Codes and Standards

Analyzing NEC 2017 changes

Several changes to the 2017 edition of NFPA 70: National Electrical Code should be noted
By Vahik Davoudi, PE, LEED AP BD+C, Arup, Los Angeles December 16, 2019
Figure 4: Part IV was added to Article 705 of the 2017 edition of the National Electrical Code to address all the issues related to microgrid systems as an interconnected electric power production source. This shows a microgrid distribution plan. Courtesy: Arup

Learning objectives

  • Understand the revision process for NFPA 70.
  • Review a general analysis of changes to the 2017 edition of NFPA 70.
  • Learn about the implications of some revisions on the design of electrical systems.

The 2017 edition of NFPA 70: National Electrical Code went through extensive changes as part of the three-year code cycle to incorporate revisions resulting from the public inputs and public comments. Every code cycle, the NFPA goes through rigorous efforts to update NFPA 70 — to keep up with new technologies and trends in the electrical industry — while maintaining the goal of facilitating the safe installation of electrical wiring and equipment.

The 2017 NEC revision process itself was changed during this code cycle in an attempt to improve the overall process. In general, there are two public meetings held for the NEC revision process during each code cycle. The first public meeting now known as “first draft,” replacing “report and proposals,” is held when all suggested changes to NEC are discussed. The suggested changes now known as “public inputs,” replacing “proposals,” that were acted upon favorably resulted in first revisions to the “first draft” of the 2017 NEC.

The second public meeting now known as “second draft,” replacing “report and comments,” is held when all comments are heard. The new comments now known as “public comments,” replacing “suggested comments” that were successful resulted in “second revisions” to the second draft.

After the two meetings, appeals were heard and voting for acceptance of the 2017 NEC took place at the NFPA Annual Conference & Expo in June 2016, which then paved the way for NFPA Standards Council to issue the 2017 NEC by August 2016. According to NFPA, there were 4,012 public inputs submitted recommending changes to the 2017 edition of the NEC that resulted to 1,235 first revisions along with 666 editorial comments to the first draft. Subsequently, 1,513 public comments were submitted that resulted in 559 second revisions to the second draft of NEC.

Figure 1: A primary current injection testing wiring diagram is shown. Courtesy: Arup

New articles added to NEC

There were nine new articles proposed for this code cycle, but only five new articles were adapted and included in the 2017 NEC:

  • Article 425: Fixed Resistance and Electrode Industrial Process Heating Equipment: Presents needed regulations for industry.
  • Article 691: Large-Scale Photovoltaic Electric Supply Stations: Addresses the requirements for large-scale PV systems (5 megawatts or higher) generation capability that are solely connected to the utility grid.
  • Article 706: Energy Storage Systems: Addresses the requirements for ESS operating at more than 50 volts alternating current or 60 volts direct current that can operate independently or interactive with power production sources.
  • Article 710: Stand-Alone Systems: Addresses the requirements for power production sources operating in stand-alone mode that are not connected to the grid.
  • Article 712: Direct Current Microgrids: Addresses requirements for independent energy distribution networks that allow the use of power from DC sources to DC loads.

Figure 2: The addition of new subsection into 2017 edition of the National Electrical Code to clarify the requirements for a permanent switching means for emergency systems that rely on a single alternate source of power. Shown here is a generator quick-connect switchboard Courtesy: Schneider Electric

Top 10 code changes

Branch circuits — general provisions: Section 210.8(B) Ground-Fault Circuit Interrupter Protection for Personnel, Other than Dwelling Units. The GFCI requirements for receptacles at commercial and industrial applications have been expanded to require ground fault protection for circuits beyond 15 and 20 amperes at 125-volt applications. The code now mandates that at “other than dwelling units” all single-phase receptacles rated 150 volts to ground or less and up to 50 amperes shall be equipped with GFCI devices. Whereas three-phase receptacles rated 150 volts to ground or less and up to 100 amperes require GFCI protection devices.

The Class “A” GFCI devices, which are designed to trip when the current to ground exceeds 4 to 6 milliamperes, have been critical safety features that have reduced the number of injuries and fatalities due to electrical shock since their inclusion into the 1968 NEC. Major equipment manufacturers provide single-phase GFCI circuit breakers through 50 to 60 amperes, but nothing higher and certainly they have no three-phase GFCI circuit breakers. There are some alternate UL listed products available in the market that could be considered to provide GFCI protection to people for higher ampere rating single-phase and three-phase circuit applications. Generally, these devices are located between the circuit breaker and the load and are self-powered with a protective relay and a contactor to open the circuit when the ground fault exceeds 5 milliamperes.

Branch-circuit, feeder and service load calculations: Section 220.12 Lighting Loads for Specified Occupancies. Exception No. 1 of Section 220.12 was introduced in 2014 NEC, which allowed lighting loads to be calculated based on energy code adopted by local authorities while meeting three listed conditions. New exception No. 2 added to 2017 NEC expands this allowance where an energy code is adopted and that energy code specifies an overall lighting density of less than 1.2 volt-amperes/square foot. It permits the unit lighting loads in Table 220.12 for office and bank areas within the building to be reduced by 1 volt-amperes/square foot.

Article 220 provides specific requirements for calculating branch-circuit, feeder and service loads. The title and scope were revised somewhat to enhance clarity of what is covered by the article and to emphasis on calculating loads in this article and deferring the branch circuit and conductor sizes to Articles 210 and 215. The recent changes that allow lighting loads to be calculated using adopted energy codes are significant steps in the right direction to reduce the electrical service size and thereby cost of equipment. Hopefully, the type of occupancies listed in exception No. 2 will expand in the near future to avoid having many buildings or tenants with oversized service.

Services Service Equipment Overcurrent Protection: Section 230.95(C), Ground-Fault Protection of Equipment — Performance Testing. The performance testing requirement for ground-fault protection system has been modified to ensure the testing is conducted by a qualified person(s) using a test process of primary current injection and that a written record of this testing is available to the authority having jurisdiction. This requirement also affects feeders listed under Section 215-10.

The addition of testing requirements was the result of many failures due to ground-fault protection systems that were improperly connected and did not function properly to provide the intended protection. The addition of testing by qualified persons and proper documentation of test results and making it readily available to AHJ for review should eliminate all the concerns related to GFPE.

Overcurrent Protection Fuses: Section 240.67 — Arc Energy Reduction. The code expands the requirement for arc energy reduction where fuses rated 1,200 amperes or higher are installed. This requirement will become effective Jan. 1, 2020. This is similar to Section 240.87 that was added to the 2011 NEC to reduce incident energy for circuit breakers rated 1,200 amperes and higher.

This new requirement will reduce incident energy to which an electrical worker or maintenance personnel could be exposed when working on the load side of an overcurrent device — in this case, fusible switches. Unfortunately, no manufacturers have developed fusible switches with an energy-reducing maintenance switching feature with local status indicator, like what is available in the market for circuit breakers. This will impact the installation costs where in lieu of a low-cost fuse, a more expensive circuit breaker with energy reduction maintenance switch has to be considered.

Figure 3: Devices like this emergency lighting branch circuit transfer relay will now be evaluated to the performance and construction requirements that is applied to traditional emergency transfer switches for use on branch circuits rated up to 20 amperes. Courtesy: Ecoflex Solutions

Overcurrent Protection Circuit Breakers: Section 240.87 — Arc Energy Reduction. The subsection (B), which covers requirements for reducing clearing time on breakers rated 1,200 amperes or more, describes three new permissible methods. Two of the three new means involve using an “instantaneous trip setting” or “instantaneous override” that is less than the available arcing current, while the third option allows “an approved equivalent means.”

This section was originally added to 2011 NEC to reduce incident energy for circuit breakers rated 1,200 amperes and higher to limit the arc-flash energy. The new methods of reducing arc flash energy required under 2017 NEC at first glance offer substantial savings compared to the ones listed under 2014 NEC by using trip unit with arc flash reduction switch, which may not be the case for many situations.

Now, instead of an expensive trip unit with arc flash reduction switch, a standard instantaneous adjustment dial could be used, if the breaker’s fixed instantaneous override or instantaneous trip setting can be set below the calculated available arcing current. However, unlike the four methods listed under 2014 NEC, the two new methods have performance requirements to demonstrate the effectiveness of this procedure. There has to be a short-circuit, coordination and arc-flash study prepared for verification that indeed the breaker settings can be set below the calculated available arcing current. The use of lower-cost breakers with standard instantaneous adjustment dial may be economical for some projects, however for larger complex buildings the additional cost for studies could easily wipe out any savings expected depending on the number of breakers involved.

Health Care Facilities Essential Electrical Systems, Sources of Power: Section 517.30(B)(2) — Types of Power Sources — Fuel Cell Systems. According to the new subsection, a battery system is no longer permitted as an alternate source of power, while the fuel cell systems will be permitted as the alternate source for a health care facility, provided that they:

  • Meet the requirements for fuel cell systems in Article 692.
  • Meet the redundancy requirement.
  • Meet the 10-second rule.
  • Meet the fuel supply requirements.
  • Have a connection for a portable diesel generator.
  • Are listed for emergency system use.

The fuel cell systems will now be permitted to serve all or part of an essential electrical system. The requirements for sources of power for essential electrical system of a health care facility was located at article 517.35 of NEC 2014, which as a minimum required two independent sources of power — a normal power source and one or more alternate power sources for use when the normal power source is interrupted. For the 2017 NEC, the requirements for two independent sources of power and an alternate source of power for the essential electrical system for health care facilities were revised and relocated to article 517.30. The most notable change was the addition of fuel cell systems to the list of acceptable sources of alternate power.

Emergency Systems Tests and Maintenance: Section 700.3(F) — Temporary Source of Power for Maintenance or Repair of the Alternate Source of Power. According to the new subsection (F), if the emergency system relies on a single alternate source of power, which will be disabled for maintenance or repair, the emergency system shall include permanent switching means to connect a portable or temporary alternate source of power, which shall be available for the duration of the maintenance or repair. The permanent switching means to connect a portable or temporary alternate source of power shall comply with five provisions listed in the code.

It shall be permissible to use manual switching to switch from the permanent source of power to the portable or temporary alternate source of power and to use the switching means for connection of a load bank.

There was a statement at the end of section 700.4(B) of 2014 NEC that said, “A portable or temporary alternate source shall be available whenever the emergency generator is out of service for major maintenance or repair.” However, there were no prescriptive requirements provided for this requirement in 2014 NEC, causing confusion, which resulted in the addition of new subsection into 2017 NEC to clarify the requirements for a permanent switching means for emergency systems that rely on a single alternate source of power.

Figure 4: Part IV was added to Article 705 of the 2017 edition of the National Electrical Code to address all the issues related to microgrid systems as an interconnected electric power production source. This shows a microgrid distribution plan. Courtesy: Arup

Emergency System Circuit Wiring: Section 700.10(D) — Fire Protection. According to modified subsection (D), emergency systems shall meet the additional requirements in (D)(1) through (D)(3) in the following occupancies:

  • Assembly occupancies for not less than 1,000 persons.
  • Buildings above 75 feet in height.
  • Health care occupancies where persons are not capable of self-preservation.
  • Educational occupancies with more than 300 occupants.

The subsection 700.10(D) in 2017 NEC was expanded by adding Health care and Educational occupancies to the requirements for fire protection of emergency system feeders in addition to high-rise buildings and buildings with high occupancy loads. All efforts shall be made at the engineering, designing, plan review and construction stages of a project for the protection of emergency circuits in Health care and other listed occupancies from damage due to a fire. The fire protection methods employed shall provide a minimum two-hour fire rating for the emergency cables or raceways and contain only emergency wiring circuits as required.

Emergency Systems Control of Emergency Lighting Circuits: Section 700.25 — Branch Circuit Emergency Lighting Transfer Switch. A new definition along with provisions and requirements have been added to the 2017 edition as part of the reason to introduce the new branch-circuit emergency lighting transfer switches into the code. Emergency lighting loads supplied by branch circuits rated at not greater than 20 amperes shall be permitted to be transferred from the normal branch circuit to an emergency branch circuit using a listed branch circuit emergency lighting transfer switch. The mechanically held requirement of 700.5(C) shall not apply to listed branch circuit emergency lighting transfer switches.

Section 700.25, along with its definition described in section 700.2, were added to ensure code compliant devices under UL 1008 standards are used. These devices will now be evaluated to the performance and construction requirements that is applied to traditional emergency transfer switches for use on branch circuits rated up to 20 amperes. In the past there were no clear definition or requirements stated in the code and over the years automatic load control relays have been used to transfer emergency lighting loads from the normal supply to an emergency supply even though this is not in compliance with section 700.26. The addition of section 700.24 to 2011 NEC did not clearly address the issue, but now the addition of 700.26 in the 2017 NEC shall eliminate any misunderstanding of the code intent.

Interconnected Electric Power Production Sources: Article 705, Part IV — Microgrid Systems. The microgrid systems also referred to as “intentionally islanded systems” and “stand-alone systems” have been getting a lot of recognition in recent years as a way to reduce energy usage, lower cost and, more importantly, add resiliency against the loss of utility power. Microgrids are small wiring systems consisting of generation, energy storage and load(s) or any combination thereof that shall be permitted to disconnect from the primary source of power or other interconnected electric power production sources and operate as a separate microgrid system.

The 2014 NEC did not clearly address the installation of microgrid systems and a new Part IV was added to Article 705 of 2017 NEC to address all the issues related to microgrid systems as an interconnected electric power production source. The code changes/additions are in response to the recent developments in microgrid systems industry to further develop a flexible and efficient electric grid, by enabling the integration of growing deployments of renewable sources of energy such as solar and wind and distributed energy resources such as combined heat and power, energy storage and demand response.


Vahik Davoudi, PE, LEED AP BD+C, Arup, Los Angeles
Author Bio: Vahik Davoudi is an associate principal at Arup. He is an expert at codes and energy standards with more than 30 years of experience in the building industry.