To play this game, you need a sharp eye, a quick mind and a 2017 National Electrical Code book.(Fill-in-the-blank questions are looking for the exact word(s) used in the NEC.)
1) Energy storage system(ESS). One or more components assembled together capable of storing energy for use at a __________.
A) Future time
B) Higher voltage
C) Different facility
D) Different frequency
2) Each vented cell of a storage battery shall be equipped with __________.
A) A stop valve
B) An indicator
C) A flame arrester
D) Sufficient clearance
3) An energy storage system connected to a PV system shall be installed in accordance with __________.
A) Article 240
B) Article 300
C) Article 408
D) Article 706
4) A listed and labeled current-limiting overcurrent protective device shall be installed __________ the ESS for each DC output circuit.
A) Ahead of
B) Adjacent to
C) In the vicinity of
D) And sized adequately for
5) Batteries constructed of __________container shall have insulating support if a voltage is present between the container and ground.
A) A metallic
B) An electrostatic
C) A metallized plastic
D) An electrically conductive
6) This article applies to all permanently installed (ESS) operating at over __________ that may be stand-alone or interactive with other electric power production sources.
A) 24 volts AC or 48 volts DC
B) 50 volts AC or 60 volts DC
C) 120 volts AC or 150 volts DC
D) 480 volts AC or 600 volts DC
7) Article 706 requirements apply to energy storage systems used for railway signaling installations.
8) Storage batteries and battery management equipment are required to be listed.
9) Provisions shall be provided to control the __________ of the ESS.
B) Discharge rate
C) Charging process
D) Battery management
10) Spaces about battery systems shall comply with __________.
B) OSHA requirements
C) Engineering specifications
D) The manufacturer’s instructions
1) A, future time. This definition of Energy storage system is found in 706.2, part of a new article for the 2017 NEC. Energy storage systems are becoming more prevalent in the electrical system, and clear code requirements are necessary to insure safe and practical installations.
2) C, Flame arrester. Section 480.11(A) requires a flame arrester for vented cells in storage batteries. The information note goes on to say that “A flame arrester prevents destruction of the cell due to ignition of gases within the cell by an external spark or flame.”
3) D, Article 706. This requirement is found in 690.71. Solar photovoltaic system installation is governed by Article 690, and these systems are often paired with an energy storage system. The requirements for those energy storage systems have been relocated to Article 706 and expanded in the 2017 NEC.
4) B, Adjacent to. Section 706.21 requires overcurrent protection for ESS circuits, and 706.21(D) requires that each dc output circuit have current-limiting overcurrent protection adjacent to the ESS. Where this protection is provided for a listed ESS, the exception states that additional current-limiting overcurrent devices are not required.
5) D, An electrically conductive. In 480.8 Insulation of Batteries, batteries that have electrically conductive containers are required to have insulating supports if a voltage is present between the container and the ground.
6) B, 50 volts AC or 60 volts DC. The new Article 706 for energy storage systems covers all systems that exceed 50 volts AC or 60 volts DC. The informational note that follows this scope contains references to twelve industry standards that apply to the installation or construction of energy storage systems or components, including standards from NFPA, IEEE, and UL.
7) B, False. In 90.2(B)(3), the term “energy storage” was added to the list of items excluded from the scope of the NEC for railway installations. For railways, the list also includes generation, transformation, transmission, and distribution of power used exclusively for operation of rolling stock or installations used exclusively for signaling and communications purposes.
8) A, True. In new section 480.3, storage batteries (other than lead-acid batteries) and battery management equipment are required to be listed. New battery technology and increasing energy density have increased the hazards of battery installations over recent years, and listing requirements help mitigate the risk. Lead-acid batteries have a long history of use in the industry and were exempted from the new listing requirement.
9) C, Charging process. Section 706.23(A) requires that the charging process have a means of control provided and that an adjustable means of control is only accessible to qualified persons. The informational note explains that certain types of energy storage equipment, such as valve-regulated lead acid or nickel cadmium can experience thermal failure when overcharged.
10) A, 110.26. Section 480.10(C) requires that spaces around battery systems comply with the requirements found in 110.26. It goes on to clarify that working space measurements shall be measured from the edge of the battery cabinet, racks or trays. Section 480.10 contains additional installation requirements specific to battery rooms dealing with ventilation, gas piping, illumination, etc.
Q. Are lead-acid batteries required to be listed?
A. No. Section 480.3 is new for the 2017 NEC. It requires that all other storage batteries be listed, but specifically indicates that lead-acid batteries do not require listing.
Christel Hunter is director of codes and standards for Cerro Wire. Chris is a senior associate member of IAEI and serves as a board member for the Southern Nevada Chapter of IAEI, the IEEE Standards Association Standards Board, and the Las Vegas Section of IEEE. Chris also serves on NEC CMP-6. Chris is a Certified Standards Professional, Master Electrician, and LEED Accredited Professional.
Randy Hunter is an instructor and consultant specializing in electrical code and installations, and co-owner of Hunter Technical Services. He holds twelve inspections certifications from IAEI, ICC and IAPMO. He is the Southern Nevada IAEI Chapter president and former Southwestern Section IAEI Secretary. Randy has been a master electrician since 1988.