Without tracking down previous editions of the code and referencing them, is anyone aware of a method to find out when a section of the code was adopted/amended? Example I saw today that brings this to mind: 3-phase 4-wire delta-connected panel. High leg was marked orange (good per NEC 384-3 (e) '99), but landed on C phase (bad per NEC 384-3 (f) '99). Don't know when the panel was installed but would say within the last 20-30 years. Was landing the high leg on anything but B phase ever acceptable (I'm sure it was at some point but that's that whole me assuming things problem). But the main question is when we are asked to “take a look at something” and it is to code but for one small thing, how do we figure out if it was acceptable at some point. I mean other than asking the question here.

I really don't know of any way of checking. I know that some utility companies require the high leg to be C phase in the meter. In the panelboards,

B phase gets the extra bracing so putting the high leg anywhere else could be a problem.

Looking at my oldest code book (1978) 384-3(f) "...The B phase shall be that phase having a higher voltage to ground."

I've come across existing installations where the high-leg is on the 'C' phase alot. I'll have to check my POCO specs book (PSE&G) and see if they're required like that around here. I know it's not what the NEC calls for, but most of the high-leg 3-phase services are identified with red tape, not orange.

There's no 384-3(f) in the 1971 NEC, nor can I see any other applicable reference within article 384.

200-6(c) in 1971 covered general identification of the high-leg:


The part I've quoted bold has the "changed from previous edition" line alongside. I seem to recall a discussion a while back in which it was decided that 1971 was the first time orange was suggested specifically.

Still nothing about the high leg having to be B phase that I can find though.