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#13816 - 09/12/02 06:09 AM guarding live parts
buddy Offline
Member

Registered: 09/11/01
Posts: 11
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 08:24 AM Re: guarding live parts
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: 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.
_________________________
Joe Tedesco, NEC Consultant

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#13818 - 09/12/02 12:56 PM Re: guarding live parts
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
50V has also been a threshold in some parts of the British "code."

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#13819 - 09/16/02 06:52 AM Re: guarding live parts
buddy Offline
Member

Registered: 09/11/01
Posts: 11
I was told that 50 volts came into the code because 48 volts is what is used for telephone/communication circuits.

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#13820 - 09/16/02 12:14 PM Re: guarding live parts
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: 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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