Wire colors for two wire loop

G

Thread Starter

Gene Giltner

What color should the return wire in a 24vdc two wire transmittere be? Black or some other color than black? Before you answer go lift the hood and see what color the return on that 12 VDC system. If its like most system its black. In more than 30 years of experience I've seen most industrial system use black as the return. However, in the utility and commercial power plants it seems the black wire is the return if it was wired by and instrument tech and its the hot if wired by the electrcian.
 
Generally in Petrochem, the positive is black and Neg is white. You are correct, in the power industry (particularly GE) they utilize white as positive and black as Neg. Ive actually been on power projects where the HRSG and BOP (Controlled by DCS) used the plant standard 'black positive' and on the turbines, everything was just the opposite.
 
P
TSP's come in three flavors: black/white; black/clear; black/red. The usual convention, driven by the electronics industry is that black is always +. When using black/red, then red is +. The most important thing is for your plant/project to establish a standard, and then stick with it.
 
I have always have used and been told by electrical engineers to use white as positive and black as negative. Plant engineer or plant sop's or best practices manual should establish the color code.
 
Top