[RE-wrenches] How do we wrenches provide pertinent advice? (was120% rule applying to conductors)

[William Miller]

Dan:

I am a bit confused by what you say below regarding "whim and 
interpretation."  In regards to the 690.64(B) 'conductor' controversy, the 
controversy is not about what the code says or how AHJs interpret it, the 
controversy is about why the word "conductors" is included in the NEC 
section at all.

There is nothing "whim" about a local authority implementing specific 
language:  It is very straight-forwards:  take the values of contributing 
circuit breakers, total them, and the conductor must be rated equal to or 
greater than 120% of the result.  This is simple arithmetic and not subject 
to interpretation.

What is capricious is the code authors failing to understand that applying 
the 120% rule to conductors that will never see excessive currents is not 
logical.

I think we should be educating the local AHJs, but all the education in the 
world will not allow them to waive a very specific code requirement.  It is 
too much to ask them to "pull rank" on the code writers.  Once they start 
nit-picking code sections, they could spend most of their time trying to 
figure out which code sections are really valid.  Should each municipality 
issue a copy of the NEC with the sections they don't agree with 
redlined?  This is unfair to ask of local building officials.

Instead, we need to direct our efforts to code writers in order to educate 
them to understand the real scenarios, using basic physics.  This is why I 
support and follow Solar ABCs and pay for and attend Mr. Brooks seminars 
whenever I can.  These are our representatives trying to inject common 
sense into the code crafting process.

I agree with you there is a problem here, I just disagree on who can make 
the necessary changes.

Sincerely,

William Miller

PS:  All of the above assumes that you and I are correct in our 
understanding of the basic situation:  a feeder conductor can never see 
additive currents from power sources at opposite ends.  I am not a 
scientist or an electrical engineer.  I have been wrong before and I am 
certainly making plans to be wrong about something else in the near future.

wm



At 01:20 PM 10/1/2012, you wrote:
>William,
>
>My point exactly.  Unfortunately, vocal inflection isn't easily
>incorporated into typed text.
>
>For an "advisory only" document, it has, in essence become the
>"law of the land" (as we're acutely aware), however subject to
>the whim and interpretation of the nationwide AHJ hierarchy and
>their governing/supervisory colleagues.
>
>
>Dan