operation of circuit breaker with covers on 70E

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the table in NFPA 70E that allows for arc flash hazard category determination based on task allows a level 0 protection for operation of a 240v circuit breaker with the covers on.

this table is to be used in lieu of an arc flash study as long as the opening time and short circuit available limitations in the text are met.

my question is, if there has been an arc flash study and say the panel has been determined to be a level 4, then would the operation of the circuit breaker be required to be done with level 4 protection with the covers on?
 
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can i assume then that there is no operation of a 240 breaker with less than level 0 protection? basically we have people in street clothes and no ppe using the breakers to turn on and off the lights and I was wondering how this is viewed in light of the arc flash requirements.

thanks
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
There are several things that come into play including, construction of the equipment, presence of ventilating lovers, age and maintenance of the equipment, and most importantly the odds of a fault occurring.

Usually I tell my customers to suit up for the worst case incident energy. However I know that some molded case breaker manufacturers say that as long as the equipment being operated within its design parameters (i.e. not closing on a fault) it is UL tested to safely, without damage, interrupt normal load currents.
 

zog

Senior Member
Location
Charlotte, NC
There are several things that come into play including, construction of the equipment, presence of ventilating lovers, age and maintenance of the equipment, and most importantly the odds of a fault occurring.

Usually I tell my customers to suit up for the worst case incident energy. However I know that some molded case breaker manufacturers say that as long as the equipment being operated within its design parameters (i.e. not closing on a fault) it is UL tested to safely, without damage, interrupt normal load currents.

Containing a fault is not part of the design parameters, unless it is designed to the standards for arc rated switchgear.
 

zog

Senior Member
Location
Charlotte, NC
my question is, if there has been an arc flash study and say the panel has been determined to be a level 4, then would the operation of the circuit breaker be required to be done with level 4 protection with the covers on?

Yes, once you do the study you need to wear PPE with an ATPV > the calculated Ei. You dont really use HRC's after the study.
 

ron

Senior Member
If the calculation indicates a PPE 4, then it is likely that the notes for using the table are not in compliance.
This is predicated on the fact that the calulation was done with "good" information.
 
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If the calculation indicates a PPE 4, then it is likely that the notes for using the table are not in compliance.
This is predicated on the fact that the calulation was done with "good" information.

i do not want to use the table, what i am trying to determine is if operating a circuit breaker is considered exposure to live parts
 

ron

Senior Member
what i am trying to determine is if operating a circuit breaker is considered exposure to live parts
It is not completely clear in the document whether doors closed constitute working on or near energized equipment.
What is clear, is that the table only applies when the notes apply. In order to use the table you must determine fault current and clearing time of the upstream OCPD. Often this information isn't available until detail calculations are done, so the PPE 4 is indicative that calcs were done and that the notes likely will not apply, although it is possible.
 
so operation of a circuit breaker in a level 4 panel with cover on would require level four protection, operation of a circuit breader in a level 3 panel with cover on would require level three protection, etc, ?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Containing a fault is not part of the design parameters, unless it is designed to the standards for arc rated switchgear.
Several manufacturers state, that circuit breaker and enclosures contain internal breaker arcing, based on UL489 and UL891 normal continuous current ratings. They do not make this claim for fault current interruption.

Arc rated gear is for arcing on the bussing (external to the breakers).
 

ron

Senior Member
so operation of a circuit breaker in a level 4 panel with cover on would require level four protection, operation of a circuit breaker in a level 3 panel with cover on would require level three protection, etc, ?
Steve,
Once compliance with the table notes are determined, whichever is the appropriate PPE level turns out to be, my opinion is that PPE is required to operate a breaker, as covers are not generally designed to contain an arc flash/blast.
That's why I think Jim said
There are several things that come into play including, construction of the equipment, presence of ventilating lovers, age and maintenance of the equipment, and most importantly the odds of a fault occurring.
The odds of a fault occurring in my opinion is higher when something is moving, like a breaker operation. That's when the little creatures run and debris moves.
 
This past week I was at the Eastern Section meeting. The OSHA presentation showed a cover of a large disconnect blown off. The operator of the circuit breaker/switch (I cannot remember which) did not survive the blast.
Unfortunately, the blast potentially has such force, that there is no PPE designed to protect against that force. That is where remote operation is literally a lifesaver.
 
thanks guys. the health and safety guys are not wanting us to consider that operation of a circuit breaker is "working on or near energized" parts. we are having a wonderful argument. the admin in a skirt and high heels who turns the lights on with the breakers is going to have to get a flash suit and some boots
 
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renosteinke

Senior Member
Location
NE Arkansas
I'm not sure that I understand the question.

"With the covers on." I understand that to mean in the enclosed state - that is, the cover is on the panel. The entire cover, not just the dead front.

I thought that's what the enclosures were for: to keep us safe from whatever might happen when that breaker trips. Whatever the loads may be in opening a fully loaded breaker, they are nothing compared to the breaker operating under fault conditions.

I wouldn't think any protective gear would be necessary.

Am I missing something?
 

ron

Senior Member
Reno,
Regular enclosures are not designed to contain an arc flash/blast. You can buy arc flash rated SWGR that will direct the results of the flash//blast upward, but that only happens when the doors are closed. Many IMO arc flashes occur while work is going on, so the doors/panel are generally open, so the arc rated stuff is not worth the extra expense in many cases.
 

McFlash

New member
There is a new product out that is made to lower the IE to HRC #0 with the doors open on lowvoltage switchgear. Its made by GE and it is called ArcVault. If you do a search you will find it out there. Pretty neat technology, it takes the arc and redirects it to a different spot by initiating very quickly another arc in the gear.
 

ron

Senior Member
McFlash,
If I recall, it senses an arc then causes a three phase bolted fault, which would draw more current and hopefully cause the upstream breaker to activate quicker (inverse time).
At least in older versions of the technology, camera flashes would trick the sensor and activate the breaker to cause a fault falsely. ;)
I'm nervous about specifying something that purposefully causes a fault, that's just me.
 

billsnuff

Senior Member
"my question is, if there has been an arc flash study and say the panel has been determined to be a level 4, then would the operation of the circuit breaker be required to be done with level 4 protection with the covers on? "

Steve, my question is, if there has been a study completed and this is a lighting panel, what were the reccomendations from the study to reduce the hazard?

. reduce fuse size
. balance load
. change fuse type

After receiving the completed study, the first thing we did was go thru the reccomendations from the study to eliminate and/or reduce the hazards was reduce fuse sizes and replace mixed fuses, etc. We are now working on individual components replacing 5k ratings with 10 or 25 and so on. Right now, with one exception, everything in this plant is HRC#2 or less, with most at HRC#0.
 
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