Beloved Arc Flash

[SiddMartin]

So everyone knows:
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I understand to wear the appr. PPE all the time and work everything DEAD all the time, I just want this explained for educational reasons.
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I know a lot of you are more educated on this then me, and thus why I ask, Is there a distance to 'live parts' that if not breached would not require the Arc Flash Rating and PPE equip? Here's my example:

Ex: You are adding a breaker in spot #30 in a dwelling 200A 240v Sin Ph., you turn off the main w/ the panel cvr on. Then remove the cover. Since the bus bars are dead, can you add the breaker w/o the PPE req. for exposure to "live parts"? I thought that I heard that if you are not within 2 in. of the exposed live parts(line side breaker/lugs) then the Arc Flash does not apply, but I need that explained to me.

Next question, is it true that if the live parts are 10kIC then you can drop a required Arc Flash rating? (Going from like a #2 which is so many calorie barrier or something, to a #1 which is basiclly hot gloves and glasses.)

I only know a little about this, and need enlightened, thanks for your help!

 

[jim dungar]

Ex: You are adding a breaker in spot #30 in a dwelling 200A 240v Sin Ph., you turn off the main w/ the panel cvr on. Then remove the cover. Since the bus bars are dead, can you add the breaker w/o the PPE req. for exposure to "live parts"? I thought that I heard that if you are not within 2 in. of the exposed live parts(line side breaker/lugs) then the Arc Flash does not apply, but I need that explained to me.

I have never seen a specific answer to this. I am sure that a judge or jury will clarify it some day. Most companies address it in their Electrical Safe Work Practices program, which are are required to have per NFPA70E.

Next question, is it true that if the live parts are 10kIC then you can drop a required Arc Flash rating? (Going from like a #2 which is so many calorie barrier or something, to a #1 which is basiclly hot gloves and glasses.)

Yes, there is a provision in the NFPA 70E task tables for making a category reduction for 240V or less systems with 10kA available, but it is not a blanket provision.

 

[eric9822]

Arc Flash PPE must be worn until the equipment is proven de-energized. So after the main is turned off, the cover is removed, and the bus bars are verified as de-energized with a meter then arc flash PPE can be removed. There is no 2" rule as far as I know for either shock or arc flash PPE. Arc Flash PPE boundaries are dictated by an arc flash study OR if you don't have one then the tables are used to determine what PPE is required. Shock protection boundaries are static distances based on voltage levels, you may be confusing that with arc protection boundaries. I don't have my NFPA70E with me and my companies rules are more conservative then required but I believe the shock protection boundaries for less then 600 volts are prohibited 1", restricted 1 foot, limited 10 feet.

 

[jim dungar]

Arc Flash PPE must be worn until the equipment is proven de-energized.

Actually all PPE must be worn, voltage and arc-flash.

 

[VinceS]

IAW 70E 130.2 Approach boundaries to live parts

IAW 70E 130.2 Approach boundaries to live parts

Open your 70E to 130.2, You might even find your specific questions answered in table 130.2(C), Limited approach boundary.

 

[bth0mas20]

exactly right.....NFPA 70E

 

[eric9822]

Jim is correct, all shock and arc flash ppe must be worn until the equipment is proven de-energized. Thanks for pointing out my error.

 

[don_resqcapt19]

With the line side terminals exposed as in most common service panels, I don't agree that you can remove the arc flash PPE after you verify that the load side bus is dead. You can remove the voltage protection PPE at that point, but, assuming that you are in the arc flash boundary, you can't remove the arc flash PPE. Remember that the approach boundaries trigger voltage protection PPE.

 

[FNCnca]

With the line side terminals exposed as in most common service panels, I don't agree that you can remove the arc flash PPE after you verify that the load side bus is dead. You can remove the voltage protection PPE at that point, but, assuming that you are in the arc flash boundary, you can't remove the arc flash PPE. Remember that the approach boundaries trigger voltage protection PPE.

I Agree, if there is live voltage in the enclosure, then you are still working hot.

 

[wtucker]

Arc Flash

Arc Flash

First of all, the PPE issue doesn't have to be as restrictive as you might think. Check out the table in NFPA 70E 130.7(C)(9)(a) --pay particular attention to Note 6) -- and Table 130.7(C)(10). You could be looking at a non-melting long-sleeve shirt, denim jeans, safety glasses and Class 00 gloves. DON'T WEAR A COTTON/POLY SWEATSHIRT! The poly can melt onto your skin.

If the line side is still live, everyone within the Flash Protection Boundary must wear PPE to protect against arc flash. (Leather gloves instead of rated gloves.) The Flash Protection Boundary can either be calculated in a formula at NFPA 70E, Art. 130.3(A), or, at voltages 600V or less, 4 ft. (based on the product of clearing times of 6 cycles and the available bolted fault current of 50 kA or any combination not exceeding 300 kA cycles (5000 ampere seconds).

PPE for protection against electrical shock must be worn within the Restricted Approach Boundary or when taking any conductive object close to the exposed part (NFPA 70E, Art. 130.3(C)), which, for 301 to 750 volts equals contact with the part (Table 130.2(C).

The Limited Approach Boundary is more important: for voltages up to 72.5 kV, don't let unqualified persons within 10 ft. of exposed current-carrying conductors unless they're escorted by a qualified person, which is defined as one who "has the skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved." (Art. 100)

Worker's Comp limits liability of you toast the apprentice (an unqualified person), but there's no limit to liability if you crisp the plumber who's walking by with a length of copper Schedule 40.

OSHA enforces this under the General Duty Clause of the OSH Act.

 

[zog]

Yes, there is a provision in the NFPA 70E task tables for making a category reduction for 240V or less systems with 10kA available, but it is not a blanket provision.

This was revoved for the 2008 70E, not safe to reduce protection at these values and this provision gets abused.

 

[zog]

With the line side terminals exposed as in most common service panels, I don't agree that you can remove the arc flash PPE after you verify that the load side bus is dead. You can remove the voltage protection PPE at that point, but, assuming that you are in the arc flash boundary, you can't remove the arc flash PPE. Remember that the approach boundaries trigger voltage protection PPE.

Exactly right Don, but I need to add that the arc flash boundary applies when there are live parts, not "Exposed live parts" like the shock boundaries. Arc Flash PPE is required if the terminals are exposed or not, as long as the panel has power in it and you are "Interacting" with the equipment.

 

[zog]

PPE for protection against electrical shock must be worn within the Restricted Approach Boundary or when taking any conductive object close to the exposed part (NFPA 70E, Art. 130.3(C)), which, for 301 to 750 volts equals contact with the part (Table 130.2(C).

.

The RAB is 1' for 301-750V

 

[jim dungar]

This was revoved for the 2008 70E, not safe to reduce protection at these values and this provision gets abused.

Yes, but the answer to the OP was about the standard in effect today, not one that may exist someday in the future. Because, if you start talking about the next 70E version my answer on required labeling will also need to be changed.

 

[zog]

True, but if it is being removed because of a safety issue, why still follow the exception today? A person can be injured today, before the standard is changed.

Same goes with the changing labeling requirements, if you know a change is coming why would you advise someone to label something today that wont meet the requirements in October?

 

[don_resqcapt19]

Zog,

Exactly right Don, but I need to add that the arc flash boundary applies when there are live parts, not "Exposed live parts" like the shock boundaries. Arc Flash PPE is required if the terminals are exposed or not, as long as the panel has power in it and you are "Interacting" with the equipment.

So if the line side terminals were in an enclosure made of the same material as the panel itself, you would still need arc flash PPE?
Don

 

[zog]

If they are covered completely with the same material the panel is made of (Which I doubt) then it depends if you are using the tables or have completed an analysis.

I assume most would be using the tables so it depends on the task you are performing, it dosent matter if the main breaker is open or closed, the potenial arc energy is the same in that panel. I suppose you could interpret your senerio as "covers on" for operating breakers but doing other work in the panel it would have the same requirements.

 

[jim dungar]

... if you know a change is coming why would you advise someone to label something today that wont meet the requirements in October?

When do you accept the next standard: at the ROP, the ROC, at acceptance, when it is published, or when it is enacted? I was not aware that the next edition had been accepted with a scheduled publishing date much less having an "effective as of" date.

NFPA 70E is a standard, a set of requirements, it is not a set of specific how-to rules. 110.7 says it is the responsibility of the employer to provide an overall electrical safety program (ESWP). If a new edition of standards are adopted it would be incumbent on the employer to merge their existing ESWP with the new requirements.

 

[don_resqcapt19]

zog,

If they are covered completely with the same material the panel is made of (Which I doubt) then it depends if you are using the tables or have completed an analysis.

It is my understanding that there is a Canadian rule that requires this cover and it must be made of the same material as required for the panelboard enclosure. If such a cover would remove the need for PPE when working on the load side of the main breaker, it would be a good idea for our code to require a cover over the line side terminals.
Don

 

[zog]

You have got to be kidding!

You have got to be kidding!

When do you accept the next standard: at the ROP, the ROC, at acceptance, when it is published, or when it is enacted? I was not aware that the next edition had been accepted with a scheduled publishing date much less having an "effective as of" date.

NFPA 70E is a standard, a set of requirements, it is not a set of specific how-to rules. 110.7 says it is the responsibility of the employer to provide an overall electrical safety program (ESWP). If a new edition of standards are adopted it would be incumbent on the employer to merge their existing ESWP with the new requirements.

I accept any valid research that show a better way to protect myself, my employees, and my students from injuries as soon as that information is made available to me. Why wouldnt you?

How would you feel if one of your emplyees was injured because of something you knew about existed to protect him but just had not become "effective"?

People need to start using common sense! Who give a mouses behind if something is gone into effect or not if lives can be saved? If your state did not have a seat belt law, but you knew it was coming later this year, and there was proof that seat belts save lives, would to have your children buckle up, or wait until the new law went into effect?