Wiring color codes

[raptor1956]

We all know that with red and black wires the black wire will tend to be the negative when connected to DC and the red the positive.  When using white and black wire the black, once again, will be the negative and white then becomes the positive.  But, what about wire that isn't colored but has a colored trace on one of the wires?  Say for example you have clear jacketed wire with a white trace on one of them which wire do we call negative and which positive?


Brian

[ataradov]

I'd go for marked wire being positive. No real reason.

[raptor1956]

I'd go for marked wire being positive. No real reason.

I've done it both ways in the past but wondered if there was a convention I should know about. 


Brian

[toxuin]

According to UL codebook (year 2013) the internal wiring of a control circuit should have the following colour coding:
Black - ungrounded wires at supply voltage.
Red - ungrounded AC stuff at less then supply voltage.
Blue - ungrounded DC control wiring.
White with blue stripe - grounded DC wire.
Yellow or Orange - ungrounded things that stay on even after you switch off the main disconnect (like lighting for service work on the enclosure internals)
(Here it starts to get weird)
White with yellow or orange stripe - grounded AC control wire that stays on after main disconnect is off.
White or Grey or Three White Stripes On NOT Green, Blue, Orange or Yellow (phew) - grounded AC wire.

These are for control cabinets. Wires smaller than AWG20 do not have to comply, but this might be helpful when decrypting stripey wiring :-D

[ajb]

In the US, two-wire single insulated lamp cord (aka zip cord) the marked (usually ridged) conductor is neutral, so when using similar wire for LVDC wiring I would tend to use the marked wire for ground or negative. 

[janekm]

According to UL codebook (year 2013) the internal wiring of a control circuit should have the following colour coding:
Black - ungrounded wires at supply voltage.
Red - ungrounded AC stuff at less then supply voltage.
(snip)

Wait, what? Isn't that back-to-front from what we're all used to? Sounds like they're having black at the supply voltage and red below that? That would totally confuse me 

[JPortici]

once upon a time i was doing an internship at a local company which makes control circuits cabinets. So one day we were four people doing this huge cabinet for a shipyard. I though it was a "stupid american thing" back then, but apparently we were just following the UL coloring scheme.

According to UL codebook (year 2013) the internal wiring of a control circuit should have the following colour coding:
[..]
Blue - ungrounded DC control wiring.
White with blue stripe - grounded DC wire.
[..]

oh gosh. all that blue. PTSD... kicking... in...
i was just a young boy. i was just a young boy. *gone crying in the dark corner of the room*

but seriously. it was a very frustrating first time for me, it was really hard to tell which wire was going where

[joseph nicholas]

What is a white wire with a black strip, and purple wire all carying 110 mains ac in a GE washing maching?

[BradC]

I was always taught "marked leg neg". I generally ignore that.

[madires]

For me the marked wire is simply wire #1. It's like the red trace of the first wire of a grey ribbon cable. Anything else is your choice, if you don't have to apply any standard. My personal preference is Gnd.

[Excavatoree]

According to UL codebook (year 2013) the internal wiring of a control circuit should have the following colour coding:
Black - ungrounded wires at supply voltage.
Red - ungrounded AC stuff at less then supply voltage.
(snip)

Wait, what? Isn't that back-to-front from what we're all used to? Sounds like they're having black at the supply voltage and red below that? That would totally confuse me 

When I took my first job at the bus manufacturer, (in the US)  I learned that the new standards required white to be the grounded wires instead of the traditional black for DC systems.    I believe this is to correspond with the color code for building (structure)  wiring.  (White is the grounded conductor, green is ground, etc.)  However, black was almost never used for power. (12 or 24 volts)

When I left to go to the next bus company, they ignored that standard completely and still used black for grounds.  The heavy equipment companies did likewise.

[rstofer]

There is the concept of an "identified conductor".  That clear jacket with a white stripe is 'identified' by the stripe (it's different).  In the electrical (vs electronic) world, that wire would be the grounded neutral or negative lead.

Ever look at 2 wire zip cord (lamp  cord)?  Ever notice that one of the wires has a pair of ridges?  That is the 'identified' conductor and it should hook up to the shell of the lampholder and the wide blade of the plug.

Electronics jumbles things up.  In the electrical world, black is hot, white is cold (grounded neutral).  There is no negotiation on a white wire - it's grounded.  In the electronics world, there may be a standard but I have never seen it.  Think about colored flat cables.  There's bound to be a white wire in there somewhere.

Note that I was careful to use 'grounded' (white) and not 'grounding' (green or green/yellow).  The grounded conductor is a current carrying neutral.  The grounding conductor carries only objectionable current flow.

[suicidaleggroll]

According to UL codebook (year 2013) the internal wiring of a control circuit should have the following colour coding:
Black - ungrounded wires at supply voltage.
Red - ungrounded AC stuff at less then supply voltage.
(snip)

Wait, what? Isn't that back-to-front from what we're all used to? Sounds like they're having black at the supply voltage and red below that? That would totally confuse me 

Yep, AC wiring is a little odd compared to typical DC convention.

Cut open an AC power cord, I bet you'll find that green is the ground, black is hot, and some other color (sometimes white, sometimes blue, etc) is neutral.

[DBecker]

It is well known, or should be to everyone here, that service wiring (building electrical wiring) uses much different color coding than electronic wiring.

Even their perspective is different.  Ask an electrician what "low voltage" and "high voltage" means.  In some parts of the world  wiring is "low voltage" if it's less than 1KV, and high voltage is where they have to worry about arc flash.

Other situations where you might run into odd wiring colors are automobiles.  German cars used to use brown for negative, and black for positive.  Making that extra dangerous is that the brown battery cable looked like faded red, especially using a flashlight at night.  Compounding the problem, they then switched to red for certain positive circuits, including the battery cable.

The best wire color coding scheme I've seen is in 1960s-era pinball machines.  The line voltage circuits used thermoplastic insulation, but all of the control circuits used colored braided insulation.  The color coding was part of the braid, with most signals using three colors.  Each one of the hundreds of circuits used a unique color code, and it is remarkably easy to identify and trace a circuit through the laced wiring harnesses.  The only problem is that you can't find matching replacement wire.