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#89417 - 09/13/04 11:16 PM History of the GFCI  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Quote
Charles Dalziel, a professor of electrical engineering at the University of California, invented the ground-fault circuit interrupter (GFCI), in 1961.

A Look at Electrical History - A Visit with Charles Dalziel

The year is 1941. You are an assistant professor of Electrical Engineering at the University of California, Berkeley.

You are awarded a grant by the California Committee on Relation of Electricity to Agriculture.

Purpose:

To find the effects of sub lethal electrical currents on the human body. You decide to use healthy human subjects.

The subjects are given physical examinations and electrocardiograms.

Only subjects in good physical condition are used.

Subjects grasp a 12 inch length of bare copper No. 6 wire in one hand and the other hand is placed on a brass plate.

Current is passed through the person from the left hand to the right hand. The subject is asked to drop the wire.

After dropping the wire the experiment is repeated using more current, again and again, until the subject can no longer keep his hand on the eight inch diameter brass plate.

Assistants are then used to hold the subjects hand on the brass plate and the experiment continues until the subject can no longer drop the wire because he cannot let go.
http://www.joetedesco.com/nec/viewtopic.php?t=1770

This experiment is repeated with 28 subjects and the maximum let-go currents are tabulated and analyzed. Frequencies are changed from 60 cycles per second to 180 cps, then 500 cps, then to 1000 cps and the experiments are repeated.

It is found that the average 60 cycle let-go current for men is 16 milliamperes and the average let-go current for women is 11 milliamperes.

Your name is Charles Dalziel and you have just begun. You will establish criteria on fibrillation currents using dogs, pigs, calves, and sheep. You become the authority on dangerous electric currents.

Your experimentation will establish the principles for protecting persons from the hazards arising from the use of electricity, and your findings will be used for the notes to the Tables in Article 725 of the National Electrical Code.

http://www.electrician.com/dal.htm
© 1996 Gerald Newton. All rights reserved.


[This message has been edited by Joe Tedesco (edited 09-23-2004).]


Joe Tedesco, NEC Consultant

2017 / 2014 NEC & Related Books and Study Guides

#89418 - 09/13/04 11:58 PM Re: History of the GFCI  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
 
Dalziel at UC Berkeley? Lived until 1986? Amazing. {Thank you, Joe, for an outstanding tribute.}

His work seems universally cited in any discussion of electric shock. I am sure nowadays similar experiemnts could not be performed without a near-universal public disapproval. This makes his work essentially irreplaceable.




[This message has been edited by Bjarney (edited 09-13-2004).]


#89419 - 09/14/04 02:36 AM Re: History of the GFCI  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Quote
Assistants are then used to hold the subjects hand on the brass plate and the experiment continues until the subject can no longer drop the wire because he cannot let go.
What a nut case!
I locked on to a generator load stud once, and as the persons with me shut it off I went from 60Hz to about 5Hz before being able to let go as the voltage decreased with it.The most painfull experiance of my life!I learned alot too! Not to do it ever again! I bet a few started swinging if they had the energy to do so after the first few times.


Mark Heller
"Well - I oughta....." -Jackie Gleason

#89420 - 09/14/04 07:35 AM Re: History of the GFCI  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden


#89421 - 09/25/04 09:21 AM Re: History of the GFCI  
CharlieE  Offline
Member
Joined: Apr 2004
Posts: 200
Indianapolis
What I found interesting is that everyone complains about the amount of verbiage in the Code but consider the following. When the GFCI was required in the bathrooms in 1975, everyone knew what a bathroom was and what to do with it. As soon as the "new" Code took effect, no one knew what a bathroom was anymore. In the 1978 edition of the Code, the definition of a bathroom had to be added.

Did you know that the Code definition of sand is "non-cohesive granulated soil"?

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Charlie Eldridge, Indianapolis Utility Power Guy


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