Positive/Negative Colors for a DC 230Mw PV Solar System

Nestor_R175

Member
Location
Florida
Occupation
Electrical Superintendent
200.6 states:
200.6 Means of Identifying Grounded Conductors
(A).
Grounded (neutral) conductors 6 AWG and smaller must be identified by one of the following means [200.6(A)]:
1) By a continuous white outer finish.
2) By a continuous gray outer finish.
3) By three continuous white stripes along its entire length on other than green insulation.
4) Wires that have their outer covering finished to show a white or gray color but have colored tracer threads in the braid identifying the source of manufacture are considered to meet the provisions of this section. The use of white tape, paint, or other methods of identification isn't permitted for grounded conductors 6 AWG or smaller.
6) A single-conductor, sunlight-resistant, outdoor-rated cable used as the grounded conductor in photovoltaic power systems as permitted by 690.31(B) can be identified by distinctive white marking at all terminations.

Grounded (neutral) conductors 4 AWG or larger must be identified by one of the following means [200.6(B)]:
1) A continuous white outer finish along its entire length.
2) A continuous gray outer finish along its entire length.
3) Three continuous white stripes along its length.
4) White or gray tape or markings at the terminations.

3 years ago I was part of constructing a Solar site that had black and white DC Output Feeder cable. In that system we received harness cable as well and on the black cable we had inline fuses rated at 20a and the white served as the negative cable. Since 200.6 (B) states for sizes 4 AWG or Larger (1) A continuous white outer finish serves as the Identification of the Grounded Conductor, why was the Black cable served as the Positive and the white as the negative? On the site that I'm on now we have stated on a detail that,
DC NEGATIVE GROUNDED CONDUCTORS SHALL BE BLACK. EQUIPMENT GROUNDING CONDUCTORS SHALL BE BARE,
COLORED GREEN, OR MARKED GREEN. So my question is what is the real requirement for 2000v PV Underground Feeder cable if we have black and white as our colors?
 

pv_n00b

Senior Member
Location
CA, USA
Functionally grounded systems do not qualify for a white conductor. Only if the current carrying conductor is physically bonded to ground is it considered a grounded conductor. Functionally grounded is ungrounded with some fancy electronics to detect grounds in the ungrounded conductors. :)
The note on the detail is incorrect but how it is incorrect depends on the actual grounding. It should read, "DC NEGATIVE CONDUCTORS SHALL BE BLACK", or " DC NEGATIVE GROUNDED CONDUCTORS SHALL BE BLACK WITH WHITE TAPE MARKINGS AT TERMINATIONS", OR " DC NEGATIVE GROUNDED CONDUCTORS SHALL BE WHITE."
 

Carultch

Senior Member
Location
Massachusetts
You need to establish whether the DC system is grounded/functionally grounded. Most these days are ungrounded meaning there are no white conductors and you can't use white conductors.
To answer the OP's question, it used to be that grounded polarities got identified white, and the other polarity was free to be any color permitted for ungrounded wires in general, with black being the most common regardless of polarity sign. In 2014, they established the standard of red for positive ungrounded, and black for negative ungrounded, or marked on the print legend with the polarity in text. A system with both polarities ungrounded would be black and red, a negatively-ground system would be red and white, and a positively-grounded system would be black and white.

Then the term functionally grounded was introduced in 2017. Most systems had been functionally grounded prior to 2017, and just not called that yet. It was either one polarity grounded through a GFCI protection device, which we called grounded, and marked the grounded polarity white. Or it was both polarities ungrounded at equal and opposite voltages to ground that were ultimately connected to a grounded grid, which we called ungrounded, and marked neither polarity white.

" Functionally grounded is ungrounded with some fancy electronics to detect grounds in the ungrounded conductors. "

It's not really that fancy. It could be a GFCI fuse or breaker that is in between the grounded polarity and the EGC. Or it could be a current sensor that measures the magnetic field around the two polarities together, and makes sure it adds up to close enough to zero. A residual current monitor, that looks for current leaking away from the wires intended to carry current. When it is a GFCI fuse or breaker that grounds one of the polarities, that particular polarity normally is grounded, and only becomes ungrounded during a fault.

I dislike that they grouped two different kinds of systems under the same term functionally grounded. I think it is a great term for what used to be called grounded systems that used a GFCI fuse or breaker, but I disagree with it also applying to non-isolated systems that we used to call ungrounded. Perhaps "grid-grounded, non-isolated", or "symmetric polarity grounded" is a term I'd recommend.
 
Last edited:

Nestor_R175

Member
Location
Florida
Occupation
Electrical Superintendent
I understand everyone’s comments but the struggle I’m having is that our engineers built the site off the 2014. The site is considered functional grounded but our engineer won’t change the wording on the negative cable. They want to keep it as a negative grounded conductor since the site was built on the 2014 so there for are they correct by keeping the wording as a negative grounded being that the site is functional grounded or do they need to apply the change to functional grounded system and stick with using red and black vs. black and white?
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
If the system was built to the 2014 code then I see no problem keeping it the way it is if we are just talking about service or repairs. Back then a conductor that was connected to ground through a ground fault detection fuse was considered grounded and colored white.

If the entirety of the system wiring was being overhauled and replaced I would bring it up to date with a new convention.
 

Nestor_R175

Member
Location
Florida
Occupation
Electrical Superintendent
If the system was built to the 2014 code then I see no problem keeping it the way it is if we are just talking about service or repairs. Back then a conductor that was connected to ground through a ground fault detection fuse was considered grounded and colored white.

If the entirety of the system wiring was being overhauled and replaced I would bring it up to date with a new convention.
I agree with you but I guess when it comes to being a young superintendent and I you mention this certain types of things people tend not listen and try to make you feel like you don’t know what your talking about? 👍
 
Top