NEC & history

[nafis]

Hi there

I have been always wondering about the history of NEC numbers and percentage where they came from . I knew it came from some calculations and testing . I want to learn more about that ,can any body tell me where to start . awhile ago I read EC&M article about the %125 i just searched but no place to be found . any advice thought greatly appreciated .


Thanks folks

 

[charlie]

. . .I knew it came from some calculations and testing . . .

Actually, many of the numbers came from somebody's guess and they seemed to work and they have never changed. Others came from collected data and have worked over time. To nail down all of them would be difficult but if you are curious about specific ones, we may be able to help. :smile:

 

[Rockyd]

Maybe this person, at this link -


http://www.electriciantalk.com/showthread.php?t=1785

Can help, they did some research.

 

[e57]

Actually, many of the numbers came from somebody's guess and they seemed to work and they have never changed.

I'll buy that for a few of them. And even some that were rumors, rules of thumb, and plain ol' myths may have become law of the land. Even some fashion related ones, like 20A bath room circuits - assumes everyone uses a 2000 watt hair dryer - added in the 80's.... Then of course industry lobby for new device sales...

 

[bphgravity]

Go to this site:

http://antiquesockets.com/nec.html



From there, you can download many early editions of the NEC and other documents from early code development that contain the little secrets to where all these seemingly random numbers and percentages come from.

PS - I hope you have a lot of reading time saved up !!!

 

[480sparky]

.....Even some fashion related ones, like 20A bath room circuits - assumes everyone uses a 2000 watt hair dryer - added in the 80's.... ...

1999, to be exact.:wink: The 2 SABCs and a laundry were all that were required in '96 (Art 220.4), and moved to 210.10 in the '99 with the addition of the bath circuit.