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#13816 - 09/12/02 09:09 AM guarding live parts  
buddy  Offline
Member
Joined: Sep 2001
Posts: 8
Why is the requirement in 110-27, that live parts greater than 50 volts be guarded? There have been fatalities, although small in number at less than 50 volts. So where did 50 volts come from?


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#13817 - 09/12/02 11:24 AM Re: guarding live parts  
Joe Tedesco  Offline
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Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
See ARTICLE 720 Circuits and Equipment Operating at Less Than 50 Volts

Been in the code for many years, and probably was the basis for the voltage indicated.


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#13818 - 09/12/02 03:56 PM Re: guarding live parts  
pauluk  Offline
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Joined: Aug 2001
Posts: 7,520
Norfolk, England
50V has also been a threshold in some parts of the British "code."


#13819 - 09/16/02 09:52 AM Re: guarding live parts  
buddy  Offline
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Joined: Sep 2001
Posts: 8
I was told that 50 volts came into the code because 48 volts is what is used for telephone/communication circuits.


#13820 - 09/16/02 03:14 PM Re: guarding live parts  
pauluk  Offline
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Joined: Aug 2001
Posts: 7,520
Norfolk, England
I think it's more to do with the calculation of the likely maximum current available with 50V based on "average" body resistance (if there is such a thing, based on another thread).

The DC supply for telephones is generally 48 or 50V, but the AC ringing supply can be 90V or more.



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