# 508A color codes for DCV



## MikeFL

If I'm reading this correctly, for a 3 conductor control wiring circuit at 24VDC, the following color codes apply (which doesn't make sense and that's why I'm questioning it):

+24VDC = Black = All ungrounded power circuit conductors regardless of voltage

-24VDC = White w/ Blue Stripe = Grounded DC current-carrying control circuit conductor

Load	= Blue =	Ungrounded DC control circuits 

Sparky has a panel with 24VDC transformer and 24VDC relay. 

He's going to power my control from the 24VDC transformer and my control is going to switch his 24VDC relay.

Seems crazy to use a black wire for +DCV. I was going to make it blue but then what do I use for the control when 508A specifically says blue for ungrounded DC control. 

Am I reading this wrong?

FYI: Customer is a POCO and exempt from listing requirements so I don't have a UL engineer to consult on this build. 

If you want to see what 508A says, Eaton has a nice overview/ guide here: http://www.eaton.com/ecm/groups/public/@pub/@europe/@electrical/documents/content/pct_2930585.pdf

Pages 32 and 45 of that document are what I'm going by.


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## pjholguin

WOW...Who came up with that color coding.:surprise: That needs to be reviewed.



MikeFL said:


> If I'm reading this correctly, for a 3 conductor control wiring circuit at 24VDC, the following color codes apply (which doesn't make sense and that's why I'm questioning it):
> 
> +24VDC = Black = All ungrounded power circuit conductors regardless of voltage
> 
> -24VDC = White w/ Blue Stripe = Grounded DC current-carrying control circuit conductor
> 
> Load	= Blue =	Ungrounded DC control circuits
> 
> Sparky has a panel with 24VDC transformer and 24VDC relay.
> 
> He's going to power my control from the 24VDC transformer and my control is going to switch his 24VDC relay.
> 
> Seems crazy to use a black wire for +DCV. I was going to make it blue but then what do I use for the control when 508A specifically says blue for ungrounded DC control.
> 
> Am I reading this wrong?
> 
> FYI: Customer is a POCO and exempt from listing requirements so I don't have a UL engineer to consult on this build.
> 
> If you want to see what 508A says, Eaton has a nice overview/ guide here: http://www.eaton.com/ecm/groups/public/@pub/@europe/@electrical/documents/content/pct_2930585.pdf
> 
> Pages 32 and 45 of that document are what I'm going by.


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## gnuuser

pjholguin said:


> WOW...Who came up with that color coding.:surprise: That needs to be reviewed.


thats why i love this site we give each other directions to so much literature. Its a benefit to all.
I knew most of the colors before but its nice to have the proper references.


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## pudge565

I worked for a 508A certified panel shop. We always just used blue for + and blue white tracer for the - on 24v DC.


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## pudge565

You are reading that chart wrong. The black is for the SUPPLY voltage of the control circuit NOT the control voltage, primary of transformer not secondary. Black is for the input to the DC power supply, the actual DC control side is blue and white with blue tracer.


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## splatz

The only one I don't know what to do with, what if you don't ground the negative on the DC power supply? White with blue stripe would be for grounded conductor...


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## pjholguin

I concur.:thumbsup:



gnuuser said:


> thats why i love this site we give each other directions to so much literature. Its a benefit to all.
> I knew most of the colors before but its nice to have the proper references.


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## MikeFL

pudge565 said:


> I worked for a 508A certified panel shop. We always just used blue for + and blue white tracer for the - on 24v DC.


That gets me +DC and -DC to power my control.

What color do I use on the control leg back to the relay? It will have +DC.


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## splatz

MikeFL said:


> That gets me +DC and -DC to power my control.
> 
> What color do I use on the control leg back to the relay? It will have +DC.


Why wouldn't you just use blue and white with blue stripe to the relay coil?


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## MikeFL

splatz said:


> Why wouldn't you just use blue and white with blue stripe to the relay coil?


Just seems odd to ship a unit with 2 blue wires and 1 blue/ white wire. I can tag the wires to indicate which powers the control and which is the control leg to the relay, but that only lasts as long as the tags. 

An A/C control has black, white, red and there's never any confusion what any of the wires are for.

So on this DC control I'm going to ship a unit with 2 blue wires and 1 blue/ white wire. Just seems strange. There seems to be no color code for a DC control leg.


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## frenchelectrican

MikeFL said:


> That gets me +DC and -DC to power my control.
> 
> What color do I use on the control leg back to the relay? It will have +DC.


I would go blue and white with blue stripe that is very common item. 

The blue is on DC positive side.

Edit.,

the color I posted is for non grounded system ( floating system ) so just be aware with dc side it can be floated or grounded on one side depending on how it set up.


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## varmit

I have used yellow with a blue tracer on "alien" DC power in panels. This color is available and seems to be compliant- yellow for separate power source and blue marking for DC. This color identification is something specific that seems to have been missed in any standard that I am aware of.


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## splatz

MikeFL said:


> Just seems odd to ship a unit with 2 blue wires and 1 blue/ white wire. I can tag the wires to indicate which powers the control and which is the control leg to the relay, but that only lasts as long as the tags.
> 
> An A/C control has black, white, red and there's never any confusion what any of the wires are for.


I was confused but I think I see what you mean now. Do you mean like a dawn to dusk motion sensor light where the supply hot is black, the switched hot (hot when motion + dark) is red, and the neutral is white? 

If that's the idea then this is my take, a control panels is a much much different animal you have so many wires and such complexity you'd quickly run out of colors if you tried to embed too much information in the color coding. The idea is to just identify voltages / references / supplies.


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## oliquir

funny that sensors doesn't follow this code
brown is 24v
blue is 0v 

black, white or gray are signals


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## splatz

Are you required to stick to the UL 508A color codes when doing maintenance in panels? For example if there are panels that are all at 120VAC supply and control voltage, and you introduce some 24VDC controls, are you required to use blue and white-blue? 

Asking for a friend. :blush:


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## MikeFL

splatz said:


> I was confused but I think I see what you mean now. Do you mean like a dawn to dusk motion sensor light where the supply hot is black, the switched hot (hot when motion + dark) is red, and the neutral is white?


Yes.



splatz said:


> If that's the idea then this is my take, a control panels is a much much different animal you have so many wires and such complexity you'd quickly run out of colors if you tried to embed too much information in the color coding. The idea is to just identify voltages / references / supplies.


I agree. But the problem is if the tags are gone, there's no way to diagnose which blue is which if I use blue for both sides, because it's a NC relay.



varmit said:


> I have used yellow with a blue tracer on "alien" DC power in panels. This color is available and seems to be compliant- yellow for separate power source and blue marking for DC. This color identification is something specific that seems to have been missed in any standard that I am aware of.


I think I like this best.


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## splatz

varmit said:


> I have used yellow with a blue tracer on "alien" DC power in panels. This color is available and seems to be compliant- yellow for separate power source and blue marking for DC. This color identification is something specific that seems to have been missed in any standard that I am aware of.





MikeFL said:


> I think I like this best.


But I don't think that's for you, that is for "alien" power, power that's not shut off when the main for the panel is shut off. The standard requires the alien power be yellow, varmit uses yellow with the stripe to indicate that the alien power is low voltage.


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## MikeFL

We source from Allied up in Tampa and they have real good engineers on staff. That's all they do. I've put an inquiry in to them. I'll let you know what they say.


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## splatz

MikeFL said:


> I agree. But the problem is if the tags are gone, there's no way to diagnose which blue is which if I use blue for both sides, because it's a NC relay.


If you number the wires at both ends and you have a well laid out, legible schematic inside the panel the person servicing it will be all set. 

I find that the wrap around wire markers you buy in booklets are pretty damn durable and if you zip up that panel tight things stay pretty nice in there. I do wish people would maybe put one right near the end of the insulation and another six inches up, for redundancy. 

The wrap-around self-laminating labels are very durable. They make write-on booklets and they make them for label printers too. You write or print on the white part at the end of the tag and then the clear part wraps around the wire a couple wraps to protect the label. I have been using the write on ones for 20-25 years and come across some of my old ones from time to time, still legible in some fairly harsh conditions.


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## MikeFL

I like your idea of tagging both ends of the leads.

I don't have control over what happens in the panel.


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## splatz

MikeFL said:


> I like your idea of tagging both ends of the leads.
> 
> I don't have control over what happens in the panel.


I see, I thought you were building the panel. I did not know that the 508A color code would apply to devices in the panel, just the wiring of the panel itself. In fact as @oliquir mentions a lot of sensors etc. just seem to make up the rules as they go along


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## MikeFL

I agree, but it would be nice if there was some sort of common sense in the color codes. If I used black, white, red someone's going to look at it and say "Oh, this is 120VAC, so this wire goes here..." and kaboom! 

The guys at Allied said I'm fine with Blue, Blue/white and Yellow/blue. 

It's done. Thanks to all. 

I will be tagging both ends as suggested.


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## pudge565

MikeFL said:


> That gets me +DC and -DC to power my control.
> 
> What color do I use on the control leg back to the relay? It will have +DC.


Blue as the standard requires. This is where drawings and wire tags come into play. I liked the heat shrink Brady labels.


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## MikeFL

pudge565 said:


> Blue as the standard requires. This is where drawings and wire tags come into play. I liked the *heat shrink Brady labels*.


+1 for that! Great stuff.


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## just the cowboy

*Sounds like a sensor*

If I was building a sensor, I would do the Brown for + Blue for - and black and white for output and not output.


Can you just get a m8 or m10 quick disconnect put on your sensor and let the customer use a cable of the proper length. It makes changing out a bad device easy, then you don't need to worry about colors.


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## MDShunk

Not so sure I'd go with an M10 connector, as they don't popularly exist. An M12 would be a lot more typical. :biggrin::biggrin:


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## MikeFL

The control does not get mounted in the panel. It connects to a cable which will connect to the panel. I mainly didn't want to use black, white, red because someone would think it's AC line voltage when in fact it's 24VDC. So in deciding what colors to use, I figured I'd match colors used in the panel as it's an industry standard.


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## MDShunk

MikeFL said:


> The control does not get mounted in the panel. It connects to a cable which will connect to the panel. I mainly didn't want to use black, white, red because someone would think it's AC line voltage when in fact it's 24VDC. So in deciding what colors to use, I figured I'd match colors used in the panel as it's an industry standard.


Then your short answer is that DC sensors are absolutely standardized. Blue for DC-, brown for DC+, and white and black for the outputs. Doing any other colors will royally screw someone up. Do what Cowboy said.


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## bill39

MDShunk said:


> Then your short answer is that DC sensors are absolutely standardized. Blue for DC-, brown for DC+, and white and black for the outputs. Doing any other colors will royally screw someone up. Do what Cowboy said.


I agree with the above. 

Are we not talking about 2 different things here? Standardized cable wire colors factory attached to a connector vs. individual wires ran in a conduit or panel?

Prox switches and photo eyes w/quick disconnect connectors line up with black for hot, Brown for load, and blue for neutral-0vdc.


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## MikeFL

MDShunk said:


> ...
> Blue for DC-,
> brown for DC+, and
> white and black for the outputs. ...


I have 3 wires.

The control is powered by 24VDC.
For that I see 
Blue = DC-
Brown = DC+

Then I have a control leg and it's DC+. 
I do not have 2 control legs.
So you're saying the control leg will be white with a black stripe?
Or were you thinking I had 2 control legs?


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## gpop

Cables are euro so brown is live blue is neutral and depending on the senser white, black or both are used.

Change ac to dc and brown is dc+ and blue is dc-


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## just the cowboy

MikeFL said:


> I have 3 wires.
> 
> The control is powered by 24VDC.
> For that I see
> Blue = DC-
> Brown = DC+
> 
> Then I have a control leg and it's DC+.
> I do not have 2 control legs.
> So you're saying the control leg will be white with a black stripe?
> Or were you thinking I had 2 control legs?



Something like this black is output only has 3 wires.
https://www.automationdirect.com/ad...les/3-Pole_Micro_(M12)_Cables/CD12M-0B-050-A1
and this mounted on your sensor.
https://www.automationdirect.com/ad...es/Micro_(M12)_Receptacles/7231-13501-9710050


Cowboy


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## Giqexove

Thanks for clear explanation guys. Have the same problem


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