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PostPosted: Tue Mar 15, 2011 7:47 am 
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The 2004 Title was 'Work on or near live parts'.
Whenever you examine a text, you need to take into account its history.
This was, and I believe remains, the intent of the article.

The reference to the Table was NOT that the risks were the same, just the opposite. The reference was to demonstrate that Art 130 recognizes that working with covers 'ON' is less risk than working with covers 'OFF'. So then the logical conclusion one would make is that covers offer some degree of protection.

The reference to light switches, to me is valid. For a logical conclusion to work it needs to work in the extreme. If you take Art 130 as applicable for live work, it works in the extreme. Higher than 40cal and the work is too hazardous to perform at all, but down to 0.00001cal there is still a requirement for minimum HRC clothing.

The only threshold where Art 130 does not apply is below 50 volts. If your claim that HRC is required for deadfront operations, then where and how, do you draw the extreme. If it is needed on a lighting panelboard why then is it not needed on the light switch. Both exceed 50 volts. There is a calculated IE at the light switch greater than zero.


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PostPosted: Tue Mar 15, 2011 8:18 am 
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There you go with the light switch. The OP has done a study and identified an incident energy somewhere between 8-25 cal/cm2. This is not a light switch and is a fairly high energy system based on the results of the analysis. What don't you get about that?


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PostPosted: Tue Mar 15, 2011 8:21 am 
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haze10 wrote:
There is a calculated IE at the light switch greater than zero.


At 18"? Not much more than zero so there is not a danger of a burn injury.


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PostPosted: Tue Mar 15, 2011 8:34 am 
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The discussion is not specific to Confuse's HRC3 issue. We are discussing whether or not the HRC3 label relates to all live work as well as all deadfront work, ie operating the breaker.

The light switch is NOT zero IE. It may be near zero, but Art 130 does not have a threshold where arc flash does not apply when IE is near zero. It only says it doesn't apply below 50 volts. There are panels fed from small high impedance transformers that can have near zero IE - does Art 130 no longer apply to them. There are light switches near high fault panels that may have higher IEs than a panel. My point is to understand the logic. For something to make sense to me, it needs to work in the extremes. Like I said, Art 130 referenced to live work only works in the extremes. I don't see how Art 130 referenced to deadfront works in the extreme.

Just saying 'don't go there because its ridiculous' is just one step further than me saying why are you going to the deadfront lighting panel with the janitor switching a 15 amp lighting circuit. If you are saying there is a risk, I agree. There is a risk is everything a human being does including breathing. My point is how Art 130 is being referenced against deadfront work.


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PostPosted: Tue Mar 15, 2011 9:19 am 
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Try reading what I posted again. You have had this same arguement with many people on this forum over the last couple years. No one seems to understand your logic. I give up trying to convince you otherwise. Why don't you write to 70E and ask what they think? Maybe you will listen to them, while you are at it, order a current revision of the standard.


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PostPosted: Tue Mar 15, 2011 9:24 am 
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100 Questions. It appears you will be better off ignoring anything Haze or myself say on your question. So how about some others chime in? Or perhaps we can make your question a poll question.

So I am done with this, what say the other people.

Does 100Q's need PPE to operate a breaker labeled HRC 3 with the covers on?


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PostPosted: Tue Mar 15, 2011 10:02 am 
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Zog wrote:
Does 100Q's need PPE to operate a breaker labeled HRC 3 with the covers on?


It is my opinion that this is considered "interacting" with a piece of equipment that has the potential to fail, thereby possibly causing an arc flash. The equipment is not rated arc resistant and has not been designed, nor tested, to withstand an arcing fault. i would advocate for operating the breaker in the same PPE as if you were "exposed to energized components".

Regardless of whether the FPN is part of the standard, i would bet that a lawyer would be able to successfully argue that it needs to be considered as such. That aside, operating the breaker with HRC #3 PPE is the way to go.

BTW haze, I hope you don't go out in the sun without complete head to toe protection with no skin exposed, if you are so worried about a light switch. Things can be argued to the nth degree, which is fine in a logic or philosophy class, but in the real world we do need some common sense and know when to stop, otherwise nothing would get done.

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Barry Donovan, P.E.
www.workplacesafetysolutions.com


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PostPosted: Tue Mar 15, 2011 10:45 am 
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I at least made the argument for my case. I have not heard the argument for where you stop considering arc flash if you apply Art 130 to deadfront equipment.

WTB, you need to read from the beginning. I am not advocating the inclusion of light switches, or anything else that is outside of that specifically references in Art 130.

There are techs all over the country performing LOTO without HRC.


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PostPosted: Tue Mar 15, 2011 6:45 pm 
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It is my opinion, that operating, not resetting, breakers with the covers on and disconnects with doors closed is not a situation 'likely to cause an electrical arc', if properly maintained and applied. This is in keeping with the FPN to the NFPA70E definition of Arc Flash, and with NRTL Listing standards (i.e. UL489) that require circuit breakers to be able to safely switch full load current on and off many 10's if not 100's of times, as well as one operation at full AIC rating.

Several big ifs, just like the rest of NFPA70E:
Properly maintained - must be clean, must be lubricated, must be operated regularly, must be replaced if it has interrupted a full level fault, the circuit must be free of faults (i.e. simple on-off without any electrical work being done on the circuit).

Properly applied - must be within its AIC level, enclosure must be rated for environment, must be within its rated life.


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PostPosted: Thu Mar 17, 2011 8:53 am 
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The line side of your 20 amp circuit breaker is most likely connected to a bus rated cat 3. There is always a potential of an arc flash occurrence when you operate the breaker.

NFPA 70E definition is:

Arc Flash Hazard. A dangerous condition associated with the possible release of energy caused by an electric arc.

FPN No. 1: An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.
FPN No. 2: See Table 130.7(C)(9) for examples of activities that could pose an arc flash hazard.


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PostPosted: Thu Mar 17, 2011 12:13 pm 
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holliday wrote:
There is always a potential of an arc flash occurrence when you operate the breaker.


Absolutely not according to the NFPA 70E definition you are quoting.

holliday wrote:
...Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.


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PostPosted: Fri Mar 18, 2011 3:39 am 
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holliday wrote:
FPN No. 2: See Table 130.7(C)(9) for examples of activities that could pose an arc flash hazard.


Is operating a breaker or switch with the covers on listed as an activity on this table?


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PostPosted: Fri Mar 18, 2011 5:30 am 
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100questions wrote:
Is operating a breaker or switch with the covers on listed as an activity on this table?


Yes it is.


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PostPosted: Fri Mar 18, 2011 7:24 am 
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If you performed an analysis on the panel, and have determined its IE value, you should not be using the tables. The tables are a short cut method based on approximations. Once you choose the analysis method, you typically no longer reference the tables. Under the analysis method, you have one IE and risk value. You are then in 'that' PPE level for all required tasks.

If you have not done an analysis, then not sure where you arrived at a label value, and you would be following the table, after you determined that you comply with the footnotes.


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PostPosted: Fri Mar 18, 2011 11:22 am 
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Zog wrote:
Yes it is.


But for 600 V and below equipment, it is listed as Hazard/Risk Category 0. Would you consider a Category 0 task an example of activities that could pose an arc flash hazard?

I think it is open to interpretation. You could reasonable conclude that tasks listed in Table 130.7(C)(9) with Category 0, like reading a panel meter while operating a meter switch, or performing non-contact inspections, would not be examples of activities that pose an arc flash hazard.


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PostPosted: Fri Mar 18, 2011 11:55 am 
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jghrist wrote:
But for 600 V and below equipment, it is listed as Hazard/Risk Category 0. Would you consider a Category 0 task an example of activities that could pose an arc flash hazard?

I think it is open to interpretation. You could reasonable conclude that tasks listed in Table 130.7(C)(9) with Category 0, like reading a panel meter while operating a meter switch, or performing non-contact inspections, would not be examples of activities that pose an arc flash hazard.


Yes but the OP stated they have done an analysis and this breaker is labeled as HRC 3, which leads me to believe that it exceeds the note limitations of the tables and poses a signifigant hazard.


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PostPosted: Fri Mar 18, 2011 12:38 pm 
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Zog wrote:
Yes but the OP stated they have done an analysis and this breaker is labeled as HRC 3, which leads me to believe that it exceeds the note limitations of the tables and poses a signifigant hazard.


No. The location of the breaker is an HRC=3, not the breaker itself.
Yes, there is a significant hazard present, if an arc is created.

But, what is the risk/probability, that a breaker designed and tested as a switch will fail during routine operation, thereby creating an arc on its line side? How is this risk reconciled with the known hazard in determining PPE?


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PostPosted: Fri Mar 18, 2011 1:31 pm 
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JBD wrote:
No. The location of the breaker is an HRC=3, not the breaker itself.
You know exactly what I meant, no need for comments like that, I find them insulting.
JBD wrote:
Yes, there is a significant hazard present, if an arc is created.
Yep

JBD wrote:
But, what is the risk/probability, that a breaker designed and tested as a switch will fail during routine operation, thereby creating an arc on its line side? How is this risk reconciled with the known hazard in determining PPE?


Ahh, the million $ question. First, I think we all understand the enclosure is not designed or rated to contain an arc flash.

Most of us also know the UL standard for switchboards only specifies wall thickness, and does not specify door thickness.

We also know the OEM's accountants will save every penny they can so the doors are noticeable thinner metal than the rest of the enclosure.

And, doors can have vents.

And, a lot of gear in most industrial plants is poorly maintained and rarely tested.

And, anyone in the breaker biz sees catastrophic failures on a regular basis.

So it is apparant that IF an arc flash were to occur the enclosure may not be counted on to contain the arc.

So, that brings us to the "IF". Was is the risk? The hazard has been identified by the arc flash study. What is the risk under a normal operation this breaker will fail? Slim to none.

However, most MCCB's are only rated for one short circuit interuption at rated current. And I doubt this breaker has a trip unit with indication of the type of trip that occured. So, what happens if the breaker trips? What sort of fault did it see? If it was a short circuit and the breaker is only designed and rated for one of those interuptions, is it being operated under "normal operating conditions"?

Let's look at OSHA 1910.334(b)(2) "Reclosing circuits after protective device operation." After a circuit is deenergized by a circuit protective device, the circuit protective device, the circuit may not be manually reenergized until it has been determined that the equipment and circuit can be safely energized. The repetitive manual reclosing of circuit breakers or reenergizing circuits through replaced fuses is prohibited.

Note: When it can be determined from the design of the circuit and the overcurrent devices involved that the automatic operation of a device was caused by an overload rather than a fault condition, no examination of the circuit or connected equipment is needed before the circuit is reenergized.


So, is the person operating this breaker trained to determine this? You think OSHA might bring this up should such a failure occur? Just asking some of the questions I have seen asked in court.

So, is there a grey area here? Sure there is. But the hazard has been identified, and if ignored falls under OSHA's willful violation fines, which are steep. So, is it better for an employer to "roll the dice" and hope this never happens? Or is it smarter to just wear the proper PPE? I know what my company does, what about yours?


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PostPosted: Sat Mar 19, 2011 3:11 am 
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THE question

JBD wrote:
But, what is the risk/probability, that a breaker designed and tested as a switch will fail during routine operation, thereby creating an arc on its line side? How is this risk reconciled with the known hazard in determining PPE?


Does anyone know anyone that even knows anyone that has ever had a SP 20A breaker blow up?

Under normal operation are the percentages in our favor in winning the lottery versus have an arc creating incident?

Where do you stop the PPE/CYA?


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PostPosted: Sat Mar 19, 2011 5:20 am 
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100questions wrote:
Does anyone know anyone that even knows anyone that has ever had a SP 20A breaker blow up?

Under normal operation are the percentages in our favor in winning the lottery versus have an arc creating incident?

Where do you stop the PPE/CYA?


Been an electrician for almost 20 years, worked on tons of different installations and have never seen a breaker blow up.. Seen a 2P70 (FPE Push-in) fail to open internally with no visible damage...A 1P40 (C/H Bolt-in) fail due to a weak solderred connection where it connects to the bus piece. The one I have seen completely destroyed was a 3P800A that was poorly maintained.. It failed on the Line side and blew a holoe through the enclosure.

Wiring failures due to loose connections is another matter... And when I have seen excessive heat damage to the wiring terminations on a breaker, that breaker is changed before it is returned to service.


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