ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Wiring methods in U.K.

Scott,

So when did the NEC first actually specify that an EGC must be green? (If not bare.)

How did the general use of colors say 40-50 years ago differ from today? Was the BOY system in use for 277/480 (was the 277/480Y even in use then, or were these systems just 480 delta?).

paul — In the 1953 NEC Handbook the green/bare permission/use limitation is stated. Reidentification was permitted "by paint or other effective means."

Living in a rural area, I came across local 480Y/277V in plants that had medium-voltage service, and in sports-field lighting. The first significant recommendation I found in text is the classic 1955 Industrial Power Systems Handbook, by Donald Beeman.

In many older plants and commercial/institutionals, coloring is black-black-black(-white)+bare or metal raceway. Differing voltages having distinct phase identification varies, but I’ve found it in 1957-vintage institutional/research facilities.

Thanks Scott.

So presumably where all phases were run in black they used tags or something similar for phase identification, where necessary?

I seem to recall a thread a while back discussing that in many areas red was used for the wild-leg on 4-wire deltas in the past, before the NEC requirement for it to be orange.