NESC question

[SolarPro]

Anyone have a copy of the NESC nearby?

I'm working with an author who is describing a fundamental difference between the NEC and the NESC?either of which could apply to a PV installation, depending on the context?and want to verify a reference. The author states that the NESC makes no mention of "listed" equipment (or NRTLs). Just want to verify that this is in fact the case.

I'm not opposed to buying a standard that I'll seldom use, but I'd rather clarify this point this week rather than next.

Thanks in advance.

 

[Hv&Lv]

Anyone have a copy of the NESC nearby?

I'm working with an author who is describing a fundamental difference between the NEC and the NESC?either of which could apply to a PV installation, depending on the context?and want to verify a reference. The author states that the NESC makes no mention of "listed" equipment (or NRTLs). Just want to verify that this is in fact the case.

I'm not opposed to buying a standard that I'll seldom use, but I'd rather clarify this point this week rather than next.

Thanks in advance.

I have one, but is is a book. I can't tell you if the word "listed" is in there or not. Someone like ZOG or Mivey may have a .pdf they can search.

What part of a PV system would come under the NESC?

 

[SolarPro]

A PV system that is utility owned and operated is generally understood to fall under the purview of the NESC rather than the NEC. This why utility-scale PV systems often use 1,000 Vdc rated PV modules and inverters—products that are listed to international standards rather than UL standards. Besides the obvious cable and balance of system benefits, the utility command and control functions are also more sophisticated in inverters built to IEC standards as compared to a UL listed product. (The UL listed inverter has to drop off line in the event of a utility disturbance, whereas the unlisted inverter can offer voltage and frequency ride through, VAR control, etc. to support the grid during a disturbance.) These are multi-MW systems with MV collection systems, MV switchgear and substations that are often built and interconnected according to the NESC. (Part of the thesis of the article is that it can be confusing for engineers and integrators as to which code applies and why.)

 

[SolarPro]

I have one, but is is a book. I can't tell you if the word "listed" is in there or not.

FWIW: It would suffice to know if the term "listed" appears in the index.

Since "listed" is key concept to the NEC, it appears in the Article 100 definitions and the index. Does the NESC include a section with definitions or an index?

 

[Hv&Lv]

It is not in definitions or index.

While the subject has come up, Just because the installation is outside ths scope of the NEC doesn't give one the right to wire as one pleases.
Many linemen feel that because their work is outside the NEC jurisdiction, they can fill conduits as full as they want, or put 30 amp breakers on 14 guage wire.

The work still must be done in accordance with accepted good practices. Good lawyers are waiting for a chance to sue someone.

 

[mivey]

The author states that the NESC makes no mention of "listed" equipment (or NRTLs). Just want to verify that this is in fact the case.

Not true, although it is rare to be worded that way. An engineering study may "qualify" the equipment. There are standards for the acceptable equipment.

NESC 2012-094B2b Made electrodes-Driven rods: "EXCEPTION: Other diameters or configurations may be used if their suitability is supported by a qualified engineering study."

NESC 2012-094B3a Buried wire, strips, or plates-Wire "EXCEPTION 2: Other lengths or configurations may be used if their suitability is supported by a qualified engineering study."

Similar in NESC 2012-094B6 & NESC 2012-094B7b


As for lab testing:

NESC 2012-124C6a: "EXCEPTION: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 8000 V (phase to phase) when the conductors meet the requirements of the NEC, Article 310-6."

NESC 2012-441A5 Temporary (transient) overvoltage control device (TTOCD): TTOCD, which are designed and tested for installation adjacent to the worksite to limit the TOV at the worksite, may be used to obtain a lower value of T. An engineering analysis, including laboratory testing, of the TTOCD shall be performed to determine and identify the range of sparkover voltages..."

NESC 2012-330: Supply Cable: "RECOMMENDATION: Cable should be capable of withstanding tests applied in accordance with an applicable standard issued by a recognized organization such as the American National Standards Institute (ANSI), the Association of Edison Illuminating Companies (AEIC), the Insulated Cable Engineers Association (ICEA), the National Electrical Manufacturers Association (NEMA), or the American Society for Testing and Materials (ASTM)."

 

[SolarPro]

Thanks for checking the index, Hv&Lv.

The NESC excerpt is also helpful. The reference to ANSI or ASTM standards is consistent with the basic distinction the author is making. The acceptable equipment standards in the NESC are more broad than in the NEC.

Under the scope of the NEC, you have a hard row to hoe if the gear you want to use isn't listed to a UL standard. And listed, identified and labeled have very specific definitions in the NEC. Other equipment standards are emphasized/allowed under the NESC.