Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC) , Jim will help you solve it. Send questions to firstname.lastname@example.org. Answers are based on the 2017 NEC .
Marinas and ESDs
Now that the nice weather is here, we recently got our boat into the water at the local marina. The owner approached me and asked how he could improve electrical distribution to all of the marina power outlets. He is concerned about the recent focus on electrical shock drowning (ESD). I researched it and was surprised to see just how many incidents and fatalities have occurred. We are still on the 2014 NEC. Have more recent editions addressed ESDs?
A marina owner can and should take many proactive steps to reduce the potential of ESDs. The 2017 NEC includes multiple significant revisions to eliminate the potential for ESDs. Revisions in Section 555.3 drove a tentative interim amendment (TIA), which was issued on April 10 and became effective on April 30, 2018 (See TIA 17-5, Log No. 1348).
This TIA added the definitions of docking facility and marina to clarify requirements, and Section 555.3 Ground Fault Protection was significantly modified. This revision requires feeder and branch circuit conductors installed on docking facilities to be provided with ground fault protection (GFP) set at not more than 30 milliamperes (mA). Coordination with downstream GFP is permitted at the feeder overcurrent protective device.
Receptacles providing shore power must have GFP set at not more than 30 mA. A new Section 555.24 Signage was added in 2017 to give notice of electrical shock hazards to persons using or swimming near a boat dock or marina. The sign must be clearly visible from all approaches to the marina or boatyard and must state: warning—potential shock hazard—electrical currents may be present in the water.
The 2020 NEC revision process is not complete at this time. However, during the first and second draft stages, significant revisions were added to improve marina safety. These revisions are available for review on www.nfpa.org.
One of the most significant revisions coming is a new requirement for a leakage current measurement device. At this time, 555.35(B) requires, where more than three receptacles supply shore power to boats, a leakage current measurement device must be available and must be used to determine leakage current from each boat that will use shore power. In many cases, the water’s voltage source is not the electrical distribution system; it is faulty wiring within a boat.
The same hazards exist where natural and artificial bodies of water covered by Article 682 include feeders, branch circuits and receptacles. TIA 1716, Log No. 1349, effective April 30, 2018, added the definition of pier and modified section 682.15 Ground Fault Protection. All 15- and 20-ampere, 125V through 250V receptacles installed outdoors and in or on floating buildings or structures must be ground-fault-circuit-interrupter protected. All feeder and branch circuit conductors installed on piers must be provided with GFP set to open at currents not exceeding 30 mA. Coordination with downstream GFP is permitted at the feeder overcurrent protective device.
Delayed implementation dates
Why is the NEC adding new rules with delayed implementation dates? I believe two rules, in particular (240.67 and 404.20), should be implemented immediately. Where there is a delayed implementation date, do these rules kick in on that date, or do we wait for local Code adoption of the next NEC edition? For example, we are on the 2017 NEC; does 240.67 kick in on Jan. 1, 2020, or do we wait for local adoption of the 2020 NEC?
The NEC revision process requires the technical committees to consider all public inputs and comments submitted to revise the NEC . In some cases, the technical committees develop requirements that will require significant equipment modification or new products. The new requirements in 240.67 are a good example of where delayed implementation was needed.
This new rule requires fuses rated at 1,200A or more—having a clearing time of longer than 0.07 seconds at the available arcing current—to provide a means of arc energy reduction. During the committee meeting discussions, it was understood that products to achieve arc energy reduction, as 240.67 would require, were not readily available. The delayed implementation date provides manufacturers with an opportunity to develop and produce products to meet this requirement.
Where a delayed implementation date is provided, the requirement is enforceable on that date. In your question, you state you are on the 2017 NEC, which means the new 240.67 and 404.22 requirements will apply on Jan. 1, 2020. The delayed implementation date for electronic lighting control switches will allow all manufacturers to develop devices that do not introduce current on the equipment grounding conductor. Additionally, this will allow manufacturers and supply houses to move the inventory presently in stock.
Surge protection in panelboards
Section 700.8 requires surge protection in all emergency panelboards. We have a design with a single feeder into a panelboard in the north electrical closet, which feeds through to a panelboard in the south electrical closet on every floor in a 16-story building. Is it permitted to provide the surge protection at the first panelboard only?
No, 700.8 requires a listed surge protective device (SPD) to be installed in all switchboards and panelboards that are part of an emergency system. To achieve the required level of surge protection, there must be a listed SPD in all switchboards and panelboards that are part of an emergency system.
Transformer secondary conductors
We recently failed an electrical inspection on a sports lighting project for the local youth baseball association. The utility company installed two pad-mount transformers with 480/277-volt (V) secondaries. We installed 1/0 copper conductors (about 15 feet long) from the transformer secondary into a wireway at each location. Below each wireway, we installed six NEMA 3R fused disconnects to supply the sports lighting. The inspector told us this is a violation because we are “tapping a tap.” We have installed many similar installations, all of which passed every electrical inspection. We believe the inspector is wrong because these conductors are feeders. The definition of feeder in Article 100 clearly includes the conductors from a separately derived system or other power source to the final branch circuit overcurrent device.
The inspector is correct, and the installation you describe is an NEC violation. See the last sentence in the parent text of Section 240.21, which states the conductors supplied under the provisions of 240.21(A) through (H) are not permitted to supply another conductor except through an overcurrent protective device. Transformer secondary conductors are addressed in 240.21(C). For transformer secondary conductors to be considered a branch circuit or feeder, they must be installed in accordance with 240.21(C)(1). It is extremely important to note this is limited to single-phase transformers with two-wire secondaries or three-phase delta-delta connected transformers with three-wire single voltage secondaries.
The secondary in your question is wye-connected at 480/277V. Therefore, the installation must comply with 240.21(6) for transformer secondary conductors not over 25 feet long. See 240.21(C)(6)(2), which requires the secondary conductors to terminate in a single circuit breaker or set of fuses.
I do agree with you that the Article 100 definition of feeder is misleading. There have been multiple attempts to add an informational note to this definition to inform the user that most transformer secondary conductors are not considered to be protected at their rated ampacity, are not feeders, and must be installed in compliance with 240.21(C).
Panelboards in bathrooms
Can you please explain why a panelboard is not permitted in a dwelling unit bathroom but is permitted in a commercial facility’s bathroom? As a multi-hat inspector, I do not claim to be a subject matter expert on electrical codes. I just do not understand why a panel board is permitted in any bathroom.
The requirement you refer to does not address panelboards; it addresses all overcurrent devices. Section 240.24(E) prohibits overcurrent devices in dwelling unit, dormitory, guest room and guest suite bathrooms. This requirement was new in the 1993 NEC and addressed bathrooms in dwelling units and hotels/motel guest rooms only. The submitter of proposal 10-84 intended to address all bathrooms containing a tub or shower.
These are plumbing fixtures that are capable of producing fog and moisture in an environment where people may contact enclosures with wet hands and bare/wet feet. The intent of this requirement is to eliminate the possibility of persons with wet hands and bare/wet feet standing on tile surfaces coming in contact with enclosures containing overcurrent devices. In a commercial bathroom, it is not typical to see tubs or showers. However, it is not uncommon for some workplaces and locker rooms to provide showers in bathrooms, and this requirement should also address those locations. This is an excellent opportunity for you to submit a public input to change the NEC in the 2023 revision cycle.