Wire (24 VDC)

kirk · Jan 26, 2021

Ok, so what are the standards?

For years I used Blue for all my 24 volt DC, 16. or 14. It seems a bit big, and can be hard to make look ..... clean.

I know another panel builder and he uses Red and Black.
It makes sense in a way, you hand anyone on the planet a pair of Jumper cables, and they know the Red is + and Black is -. I see the logic for DC

The problem becomes in AC voltage black is Positive

But then you have cable(Belden 18-4, for instance) where Blue isn't even an option.

Then I came across some Black and red paired "Primary OFC" comes in the gauges I need for inside a panel, but It looks like it may be speaker wire. Well, that isn't very professional, so I am guessing that is out, right? Or no?

what are the rules?

rQx · Jan 26, 2021

IEC state dark blue positive and negative. However I use white as negative. To use one color for both positive and negative isnt really good in my opinion .

Wire thickness is relative to your fuseing

Snyd1 · Jan 26, 2021

For 24VDC I always use solid blue for + wht/blu for -. In panels where I have had a handfull of low voltages. I have used blk/red for 12V+ red/blk for 12V-. Pretty sure NEC only specifies two colors if I remember correctly, Orange and Green. Orange for where line voltage is still present, green for grounds. Sure I will get corrected if wrong.

Edit: Well think I was wrong on NEC for orange NEC article 110.15 says for the high leg, maybe I got the Orange for line voltage still present from NFPA.

looks like a nice collection of info: https://www.electricaltechnology.org/2020/07/electrical-wiring-color-codes-nec-iec.html

_Dock_ · Jan 26, 2021

NFPA 79 is the "electrical standard for industrial machinery". whether your equipment falls into this standard is up to you to determine. If so, the wire colors that are "standard" are outlined for you in chapter 13. NFPA 79 is available for free online viewing if you register an account.

NetNathan · Jan 26, 2021

I use blue for 24VDC+ and Blue with white stripe for 24VDC-

TWS · Jan 26, 2021

Quote"I use blue for 24VDC+ and Blue with white stripe for 24VDC-"
+1

goghie · Jan 26, 2021

kirk said:
Ok, so what are the standards?

The problem becomes in AC voltage black is Positive

There is no such thing as AC positive. There is AC phase and AC neutral. According to IEC DC conductors are dark blue, but it is allowed for DC- to have stripe.
AC phases are black.
AC neutral is light blue.
If we have AC from isolated transformer which is used in control circuits then the colors for both conductors is red, but it is allowed for neutral to have stripe.
When it is question about interconnection then it is orange.

Ground is always green/yellow.

All previous is regarding to conductors that are not in cable, when there is cable there are different set of rules.

Ken Moore · Jan 26, 2021

Most of the panel shops I deal with, follow UL508A color codes, even when it's not a UL panel.

GaryS · Jan 26, 2021

As far as I know there is no code standard for 24V systems but what I use and I find it works fairly well is
24- from the supply Blue with White stripe
25+ from the supply Blue with Black stripe
controls wires just Blue
safety circuits connected to safety monitor relay Blue with a Red stripe
all are normally 18ga unless their is reason to increase it
the this color pattern makes it easy to identify them later nd keeps the DC nut separate from the 120vac Nut

lfe · Jan 26, 2021

I used light blue for the neutral, which is the same for AC and DC, all the neutral cables for AC and all the 0V cables for DC come from a unique insulated bare copper bar connected in a single point to the main ground, located on the main cabinet near the connection terminals and that saves many terminals.

The neutral and 0V cables from outside go direct to the neutral bus bar without going through terminals.

For AC phase cables black color, for + 24VDC dark blue

Jim3846 · Jan 26, 2021

DC Volt = Dark Blue = brown (European)
DC com = White/blue strip = dark blue (European)
AC volt = Red
AC neutral = white
3 phase volt = red/yellow/brown = black
interlock wiring between panels = orange
ground = green = green/yellow strip

muusic_man · Jan 26, 2021

In my plant the electrician uses whatever color wire is laying around in the back of the van. Makes it hard to figure stuff out sometimes.

When I design a panel it's
24+ Blue
24 common blu/wht

120VAC unswitched black
120VAC control red
120VAC grounded conductor white

Snyd1 · Jan 26, 2021

I am sure it is clear as mud now. So it is likely going to depend more on the standard you want or are building panels to. If you are not building to a certain standard then NEC is fairly open, minus the ground and neutral requirments from what I can tell.

Here is another nice little thread from Mike Holts that has snips of UL508A and NFPA79

https://forums.mikeholt.com/threads/ul508a-wire-color-code.127326/

JaxGTO · Jan 26, 2021

Every plant I have been in that has a standard (and ours) is:
Black: 120vac hot for circuits like lights, plugs AC powered devices in the panel, power to an AC output card.
White: AC neutral only.
Red: AC control wiring input and output.
Green (or EU green/yellow): Ground only. Never ever potential of any kind.
Blue: +24vdc
Blue/white (and sometimes white/blue): 0vdc. Even if 0vdc tied to ground or neutral.
Yellow: External wiring that could have any external potential on it.

Those are the major ones. Other vary from plant to plant.

roxusa · Jan 27, 2021

I use Brown for my DC+, White/Blue DC- and Blue for all my DC inputs/outputs

Wire (24 VDC)

kirk

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rQx

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TWS

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