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 Post subject: Interacting With Equipment
PostPosted: Fri Apr 17, 2009 12:10 pm 
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Interacting With Equipment is discussed on various threads. Is there a general consensus on what this means, other than what's in the
130.7(C)(9) tables? There are a couple specific cases that come to mind, these both apply to facilities with calculated IE levels and AFBs:

  1. Branch Circuit work in a panel with a main. After the breaker is opened, (or just before ;) ) appropriate PPE is donned, the panel is checked dead on the load side. Now that the load side is dead, does working in the vicinity of energized line-side bus mean that this is live work? Does it matter if this work does not put the electrician within the limited or restricted approach boundary?
    .
  2. Changing fuses on a main BPS. This is on a service switchboard, with IE>40 cal/in2. The BPS would be opened, so the fuse terminals would be de-energized. I'm told that the fuses can be changed through a hinged access door, and the BPS has the line side up, so there's no hazard of dropping something onto live bus. Depending on the size of the BPS, there is anywhere from 6" to 12" from the top of the fuse terminals to the line side contacts. It may even take a fish tape to get up there, working through the fuse access door.


Both of these aren't uncommon evolutions. Are they considered live work? Interaction with equipment in a manner which may cause an arc flash? I appreciate input from the arc flash community.


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PostPosted: Fri Apr 17, 2009 12:17 pm 
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70E defines live work as work within the LAB, so IMO both are live work. (#1 may depend on the configuration of the equipment)


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PostPosted: Fri Apr 17, 2009 12:28 pm 
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Zog, I see the definitions for "exposed" and for "working on" in 70E.

"Working on" is explicitly defined as direct contact.

"exposed" is a little vague.

Using the limited approach boundary to define live work puts us at 3'-6" for LV systems, which would include just opening doors or IR scanning in the hot work category. It seems like those things can be done without even breaking the plane.


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PostPosted: Fri Apr 17, 2009 1:00 pm 
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Hmm, the 2004 version made that clear but you are right, they changed the definition to "clarify" it, which now has me confused. Now I am going to have to re-think this one.

Geez, just when you think you have it all figured out :)


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PostPosted: Wed Apr 22, 2009 4:49 am 
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[quote="Ex twidget"]Interacting With Equipment is discussed on various threads. Is there a general consensus on what this means, other than what's in the 130.7(C)(9) tables? QUOTE]

Et:

I think the answer to the interaction question is in section 90.2 Scope (A) Covered, which reads:
This standard addresses electrical safety requirements for employee workplaces that are necessary for the practical safeguarding of employees during activities such as the installation, operation, maintenance, and demolition of electric...... I think those italicized words represent "interaction".
.. which means that an operator of the equipment is at risk wihile within the Arc-Flash Boundary (AFB), and therefore needs exposed-bus PPE.
And, if you're working on a BPS that's been isolated, but is within the AFB of another panel, I'd think you'd need to meet the other panels PPE requirement while interacting; installing fuses.

John M


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