Color Coding on Negatively Grounded DC Systems

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Clarkent404

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All,

I'm in dire need of help. I'm installing a facility where the negative of our DC system (24VDC and 125VDC) is grounded - thus we're using single pole breakers in our panelboard for our branch circuits. We are using RED (+) and BLACK (-) color coding on our insulators. While my facility is brand new and still under construction, my company has several existing/operating facilities with this exact set up.

Our tyipcal DC system is 2 100% chargers that charge these batteries and supply the load through a DC distribution panel. If both chargers fail or there is a loss of AC, then the batteries supply power to the loads through the DC distribution panel. Our typical DC loads are...transmitters, detectors, relays, etc...

I've been informed that this color code scheme possibly violates code, specifically NEC 200.7, 2005 Edition. I've been informed that not only does the cable that goes from the negative post of the battery to ground must be WHITE, all other DC power cables in all circuits should also have its (-) conductor coded WHITE as well, since ultimately it's tied back to ground.

Have I violated code? Please explain,

Thanks,

Confused
 
I have seen every combination I can think of, BUT In my opinion Red is Positive, Black is Negative, green is ground. Some site have specific Specs particular when they have two or three different systems -24VDC, +24 VDC and +48 VDC for example. then in my experience the owner/engineer had a standard they follow. Code does not dictate with exception of Green ground, White neutral and for high leg.

Though I would like to have seperate systems have different colors maybe Red, Orange.

As noted check specs.
 
color coding

color coding

An opinion...

I am going to defer John Wiles...the guru of Art. 690 and Photovoltaic systems [DC current].

I will quote directly from his " Photovoltaic Power Systems & the 2005 NEC: Suggested Practices"....he also publishes an 'Inspector Checklist'.

"PV systems are being installed in an arena covered by the NEC and, therefore, MUST comply with NEC standards that apply to both ac and dc power systems. In a system where one conductor is grounded, the insulation on all grounded conductors MUST be white, gray or have three white stripes ..."

SO - IMHO - if your wiring system is covered by the NEC, I would say your grounded conductor must comply with Art. 200.
 
dana1028 said:
SO - IMHO - if your wiring system is covered by the NEC, I would say your grounded conductor must comply with Art. 200.
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I agree, if the installation is under the NEC the grounded conductor must be white, there are no exceptions.
 
Well I say most of you are all wet, because I have been designing installing 24, 48, 130, and 390 VDC plants for about 30 years. Mostly both positive and negative polarities are both black, even frame ground, but sometimes when I fell like confusing people I will use green for frame ground, and Red for the hot ungrounded conductor to shake things up a bit.

Now I have seen all combinations especially when there is a mix of say both 48 positive ground, and 24 negative ground systems where the hot on 48 is red, and hot on the 24 is blue, the grounded is always black or grey cloth.

The only logic applied if colors are use is the hot or ungrounded with be a color like red or blue, and the grounded is black. Doesn?t matter which polarity is grounded. The thinking is black is the color of earth or dirt, and hot is a bright or warm color.
 
If the NEC applies (and it pays to confirm this!), then grounded conductors are required to be identified as per 200.6 and 200.7

If you want to maintain consistency with your other installations, then you could use 'three continuous white stripes on other than green insulation along its entire length' and get black conductors made up that meet the spec.

-Jon
 
dereckbc said:
Well I say most of you are all wet, because I have been designing installing 24, 48, 130, and 390 VDC plants for about 30 years. Mostly both positive and negative polarities are both black, even frame ground, but sometimes
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Your installations where not under the NEC.

If they where they where in violation. :smile:
 
iwire said:
Your installations where not under the NEC.

If they where they where in violation. :smile:
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Bob I was hoping you would challenge me. Yes many were made under NEC, even though it is a phone company. A lot of the systems are in multiple occupancies like high rise buildings. Now please ask me why me or any ones else does not have to obey any color code with is type of application? :)
 
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As for the DC grounded conductor, if it falls under the NEC, it sure seems to me that it should be white or gray. Now, if it is part of a telecommunications system, then perhaps it is exempted as in 90.2(B)(4). But that means it isn't covered....
 
The reason there is no color code for conductors used in this manner is because they are NOT PREMISES WIRING

Premises wiring ends at the rectifiers. Read the definition very carefully, especially the part that extends from the service point of the source to the outlets

Rectifiers are utilization equipment (OUTLET) and the end point of NEC requirements.
 
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Woah, I am not convinced that a DC system isn't premises wiring. But it is really good food for some thought and debate.

I am predicting quite a bit of arguing on that point. I'm not so sure that a rectifier is considered as utilization equipment. And I'm not so sure that the point where the DC wiring feeds its loads wouldn't be outlets.

wouldn't a rectifier be a "device" by the Art 100 definition? It doesn't use electricity, it actually controls it by making AC to DC?

Again, good point!
 
Food for thought indeed! I think that it depends upon the specifics of the installation; if you have a machine that includes a rectifier, storage battery, panelboard, and DC distribution wiring, then I entirely agree: this is not premises wiring.

For what its worth, the OP described panelboards and branch circuits. This sure sounds like premises wiring. Wiring from stationary installations of storage batteries must conform to ordinary code (see 480.3) and article 250 specifically describes grounding of DC systems. It seems to me that if you have a _building_ with permanant wiring in or on the walls, then that wiring is premises wiring even if supplied via a rectifier and battery, in the same way that it would be premises wiring even if supplied by a transformer or a DC generator.

Additionally, it may very well be the case that you have such entrenched industry practise in this color coding for DC wiring that the strict NEC does not get enforced...and that strictly following the NEC might even _increase_ danger.

-Jon
 
crossman said:
...wouldn't a rectifier be a "device" by the Art 100 definition? It doesn't use electricity, it actually controls it by making AC to DC?
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So does a wall wart!
 
dereckbc said:
The reason there is no color code for conductors used in this manner is because they are NOT PREMISES WIRING
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Dereck, you are looking at this from only your perspective.

The name of the thread is "Color Coding on Negatively Grounded DC Systems" there are Grounded DC Systems that are premises wiring systems. Such as solar that I recently asked about.

Premises wiring ends at the rectifiers. Read the definition very carefully, especially the part that extends from the service point of the source to the outlets

Rectifiers are utilization equipment (OUTLET) and the end point of NEC requirements
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Interesting, so when I install a UPS system it is also utilization equipment, so by your interpretation the AC conductors on the load side of that UPS are also not under the NEC.

I can not agree with that.

As far as the NEC ending at the outlets I can show many sections that specifically pass the outlets.
 
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winnie said:
if you have a machine that includes a rectifier, storage battery, panelboard, and DC distribution wiring, then I entirely agree: this is not premises wiring.
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I agree entirely with that. :smile:

For what its worth, the OP described panelboards and branch circuits. This sure sounds like premises wiring. Wiring from stationary installations of storage batteries must conform to ordinary code (see 480.3) and article 250 specifically describes grounding of DC systems. It seems to me that if you have a _building_ with permanant wiring in or on the walls, then that wiring is premises wiring even if supplied via a rectifier and battery, in the same way that it would be premises wiring even if supplied by a transformer or a DC generator.
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I also agree with that entirely. :smile:

Additionally, it may very well be the case that you have such entrenched industry practise in this color coding for DC wiring that the strict NEC does not get enforced...and that strictly following the NEC might even _increase_ danger.
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And that makes three. :smile:
 
iwire said:
Dereck, you are looking at this from only your perspective.
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Bob I agree with that 100%

Here is my main point: Over 30 years this debate has come up numerous times in my industry, and what always ends the debate is the listing of the equipment (RECTIFIER). Every Rectifier I have used in my applications is listed as UTILIZATION EQUIPMENT. That is all the inspector and I needs to know. :D

We take many liberties like cable dearating on cable racks. Even though we may use 4-750 MCM cables per polarity on a 600-amp fuse it is still not enough to satisfy NEC for the number of conductors (circuits. we stack on a 36-inch rack. So tell me where to find white or gray 750 MCM DLO/RHH/RHW-LS2 cable at without a custom order at?:D
 
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Ungrounded DC

Ungrounded DC

When we build substation DC systems, 48VDC or 125VDC, we do not ground either side of the DC, ever. We use DC ground detection system to monitor that the DC is ungrounded. The color varies and is up to the installer but we carefully mark everything. However, we do not need to comply to NEC since these are POCO facilities.
 
beanland said:
When we build substation DC systems, 48VDC or 125VDC, we do not ground either side of the DC, ever. We use DC ground detection system to monitor that the DC is ungrounded. The color varies and is up to the installer but we carefully mark everything. However, we do not need to comply to NEC since these are POCO facilities.
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Been there done that too working for PSO as a substation engineer. However it requires both positive and neagative polarities to be fused which adds a lot of expense. That is why Telco's and others reference one polarity to ground at the expense of system failure in the event of a ground fault on one of the ungrounded circuit conductors.
 
I would only say 100% of the DC systems I have seen violate the NEC, because of all the colors I have seen from black to blue and purple NONE ever use white for anything.

This includes 120 VDC systems for Switchgear controls where the negative is grounded, not just telco systems.
 
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