Wire (24 VDC)

Robb B said:

Just to make things more fun, here in BC at least not sure about other provinces, the local supply authority (BC Hydro) uses Brown as L1, and forbids the use of black wires anywhere. As far as I know, this is only within their distribution network, and once it reaches customer supply it is normal Red Black Blue White Green colours.

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I guess that's the biggest problem with "standards" - everyone wants theirs to be THE standard !!
Here in the UK, for domestic single-phase wiring, it used to be RED-HOT, BLACK-COLD, the "earth" connection is uncovered, but we used piping GREEN-GRASSY EARTH.

Now it's BROWN-HOT (A bit "earthy"), BLUE-NEUTRAL (because blue is a "vibrant" colour), and GREEN/YELLOW STRIPED for EARTH (isn't earth coloured brown, it is in my garden).

I'm beginning the think a much better "standard" would be to use one colour throughout, and use cable idents from the schematics, which incidentally, never showed cable colours !!

Possibly the best "standard" that could be adopted is....

RED-DANGER, this wired could be HOT at times, not always though, so check it out with your meter.

BLACK-SAFE, this wire is most often not dangerous, usually connected directly, or indirectly to ground, but could have become disconnected, so check it out with your meter anyway.

GREEN or GREEN/YELLOW, this wire is nearly always safe to touch, its colour indicates it is connected directly to ground, and should have no nasty surprises on it, but it might have got disconnected, so check it out with your meter anyway.

goghie said:

The picture represents wire colors in CABLE, "UK New" is in fact EU standard.

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But we've left the EU now, so do we go back to the original colour scheme ?

P.S. Please do NOT start any debate over whether we should have left or not.... too many dark horses trampling that debate as it is....

daba said:

But we've left the EU now, so do we go back to the original colour scheme ?

P.S. Please do NOT start any debate over whether we should have left or not.... too many dark horses trampling that debate as it is....

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I never ment to start political debate. Nearly all UK standards are harmonized with EU standards so I noted the reason. Also I noted that there is big difference when we are talking about colors of wires in cable and colors of wire in electrical cubicle.

Just adding in to what I have seen in the USA, and what should normally be used...

In Control Panels...

Red = 120V circuits

Black = Circuits with voltages higher than 120V (up to 480V three phase). Normally I use all black wires for three phase.

White = Neutral

Green or Green with Yellow Stripe = Ground

Purple, Yellow, Orange or these colors with a red stripe = Usually 120V control voltage that is for interlock circuits from other panels that are externally powered (from a different cabinet) and will still be live when you switch off power on the local control cabinet. Think of this as wiring into a relay in your local panel that switches the contacts off when that panel drops out and sending that signal back to the other panel. It is still live since powered externally.


(I normally use same color blue for COM, +, and all 24VDC signal wires)
Blue = 24VDC both + and COM.

Blue w/ white stripe = Usually 24VDC COM, but I've also seen it used as 24VDC+

Blue w/ black stripe = Usually 24VDC COM

(For these next two pairs of 240 and 480 it's perfectly fine to use colored tape on the ends of black wires for large conductors that would cost more money)
Brown, Orange, Yellow = 480V Three Phase

Black, Red, Blue = 240V Three Phase

-------- CABLES --------
Gray sheathed cables normally specify signal carrying conductors inside

Black sheathed cables normally specify power carrrying conductors (120V supply, or three phase)

Orange Cables normally mean servo power cables

Green Cables normally mean servo encoder cables

I have seen blue wires in control cabinets for 120V (bad practice) only at one job. The majority of panels I have worked with are wired correctly and with these colors. Most electricians take pride in their work and keep the colors standard to prevent confusion.

PLCstarter1884 said:

Most electricians take pride in their work and keep the colors standard to prevent confusion.

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But to who's "standard" ? That is the question ...

daba said:

But to who's "standard" ? That is the question ...

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I guess that's a good way to look at it and point that out Daba. It's a universal standard that many electricians follow even if they don't know the exact name of the standard.

I also wanted to mention that when dealing with sensor wires, it's common to see
1.) Brown wire for +24VDC
2.) White wire usually for NC output but can have different purposes.
3.) Blue wire for COM 0VDC
4.) Black wire for Sourcing output signal or relay output

The one thing I have to point out is that if you are visiting an installation that has been wired to a "standard", you could, or most likely, be there under "fault" conditions.

For some strange reason, rats do like to eat the PVC insulation off cables, causing short circuits. Rats do not care about the colours, and neither should you.

Don't assume that an XXXXX coloured cable is carrying a voltage that will not harm you.

Your best friend is your meter or voltage probe, not your colour vision.

In the old days it was RED for Live, Black for Neutral, however, I think it was in the 70's (before we joined the EU, flexible cables were changed to Brown for live & blue for Neutral, this was because people with colour blindness could not distinguish the RED & Black, apparently all cables looked brown to them (my Manager in those days asked me to wire a plug because of his colour blindness). The UK changed the colours in line with the EU for fixed wiring in 2003 (I think), so instead of the 3 phases being red, blue, yellow these changed to Brown, black, grey (earth did not change, however, in the early days it was green then changed to green/yellow stripes to help colour blindness).
I also believe there was a second background reason for the colour change in the UK, in 2005, the introduction of Part P building regulations. Part P was a joke.

Be careful with the white wires.

If the wire is mostly white with a blue stripe, for example, it is assumed/expected that the conductor is bonded (grounded). If you want to use an ungrounded/not bonded 24VDC system, use a blue wire with a white stripe if you don't want to use blue for everything.

Don't know if it's the same, but in the 80's we had some Japanese machines where white & green were the conductors & Red was the earth

Can't we simply follow the IEC standard? I for International?

rQx said:

Can't we simply follow the IEC standard? I for International?

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Heh, that's a good one. Then we'll all sing kumbaya.

https://www.plctalk.net/qanda/showthread.php?p=875102#post875102


Maybe someday.

rQx said:

Can't we simply follow the IEC standard? I for International?

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A lot of countries are slowly doing that. Aus / NZ for example have lots of standards which are "IEC Harmonized". As DrBitboy says... its still another standard, but the basis is IEC.

Over time, as the old stuff gets replaced (including the people designing / installing systems!) It should be possible to just fully adopt the parent standard as all the grandfather clauses fall away.

Give it another 1000 years or so, once we've finally given up on national boundaries ( or have screwed up the world so bad all we'll be able to standardize on is the sharp sticks we're poking each other with in our caves)

Yeah, the problem is it will never get harmonised, these think tank people are only interested in getting paid, a couple of years down the line they sit there contemplating "well what can we dream of next or how can we justify our wages".

daba said:

The one thing I have to point out is that if you are visiting an installation that has been wired to a "standard", you could, or most likely, be there under "fault" conditions.

For some strange reason, rats do like to eat the PVC insulation off cables, causing short circuits. Rats do not care about the colours, and neither should you.

Don't assume that an XXXXX coloured cable is carrying a voltage that will not harm you.

Your best friend is your meter or voltage probe, not your colour vision.

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Daba is the Man!

Years ago I used to work in the Pharma world - we used to buy machinery from every part of the planet. You should have seen our mezzanine - littered with step down, step up, blah.blah blah transformers with every voltage available!

Working on any type of electrical system requires that you USE YOUR METER!