existing locations. Section 240.87 does not apply to fuses.

Q: There must be a slightly increased risk of actuating the overcurrent device when using the "reduced arc energy maintenance switch." Do you have to wear the appropriate FR clothing for the arc flash rating prior to adjustment of the switch – and then reduce your arc flash clothing to meet the new level?

  • A: Thomas: The attractive feature of the Arc Reduction Maintenance Switch is that the switch can be activated remotely and with doors closed.

Q: Is there a code that requires the labeling of arc flash hazards or is it just a best known practice based on NFPA 70E?

  • A: Jim: Labels are addressed in NFPA 70E 2012 in 130.5(C). The 2015 edition of 70E will clarify that the owner of the equipment is responsible for the label.

Q: What type of clothing must be worn underneath the Arc Flash Suit?

  • A: Jim: Natural fiber clothing only, no meltables. See 130.7.

Q: [Are] programmable trip breakers with Arc Flash Mitigation going to be addressed by NFPA 70E in the future?

  • A: Jim: NFPA 70E is a workplace safety standard and not an installation standard. There is a good chance that CB’s and other equipment equipped with a means to ensure arc energy reduction gets addressed in 70E with respect to how justified energized work is approached.

Q: What safety gear should we be using to protect ourselves prior to opening up switchgear equip ment, and is there any specific type of safety gear such as the thickness of rubber/leather gloves, shoulder wear, eye wear, etc? Thank you.

  • A: Jim: PPE, other protective equipment, insulating and shielding materials must be selected for the equipment on which justified energized work will be performed. This is after a shack hazard analysis and an arc flash hazard analysis is performed. For examples see the HRC Tables in 130.7(C)(15)(a) with Table 130.7(C)(16) and Table H.3(b) in  Annex H NFPA 70E 2012.

Q: Live work and OSHA’s stance?

  • A: Jim: See 1910.333 where OSHA mandates that energized work is justified as done in 70E.

Q: There’s seems to be a conflict between A/F and selective coordination (in ’14)?

  • A: Thomas: This technology is meant to reduce incident energy. Should an event occur, selective coordination would have been lost as well. This technology, especially when using the Arc Reduction Maintenance switch, damage is limited and the facility can be up and running very quickly just as in the success story documented in the presentation today.

Q: Your discussion seemed to address maintenance more than normal run time. Do the injury stats – perhaps – include mere out-of-the-blue accidents that might include end users?

  • A: Jim: Normal operation of properly installed and maintained equipment does not expose the employee to hazards. When energized work is performed, the likelihood of an incident is exceptionally higher.

Q: What is the fundamental difference between the IEEE 1584 AND NFPA70E requirements.

  • A: Jim: See NFPA 70E 2012 Table D.1 in Annex D. 1584 is one of several calculation methods available. NFPA 70E does not mandate the calculation method used. 

Q: Can you identify specific language in NEC & NFPA70E that requires FM’s to conduct an AF Study?

  • A: Jim: The requirement is that an arc flash hazard analysis be performed. It can be achieved through a study or the use of the HRC Tables. See NFPA 2012 130.5.

Q: It seems the tables in 70E for PPE are nearly worthless after you read the fine print. Basically, without doing an arc fault study, it still a guess if they apply. How do you use them?

  • A: Jim: The tables work. When we look at all of the legacy equipment in the world there is an extremely minute amount that has a study performed. The tables work where we can determine an assumed amount of available fault current and clearing time. When you get into larger devices such as LVPCB’s the user may not be able to determine an assumed clearing time and they cannot use the table.

Q: Any 70E updates?

  • A: Jim: There are a lot! Maybe that could be another Eaton webinar!

Q: Mandatory changes to arc flash labeling system per the latest NFPA 70E. How do we standardize the method of calculations in various plants with different installation contractors? What the areas of the world that currently have mandatory arc flash labeling systems?

  • A: Jim: There are multiple excellent questions here! We could build a webinar on your question. It is just too much to do at this time.

Q: How do I contact the presenter(s)?

  • A: Thomas: Please visit and there are also references if you download a PDF of the slides under "Event Resources" on the left side of your screen.

Q: What is the change in stringent requirement between 2009 70E and 2012 70E?

  • A: Jim: There are so many we could do a webinar on that alone.

Q: Do we need to install hazard level for all equipment above 50 volts or only for equipment between 50 volts and 240 volts with transformer rating above 112.5 KVA??

  • A: Jim: That was deleted in the 2012 70E. There is no longer an exception for given sizes of kVA and voltage.

Q: Is a maintenance switch a standard feature for breakers greater than 1000A, such as for all major manufacturers?

  • A: Thomas: I would not say it is a standard feature. Specify Arc Reduction Maintenance Switch on your next design.

Q: Arc Flash protection for Line Side 480 VAC installations and use (and problems) with utilizing the NFPA-70E Tables?

  • A: Jim: Use of the HRC tables mandates that the user determine an assumed maximum available fault current and clearing time. While one may be able to determine an assumed maximum available fault current by determining the maximum fault current on the secondary of a utility owned transformer assuming an infinite primary, there is no clearing time. The parameters of the tables cannot be met in service equipment unless the line side of the main OCPD is enclosed.

Q: 240.87 does not appear to actually "require" that circuit breakers be used. It also does not seem to "require" that solid-state trip units are necessary; it says, "Where the highest current rating… is installed." What about if "Fuses" are provided?

  • A: Jim: Section 240.87 does not apply to fuses. It falls under the section entitled "Circuit Breakers".

Q:  What is the OSHA interpretation of live? Especially in Lockout/Tagout off confirmation operations, how realistic is it to reduce hazard areas and still have selective coordination?

  • A:  Jim: Where exposure to energized conductors or circuit parts exists, the worker is exposed to live parts. Your second question is one that owners must seriously ponder. If you have a system that is selectively coordinated, do you really want to enetertin energized work? You could take the enetire system down. If a fault occurs you will have an outage, that is a given. It is prudent to apply a means of arc energy reduction which will limit the energy, reduce exposure to workers and reduce equipment damage to your selectively coordinated system.

Q: Referring to NFPA 70E-2012, article 130.5, I’ve encountered many people who believe arc flash hazard analysis now has to be done to circuits below 240v, fed by 125KVA and lower, just because NFPA 70E doesn’t have the statement anymore. Is this correct?

  • A: Jim: Yes, that is correct. Perhaps the collaborative efforts of NFPA, IEEE and many major players in the industry will provide the data we need to address this issue.

Q: Tom, With the maintenance switch in place, is it a good idea to provide two different arc flash hazard labels for the two different time curves?

  • A: Thomas: I have seen this done in the past. I do not see any harm in doing so and more information, I would think, is better than less. 

Q: Any 70E 2012 changes?

  • A Jim: There are far too many changes in the 2012 and 2015 editions of NFPA 70E to comment at this time.

Q: Ken White, In the case study, was the breaker in Cubicle 4 a feeder or main? How much of the electrical system was interrupted? Voltage, ground system?

  • A: Ken: The main is in cubicle 1 cubicle 4 feeds an air compressor.

Q: What role does OSHA play regarding these requirements?

  • A: Jim: OSHA requires that employers protect their employees from recognized hazards. Utilizing a means of arc energy reduction is a significant step to reduce exposure where justified energized work must be performed.

Q: How do you handle a situation where you cannot get below a CAT4?

  • A: Jim: When incident energy is in that range there is an extremely high amount of thermal and explosive energy. In the past there were proposals to go to an HRC 5 at even higher levels of energy. The 70 E committee rejected that idea because science can tell us how to predict an protect against the thermal energy but not the exposed arc blast and associated shrapnel. See NFPA 70E 130.7(A) Informational Note No. 3 where the committee suggests that in excess of 40 cal/cm2 a greater emphasis on reenergizing is necessary.

Q: Can you discuss the arc flash 208v and nfpa 70e requirement?

  • A: Thomas: NFPA 70E 2012 requires a shock and arc flash hazard analysis for all voltages 50 volts and higher. Systems less than 50 volts must also be evaluated for capacity and overcurrent protection to determine exposure to arch flash and the hazards associated.

Q: What is the most economical and effective arc flash reduction strategy?

  • A: Thomas:  The Arc Reduction Maintenance switch is your fastest, easiest to employ and specify.  The ARMs solution will come as part of the equipment and can be wired at the manufacture for local indication to meet the NEC requirements. 

Q: What is the consultant’s role in meeting the code requirement?

  • A: Thomas: A consultant’s role in system design and the Code is to design a system that meets the Code or exceeds it. 

Q: Why is there no time reduction in seconds as indicated in 240.87? By how much should clearing time be reduced?

  • A: Thomas: By implementing these technologies, reduced clearing times are implemented. The code currently does not have a maximum clearing time for arcing current.

Q: Can you discuss the trade-offs between arc flash mitigation and selective coordination?

  • A: Thomas: Achieving selective coordination places intentional delays in upstream overcurrent protective devices. This can be the cause of increase incident energy, arc flash values higher up in the system.  Section 240.87 addresses this issue by requiring arc reduction techniques up stream in the system. This requirement will hopefully educate many on the cost effective solutions available so that it is applied even further downstream in the system.

Q: Clarification: Does 240.87 apply to non-adjustable breakers?

  • A: Thomas: It applies to ALL circuit breakers 1200Amps and above. And that can be adjusted to 1200Amps. It does not provide any relief for non-adjustable circuit breakers.

Q: Please discuss the implications of arc flash hazard reduction vs. protective device coordination.

  • A: Thomas: Achieving selective coordination places intentional delays in upstream overcurrent protective devices. This can be the cause of increase incident energy, arc flash values higher up in the system. Section 240.87 addresses this issue by requiring arc reduction techniques up stream in the system. This requirement will hopefully educate many on the cost effective solutions available so that it is applied even further downstream in the system.  The implication here is that reliability of the power distribution system can be increased with this section of the NEC as after the event, the distribution system has a faster re-energizing time than those that do not employ these technologies and have to be replaced after the event.

Q: Ken, was there a safety observer during the work who was not participating in the work? If not, why not?

  • A: Ken: The second electrician was considered as the safety person.

Q: Are arc fault breakers required to be installed when gfci receptacles are to replace conventional receptacles in kitchen?

  • A: Thomas: Although not a part of this program, I can address this question. The act of replacing a receptacle 406.4(D)(4) is your code reference. If you are NEC 2014, this section of the NEC says you can put a breaker in or put an OBC AFCI device at the first outlet. But if you are on NEC 2014, it did add kitchens to the list of protected rooms and so a kitchen receptacle replacement would trigger AFCI protection as well.

Q: What methods are available for arc flash reduction in older switchgear? How does the size of the upstream transformer affect arc flash calculations?

  • A: Thomas: Always keep in mind that the incident energy heavily relies on the amount of current and time it is permitted to flow. The challenge with existing older systems is to get them to respond faster to arcing faults. Upstream transformers can reduce the available fault current but it doesn’t help an overcurrent protective device respond faster. You must model the system and review ways to reduce clearing times. Retrofitting technology into existing equipment is possible in many cases.

Q: Please recommend software for arc fault calculations.

  • A: Thomas: SKM software is a good resource but you can always look at others like EDSA.

Q: Can you discuss employing arc reduction strategies in existing facilities, retroactively? And also how to convince owner/managers to have arc flash studies performed in order to implement arc reduction strategies?

  • A: Thomas: Arc reduction strategies and the work it takes to convince owners and managers to make the decisions necessary to address is and probably always will be difficult. Unfortunately it takes fines and events to convince some individuals who say it can never happen hear or it never happens to us. Now that we are seeing National Electrical Code changes in this area, more will be aware of how simple it really can be to address incident energy. Education and codes will change some people’s minds but unfortunately for many it will take time. Retrofitting these technologies into existing systems is possible. 

Q: First, can you explain/discuss the effect of barriers (switchgear/MCC doors, plexiglass covers, etc.) on the level of arc flash energy just outside the equipment where people are likely to be standing? In addition, can you discuss the difference in arc flash hazards to personnel?

  • A: Thomas: Arc-resistant switchgear is designed to prevent operator injury based on redirecting the arc energy away from the operator in the event of an arc fault, as determined by testing included in ANSI C37.20.7. The standard for personal protective equipment (PPE) is outlined in NFPAt 70E, which states that arc-resistant switchgear (as defined by ANSI C37.20.7) carries a hazard risk category of zero for the following activities:
    • 1. Circuit breaker operation with doors closed and latched
    • 2. Racking of breakers in cubicles with doors closed and latched
    • 3. Racking of ground and test devices in cubicles with doors closed and latched
    • There are various types of arc resistant equipment that include:
    • Type 1—Must be arc resistant in the front of the equipment only
    • Type 2—Must be arc resistant around the entire perimeter of the equipment
    • Type 2B—Must be arc resistant around the entire perimeter of the equipment, even with instrument or control compartment doors open
    • Type 2C—Must be arc resistant between adjacent compartments within the assembly, as well as around the entire perimeter of the equipment"

Q: Can you discuss arc resistant construction vs. arc termination/interruption? In addition, can you discuss cost-effective arc mitigation strategies and compare arc-flash mitigation vs. OCPD selective coordination?

  • A: Thomas: Arc-resistant switchgear is designed to prevent operator injury based on redirecting the arc energy away from the operator in the event of an arc fault, as determined by testing included in ANSI C37.20.7. The standard for personal protective equipment (PPE) is outlined in NFPAt 70E, which states that arc-resistant switchgear (as defined by ANSI C37.20.7) carries a hazard risk category of zero for the following activities:
    • 1. Circuit breaker operation with doors closed and latched
    • 2. Racking of breakers in cubicles with doors closed and latched
    • 3. Racking of ground and test devices in cubicles with doors closed and latched
    • Ac interruption equipment will reduce the incident energy values and save not only workers but also reduce damage to the equipment.  In the case study presented today, the equipment did not have to be replaced.   The most cost effective arc mitigation technology is the Arc Reduction maintenance switch and the most cost effective arc mitigation strategy is one that includes this technology. Selective coordination adds intentional delays for upstream overcurrent protective devi  That can increase incident energy values.  Section 240.87 goes a long way to addressing this 

Q: How do we best close the gap between the newer approaches to safety with its cumbersome methods and old school thinking? Is it just by education, education, and more education?

  • A: Thomas: Good question. This is very challenging but education has got to be at the core.

Q: Arc-proof gear vs. arc-mitigation gear — what are the pros and cons?

  • A: Thomas:  I am assuming you are referring to Arc Resistant equipment.  When it comes to those who must engage with energized equipment, the drawback with arc resistant equipment is that it is no longer arc resistant when the doors are opened.  The equipment does provide an advantage for any work that can be performed while the door is closed.  there is more and more equipment being made to accommodate more work that can be performed while the doors are closed including but not limited to racking in and out of the circuit breaker.

Q: Do instantaneous trip breakers comply?

  • A: Thomas: Only where the arcing current is into the instantaneous region of the circuit breaker’s trip curve.  

Q: Does a properly set instantaneous trip (set below the expected arc current level) meet the code requirement as an approved equivalent means or an active mitigation system?

  • A: Thomas: Only if the arcing current is well into the instantaneous pickup of the circuit breaker. If the arcing current is below this area of the curve, instantaneous on the device is not functioning to reduce incident energy and so would not meet the intent of the NEC.

Q: Why define the requirement for additional measures by amperage when that is not necessarily a predictor of high incident energy?

  • A: Thomas: This approach was taken as the only way to limit the impact from a code perspective. I agree with you that you can still have serious arc flash issues lower in the distribution system. My only suggestion is that you can exceed the NEC requirements.

Q: When identified through calculation that the safe approach boundary is not even in the room where the equipment is located, what is our responsibility beyond labeling with a danger sticker?

  • A: Thomas: This type of question will typically stir much debate as there are many that believe simply standing in the same room and no interaction with the equipment requires one to be suited up with appropriate arc flash PPE. Others feel that you need to be interacting with the equipment to require the appropriate PPE for the job. I guess you have to determine what side of that fence you are on.  If you feel that simply walking into the room presents a hazard and can meet the definition of interacting with the equipment, you need to make the appropriate decisions. If not, then labeling the equipment as required by NFPA 70E is adequate. 

Q: Can you discuss arc flash reduction with respect to coordination, particularly for emergency and standby systems?

  • A: Thomas: None of the solutions listed in Section 240.87 are designed to shut down the power distribution system needlessly. Should an event occur and the technology clear the fault, reducing incident energy, the device has done its job and power would have been lost anyway. The benefit of employing these technologies is to reduce damage and downtime.

Q: When do you expect the 2014 NEC to be adopted in Pennsylvania?

  • A: Thomas: Well your guess is as good as mine. We have been heavily involved with trying to educate and raise awareness of the importance to adopt the latest version of the Code. Stay tuned and your help and voice can be helpful at public hearings. Attend when you can.

Q: Can you discuss breakers without instantaneous, less than 1200A?

  • A: Thomas: Power circuit breakers can have no instantaneous at amperages below 1200Amps. This is true. When trying to address the language of the code that could reach consensus, the panel elected to use that which is in the NEC 2014. If better language can be created to expand this requirement to those circuit breakers that do not have an instantaneous, in the words of my friend Mark Earley, "I look forward to your public input."

Q: Will existing arc flash studies need re-evaluated and certified? 2How does the new regulation affect old (1970’s & prior) plants? And how can the regulation & NEC 2014 Section 240.87 be obtained for free — is a corporate membership needed?

  • A: Thomas: Section 130.5 of NFPA 70E version 2012 states that the Arc Flash Hazard analysis shall be updated when major modifications or renovations take place and reviewed periodically not to exceed 5 years. The NEC is typically referenced when new construction is conducted. Older facilities always provide challenges but I would say safety, and the new solutions available, should always be considered when systems are being reviewed for upgrades or other similar activities. It’s wise to plan to keep the power distribution system updated with new technologies.

Q: What is the definition of arc flash?

  • A: Thomas: Surprisingly, after a search for a definition of the term Arc Flash, I could not find a formal definition in IEEE, NFPA or other similar publications. These documents define “Arc Flash Boundary”, “Arc Flash Incident Energy”, “Arc Flash Hazard” and other similar terms but not “Arc Flash”. So I am taking a liberty here to provide a definition that I have put together based on reading many different documents relating to arc flash and arc flash energy. An arc flash is the light, heat, sound and gases produced as a result of a rapid release of energy due to an arcing fault sustained by the establishment of a highly-conductive plasma. The severity of the event is not in the definition above as that aspect of an arc flash event is addressed by some of the other definitions above which address boundaries and incident energy.

Q: If an Arc Flash study shows that no hazard exists, is compliance with 240.87 really necessary?

  • A: Thomas: That would be up to the Authority Having Jurisdiction. Be careful about using frases as "No hazard exists". An Arc Flash Study only indicates the level of incident energy. It by no means indicates that "No hazard exists.".

Q: What are the benefits of ARMS vs. ZSE?

  • A: Thomas: The arc reduction maintenance switch responds faster than zone selective interlocking. An ARMS switch will clear the fault within, approximately, 40ms. Zone selective interlocking can take as long as 100ms.

Q: What cities are adopting this  and when will the new codes be in effect?

  • A: Thomas: The following states have adopted the latest version of the NEC, NEC 2014, which includes the 1200Amps and above language: Colorado Effective 7/1/2014, Idaho Effective 7/1/2014,  Massachusetts Effective 1/1/2014,  Nebraska Effective 4/9/2014. The following states have adopted the language of 240.87 as shown in NEC 2011: AL, AK, AR, CA, DE, GA, IA, KY, LA, ME, MI, MN, MT, NE, NH, NJ, NC, OH, OK, OR, RI, SC, SD, TX, UT, VT, WV, WI, WY. Some states that adopt locally have adopted either NEC 2011 or even NEC 2014. You should check your local state code laws for accurate information.

Q: What have been the number of arc flash incidents over the past 25 years, and is the number going down?

  • A: Thomas: The information I have was included in our presentation. I do not have a source of information that shows a trend. An electrical industry 10-year study of 120,000 workers reveals:
    • 125 injuries per year
    • 77% electrical arc injuries
    • 21% permanent disabilities
    • 2.4% fatalities

Q: What are some arc protective accessories for a warehouse operation?

  • A: Thomas: The type of facility is not of concern. There are solutions for all types of power distribution systems. When work is being performed, arc protection should be considered. Section 240.87 applies to all circuit breakers that are rated for or can be adjusted to 1200amps and higher. There is no special considerations by what type of facility they are in. 

Q: With all covers on equipment and only an operating handle exposed, does the operator need PPE to operate the circuit breaker/switch?

  • A: Thomas: This type of question will typically stir much debate as there are many that believe simply standing in the same room and no interaction with the equipment requires one to be suited up with appropriate arc flash PPE. I would say the key to answering this question is in the knowledge of the maintenance of the equipment in question. Properly maintained equipment shouldn’t be treated as hazardous, especially when you are operating the device as it is intended to be operated. The challenge is determining if the subject equipment has been properly maintained.

Q: For land-based facilities, is arc flash PPE required to open an enclosure, or is it only if something is done that can generate an arc?

  • A: Thomas: When you open equipment and expose energized parts, I would say you are interacting with that equipment in a way that is outside of normal operation. I would error on the side of caution and dress for the work.

Q: For Mr. White, which energy-reducing methodology was used? i.e. light detection, maintenance switch on main, etc.

  • A: A maintenance switch on the main was used in this incident.

Q: Was there QC or other sign-off as the work was being performed during the case incident? Was "change of equipment to be used to perform the work" discussed during the pre-job plan? Would a lesson to be learned by the near miss, be to have a sign off during the performance of the work by QC of craft safety personnel?

  • A: Thomas: For this incident there was no QC involved. There was not a discussion about the change of equipment.

Q: Who determines that the equipment is likely to be worked on while live?

  • A: Jim: The same entity that decides to implement safe electrical safe work practices in accordance with NFPA 70E.

Q: Why did the entire plant shutdown if you only shutdown 480V breaker feeding your lineup? Was coordination lost so the main breaker also tripped?

  • A: Only that 480 substation was electrically shutdown but that resulted in a process shutdown

Q: Is ARMS purely a maintenance tool, or are there specific load profiles or site configurations that tolerate an always-on incident energy reduction design?

  • A: Thomas: ARMs was designed for maintenance.

Q: Will the maintenance switch operate the breaker any quicker than it would with the trip unit instantaneous setting in its min setting? I find that if you keep the instantaneous setting below the arcing current you can’t do any better. This would be my equivalent means. Unless the breaker can operate quicker you can’t do better as long as the settings will allow the inrush of downstream equipment.

  • A: Thomas: Yes, the ARMs switch will operate faster than instantaneous. The ARMs technology bypasses the microprocessor. It uses an analog circuit and so can operate faster than instantaneous.  

Q: If the maintenance switch is quicker than setting the instantaneous to its minimum setting, do modeling software’s such as SKM & Easypower have the published trip times for this in their software library? Is this a setting in the software?

  • A: Thomas: SKM should have these curves in their library. I will make an effort to correct any place where these curves are not. If you have an immediate need, you can talk with your local sales office who will engage the right people within Eaton who can address the missing curves.

Q: Can you do a differential protection scheme with molded case circuit breakers without having to install a bunch of additional CTs? The ZSI system works well with molded case breakers without a bunch of additional hardware.

  • A: Thomas: Differential protection is usually a relay application. ZSI is what you would employ for circuit breaker applications. I agree with your statement that ZSI works good with molded case circuit breakers without a bunch of additional hardware.

Q: How do the proposed arc flash reduction requirements for 1200AF breakers and above affect maintenance work on existing installations?

  • A: Thomas: Existing distribution systems can present challenges but they can be retrofitted with technology to address incident energy.  

Q: Which manufacturers have a maintenance switch?

  • A: Thomas: Eaton manufacture the Arc Reduction Maintenance Switch as well as many other safety products, please visit for more information.

Q: Do you have to have a separate Arc Flash label for the maintenance setting?

  • A: Thomas: I have seen some label the equipment with the incident energy with and without the technology employed.

Q: If you have a 1200 amp breaker with a 400 amp rating plug, does this apply? I.e. if the breaker requires a physical replacement of the rating plug does this need to meet 240.87?

  • A: Thomas: If the breaker can be adjusted to 1200Amps, yes. I think the AHJ would be better to ask this question but to be safe, I would suggest employing arc reduction technologies as identified in 240.87.

Q: Tom, Does the new Article 240.87 require arc reduction devices on mains and feeders in the same equipment (i.e. 3000A Main Breaker in SWGR + 1200A feeder breaker)?

  • A: Thomas: If you read the language of the code, any breaker 1200Amps and higher, or can be adjusted to 1200Amps or higher, must employ this technology. The only time you really get benefit from this is when you employ an arc reduction technology that can help downstream, outside of the gear that the technology is in.

Q: If a short power outage occurs while the reduction switch is active, will the trip timing be impacted?

  • A: Thomas: I’m not sure I understand the question. If a power outage occurs while the arc reduction switch is on, timing is not affected.

Q: Given that all of the four prescribed methods rely on their operation on the arcing fault current, what proof must be offered for their effectiveness?

  • A: Thomas: Incident energy values tell the tale. Provide arc flash labels as required by NFPA 70E and maintenance personnel can dress for the occasion.

Q: How will energy-reducing maintenance switching affect selective coordination requirements?

  • A: Thomas: It doesn’t impact selective coordination unless an event occurs in which case selective coordination would have been impacted anyway. It has a good chance of increase reliability by enabling the system to be up and running after an event as was the case with the success story shared today.

Q: Reference 240.87: Is there ever an incident where reduction clearing time should be considered with a breaker rated at less than 1200 Amps?

  • A: Thomas: Just because the NEC has established 1200Amps as the number used to trigger Arc Flash reduction technologies, that does not mean you cannot employ this technology lower in the distribution system. High incident energy values can be located lower in the distribution system.

Q: Tom, I just started working at a higher education facility in which in-house maintenance have limited knowledge plus no arc-flash analysis. I am pushing hard to convince the need for identification, but always get questioned, is ARC-Flash survey a law?

  • A: Thomas: Good question. OSHA enforces NFPA 70E but unfortunately not until after the event. OSHA requirements is your fall back.

Q: Is 240.87 Arc Energy Reduction only an attempt to reduce the clearing time? Does it not require a specific reduction in the calculated incident energy, say from 15 Cal/cm^2 to 3 cal/cm^2?

  • A: Thomas: Section 240.87 does not reference incident energy values. The level of reduction will depend upon the technology employed.

Q: How do these requirements effect retrofitted switches?

  • A: Thomas: State code enforcement requirements vary by state. Check with your local AHJ for proper guidance from a code perspective. From a safety perspective, any opportunity to take advantage of the latest safety technologies on the market should always be considered.

Q: Can you discuss the code that states 1200 A and above should have an arc flash mitigation technique outlined by NEC 240.87? What is direction if the calculation at the equipment is CAT 0? Does this already meet criteria Five?

  • A: Thomas: That is at the discretion of the Authority Having Jurisdiction. My opinion on that matter would not carry weight.

Q: In a line up with multiple 1200 A devices and a MAIN, does only the MAIN need the technology? Or on all 1200 A devices?

  • A: Thomas: Per 240.87, any breaker that is greater than or can be adjusted to 1200Amps must be equipped with the technology. In actuality, especially if you employ ARMs, applying the technology on feeder circuits minimizes the outage should an event occur.

Q: How does an Arc Flash Reduction Maintenance Switch really differ from dialing down the short time trip setting during maintenance? I suppose this may not be a best practice as it would then have to be reset to ensure coordination, but would this meet the same intent of a maintenance switch?

  • A: Thomas: The ARMs switch is designed with arc energy reduction in mind. There is not act of "dialing down" necessary. There is local status indication as well. I would not advise "dialing down" the instantaneous.  

Q: Is an ARM switch available for Eaton’s N-Frame (1200A) molded case, electronic trip circuit breakers?

  • A: Thomas: The N-frame breaker uses the Digitrip RMS 310+ trip unit and yes, it does have the ARMs technology.

Q: Tom: For the N & R frame breakers, is the ARMS enabled solely by manual manipulation of the dial (inside the arc flash zone), or is it enabled from a digital input (outside the zone)?

  • A: Thomas: No, it is not solely engaged by manual manipulation. Customers have employed other ways to automatically turn this technology on including but not limited to a switch on the inside of the gear door that when opened engages ARMs as well as motion sensors in the room.

Q: Is it common for typical electronic trip breakers over 1200 A to be equipped with Arc-fault reduction devices standard from the factory?

  • A: Thomas: When specified by the consultant.

Q: Can you explain a bit more on the zone interlock. For example, how many levels does it need to interlock?

  • A: Thomas: Zone selective interlocking technology works between two breakers. The more layers you have, the more zones of protection, the better. I think two levels is a good start.

Q: Ken – OSHA (29 CFR 1910.333) emphasizes that no work should be performed on live electrical equipment above 50 V, except where: (1) de-energizing equipment would cause a greater safety hazard; or (2) where de-energizing is not possible due to equipment design or the nature of the work being performed. Did the work where you had the near miss, meet this criteria?

  • A: When this happened we were in the opinion that this work meet that criteria. Since then the policy has been modified.

Q: What are other recommended ways to mitigate line side of main breakers other than method 1, 2 or 3?

  • A: Thomas: The line side of main breakers presents a challenge as the utility manages that portion of the system. Arc reduction techniques on the line side of the utility can come in the form of Arc Reduction Maintenance technology on relays.

– Edited by Jessica DuBois-Maahs, associate content manager, CFE Media, jdmaahs (a)