Color of positive and negative string wiring

[MLynch26]

Labeling of the positive and negative string wires coming from the modules. Is the positive red and black negative or the other way around?

 

[iwire]

Labeling of the positive and negative string wires coming from the modules. Is the positive red and black negative or the other way around?

Either.

But if one of them is a grounded conductor that conductor must be white or gray.

 

[don_resqcapt19]

Either.

But if one of them is a grounded conductor that conductor must be white or gray.

The rules in 210.5(C)(2) or 215.12(C)(2) do not apply?

 

[jaggedben]

The rules in 210.5(C)(2) or 215.12(C)(2) do not apply?

I would say that PV source or output circuits do not fit the definition of either a branch circuit or a feeder. So, no, they do not apply.

With that said... they should generally be followed anyway, at least for conductors that are not exposed. For a grounded conductor, see 200.6(6).

I do not believe that exposed PV wire or USE-2 should be required to have a colored finish. Black is recommended for sunlight resistance, and colors like red will fade. However such conductors should be marked at all terminations and conductors in raceways should follow a color code. None of this is in the code, but it probably should be.

 

[SolarPro]

Correct. We addressed this in an article about NEC 2014 and its implications for PV systems:

Sections 210.5(C) AND 215.12(C) ?Identification of Ungrounded Conductors?

A subgroup of a dc task group established by the NEC TCC developed new language for these sections to specifically address conductor identification in dc applications. According to the National Electrical Code Committee Report on Proposals (ROP) (see Resources), the intent of these changes is to standardize the polarity identification schemes used across different dc electrical applications, including electrical vehicle charging, small wind systems, dc microgrids and PV systems. It is important to recognize that these new identification requirements apply to ungrounded branch circuit [210.5(C)(2)] and feeder [215.12(C)(2)] conductors in dc utilization (load) circuits only. CMP No. 4 rejected a proposal to add these color-coding requirements to Section 690.4(B), noting: ?The proposed wiring method is too prescriptive and may disallow other legitimate marking methods.?

According to Greg Ball, a principal engineer with DNV GL Renewables, ?PV source and output circuits should not be confused with dc branch circuits and feeders in a way that supersedes Article 690.? Whereas feeders supply power to branch circuits, PV output circuits aggregate power from PV source circuits. These circuits may be analogous, but they are not identical. Since Article 690 refers to Article 210 only in relation to dc utilization circuits?circuits supplying dc loads, in other words?the ungrounded dc branch-circuit conductor identification requirements in Section 210.5(C)(2) do not apply to PV source circuits. Likewise, the ungrounded dc feeder conductor identification requirements in Section 215.12(C)(2) do not apply to PV output circuits.

For the OP, here's a excerpt from an article on common PV system code violations:

Color coding. A longstanding convention in PV installation is to mark the positive dc circuit conductor red and the negative conductor black. While this may be recognizable to PV professionals, it is not a correct method per the NEC nor is it safe. It may lead to confusion. Article 200.6(A) dictates that grounded current-carrying conductors smaller than 6 AWG ?shall be identified by a continuous white or gray outer finish or by three continuous white stripes on other than green insulation along its entire length.? There is an exception to the size restraint in 200.6(A)(2). This allows PV source conductors to be installed and marked at their terminations. The use of white tape, for example, can identify a PV source conductor as grounded.

When describing and calling out conductors, it is more appropriate to refer to nongrounded current-carrying conductors and grounded current-carrying conductors. The former is typically the positive conductor, and the latter typically the negative. This is more descriptive and identifies the conductor?s role in the circuit to qualified personnel. Under this nomenclature, color coding is also clarified.

The nongrounded current-carrying conductor may be any color other than white, gray, green or green with yellow stripes. Typically, this conductor is red, which is acceptable per the NEC and stands out to a technician servicing the system. When a positively grounded PV system is employed, it may be in the installer?s best interest to use both proper color coding and additional labeling to identify the system as positively grounded.

 

[jaggedben]

For the OP, here's a excerpt from an article on common PV system code violations:

It should be noted that since that article was published, ungrounded systems have become a lot more common. We just installed a grounded system that was the first one we've done in about 8 months. It's come back around to where the original non-compliant practice is okay in many instances.

 

[SolarPro]

True dat. Red and black are fully compliant w/ a non-isolated inverter since there are no grounded conductors.

 

[ggunn]

I do not believe that exposed PV wire or USE-2 should be required to have a colored finish. Black is recommended for sunlight resistance, and colors like red will fade.

John Wiles agrees. In a course he gave a couple of years ago he showed us examples of red USE-2 conductors that had been in the sun for a few years. They were bleached white, or nearly so, and the insulation had lost a lot of its elasticity - bend it a few times and it began to break off.

 

[SolarPro]

Here's some content related to color-coding in ungrounded PV power system:

Inverter input and PV output conductors. One of the easiest mistakes for installers to make is to instinctively grab white wire off the truck for use in an ungrounded PV array. System designers can make the same mistake and specify white wire in their drawings, especially if they start working from existing plans for a grounded PV array. Ungrounded PV power circuits may not use conductors with white insulation.

Conductors with white insulation are commonly used in positively or negatively grounded PV systems to identify the grounded conductor. However, both of the current-carrying conductors in an ungrounded PV system are floating with reference to ground, so there is no grounded conductor. Therefore, according to Section 200.7 of the Code, neither polarity in an ungrounded PV system can be wired using conductors with a continuous white insulation. This section also excludes the use of conductors with continuous gray insulation or with three continuous white stripes for ungrounded PV array circuits. These colors are reserved for grounded circuits. Insulation that is green or green with yellow stripes can be used to identify grounding conductors only; see Section 250.119.

Aside from these restrictions, the NEC does not dictate what color code to use for conductors in an ungrounded PV system. Just be sure to use different colors for PV positive and PV negative conductors to make it easy to maintain the correct polarity throughout the system. Many dc circuits in the US use red for positive and black for negative. Since these colors are probably already in your inventory, this is a logical convention to follow. However, the Code provides installers with a great deal of leeway to do otherwise. In the event that specific color codes do apply, the local AHJ dictates them.

 

[69gp]

Thought I would add a few pictures to confuse a few people. Opened a re combiner and could not understand the color coding. after opening a combiner box I finally figured it out.

Combiner box

Re combiner