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 Post subject: I'm Confused part II - swithing 20A 10k breakers
PostPosted: Sat Mar 12, 2011 4:59 am 
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Thanks to haze10 and his insight I'm starting another thread. I'm fully behind the need for PPE to do hazardous tasks. My non-engineer self is trying to better understand the risks as the company I work for works through the calculations and starts adding labels. I have "seemingly" all the crazy stuff. One of my biggest challenges is better understanding the need to be in CAT. 3 gear to operate a breaker WITH the covers on. Haze10 has put more questions back in my mind and that is a good thing. "In my opinion" I'm a very black and white person so my life would be a lot easier if someone can help me understand why I should be wearing CAT. 3 gear to open and close a 20A breaker. Thanks


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PostPosted: Sat Mar 12, 2011 7:55 am 
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Location: Charlotte, NC
Are you saying you have done an arc flash analysis and the resulting Ei requires HRC 3 PPE to operate a 20A breaker?

If yes, then what voltage? What is the protcetive deive upstream of that 20A breaker? What is the size of the upstream transformer?

If you have HRC 3 on a 120V 20A breaker from an arc flash study it is likely someone screwed up.

Is a qualified company doing the analysis or is this one of those times where your company threw this on the EE's desk and said go do this?


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PostPosted: Sat Mar 12, 2011 9:59 am 
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Zog wrote:
If you have HRC 3 on a 120V 20A breaker from an arc flash study it is likely someone screwed up.


Zog, sometimes you need to consider what the real world is like.
It is very easy to have this high HRC situation. Probably, the most common occurrence is a 150kVA transformer feeding a 400A 208Y120 panel with an integral main breaker.

In most of these case, the recommended mitigation is to install a 'new' secondary main device external to the breaker panel.


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PostPosted: Sat Mar 12, 2011 12:42 pm 
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We have

done the studies and one of the commonalities I see is Bus duct but that is not always the case. We do have these situations on 208v systems and yes we have an electrical engineer doing the work. For what it means I do greatly respect him and from my NON engineer self he does appear to know what he is talking about. I just have a hard time understanding a panel in a public area with all this potential danger and look down and see a little ol run of the mil 20A breaker being the one thing that is between you and "death". I do appreciate all the input. My personality does not like not understanding things so excuse all the seemingly dumb questions. Now everyone knows why my name is what it is. Thanks again.


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PostPosted: Sat Mar 12, 2011 5:48 pm 
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JBD wrote:
Zog, sometimes you need to consider what the real world is like.
It is very easy to have this high HRC situation. Probably, the most common occurrence is a 150kVA transformer feeding a 400A 208Y120 panel with an integral main breaker.

In most of these case, the recommended mitigation is to install a 'new' secondary main device external to the breaker panel.


If you have adjustable trip settings on the 400A breaker, drop them down from the "Max" or "10" to a much lower number... It is doubtful these settings need to be as high as they are for proper coordination... Doing that will drop your AF alot..

If they aren't adjustable, look at installing and AF reducing relay...


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PostPosted: Sun Mar 13, 2011 7:38 am 
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JBD wrote:
Zog, sometimes you need to consider what the real world is like.
Real world? It cracks me up when people say that. where exactly do you think I live?

JBD wrote:
It is very easy to have this high HRC situation. Probably, the most common occurrence is a 150kVA transformer feeding a 400A 208Y120 panel with an integral main breaker.

In most of these case, the recommended mitigation is to install a 'new' secondary main device external to the breaker panel.


You are making assumptions, until the OP posts some actual data any discussions about the true hazard are moot.


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PostPosted: Sun Mar 13, 2011 7:41 am 
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100questions wrote:
yes we have an electrical engineer doing the work. For what it means I do greatly respect him and from my NON engineer self he does appear to know what he is talking about.


I am sure they are very smart guys, but how many arc flash studies have they done before this one? What sort of training do they have? What software are they using?

The guys here that do this for a living will all admit that if they went back and looked over the first arc flash study they ever did there would be many things they would do different and likely did some things wrong. Experience is crucial on doing these studies.

100questions wrote:
I just have a hard time understanding a panel in a public area with all this potential danger and look down and see a little ol run of the mil 20A breaker being the one thing that is between you and "death". I do appreciate all the input. My personality does not like not understanding things so excuse all the seemingly dumb questions. Now everyone knows why my name is what it is. Thanks again.


I have a hard time believing that too, and keep the questions coming.


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PostPosted: Sun Mar 13, 2011 10:22 am 
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Zog wrote:
Real world? It cracks me up when people say that. where exactly do you think I live?
You regularly make comments that are focused on the large industrial electrical systems while seemingly ignoring the vast majority of small industrial and commercial installations that use molded case breakers and often do not exceed 1500kVA in capacity. You seem to admit this shortcoming in the other "confused" post where you said:
Zog wrote:
You do make a good point, as a switchgear guy when I think of operating breakers I am thinking high energy systems.


Zog wrote:
You are making assumptions, until the OP posts some actual data any discussions about the true hazard are moot.

You specifically said "it is likely someone screwed up", inferring it was unlikely that a 208Y/120VAC panel would have an HRC=3 condition. I pointed out that this is not an uncommon occurrence, and in fact it is extremely likely if the installation is a panel with an internal main breaker fed from a 150kVA transformer.


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PostPosted: Sun Mar 13, 2011 11:49 am 
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So switchgear does not exist in the real world?


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PostPosted: Sun Mar 13, 2011 12:57 pm 
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Zog wrote:
So switchgear does not exist in the real world?


No, the real world involves more than switchgear.

The vast majority of facilities, subject to NFPA70E, purchase their power at 208V or 480V with service sizes of 2500A or less and panelboard mounted molded case circuit breakers and fusible switches are the predominant protective devices. There is rarely any compartmentalization, much less separation, between a main device and its branch devices at service entrances and on transformer secondaries.


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PostPosted: Mon Mar 14, 2011 5:45 am 
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JBD wrote:
No, the real world involves more than switchgear.

The vast majority of facilities, subject to NFPA70E, purchase their power at 208V or 480V with service sizes of 2500A or less and panelboard mounted molded case circuit breakers and fusible switches are the predominant protective devices. There is rarely any compartmentalization, much less separation, between a main device and its branch devices at service entrances and on transformer secondaries.


Amazing, that is exactly how it is in my non-real world.


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PostPosted: Mon Mar 14, 2011 5:56 am 
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Confused:
Do you understand that the HRC3 is 'only' for when you remove the covers to work live.

If you are just operating the breaker with covers on, you need either no PPE or to follow the Matrix Table for HRC0.

Why do you keep saying you need HRC3 to operate the breaker. Hasn't it been made clear that this is a rating for only when the covers are off.


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PostPosted: Mon Mar 14, 2011 6:37 am 
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Thus

the need for me to be asking my questions.

Haze10 - you and others keep saying I do not need CAT. 3 to operate the breaker. Others and myself keep saying you all are incorrect. This is why I am so confused. If you all are correct my job got a heck of a lot easier. Unfortunately I need a little more facts and data to go back to my electrical engineer, safety committee etc. and let them know how wrong they are. As things stand now where I work you will be in the proper PPE to interact with the device. Covers on do NOT matter. I am not saying everything on my end is being done correctly but me better understanding things will at least help lead us in the proper direction. My stance would still be if the HRC3 hazard exists and you have a failure with a device in the enclosure you may really wish you had the elevated PPE on.

Your future input is greatly appreciated.


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PostPosted: Mon Mar 14, 2011 7:49 am 
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glen1971 wrote:
If you have adjustable trip settings on the 400A breaker, drop them down from the "Max" or "10" to a much lower number... It is doubtful these settings need to be as high as they are for proper coordination... Doing that will drop your AF alot..

If they aren't adjustable, look at installing and AF reducing relay...

Changing the main breaker settings will not solve the problem if the high IE is on the line side of the main breaker.


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PostPosted: Mon Mar 14, 2011 5:11 pm 
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haze10 wrote:
Confused:
Do you understand that the HRC3 is 'only' for when you remove the covers to work live.

If you are just operating the breaker with covers on, you need either no PPE or to follow the Matrix Table for HRC0.

Why do you keep saying you need HRC3 to operate the breaker. Hasn't it been made clear that this is a rating for only when the covers are off.


Because he does, show us the basis of your thinking that no PPE is needed.


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PostPosted: Mon Mar 14, 2011 7:09 pm 
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The Title of Art 130 is 'Work on or near live parts'.
The entire article talks about electrocution and the risk of working on or near live parts.

Deadfront is an industry term that defines that there is NO accessibility to live parts. Hence, Art 130 doesnt' apply.

This logic is reinforced by NFPA text for the one exception where Art 130 specifies the continued use of HRC clothing when switching significant energy sources. The industry typically defines this as Switchgear or other high energy devices. Only the uber conservative would take it down to a small lighting circuit breaker.

Why would Art 130 need to inject this qualifier if their intent is to require the same HRC when operating deadfront devices compared to working on energized parts?

Lastly, the only other reference to using HRC clothing when operating breakers is from the Task Table.
Even here they consistantly specify a lower HRC when operating breakers with covers on versus when performing work on live parts, like voltage checking. IF the risks are the same - then why isn't the required HRC the same?

Work ON or near energized parts. Trying to extend this down to work on NOT live or NOT near energized parts, down to the deadfront level is NOT what this code is about.

Let me ask you, if your logic extends to operating lighting circuit breakers in a deadfront panel - then what is logic for stopping there. Why not go down operating a light switch on the wall, or pushing the button on your computer? The code references 50V as the threshold, there is no reference to a minimum fault current. Maybe its because its only relating to live and energized parts like the Title implies.


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PostPosted: Mon Mar 14, 2011 8:18 pm 
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jghrist wrote:
Changing the main breaker settings will not solve the problem if the high IE is on the line side of the main breaker.


True enough..But changing them has the potential to lower the AF rating on the LOAD side, which in the case of the original post was an HRC3 rating on a 20A breaker...


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PostPosted: Tue Mar 15, 2011 3:44 am 
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Haze10

First of all - thank you for being the voice of the other side of thinking. That is a foremost need in my/our learning. I am still digesting your last post so I can TRY and debunk it. :D :D


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PostPosted: Tue Mar 15, 2011 5:42 am 
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haze10 wrote:
The Title of Art 130 is 'Work on or near live parts'.


In my very own copy of NFPA 70E-2009, Art 130 Title reads 'Work involving Electrical Hazards', not 'Work on or near live parts', which was the title for Art 130 in previous versions. Maybe someone should consult the current version before the 2012 version comes out...

haze10 wrote:
This logic is reinforced by NFPA text for the one exception where Art 130 specifies the continued use of HRC clothing when switching significant energy sources.


Can you find the exact wording of it please, or the page it is on? The only exceptions I can find in Art 130 are:
  • 130.3 Exceptions 1 and 2 (arc flash analysis for small circuits or the use of the task tables)
  • 130.7(C)(6)(a) (no leather protectors over rubber gloves)
  • 130.7(C)(12)(c) (incidental amount of elastic in underwear and socks)
  • 130.7(C)(14) (some blends are admitted if they pass ASTM F 1506)
  • 130.7(C)(15) Exceptions 1 and 2 (nonmelting materials as underlayers and special permission from AHJ for multiple hazards)


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PostPosted: Tue Mar 15, 2011 6:06 am 
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haze10 wrote:
The Title of Art 130 is 'Work on or near live parts'.
The entire article talks about electrocution and the risk of working on or near live parts.

Deadfront is an industry term that defines that there is NO accessibility to live parts. Hence, Art 130 doesnt' apply.

This logic is reinforced by NFPA text for the one exception where Art 130 specifies the continued use of HRC clothing when switching significant energy sources. The industry typically defines this as Switchgear or other high energy devices. Only the uber conservative would take it down to a small lighting circuit breaker.

Why would Art 130 need to inject this qualifier if their intent is to require the same HRC when operating deadfront devices compared to working on energized parts?

Lastly, the only other reference to using HRC clothing when operating breakers is from the Task Table.
Even here they consistantly specify a lower HRC when operating breakers with covers on versus when performing work on live parts, like voltage checking. IF the risks are the same - then why isn't the required HRC the same?

Work ON or near energized parts. Trying to extend this down to work on NOT live or NOT near energized parts, down to the deadfront level is NOT what this code is about.

Let me ask you, if your logic extends to operating lighting circuit breakers in a deadfront panel - then what is logic for stopping there. Why not go down operating a light switch on the wall, or pushing the button on your computer? The code references 50V as the threshold, there is no reference to a minimum fault current. Maybe its because its only relating to live and energized parts like the Title implies.


You are confusing hazard and risk. When you refer to the tables and say "the risk is the same" it shows me you are confused about the differences. The tables are task based, or risk based, and come from the gut feel of the commitee. Risk is very difficult to put a value on because there are too many variables. Are all the screws in place, are there vents on the doors, are the breakers maintained and tested, what is the physical condition of the enclosure. An ecclosure MIGHT contain an arc, it might not. But with the doors closed there is a lower risk.

Then there is "hazard", in this case there has been an arc flash analysis so the hazard has been identified at a certian level. All we know is HRC 3 so somewhere between 8 and 25 cal/cm2 I have to assume. That is a "signifigant energy source" and I think it is safe to say that this system is outside the limits of the tables. The table based HRC is only 1 with the covers off and the calulated HRC is 3.

So if the breaker in question is outside the limits of the tables the table can not be used, so your whole point of using HRC 0 with the covers on is moot.
The OP has identified this as a HRC 3, and the equipment is not arc rated. So if someone gets injured not wearing PPE if an arc flash occurs. What do you think the court will say?

130.7 (C) PPE - When an employee is working inside the AFB, PPE shall be worn. Hmmm, the OP did not tell us what the AFB was but with a HRC 3 I bet it is large enough the person operating the breaker is within the AFB.

Everytime you try to make this point, which you have for years many times, you always refer to turning on your computer, or turning on a light switch. No one that has ever discussed this with you has ever implied turning on either of those things, or anything similar is hazardous so just stop going there.


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