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 Post subject: Definition of "Arc In A Box"
PostPosted: Tue Aug 03, 2021 11:55 am 

Joined: Mon Apr 29, 2019 5:24 pm
Posts: 15
Location: Phoenix, AZ USA
While most of are aware of the term "arc in a box" and the term seems to be self-explanatory, I have to ask is there and in what document is it officially defined?

NFPA 70E, IEEE 1584, NESC, OSHA 1910.269, all refer to it in some manner and in similar context to an arc flash that occurs inside an enclosure of some type versus in open air, I'm unable to find an official definition of this very commonly used term.

Many of the documents listed above point back to "Doughty, Neal, and Floyd, 'Predicting incident energy to better manage the electric arc hazard on 600 v power distribution systems'".

I've also found a few unofficial definitions out there on the web but they don't point back to a source for their definition.


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 Post subject: Re: Definition of "Arc In A Box"
PostPosted: Wed Aug 04, 2021 3:41 pm 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 543
Location: Wisconsin
In an 'arc in a box' the incident energy is reflected or focused in the direction of the opening, which is usually towards the employee. Probably 99% of indoor industrial locations are' arc in a box'
In 'open air' the incident energy is spread uniformly in all directions. About the only true open air locations are conductors and switches on poles.


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 Post subject: Re: Definition of "Arc In A Box"
PostPosted: Thu Aug 05, 2021 6:15 am 

Joined: Mon Apr 29, 2019 5:24 pm
Posts: 15
Location: Phoenix, AZ USA
Thanks JBD,

I'm aware of what an arc in the box is, the equipment associated with it and the arc flash hazard compared to open air. However, I'm asking if anyone is aware of an official definition contained in a standard somewhere.


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 Post subject: Re: Definition of "Arc In A Box"
PostPosted: Fri Aug 06, 2021 12:19 pm 
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1615
Location: Scottsdale, Arizona
The 2002 Edition of IEEE 1584 mentioned enclosed equipment 4 times in the main text but never defined it as it was implied.

The 2018 Edition of IEEE 1584 uses the word “enclosed” 8 times in the main text and the word “enclosure” is used 165 times. However, a formal definition of “enclosure” or “enclosed” is not provided.

There are descriptions in the text such as Annex G The metal enclosures used in the test are with an open front end. Also, photos of the enclosures “boxes” are provided including VCB, VCBB and HCB and dimnesions are provided but no "official" definition. other than under "electrode configuration"


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 Post subject: Re: Definition of "Arc In A Box"
PostPosted: Tue Aug 10, 2021 7:32 am 

Joined: Mon Apr 29, 2019 5:24 pm
Posts: 15
Location: Phoenix, AZ USA
Thanks Jim for the references.

But I was wondering if an official definition for "arc in a box/arc in an enclosure" and "arc in open air" is warranted in IEEE 1584 and/or 70E? Or do you think it's not necessary?


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 Post subject: Re: Definition of "Arc In A Box"
PostPosted: Wed Aug 11, 2021 6:54 am 
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Location: Scottsdale, Arizona
GTCole wrote:
Thanks Jim for the references.

But I was wondering if an official definition for "arc in a box/arc in an enclosure" and "arc in open air" is warranted in IEEE 1584 and/or 70E? Or do you think it's not necessary?


George: Now that you pointed it out, it might not be a bad idea. Especially in IEEE 1584 since that is where is is most directly used. Nothing on the radar screen for a 3rd edition yet but when that time comes, this might be good to add. Thanks


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