NFPA 70E

[jedstump]

Under Table 130.7(C)(9)(A) in the NFPA 70E 2004 in working on energized parts on panelboards from 240V to 600V it states "hazard risk category 2*"

In the notes it states a double layer switching hood must be used. I beleive that a double layer hood would put you into category 3.

Am I right to assume that this is because the Table 130 is just an estimated guideline for certain tasks and therefore may be subject to over protection?

If so in order to get a more accurate level of protection an arc flash analysis should be performed?


Terry Smeader
(edited to remove url)

[ December 28, 2005, 06:43 AM: Message edited by: don_resqcapt19 ]

 

[zog]

Re: NFPA 70E

You are correct that a more detailed analysis should be done, the tables have many limitatations and are designed to be used on a temp basis until you complete your study.

The basis for the hood requirement is the placement of the head for certian tasks. When you are operating a breaker in that panel your head is probally >18" away when you do the operation (stand off to the side and turn your head away), when you are working on energized parts or doing voltage testing you typically have to put your head in there close to see what you are doing and your head may be closer than it would for other tasks, your head may even be in the panel so the arc would engulf your head, thus the hood requirement.

 

[bphgravity]

Re: NFPA 70E

Terry,

Who and what is your typical market that you are selling to? I am curious as to what sectors of our industry is engaged in energized work that would require PPE.

 

[jedstump]

Re: NFPA 70E

Thank you. Zog

That is what I thought. I just wanted to make sure I am understanding this correctly.

Zog do you have any suggesting on reading material a person could obtain in order to get more education on the 70E and how it relates to OSHA.

Although I must admit this forum is good as you get to hear real life experiences.


Terry

 

[jedstump]

Re: NFPA 70E

Hello Brian

I am getting enquiries all across the sectors from shools to small utility companies. Mostly what I am selling is the 10 cal face shields with hard hats and low voltage gloves.

I am not sure who the customer was that was asking about the arc flash hoods as we just had a brief conversation.

I believe that quite a few people are in the process of seeing what there options are and the costs involved.

I believe the publicity of the NFPA 70E 2004 is starting to spread and this is why I have been studying certain literature on the subject so I can help my customers on compliance issues.

I am sure you will be hearing more from me as this forum appears to have a good amount of traffic.


Terry
edited to remove URL

[ December 28, 2005, 11:17 AM: Message edited by: don_resqcapt19 ]

 

[jim dungar]

Re: NFPA 70E

You are selectively reading parts of NFPA70E. A double layer switching hood is only one part of the PPE requirements for Category 3.

Due to the increased risk associated with using a voltage test meter on an un-evaluated system the task table 130.7(C)(9) requires additional protection, that is why voltage testing is listed as 2*. This may be based on the probability that the user will have their face closer than 18" to the meter (look at the last couple of sentences in 130.3(B)) and the generalizations of the task table.

This is one reason to pay for an engineering anaylsis. If you know the available incident energy is a Category 2 you do not have to worry about the 2* task.

 

[jbwhite]

Re: NFPA 70E

Originally posted by bphgravity:
I am curious as to what sectors of our industry is engaged in energized work that would require PPE.

The saftey inspectors where I work have said that PPE is required anytime there are exposed live terminals. This would mean that to open the cover of a residential panel would requre PPE.

I too would like some more information on this subject.

We work in live panels all the time and those suites are hot in the winter, and miserable in the summer.

I would think that all sectors of the electrical industry would require this, save purhaps certain periods of new construcion before equipment is energized. Until you have tested a panel, or circuit, we must assume that it is hot, even though we have just switched it off and locked it out.

 

[don_resqcapt19]

Re: NFPA 70E

Bryan,

Who and what is your typical market that you are selling to? I am curious as to what sectors of our industry is engaged in energized work that would require PPE.

Even if you are not actually working the equipment live, the PPE is required to be used when you are troubleshooting and when you are using a voltage tester to verify lockout.
Don

 

[MJJBEE]

Re: NFPA 70E

bphgravity-
Our company regularly does hot work. I work in the utility buisness and you can not shut down some critical processes without endangering public saftey and reliablity. So Linemen do hot work. Currently our linemen don't wear any arc protection. (I know this is wrong but I'm just an engineer and can't force the changes to move faster)

 

[don_resqcapt19]

Re: NFPA 70E

jb,

The saftey inspectors where I work have said that PPE is required anytime there are exposed live terminals. This would mean that to open the cover of a residential panel would requre PPE.
We work in live panels all the time and those suites are hot in the winter, and miserable in the summer.

In many cases the fault current levels at a residential panel will not require a "suit". FR shirt and pants are available to meet the Level 2 PPE requirement. These are worn as you normal work clothes, and for energized work, you add voltage rated gloves and the required face and head protection.
By the way, OSHA does not permit you to work in live panels!!
Don

 

[jbwhite]

Re: NFPA 70E

Originally posted by don_resqcapt19:
By the way, OSHA does not permit you to work in live panels!!
Don

How is it that we do it all the time? The installation that I work on doesnt want to shut down opperations every time we need to tie a wire to a breaker.

Not trying to be rude here, just trying to learn something new.

edit, i dont do alot of residential, that was just an exmple. but on that note, should we get the utility to shut off the power every time we install a breaker in a house?

[ December 28, 2005, 12:02 PM: Message edited by: jbwhite ]

 

[8TWD192]

Re: NFPA 70E

quote originally posted by jbwhite:
"...should we get the utility to shut off the power every time we install a breaker in a house?"

I was wondering the same thing so I talked to some people and found out that it was addressed in IEEE 1584 "Guide for Performing Arc-Flash Hazard Calculations". It was too expensive for me to purchase, but I recieved this information from a breaker manufacturer
Regarding Arc Flash Hazards, IEEE1584, Article 4.2 states:
"Equipment below 240 V need not be considered unless it involves at least one 125 kVA or larger low-impedance transformer in its immediate power supply."
Its a shame that the same information can't be found in NFPA 70E which is much more affordable

 

[jbwhite]

Re: NFPA 70E

I work on larger kva transformers, and 480v all the time.

it is the part about osha not allowing this that has me curious. someone is going to have to tell the marine corp that they need to shut down opperations so i can add a breaker for the new coffee maker. i dont think they are going to like this.

 

[don_resqcapt19]

Re: NFPA 70E

jb,

How is it that we do it all the time? The installation that I work on doesnt want to shut down opperations every time we need to tie a wire to a breaker.

Just because "we do it all the time" does not make it right or safe.

1926.416(a)(1)
No employer shall permit an employee to work in such proximity to any part of an electric power circuit that the employee could contact the electric power circuit in the course of work, unless the employee is protected against electric shock by deenergizing the circuit and grounding it or by guarding it effectively by insulation or other means.

1910.333(a)(1)

"Deenergized parts." Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. Live parts that operate at less than 50 volts to ground need not be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.


Note 1: Examples of increased or additional hazards include interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment, or removal of illumination for an area.


Note 2: Examples of work that may be performed on or near energized circuit parts because of infeasibility due to equipment design or operational limitations include testing of electric circuits that can only be performed with the circuit energized and work on circuits that form an integral part of a continuous industrial process in a chemical plant that would otherwise need to be completely shut down in order to permit work on one circuit or piece of equipment.

Don

 

[jim dungar]

Re: NFPA 70E

8TWD192,

Be careful, the IEEE standard says equipment BELOW not equal to 240V. Also there is no methodology for performing arc flash calculations on any single phase system.

However, as Don has pointed out, working on energized equipment (over 50V) is always discouraged due to SHOCK hazard.

 

[don_resqcapt19]

Re: NFPA 70E

8TWD192,

Regarding Arc Flash Hazards, IEEE1584, Article 4.2 states:
"Equipment below 240 V need not be considered unless it involves at least one 125 kVA or larger low-impedance transformer in its immediate power supply."
Its a shame that the same information can't be found in NFPA 70E which is much more affordable

That does not match up with 70E. Table 130.7(C)(9)(a) shows that working on energized parts in a panel rated 240 volts or less is a hazard/risk category of 1. The work on live parts, including voltage testing, requires voltage rated gloves and tools along with a long sleeve FR shirt and pants (rated at 4cal/cm^2 or greater). The nost says that standard cotton denim jeans of 12 oz/yd^2 fabric can be used in place of the FR rated pants. This table only applies if the available fault current is 25kA or less with a clearing time of 2 cycles or less. There is an additional note that would permit the use of a long sleeve shirt and pants of non-melting fabric if the available fault current is less than 10kA. Voltage rated gloves and tools are still required.
Don
Don

 

[8TWD192]

Re: NFPA 70E

The table isn't of use to me because the breaker I was looking at has a 3 cycle instantaneous clearing time. I was doing an analysis on one of our 120/208V 3 phase station service panels and was curious if there was a lower limit at which there wasn't enough energy present to be an arc flash concern, which is when I found out about the under 240V and 125kVA reference. I was told the reason for this is because they had trouble sustaining an arc at under 240V but knew that some 208V systems could sustain an arc for short duration if the gap was small enough and the current high enough, hence the kVA limit for systems under 240V.

 

[MJJBEE]

Re: NFPA 70E

Originally posted by jim dungar:
8TWD192,

there is no methodology for performing arc flash calculations on any single phase system.

Here is the problem I have recently encoutered my saftey people want arc flash values.(for the entire T&D System) But I can't get them because there are no single phase equations. This is an area that must be addressed.

The other area yet to be dealt with is DC I know in certian aplications there are uses for high voltage DC. Which should be able to arc flash. And there are no reliable methods for calculating arc flash in dc systems.

Edited to repair Typo's

[ December 28, 2005, 07:23 PM: Message edited by: MJJBEE ]

 

[don_resqcapt19]

Re: NFPA 70E

The other major problem with the required arc flash calculations, is that there is no way to get a fault current number from a utility that is suitable for use in these calculations. Their systems are too dynamic. They have no problem in giving you an maximum available fault current for equipment selection purposes, but that current is not suitable for arc flash calculations. The reduction in available fault current results in a longer clearing time, that results in a higher incident energy and in turn that requires a higher level of PPE.
Don

 

[MJJBEE]

Re: NFPA 70E

Don

I have the same problem it is not possible for me to get the corect value of fault current. (I work for the serving utility) Beacuse we don't know what it will be at any given moment a generator can go off line we may have to switch a transmision line on or off ect. The bottom line from an engineering standpoint is that we can't give a good value of avalible fault current at any given time. However it is easy to give the maximum avalibe fault current. Also what happens when a change is made that affects that realistic number? Who makes people aware for changes to the system? Do you call and calculate every customer's avalible fault current? Or let them try to get it from us. (can you imagine trying to call customer support and trying to get an answer to this question every day?) There are so many unanswered questions about arc flash and so little time to implment solutions.

Another thing that has recently caught my eye is the new OSHA Regulation on arc flash that will be implmented in about mid 2007 (or so my saftey experts tell me). They currently read that an arc flash hazard anylsis must be done prior to any live work being done above 600 V. (thats right not the 240 and 125 kVA that the IEEE says) That means you could work on a 480 V system hot with no arc flash protection (by the new OSHA rules).