In the July 2013 issue of FRONT of HOUSE, our second article on portable power distribution discussed grounding and bonding specifics of portable generators, including small generators that are “floating neutral” configured. This third article should not be viewed as independent of the other two, and readers are encouraged to read the articles in the June and July issues. In this third article we’ll focus on proposed changes to the 2013 National Electric Code that, if enacted, will have ramifications for generators 15 kW and below.
Disclaimer: Let me clearly state up front that I am not a licensed electrician, and implore readers to consult with an experienced electrician or their Authority Having Jurisdiction (AHJ) for clarification about electrical matters. Equally important is realizing that knowledge gained from an article like this one is no substitute for direct experience in practicing safe handling of electrical equipment in the field. A solid conceptual understanding of portable electrical power distribution should be a goal for all pro audio pros, especially when discussing the code with AHJs.
Background on the NEC
This article will reference sections of the National Fire Protection Association’s (NFPA) NFPA 70: National Electrical Code. Thus this article will be particularly U.S.-centric in its discussion. The NEC is not universally adopted in all U.S. jurisdictions. Some locations may have exceptions to the NEC; others have additional requirements beyond the code. Because of the way the code is adopted, your local AHJ should be considered the ultimate resource for understanding code compliance of your pro audio endeavors.
Further, the NEC is an evolving document and has been revised extensively over the years. When reading the code for yourself, please reference code cycle 2002 or later (i.e., 2008 or 2011). My code reference for this third article is the proposed 2013 code draft to be officially released in 2014. A digital version of the NEC 2008 is an affordable download ($9.99 U.S.) for Apple devices on the iTunes store, and I encourage readers to purchase a digital copy of it. Having a digital copy of the code will allow you to read the code more thoroughly. Your local AHJ can clarify what code cycle is the current one in your area.
Potential Changes for Generators
Generator-related details are sprinkled throughout the NEC. They are mentioned in places including NEC 240.21, 250.34, 430.14, 445, 590.6, 700.10, and 702. Before launching into this series on generators, I investigated generator-relevant locations in the 2013 code draft. One new section stood out as having relevancy for smaller production generators. The proposed new section, NEC 445.20, addresses the use of Ground-Fault Circuit Interrupters (GFCI’s). The full text of the proposed 445.20 is included as a sidebar to this article. 445.20 requires either GFCI protection for 120 volt receptacles, or the disconnection of those receptacles from operation when a locking connector is in use. Before looking further at how 445.20 fits in the code, we first briefly introduce the GFCI and how it operates.
GFCI Overview
In brief, GFCI’s disconnect a circuit if there is any “leakage” current outside the circuit. Leakage is any current traveling on a path outside the one defined by the circuit. A GFCI is agnostic about the path traveled by the leakage current, but by detecting small currents (i.e. 5 to 30 milliamperes) and disconnecting quickly enough (i.e., <30 ms), these help prevent electrocution should the leakage path be across someone’s heart. By contrast, conventional circuit breakers or fuses only break the circuit when the total current is excessive, a value that is usually far in excess of the current at which a GFCI responds.
GFCI’s measure the current balance between two conductors of a circuit using a differential transformer. This measures the difference between the current flowing through the live conductor and that returning through the grounded conductor (or another phase). Normally these currents are identical, and therefore, their respective magnetic fields at the transformer sum to zero. If these currents do not sum to zero, there is a leakage of current somewhere else (e.g., to earth) and the GFCI will open the circuit. Fig. 1 shows the components of a GFCI.
NEC 445.20 in Context
The most similar existing location in the NEC to 445.20 that I am aware of is NEC 590.6. The “Ground Fault Protection for Personnel” section is introduced as follows:
590.6 Ground-Fault Protection for Personnel. Ground fault protection for personnel for all temporary wiring installations shall be provided to comply with 590.6(A) and (B). This section shall apply only to temporary wiring installations used to supply temporary power to equipment used by personnel during construction, remodeling, maintenance, repair, or demolition of buildings, structures, equipment or similar activities. This section shall apply to power derived from an electric utility company, or from an on-site-generated power source.
Thus, the scope of 590.6 is targeted specifically at construction-like circumstances. We then look at NEC 590.6(A)(3) to see the GFCI requirement for generators in these settings:
590.6(A)(3) Receptacles on 15-kW or less Portable Generators. All 125-volt and 125/250-volt, single-phase, 15-, 20- and 30-ampere receptacle outlets that are a part of a 15-kW or smaller portable generator shall have listed ground-fault circuit-interrupter protection for personnel. All 15- and 20-ampere, 125- and 250-volt receptacles, including those that are part of a portable generator, used in a damp or wet location shall comply with 406.9(A) and (B). Listed cord sets or devices incorporating listed ground-fault circuit interrupter protection for personnel identified for portable use shall be permitted for use with 15-kW or less portable generators manufactured or remanufactured prior to January 1, 2011.
The language at the end of 590.6(A)(3) allows for the use of external GFCI cords and devices to grandfather-in GFCI-based operation for older generators. Also, NEC 590.6(A) has a specific exception:
Exception: In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified personnel are involved, an assured equipment grounding conductor program as specified in 590.6(B)(2) shall be permitted for only those receptacle outlets used to supply equipment that would create a greater hazard if power were interrupted or having a design that is not compatible with GFCI protection.
This exception allows the use of an equipment grounding conductor (EGC) with conventional overcurrent devices (i.e., the manner that was discussed in the first two articles of this series) under specific circumstances.
The proposed NEC 445.20, which applies to all small portable generators regardless of operational context, has some similarities in form to 590.6(A)(3) for 120 volt operation, but applies a less restrictive standard for use of GFCIs on generators less than 15 kW. Generators without locking 120/240 volt receptacles appear excluded from the GFCI requirement, and those with a locking receptacle can choose to utilize GFCIs on 120 volt receptacles, or disable them during operation of a locking receptacle (e.g. NEMA L14-30 or CS 6365).
Since essentially all generators under 15 kW that are used in the pro audio context have a locking receptacle on board, the proposed code change has the potential to render the industry-relevant range of generators out of compliance, as many do not currently equip their 120 volt receptacles with GFCI’s. Unlike 590.6, 445.20 does not provide any exceptions, nor does it grandfather-in previously manufactured generators with the use of external GFCI’s.
The portable generator manufacturers’ association (PGMA) filed tentative interim amendment (TIA) 1097 with the NFPA in an attempt to bring the NEC 445.20 more in alignment with NEC 590.6 by requesting that the code not apply retroactively to existing generators. To date, various NEC committees have voted against the interim amendment twice. As of presstime, the PGMA is waiting on a decision from NFPA after an appeal hearing on July 30, 2013. A decision should be rendered approximately a month from the hearing.
Conclusion
In the event that the PGMA’s appeal is unsuccessful and 445.20 proceeds, jurisdictions adopting the new code cycle will potentially start noting lack of compliance of products in the field. This adds yet another wrinkle of complexity for small production generators on top of understanding the operation of floating neutral configurations.
A practical takeaway for the production house is to exercise prudence in what small generators they bring into rental inventory until the regulatory season closes. If NEC 445.20 is ratified, and your jurisdiction rapidly adopts the newest code cycle, any small generator purchases in the remainder of 2013 should be of models that are already compliant with the new article. When in doubt on the finer points of portable power, a production house is well-advised to rent a properly bonded and earthed generator for their events.
This concludes our article series on generators. We hope that these articles have helped you understand concepts like bonding and grounding, while exposing you to a small sliver of the NEC specific for generators. Electricity is a powerful force, and the complex regulatory code we have reflects that. With the basics from these articles and an electronic copy of the NEC, it is our hope that readers will dive deeper into understanding, referencing, and practicing the code. Electricity is the life blood of the industry, and we desire its safe, respectful handling every time we use it.
NEC for Portable Production Power
Through three articles discussing grounding, bonding and generators, we have not touched on the downstream electrical cabling, panels, and other hardware that distributes power to pro audio equipment. This derives from an interest in emphasizing fundamentals, and from the breadth of material that would need covered. To learn further about production power downstream of the generator(s), the reader is referred first to NEC chapters 100, 200 and 400, as they build much of the foundation for the remainder of the NEC. Beyond these three chapters, NEC articles 520, 525, and 640 are the ones commonly referenced for code compliance in pro audio:
ARTICLE 520 – Theaters, Audience Areas of Motion Picture and Television Studios, Performance Areas, and Similar Locations
ARTICLE 525 – Carnivals, Circuses, Fairs, and Similar Events
ARTICLE 640 – Audio Signal Processing, Amplification, and Reproduction Equipment
It is also possible that an AHJ might choose to apply article 590, Temporary Installations, to a pro audio circumstance, in which case NEC 590.4 and 590.6 are most relevant to the audio professional. —Phil Graham
Text of Proposed NEC 445.20
445.20: Ground-Fault Circuit Interrupter Protection for Receptacles on 15 kW or Smaller, Portable Generators. All 125-volt, single-phase, 15-and 20 ampere receptacle outlets, that are a part of a 15 kW or smaller, portable generator, either shall have ground fault circuit interrupter protection for personnel integral to the generator or receptacle, or shall not be available for use when the 125/250 volt locking-type receptacle is in use. If the generator does not have a 125/250-volt locking-type receptacle, this requirement shall not apply.
