Recent testing question

[Thim]

Go here
http://www.nfpa.org/categoryList.asp?categoryID=124&URL=Codes%20&%20Standards
on your left side you can choose list of nfpa codes, this gets you here
http://www.nfpa.org/aboutthecodes/list_of_codes_and_standards.asp
then choose your code 79, this gets you here
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=79

At the bottom of the last page you can see a link view Code of 2002 and one of View Code of 2007 click it and you can see it
Somewhere on the way they will ask you to fill in you login but with name "stupid" and adress "nothing" i'm sure i don't pay for it

 

[TConnolly]

I'm not sure why the NFPA board would do something stupid like this. To allow yellow as a color for years then all of a sudden to change it knowing the installation base of that section would cause confusion for generations of industrial technicians and engineers is a bad move. This sounds like a good reason not to adopt some of the national consensus standards.

I think the use of yellow was deprecated because it is reserved in the IEC and ground wires that are either green with a yellow strip or yellow with a green stripe are so common.

We have used both yellow and orange conductors for conductors that remain energized, but since 2007 we have been sticking with orange.

As for the matter of if the code should be followed or not, well thats an endless can of worms. Sometimes when trade practice and the code clash the looser is common sense - if the tradesmen know what yellow means but not orange then IMO there is one good reason to keep using yellow. But if one wants to follow the code just for the sake of compliance then its time to retrain the tradesmen.

The best practice IMO is to clearly label everything and place appropriate warning labels on/in the enclosure.




Edit to add: Even the choice of orange is not without the potential for some confusion. Brown-Orange-Yellow (BOY) is routinely used for phase identification in 480V.

 

[geoplc]

So then the correct test answer should be: 1.) yellow wire indicates an external power source on machinery built prior to 2005, 2.) yellow indicates an external power source on machinery built between 2002-2005 by a MTB who didn't have any orange wire, or 3.)yellow indicates an external power source on machinery built after 2005 by a MTB with an outdated code book

 

[leitmotif]

One question I was asked during an interview was:
If you see a yellow wire in an enclosure, what would that tell you?
I had to ask what the answer was, had never heard of it. I am a Master electrician, with fifteen years experience, but it was new to me.
Any takers on this one?

Common practice for 450 3 phase is brown orange yellow here in USA. Which gets a little interesting
Orange is supposed to mark high leg on 240 delta with one phase center tapped for 120.

I have seen so many different schemes for wire coloring (some with no logic at all) that I do not trust anyones wire coloring scheme any more until I have confirmed what is going on.

With respect to the transformer question as poorly written as it was - I think you gave the most correct and comprehensive answer - BUT
is that what they wanted??

Dan Bentler

 

[TConnolly]

Common practice for 450 3 phase is

Yeah, 450... 451, whatever it takes.