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 Post subject: "Exposed" for arc flash versus shock safety and NFPA 79
PostPosted: Mon Jun 01, 2009 12:37 pm 

Joined: Mon Jun 01, 2009 12:24 pm
Posts: 1
Hello all,

I'm confused concerning the definition of "exposed" regarding shock safety and arc flash, and how it relates to the 2 inch ball test in NFPA 79.

In our business (controls) we hear the keyword "touchsafe" concerning equipment and parts all the time. Does this simply mean that it meets the requirements of the 2 inch ball test in NFPA 79 and therefore allows you to use some of the exceptions to various situations ??

Additionally, if I have a 480V panel for instance, that uses parts that are all non contacting by the 2 inch ball basis, and there are no unisulated conductors, do I need to wear any shock safety PPE to go within the restricted boundary as a qualified worker ?? What about the prohibited boundary to take voltage measurements ??

I'm pretty sure I would need to wear arc flash PPE though not matter what, so what is the point of having these little exceptions and things for the shock safety aspect if I'd have to go and wear extensive arc flash PPE anyway ?? What does this gain me ??

Thanks much, and please pardon my ignorance. I'm just beginning to understand these requirements but have been in some form of the electrical business for 25 years.

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PostPosted: Mon Jun 01, 2009 5:47 pm 
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Joined: Thu Jan 10, 2008 8:49 pm
Posts: 516
Location: New England
exposed is referring to any components designed to carry electricity which is not fully insulated. So cable that is insulated is not exposed. But where the cable terminates to a fuse clip or motor starter, the point of termination is typically exposed.

If you are taking voltage readings then you obviously must have an exposed point to make contact with the volt meter probes.

The boundaries are a bit arbitrary in my opinion. The Limited approach boundary is the point at which you need to be qualified, this is best understood to say you have to be an 'electrician' althought the word electrician is never mentioned. But you need similar training and understanding of electricity. You can escort a non-electrical person into the Limit Approach boundary but must stop him at the Restricted Approch Boundary. The Restricted AB is the point at which the electrically qualified must don shock protection, ie, gloves. Only qualifed electrical persons can pass the Restricted AB even if accompanied by qualified electrical person. The Prohibit AB is the point at which you are so close to the live part that the work is considered the same as touching the live bus. So say you need special training for live work.

Welcome aboard.

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PostPosted: Tue Jun 02, 2009 2:05 pm 

Joined: Tue Jun 02, 2009 1:40 pm
Posts: 19
Anytime you are testing on live equipment your required to wear appropriate PPE to protect "HEAD, FACE, TORSO, HANDS AND ARMS". Even ignoring the whole issue of 70E, if an employee gets injured by arc flash while taking voltage measurements the employer is in direct violation of the general duty clause to protect the employee from harm whenever possible. As Ford found out, it is a very expensive fine when OSHA finds out that the employer was aware the employee was not wearing the necessary PPE.

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