Get out your moon suit...

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arcsnsparks98

Senior Member
Location
Jackson, TN USA
Just sat through about 8 hours of NFPA 70E training today. It was difficult but I try to keep an open mind. I come from the old school (well, thats relative I guess) where people just know that you don't stick your finger/hand/etc where it doesn't belong when it comes to electrical stuff. Common sense smarts and all. Personally I feel that 70E is a bit overdone and possibly to the point that it coddles stupidity. Before anyone asks I will say yes, I am a fan of natural selection. :D I am well aware that there are considerable differences between single phase and 3 phase when it comes to incident energy. Also when dealing with 208 or 240 phase-phase as opposed to 480 phase-phase. What really did it for me was the requirement for PPE to reset (or even operate, for that matter) a breaker in a panel at 240 volts or less. Before I take a tongue lashing, I understand that that same simple breaker operation in a 480 panel with 20kA of fault current available is entirely different and should be treated as such. And the NFPA 70E 2015 will be even more stringent. Grrrr.....
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Just sat through about 8 hours of NFPA 70E training today. It was difficult but I try to keep an open mind. I come from the old school (well, thats relative I guess) where people just know that you don't stick your finger/hand/etc where it doesn't belong when it comes to electrical stuff. Common sense smarts and all. Personally I feel that 70E is a bit overdone and possibly to the point that it coddles stupidity. Before anyone asks I will say yes, I am a fan of natural selection. :D I am well aware that there are considerable differences between single phase and 3 phase when it comes to incident energy. Also when dealing with 208 or 240 phase-phase as opposed to 480 phase-phase. What really did it for me was the requirement for PPE to reset (or even operate, for that matter) a breaker in a panel at 240 volts or less. Before I take a tongue lashing, I understand that that same simple breaker operation in a 480 panel with 20kA of fault current available is entirely different and should be treated as such. And the NFPA 70E 2015 will be even more stringent. Grrrr.....

So now we have to calculate the available fault current at every resi panel and figure out what level of gear to use while flipping a 15 amp breaker??
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Was that class based on the 2012 edition or the 2015 edition? I thought that the 2015 was going to say that you don't need any special PPE for "normal" breaker interaction.
 

kentirwin

Senior Member
Location
Norfolk, VA
Was that class based on the 2012 edition or the 2015 edition? I thought that the 2015 was going to say that you don't need any special PPE for "normal" breaker interaction.

2015 70E states no ppe IF the equipment has bee properly maintained. See table 130.7(C)(15)(A)(a) Arc Flash Hazard Identification for Alternating Current (ac) and
Direct Current (dc) Systems. From my experience not many facilities follow manufacuter's recommended maintainence for circuit breakers.
 

jxofaltrds

Senior Member
Location
Mike P. Columbus Ohio
Occupation
ESI
A Mike Holt article for a start. Scroll down to part 6 of the article: http://www.mikeholt.com/mojonewsarchive/EES-HTML/HTML/ElectricalCircuitBreakers~20030621.htm

Then there's injection testing, thermal imaging, lubrication, etc.

My favorite:

"The load should be operated at full load for three hours, or until the breaker reaches normal load temperature; scan the breaker with an IR type non-contact thermometer and record the readings."

So two - three weeks for a 40 space panel?

Does this include the main?
 

kentirwin

Senior Member
Location
Norfolk, VA
My favorite:

"The load should be operated at full load for three hours, or until the breaker reaches normal load temperature; scan the breaker with an IR type non-contact thermometer and record the readings."

So two - three weeks for a 40 space panel?

Does this include the main?

I don't imagine too may people will be performing maintenance on 20A mini breakers despite 70E.
 

wtucker

Senior Member
Location
Connecticut
What really did it for me was the requirement for PPE to reset (or even operate, for that matter) a breaker in a panel at 240 volts or less... And the NFPA 70E 2015 will be even more stringent. Grrrr.....

Hmmm. NFPA 70E-2012, Table 130.7(C)(15)(a) says circuit breaker operation with the covers on is HRC 0. The only PPE required inside the Arc Flash Boundary of 19" is clothing of untreated cotton, wool, rayon or silk with a fabric weight of 4.5 oz per cubic yard, safety glasses, hearing protection and heavy leather gloves (as needed).

70E-2015, Table 130.7(C)(15)(A)(a), says there's NO arc flash hazard (and therefore no arc-rated PPE required) in normal operation of a CB that's properly installed and maintained, covers closed and secured, and no evidence of impending failure.
 

wtucker

Senior Member
Location
Connecticut
Not resi. Nor most commercial. Only facilities that use NFPA 70E for their electrical safety program.

Not unless you don't cotton to the nice folks at the burn unit peeling melted polyester out of your 3rd-deg. burns for half a year.

It doesn't matter if a facility we're working in uses 70E or not, we do.
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
[70E-2015, Table 130.7(C)(15)(A)(a), says there's NO arc flash hazard (and therefore no arc-rated PPE required) in normal operation of a CB that's properly installed and maintained, covers closed and secured, and no evidence of impending failure.]

Huh? What does impending failure look like?

I know most have heard the old saying..."Hope for the best and plan for the worst". It's the unexpected that gets ya. Short story....we had a substation that blew a primary (60KV) fuse due to a car/pole accident outside the sub. It was my first week on the job. The lineman changed the fuse, and after the pole was repaired and the fuse replaced, he was ready to "close in" to re-energize the sub. I asked if it might not be a good idea to test the transformers to make sure there was no damage. He looked at me like I was nuts, then said, "this always happens on a close-in fault."

Well, I decided to stand by the fence, a goodly distance from the equipment while he closed the high voltage switch. When he closed in, one transformer started humming REALLY loud. He figured something was wrong, so he pulled the switch back open to kill the sub. Unfortunately, the faulted transformer shot oil from the pressure relief into the switch and when he opened it, the arc caused a HUGE fireball just like you see in the movies. Bottom line, always assume bad things can happen. I know most of us have watched the videos of what a fault can do, but why risk it. Just because the "rules" say you don't have to wear PPE, if you think you should, DO IT! OK, enough preaching.:) Just an ORF (Old Retired Fart) giving his opinion.
 
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arcsnsparks98

Senior Member
Location
Jackson, TN USA
There is a minimum voltage/current level necessary to maintain an arc once it is initiated. By maintain I mean carry it past 1/2 cycle. Thats why 120v is practically incapable of creating an arc flash that crosses the 1.2 cal/cm^2 threshold. 240 single phase as well. 208/240 3 phase COULD become a concern under very specific conditions. 277/480 is where the 'could' and 'specific conditions' get thrown out the window. An interesting point is that the manual calculation in 70e for determining the incident energy and corresponding PPE takes the spacing between terminals into account. They have a reference chart showing some default values but to find the exact value you would need to remove the cover and measure. Hmmm...and PPE hasnt been determined yet. :)
 

kwired

Electron manager
Location
NE Nebraska
A Mike Holt article for a start. Scroll down to part 6 of the article: http://www.mikeholt.com/mojonewsarchive/EES-HTML/HTML/ElectricalCircuitBreakers~20030621.htm

Then there's injection testing, thermal imaging, lubrication, etc.

I don't imagine too may people will be performing maintenance on 20A mini breakers despite 70E.
This testing is not done on "miniature" breakers used in common lighting and appliance panels. For one thing the cost to just replace those breakers (especially single pole and low amperage double pole units) is less then the cost to test them.

Since OSHA applies to "all" employees, the average office worker that goes to the breaker panel to reset a breaker is subject to 70E when performing that task, yet is probably not even aware of 70E or that there is such hazards when performing that task.

People who work in industrial establishments even if their primary job is in an office are likely to be more aware of such hazards just because of increased awareness in general of electrical safety in the workplace in those kind of places.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
Most people seem to look only at the possible outcome (protection against an amount of cal/cm^2) rather than the probable outcome (no event occurs).

Picking and choosing to follow or ignore individual parts of standards is typically not encouraged.

NFPA70E, in particular the new 2015 edition, specifically requires that the risk of an arcing fault be considered.
 

kwired

Electron manager
Location
NE Nebraska
Most people seem to look only at the possible outcome (protection against an amount of cal/cm^2) rather than the probable outcome (no event occurs).

Picking and choosing to follow or ignore individual parts of standards is typically not encouraged.

NFPA70E, in particular the new 2015 edition, specifically requires that the risk of an arcing fault be considered.
Worst case scenario will always be what is challenged in a court when something bad has happened.
 
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