It is currently Thu May 28, 2020 7:42 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Basic Arc questions
PostPosted: Tue Apr 24, 2012 6:11 am 

Joined: Wed Jun 08, 2011 7:08 am
Posts: 5
Hey all, New to the forum and have had quite an education thus far. A couple trivial questions I have encountered and just want clarification with.

Is the >50 volt value the beginning for the need to wear electrical gloves, or is it the task at hand that makes it necessary? Meaning, using a volt meter for 120v outlet testing vs 120v testing of exposed wires? I'm assuming the former has no glove need, but the latter does?

Can 120v produce an arc that can cause serious injury potential?

Thanks in advance,
Eric


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 24, 2012 1:21 pm 

Joined: Mon Apr 23, 2012 3:05 pm
Posts: 1
Location: Canada
Yes


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Apr 25, 2012 6:09 pm 
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
Is the >50 volt value the beginning for the need to wear electrical gloves, or is it the task at hand that makes it necessary? Meaning, using a volt meter for 120v outlet testing vs 120v testing of exposed wires? I'm assuming the former has no glove need, but the latter does?[/quote]

The requirement is that you MUST use a work method to avoid a potential shock hazard. More people die from shock at 120 VAC than at any higher voltage. If you have a receptacle where inadvertent contact is not possible then you don't need to worry about shock protection.

The story changes even by inserting meter probes into the receptacle because now even though the prohibited approach boundary is essentially direct contact, you've crossed the line with tools or parts of your body. You MUST follow one of the 4 acceptable work methods for dealing with shock:
1. De-energize it (electrical LOTO).
2. Bare hands, live line (hard to even do in this case).
3. Insulated tools.
4. Rubber glove method.

Nearly all meter probes on the market meet the requirement of insulated tool work method (insulated against phase-to-phase contact as well as protecting the worker from crossing the prohibited approach boundary).

Thus, BOTH situations you describe are identical. You can use either the meter by itself or use rubber gloves (to stick an eating utensil in the receptacle I guess), or both.

70E does NOT explicitly explain this at all. It is better explained in IEEE standards.

Quote:
Can 120v produce an arc that can cause serious injury potential?


Do not intermix shock and arc flash hazards. They are different. At 120 VAC, it is difficult to get an arc to be self sustaining. IEEE 1584 at least chooses to ignore it and most other folks do as well. Due to the fact that this section is under discussion for potential changes with the IEEE 1584 group, the NFPA Committee deleted the "exception" in the 70E-2012 version. Thus you should refer to the methodology you are using for determining whether an arc flash is a concern or not (hint, hint).


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Apr 26, 2012 7:31 am 

Joined: Wed Jun 08, 2011 7:08 am
Posts: 5
Thanks for the information, this helps out.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2019 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883