Arc Flash- struggling to understand

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Sparketta

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Recently, my company has gotten concerned about the implications of arc flash. I think this is great, and long overdue. But I think that there are some misconceptions about when arc flash PPE is required, and I am looking for guidance.

For example, there is a certain task that we perform on a regular basis, verifying a ~115 volt reading and a 400Hz reading with a Fluke 87 via banana jacks on the front of a rack mounted component. See photo attached for the actual component. The screen readout shows the voltage, but we are required to verify it with another meter.

I have been told that we will be required to wear PPE to take this reading, but it just doesn't seem right because the voltage is so low and there are no exposed conductors. Is this even something that should be assessed as a class 0 rating? Please help, I really want to know the answer to this.

Because my company tends to overreact, they are saying that we will have to wear FR coveralls, hearing protection, safety glasses, safety shoes, and gloves, even for class 0.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Your company gets to set the rules as to what PPE they will require. They are required to create an Employee Safe Work Practices program, which, among other things, should detail PPE and other requirements for common/routine tasks.

But yes, it is true that a 120V circuit fed from a transformer not larger than 125kVA would be considered a category 0. And NFPA70E does not require FR clothing for hazard risk category 0.
 
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shockin

Senior Member
JD -

While I would agree that a HRC of 0 is probably correct. A level 0 would IMO still require a long sleeve natural fiber shirt and natural fiber jeans as well as saftey glasses and a hard hat. It's not required to be FR rated as you had said as well.
 
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Sparketta

Member
I'm not sure I understand why this would even be an HRC 0, if plugging something in to a standard electrical outlet is not. Can someone explain what the difference is?
 
zog

zog

Senior Member
Location
Charlotte, NC
Sparketta said:
Recently, my company has gotten concerned about the implications of arc flash. I think this is great, and long overdue. But I think that there are some misconceptions about when arc flash PPE is required, and I am looking for guidance.

For example, there is a certain task that we perform on a regular basis, verifying a ~115 volt reading and a 400Hz reading with a Fluke 87 via banana jacks on the front of a rack mounted component. See photo attached for the actual component. The screen readout shows the voltage, but we are required to verify it with another meter.

I have been told that we will be required to wear PPE to take this reading, but it just doesn't seem right because the voltage is so low and there are no exposed conductors. Is this even something that should be assessed as a class 0 rating? Please help, I really want to know the answer to this.

Because my company tends to overreact, they are saying that we will have to wear FR coveralls, hearing protection, safety glasses, safety shoes, and gloves, even for class 0.
Click to expand...

There is no arc flash or shock hazard for that task, your company is overeacting but that is thier progotive. They can go above and beyond the requirements if they want.
 
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Sparketta

Member
zog said:
There is no arc flash or shock hazard for that task, your company is overeacting but that is thier progotive. They can go above and beyond the requirements if they want.
Click to expand...

Thanks for the response, that is what I was looking for. I know they can go overboard if they want, and they probably will, but I may be able to influence the decision. Is there a specific part of the 70E that I can point to that gives direction on when a task is below the arc flash/shock hazard threshhold?
 
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Sparketta

Member
shockin said:
Table 130.7 (C) (9) (a) will give you a little help.
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I took a look at it, but I couldn't find anything in the table that indicates when a task is not a potential hazard at all. The lowest hazard class is 0, and that still requires a certain amount of PPE. If some tasks (such as the voltage reading I described) are virtually the same as plugging an appliance into an electrical outlet, is there anywhere in the 70E that gives guidance on this?

Referencing the table, it would appear that the task still falls under a 0 rating (Work on energized electrical conductors and circuit parts, including voltage testing- we are plugging meter leads into banana jacks), though it would seem to be overkill, as we do not require everyone to wear a long sleeved cotton shirt, safety glasses, etc. when plugging things into standard electrical outlets.

I imagine we are to use a certain amount of "common" sense, but it really isn't quite so common anymore :)
 
zog

zog

Senior Member
Location
Charlotte, NC
Look in the definitions section.

Electrical Hazard - gives some guideance
Arc Flash Hazard FPN1
Exposed - Should do the trick for you
 
J

jhaas5

Member
proper ppe

proper ppe

Sparketta said:
Recently, my company has gotten concerned about the implications of arc flash. I think this is great, and long overdue. But I think that there are some misconceptions about when arc flash PPE is required, and I am looking for guidance.

For example, there is a certain task that we perform on a regular basis, verifying a ~115 volt reading and a 400Hz reading with a Fluke 87 via banana jacks on the front of a rack mounted component. See photo attached for the actual component. The screen readout shows the voltage, but we are required to verify it with another meter.

I have been told that we will be required to wear PPE to take this reading, but it just doesn't seem right because the voltage is so low and there are no exposed conductors. Is this even something that should be assessed as a class 0 rating? Please help, I really want to know the answer to this.

Because my company tends to overreact, they are saying that we will have to wear FR coveralls, hearing protection, safety glasses, safety shoes, and gloves, even for class 0.
Click to expand...

If it has been determined that work will be performed within the flash protection boundary of the electrical equipment, a flash hazard analysis must be performed. This analysis will determine the incident energy exposure of the worker and the level and type of ppe required based on the working distance of the face and chest from a possible arc source and for the specific task to be performed. In your case catagory "0". Requiring your people to wear the ppe you mentioned isn't a bad thing. Have you done a arc flash study? Does your equipment have the proper arc flash and shock hazard labels? The current nec has implemented equipment labeling requirements regarding arc flash and shock hazards. this version has been adopted in all 50 states.
 
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wtucker

Senior Member
Location
Connecticut
Sounds like your employer is assuming that the Flash Protection Boundary is 4 ft. NFPA 70E 130.3(A) allows one to make that assumption, thereby avoiding taking the time and exercising the brain to do an Incident Energy Analysis. But, if they use 70E Annex D and actually calculate the Incident Energy, they may find the Flash Protection Boundary is on the order of inches, not 4 ft. This could save lots of money in time and equipment costs.

But yes, they have the right to do it the way they've chosen, and yes, it's akin to sticking a plug into a receptacle. Only a little less dangerous than taking the covers off the outlet boxes to paint the wall...
 
K

kencybart

Member
Location
Des Plains, IL
NFPA 70E Table 130.7(C)(9)

NFPA 70E Table 130.7(C)(9)

NFPA 70E-2009 Article 130.3(B) requires either an incident energy analysis, or the use of Tables 130.7(C)(9), 130.7(C)(10), and 130.7(C)(11) to determine the Hazard Risk Category and required PPE for the task. Table 130.7(C)(9) assigns HRC 0 to tasks performed on equipment 240 volts and below, even if the doors are closed, or covers are on.
It would be probably be best practice to use HRC 0 PPE for your task, however, Article 130.3 does not require an arc flash hazard analysis if the circuit is rated 240 volts or less and the circuit is supplied by a single transformer rated less than 125 kVA. Therefore, no arc flash PPE is required by NFPA 70E if you can verify the transformer is less than 125 kVA.
It is important to remember that there is still a shock hazard and appropriate shock PPE is required by NFPA 70E.
 
zog

zog

Senior Member
Location
Charlotte, NC
This

kencybart said:
NFPA 70E-2009 Article 130.3(B) requires either an incident energy analysis, or the use of Tables 130.7(C)(9), 130.7(C)(10), and 130.7(C)(11) to determine the Hazard Risk Category and required PPE for the task. Table 130.7(C)(9) assigns HRC 0 to tasks performed on equipment 240 volts and below, even if the doors are closed, or covers are on.
Click to expand...

Is the opposite of this

kencybart said:
Therefore, no arc flash PPE is required by NFPA 70E if you can verify the transformer is less than 125 kVA.
Click to expand...

kencybart said:
It is important to remember that there is still a shock hazard and appropriate shock PPE is required by NFPA 70E.
Click to expand...

Not if you are talking about the equipment pictured in the OP, there are by definition no shock hazards or PPE required to take measurements on those external test points.
 
K

kencybart

Member
Location
Des Plains, IL
NFPA 70E - 2009 Article 130.3

NFPA 70E - 2009 Article 130.3

NFPA 70E -2009 Article 130.3 states that an arc flash hazard analysis determines the Flash Protection Boundary and the required PPE to be used within the Flash Protection Boundary. However, it goes on to say that an arc flash hazard analysis is not required where all of the following conditions exist:
(1) The circuit is rated 240 volts or less.
(2) The circuit is supplied by one transformer.
(3) The transformer supplying the circuit is rated less than 125 kVA.
If these three conditions exist, an arc flash hazard analysis is not required, which would have identified the Flash Protection Boundary.
Paragraph (B) specifically refers to work within the Arc Flash Protection Boundary. If there is no Arc Flash Protection Boundary, then the incident energy analysis or use of the Tables is not required.
As I stated before, it is probably a good practice to use HRC 0 PPE (long sleeve shirt, long pants, safety glasses, hearing protection, and leather gloves) as a minimum daily wear for workers to protect themselves when testing, or interacting with a switch or breaker with the doors closed, or covers on. Hope this clarifies my answer.
 
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