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ekstra   ara
PostPosted: Sat Nov 21, 2020 3:37 pm 

Joined: Thu Nov 19, 2020 1:17 pm
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I have a system that requires category 2 arc flash warning labels using the table method. The question is should the monitoring system, which uses 277Vac single phase, be required to have the label as well? Does NFPA 70E allow for engineers to use any discrepancy here?

The components of risk are: (1) the likelihood of occurrence of injury or damage to health, and (2) the potential severity of injury or damage to health.

My scenario:

**Looking at the actual connection of the conductor in the enclosure;

Is it reasonable to say that the bare tip of the wire pushed into the power supply block is not exposed? Examination of insulated cable with no manipulation of cable does not require arc flash PPE. The thought here being that the power supply block itself is not a control circuit that would require maintenance while energized.

Other than the power supply block, no other equipment/components of the communications enclosure (NEMA4) operate above nominal 125 ac or dc. Working on control circuits under these conditions does not require arc flash PPE. The monitoring equipment is commercial. Any maintenance will be provided by the licensed and trained individuals whom installed the equipment. The system would be de energized for any maintenance other than the control circuits. I welcome your thoughts. Thank you for your time.

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PostPosted: Mon Dec 07, 2020 8:50 am 
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Joined: Tue Jan 19, 2010 2:35 pm
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I think I understand your questions. A couple of things. First you mentioned “working on” and 125 ac or dc. I believe the Standard states if you’re exposed to 50 volts or more, voltage rated PPE is required. So, that means if you're testing for voltage or cross the 12" boundary, you wear voltage PPE. And in regard to working on, for me, working on means the same as maintenance. Maintenance rules are different than the rules for testing.
You talk about doing maintenance by trained individuals. Like I said, the rules for maintenance are not the same as for testing. NFPA 70E requires the equipment to be off if doing maintenance. If you're testing, you can leave the power on, but it must be off to do maintenance. For example, tightening a lose connection is maintenance, not testing. The device would need to be turned off to touch a connection with a tool. This part of the Standard is pretty tight. To leave the power on and to do maintenance you’d need to fill out an energized work permit and it has to be cosigned by your manager and the person doing the work and there’s a lot more to this than can be reasonably described here. One more thing, if you aren’t using energized work permits, I’d suggest you Google the term to see a few good examples. Last, you mentioned a level 2 arc flash hazard. Just having the door to the area where you might be exposed, means you wear arc flash PPE.

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