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How will deleting the 4 ft. rule and adding boundaries to the HRC tables affect you?
The change will make it easier
The change will make it more complicated
Not Applicable - We use calculated Arc Flash Boundaries instead
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 Post subject: 2012 70E - 4 Foot Rule Deleted
PostPosted: Sun Jun 19, 2011 3:02 pm 
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1637
Location: Scottsdale, Arizona
The “4 foot rule” for the Arc Flash Boundary is being deleted from the 2012 Edition of NFPA 70E. Instead, more specific boundaries have been added to the Hazard / Risk Category tables based on the upper limits of short circuit current and clearing times.

How will this change affect you?

  • The change will make things easier
  • The change will make it more complicated
  • Doesn't matter - We use calculated Arc Flash Boundaries instead.

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Jim Phillips, P.E.
Brainfiller.com


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PostPosted: Mon Jun 20, 2011 9:49 am 

Joined: Fri Nov 14, 2008 7:35 am
Posts: 4
Location: Cape Girardeau, MO
We have completed the study and applied resultant labelling from the 161kv switchyard down to the line-side 480V MCC level.

We still need to continue the study on down from the load side of the MCCs to power panels, local disconnects and the like.

Until we get complete the remainder of the study - we've made the default PPE and distance for anything not included in the original study >= 240V as level 2 PPE with a 4-foot boundary.

We are enforcing identified practices and PPE across the board.

Some questions/concerns on whether the tables can be still be used when a study has been done within the plant, but not on the equipment in question?? Certainly not on equipment that doesn't meet the limits of the table footnotes.

At any rate, taking away the 4-foot boundary brings up a case of, 'now what'?


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PostPosted: Mon Jun 20, 2011 5:10 pm 
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Joined: Sat Jun 07, 2008 5:11 pm
Posts: 143
Location: Connecticut
Our standard is 4ft or the calculated distance if it exceeds 4ft. The greatest benefit of the 4 ft rule is it keeps nosy Neds out of the work space.


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PostPosted: Thu Jul 14, 2011 2:20 pm 

Joined: Sat Nov 20, 2010 10:17 am
Posts: 13
Location: Victoria British Columbia
we adopted the four foot rule for standardization purposes. In most cases we found our calculated distances to be much less; however to avoid confusion and to try and simplify what PPE required we felt the four foot rule was a good basis for a starting point. Too many options create confusion and frustration. Eventually the techs start to figure AH it will only take a second why go back and get some more PPE!


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PostPosted: Wed Apr 04, 2012 6:39 am 
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Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
So what does a company do if they used the 4 foot AFB and are using the tables? Do they have to go re-label everything? And do you put an AFB for each task or are people putting the highest AFB listed in that part of the tables?


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