Code FAQs: Service Conductors, Sunlight Resistance and More

Published On
Sep 10, 2020

Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at Answers are based on the 2020 NEC.

Service conductors

Does the NEC permit branch circuits and feeders to be in the same raceway as service conductors for a short distance? If not, can they share the same pull box?

The NEC prohibits branch circuits and feeders from being installed in the same raceway or cable assembly as service conductors. See Section 230.7. Two exceptions to this general rule permit grounding electrode conductors, supply-side bonding jumpers/conductors and load-management control conductors having overcurrent protection to be installed in service raceways. Article 230 is silent with respect to service conductors occupying the same pull box as other conductors. Perhaps public input is needed to provide clarity. Get involved in the process; you can change the Code.

Sunlight resistance

We installed SOW cord per manufacturers’ instructions to supply equipment that is located outdoors. We were questioned about the cord’s sunlight resistance, which is usually marked on cables. Is there a type of SOW cord that is sunlight-resistant?

For information on the use of flexible cords and flexible cables, see Section 400.4 and Table 400.4. Type SOW cable is identified in the table as a thermoset, hard-usage cord, that is permitted in damp and wet locations. It is important to note the superscript numbers that follow Code cable designations such as SOW7,9 in Table 400.4. These superscripts steer the Code user to mandatory and enforceable table notes (at the end of the table). Note (9) permits listed cords complying with the requirements for outdoor cords to be designated as weather- and water- resistant with the suffix “W” after the code type (such as SOW) designation. This note also recognizes that cords with the “W” suffix are suitable for use in wet locations and are sunlight-resistant.

Temporary cables

You were involved in revisions that resulted in text prohibiting extra-hard-usage temporary cable from being allowed to lay on the ground or floor in 590.4(J). I was wondering what solution you propose in outdoor, industrial environments where no nearby structures or overhead structures exist?

In order to answer your question, we need to follow the NEC-revision process and all the archived information supporting this requirement. This safety-driven revision is necessary to comply with long-standing OSHA requirements for temporary power and impacts temporary wiring only. Section 590.4(J) prohibits cable assemblies and flexible cords and cables installed as branch circuits or feeders from being installed on the floor or on the ground. Requirements in 590.6(A) address 125V, single-phase, 15, 20 and 30A receptacle outlets (temporary receptacle installations and receptacles that are part of permanent wiring) and GFCI protection for anything that gets plugged into a receptacle outlet, such as power tools or extension cords.

Requirements in 590.6(B) address   receptacle outlets other than 125V, single-­phase, 15, 20 and 30A and require either GFCI protection or an assured equipment grounding conductor program (AEGCP) be implemented. The second-to-last sentence of 590.4(J) clarifies that extension cords are permitted to be laid on the ground, because there are requirements for GFCI and AEGCPs for receptacle outlets that provide a level of protection for cords or cable assemblies that are laid on the ground.

In an industrial environment, you can meet this requirement in many ways. Temporary stands could be constructed and moved as needed to support cables. Another method would be to provide GFCI or AEGCP in accordance with 590.6 under special permission.

Everything listed?

Does the NEC require that all equipment, conductors, etc., be listed?

No, there is no blanket requirement that all conductors and equipment be listed. Throughout the NEC, there are requirements that mandate that equipment be listed. This includes, but is not limited to, xxx.6 sections for cable assemblies and raceways, appliances, luminaires and more. The general rule (110.2) for conductors and equipment covered in the NEC is that they be acceptable only if approved. This means that all equipment and conductors must be acceptable to the authority having jurisdiction (AHJ). The AHJ may require listed products or a field evaluation where it is considered necessary.


With respect to the application of Section 220.11 for calculated floor areas, the Code says not to include open porches, garages, unused or unfinished spaces not adaptable for future use. I recently took an exam that had a question on calculated floor space in a home with an unfinished basement. The right answer required the unfinished basement be included. This is confusing. How do we apply such a rule?

Section 220.11 requires the floor area to be calculated from the outside dimensions of the building or other structure. As you stated, this section clearly omits open porches, garages and unused or unfinished spaces that are not adaptable for future use. In each case, installers and enforcers must consider each space and determine if the space is adaptable for future use. In almost all cases, an unfinished basement in a dwelling unit is adaptable for future use and must be included in the floor-area calculation.

Service conductors?

Does the ownership of an outdoor pad-mount transformer impact the rules for the supply to a building? Consider two scenarios. 1. The utility supplies the primary and owns the transformer. 2. The utility supplies the primary, but the transformer is privately owned. In both cases, the secondary conductors would be service conductors, right?

Yes, the ownership of a transformer or any equipment or conductors impacts NEC requirements.

No, the secondary conductors would not be service conductors in both scenarios.

It all comes down to defined terms “service point” and “premises wiring.” The service point is defined in Article 100 as the point of connection between the facilities of the serving utility and the premises wiring. An informational note after this definition clarifies that the service point can be described as the point of demarcation between where the serving utility ends and the premises wiring begins.

Let’s look at each scenario you described. In scenario one, the utility owns the transformer, which means it also owns the primary disconnect and overcurrent protective devices, if any. This means that the secondary terminals of the utility-owned transformer where the customer-owned conductors terminate is the service point, and the customer-owned conductors would be service conductors as defined in Article 100.

In scenario two, the customer owns the transformer, which means they also own the primary disconnecting means (450.14) and must provide overcurrent protection in accordance with 450.3(A). The service point in this scenario is on the line side of the primary disconnecting means. This means the secondary terminals of the customer-owned transformer will supply a feeder as defined in Article 100.

About the Author

Jim Dollard

Code Columnist

Jim Dollard is the safety coordinator for IBEW Local 98 in Philadelphia. He is a member of the NEC Correlating Committee, NEC CMP-10, NEC CMP-13, NFPA 70E, NFPA 90A/B and the UL Electrical Council. He can be reached at

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