Type of Change: New and Revised
- Definitions Relocated to Article 100. Several existing definitions that appeared in particular articles have been relocated to Article 100 because these terms are also found in other articles, not just the article where the previous definition was located. An example of this would be the definition of “coaxial cable” relocated from 820.2 to Article 100 since this term appears in four articles of the NEC. The NEC Style Manual (see section 2.2.2.1) requires that Article 100 contain definitions of terms that appear in two or more articles of the NEC. Another example would be the relocation of fourteen existing definitions from 500.2 to Article 100. These “hazardous location” definitions also appear in two or more articles.
- Limited Access Working Space in Article 110. Electrical equipment is often installed in spaces with limited access, such as above a lay in suspended ceiling or in a crawl space. The working space rules in 110.26(A) apply to all equipment that is likely to require examination, adjustment, servicing, or maintenance while energized. Strict compliance with all of the working space rules in these ceiling spaces and crawl spaces is not always possible. The electrical industry has been installing and accepting equipment in such spaces for decades.
- Prescriptive requirements for equipment installed in those spaces has been sorely lacking for that same time period. This limited access provision is an attempt to provide relief for both the installer/maintainer and the enforcement community. Since it is located in Article 110, this limited access provision will have an impact on all electrical equipment across the Code, provides clarity and usability, and eliminates potential conflict and confusion from one a1ticle to another.
Continued Migration Throughout the NEC from the 600 Volt
Threshold to 1000 Volts
The journey to raise the voltage threshold in the NEC from 600 volts to 1000 volts continued in the 2017 NEC. These changes are implemented from Public Inputs and Public Comments from a High Voltage Task Group (HVTG). The NEC Correlating Committee appointed the HVTG to address issues with installations over 600 volts. This task group began work at the end of the 2008 NEC cycle. The HVTG was charged with reviewing all NEC requirements and/ or the lack of requirements for circuits and systems operating at over 600 volts.
This review resulted in numerous changes throughout the 2014 NEC from 600 volts to 1000 volts. Not all locations where 600 volts was referenced were changed in the 2014 NEC. Eighty-two percent of the proposals submitted to raise the voltage threshold during the 2014 NEC Code cycle were accepted in some form. Where a code-making panel felt there was a safety issue or where manufacturers did not want to pursue having their products evaluated at 1000 volts, the 600-volt threshold was left intact. For the 2017 NEC, 600 volts was raised to 1000 volts in about thirty different locations as a result of the work of the HVTG.
For the 2017 NEC, the HVTG was charged with the task of resolving issues with actions taken by Code Making Panels 1 and 8 on proposals and comments in the 2014 NEC Code cycle relative to changing the voltage threshold in articles under their purview from 600 volts to 1000 volts, addressing indoor and outdoor electrical substations, and evaluating other higher voltage threshold requirements to be included relative to present trends.
Documentation of Available Short-Circuit Current
There were several new requirements added throughout the NEC involving the documentation of the available short-circuit current (fault current) at specific types of equipment and the date the short-circuit current calculation was performed, with this documentation made available to the AHJ. While the earlier NEC editions required this documentation in many places, this requirement was added in nine locations throughout the 2017 NEC. The requirement for available short-circuit current documentation was added for such things as industrial control panels, motor control centers, air-conditioning equipment, elevators and industrial machines.
Also included in these requirements is emergency system transfer equipment for emergency systems, legally required standby systems, optional standby systems, and critical operations power systems (COPS). Inspectors have a difficult time enforcing proper short-circuit current ratings on such equipment as industrial control panels (which is required by 409.22). The equipment is usually properly marked with the short-circuit current rating by the manufacturer, but typically there is no information on the job site as to the available short-circuit current at the equipment. These new requirements for documentation of the available short-circuit current will make it much easier to assure that the equipment is being properly protected.
National Electrical Code
New Articles for the 2017 NEC
Article 425 Fixed Resistance and Electrode Industrial Process Heating Equipment – This article covers fixed industrial process heating employing electric resistance or electrode heating technology (boilers, electrode boilers, duct heaters, strip heaters, immersion heaters, process air heaters, or other approved fixed electric equipment used for industrial process heating).
Article 691 Large-Scale Photovoltaic (PV) Electric Power Production Facility – This article covers the installation of large-scale PV electric power production facilities operated for the sole purpose of providing electric supply to a system operated by a regulated utility for the transfer of electrical energy with a generating capacity of no less than 5,000 kW (generating stations, substations, associated generator, storage battery, transformer, and switchgear areas).
Article 706 Energy Storage Systems – This article applies to all permanently installed energy storage systems (ESS) operating at over 50 volts ac or 60 volts that may be stand-alone or interactive with other electric power production sources.
Article 710 Stand-Alone Systems – This article covers electric power production sources operating in stand-alone mode.
Article 712 Direct Current Microgrids (DC Microgrids) – This article applies to direct current microgrids, which is a power distribution system consisting of more than one interconnected de power sources, supplying de-de converters(s), de loads(s), and/or ac loads(s) powered by dc-ac inverters(s).
Type of Change: New
Analysis of the Change:
Article 425 Fixed Resistance and Electrode Industrial Process Heating Equipment – In previous editions, the NEC did not adequately address requirements for industrial process heating equipment. Article 422 for appliances had some requirements for infrared heat lamps, but those requirements have been relocated to the new Article 425 for Fixed Resistance and Electrode Industrial Process Heating Equipment. This new article applies to such things as boilers, electrode boilers, duct heaters, strip heaters, immersion heaters, process air heaters, or other approved fixed electric equipment used for industrial process heating.
This article will not apply to heating and room air conditioning for personal spaces covered by Article 424, fixed heating equipment for pipelines and vessels covered by Article 427, induction and dielectric heating equipment covered by Article 665, and industrial furnaces incorporating silicon carbide, molybdenum, or graphite process heating elements. This new article will provide clear requirements for installation and enforcement for industrial process heating equipment, including working space, listing requirements, marking of equipment, overcurrent protection, protection from physical damage, installation in damp or wet locations, and spacing from combustible materials.
Article 691 Large-Scale Photovoltaic (PV) Electric Power Production Facility – In the last few years, large-scale PV systems producing in excess of 5 megawatts have become commonplace in the United States. Some pf these systems can produce upwards of so megawatts. A 50 megawatt PV system produces the equivalent energy of roughly 25,000 residential PV systems. While the number of large-scale PV systems is relatively small, the volume of electricity generated by these systems is greater than the combined output of all residential and commercial PV systems addressed by Article 690.
The rapid increase in the number of large-scale PV electric power production facilities presents new challenges to the AHJ when facing inspection and approval of a PV power plant within his or her jurisdiction. These large-scale PV systems are difficult, if not impossible, to fit under the current umbrella of Article 690. With this in mind, a new article has emerged in the 2017 NEC for these larger-scaled PV systems. This article covers the installation of large-scale PV electric power production facilities operated for the sole purpose of providing electric supply to the utility transmission or distribution system with a generating capacity of no less than 5,000 kW. Facilities covered by this article have specific design and safety features unique to large-scale PV facilities.
Photovoltaic technology has experienced rapid changes over the last decade. The pace of change has created challenges for laboratories responsible for listing electrical equipment and for the organizations responsible for writing standards and for the NEC. One of the key determinants of whether a PV system is covered by Article 690 is that the PV system is connected on the customer’s side of the meter and the electricity generated is primarily used to offset the local facility’s normal electrical loads. Back.feeding the electrical grid is allowed but is incidental to the purpose of the system. Large-scale PV systems connect to the grid on the utility side of the metering system rather than on the customer side. Typically, they are connected at medium voltages (4.16 kV to 34.5 kV) or even transmission voltages (69 kV or higher) rather than at 480 volts or lower. This article will help the AHJ when assessing compliance oflarge-scale PV electric supply stations and will enable system engineers to use engineering best practices in the design of large-scale PV electric power production facilities.
Article 706 Energy Storage Systems – Added to Chapter 7 was an article addressing permanently installed energy storage systems (ESS) that may be stand-alone or interactive with other electric power production sources. An ESS is defined as a device, or more than one device together, capable of storing energy for use at a future time. An ESS could include but is not limited to electrochemical storage devices (e.g., batteries), flow batteries, capacitors, and kinetic energy devices (e.g., flywheels and compressed air). These systems can have ac or de output for utilization andcan include inverters and converters to change stored energy into electrical energy. This article is primarily the result of the work developed by a DC Task Group formed by the NEC Correlating Committee.
Article 710 Stand-Alone Systems – This article covers electric power production sources operating in stand-alone mode. Stand-alone systems are defined as a microgrid that operates independently of a primary power source. Stand-alone systems are also known as isolated microgrids, islands, and prime power systems. Microgrids are getting recognition as a way to add resiliency against loss of power in premises wiring systems. These requirements were initially proposed and accepted as part of Article 705 (Interconnected Electric Power Production Sources). However, the requirements for stand-alone systems do not fit well in Article 705. For stand-alone systems to remain in Article 705, the scope and title of Article 705 would have had to be changed to encompass both interconnected and non-interconnected systems.
Creating new Article 710 was logical and is supported by the original submitter, which was the DC Task Group created by the NEC Correlating Committee. Currently, stand-alone system requirements exist in Articles 690, 692 and 694 of the 2014 NEC. Creating a new article for stand-alone systems is important to other power sources, such as engine generators. The need for regulations for stand-alone systems is the same whether the source is a generator or an inverter.
Article 712 Direct Current Microgrids (DC Microgrids) – A new article has been developed for direct current microgrids. A de microgrid is defined as a power distribution system consisting of more than one interconnected de power source, supplying de-de converters(s), de loads(s), and/or ac loads(s) powered by dc-ac inverters(s). A de microgrid is typically not directly connected to an ac primary source of electricity, but some de microgrids interconnect via one or more dc-ac bidirectional converters or dc-ac inverters.
Loads such as LED lighting, communications equipment, computers, variable-speed motor drives, etc. Direct utilization of de, whether generated by PV systems, fuel cells, or other means (without intervening dc-ac and ac-dc conversion steps) leads to higher efficiencies and potentially smaller and lower-cost equipment than ac-coupled methods. DC microgrids with energy storage also offer inherent resilience and security from the failure of primary power sources. They also allow significantly simpler interconnection of power sources than ac microgrids, as no synchronization equipment is needed with de. The need for higher efficiency in telecom and data centers has driven these industries to implement de microgrids in hundreds of data centers around the world. It is a trend that will likely continue to grow. In addition to use in data centers, de microgrids are being demonstrated in governmental, academic and commercial facilities.
As with Articles 706 (Energy Storage Systems) and 710 (Stand-Alone Systems), this new article was the result of the work of the DC Task Group of the NEC Correlating Committee. While the basic requirements for wiring methods, overcurrent protection, and grounding are specified in other articles of the NEC, they do not cover all of the issues involved when de multiple sources and de loads are interconnected. This lack of coverage alone would justify the need for this new article. This DC micro grid article is an important first step and a place-holder for future requirements in this rapidly developing arena.
Type of Change: Revision
Change at a Glance: Chapters 5-7 may supplement or modify the general requirements in Chapters 1 through 7 (not just Chapters 1-4).
Code Language: 90.3 Code Arrangement
This Code is divided into the introduction and nine chapters, as shown in Figure 90.3. Chapters 1, 2, 3, and 4 apply generally; Chapters 5, 6, and 7 apply to special occupancies, special equipment, or other special conditions. These latter chapters and may supplement or modify the general rttles-:-requirements in Chapters 1 through 7. 4 apply except as amended by Chapters 5, 6, and 7 for the conditions.
Chapter 8 covers communications systems and is not subject to the requirements of Chapters 1 through 7 except where the requirements are specifically referenced in Chapter 8.
Chapter 9 consists of tables that are applicable as referenced.
Informative annexes are not part of the requirements of this Code but are included for informational purposes only.
2017 NEC Change
Revision to 90.3 and Figure 90.3 will now indicate that Chapters 5, 6, and 7 can supplement or modify Chapters 1 through 7.
Analysis of the Change:
To know and understand the NEC, the first place to start is 90.3 and Figure 90.3. This section and the accompanying figure give a “roadmap” of the NEC. Without a clear understanding of 90.3, it is common for a novice of the Code to interpret that conflicts exist from one chapter to another in the NEC. An example of this can be found by comparing the location of a service disconnect for a fire pump described at 695.4(B)(3)(4) with the grouping requirement for service disconnects found at 230.72(A). The rule in Article 695 (Chapter 6) for fire pumps requires the disconnect to be located “sufficiently remote” from other disconnecting means while the rules in Article 230 (Chapter 2) demand that all service disconnecting means be “grouped” in one location. A understanding of 90.3 would clear up this seeming conflict as this section explains that the rule in Chapter 6 would supplement or modify the grouping rule in Chapter 2.
Previous Code text at 90.3 indicated that Chapters 5, 6, and 7 modified only Chapters 1 through 4. There are requirements in Chapter 5, 6, and 7 that modify requirements in other articles within Chapters 5, 6, and 7 as well as the first four chapters of the Code. A good example of this is found at 645-4, which explicitly states that Article 645 (Information Technology Equipment) is permitted to provide alternate wiring methods to Articles 708, 725 and 770. For this reason, 90.3 was revised to permit the rules in these latter chapters to not only modify Chapters 1 through 4 but to modify each other as well.