2017 National Electric Code
An Accurate Review White Paper, Summer 2017
By: Alex Hothan, Architect
Solar Photovoltaic Alternative Energy Sources
in NEC 2014 & 2017
Photovoltaic energy sources have introduced some interesting challenges to electrical safety. Traditionally, the National Electrical Code (NEC) separates its requirements into the “supply” side electricity send to a facility from the “Load” side of electricity. In other terms this is the separation from the utility company power source and the end electricity user. Generally understanding electrical power source and end destination is a key concept to comprehending the overall framework of the National Electrical Code. This brief white paper will discuss a few NEC provisions addressing Photovoltaic Alternative Energy Sources.
PROXIMITY TO END USER OR LOAD
In the case of utility power supply, power generation is located at strictly controlled substations where only qualified and trained personnel have access. However, some Alternative Energy Sources are designed to be located near the end user. The NEC provides for special safeguards when considering systems that are generating power near the end user, in commercial, industrial, or residential settings.
Article 705 Energy Storage Systems and Article 690 Solar Photovoltaic Systems of the NEC give requirements meant to safeguard equipment and users. These articles address separation distances, disconnecting means, possible imbalances, ventilation, identification, and more. Here are a few specific examples:
SMALL SCALE VS. LARGE SCALE PHOTOVOLTAIC SYSTEMS
The NEC makes a distinction between small scale (Article 690) and large scale (Article 691) Photovoltaic Systems. An important distinction is that large scale systems (generating 5,000 KW and over) are subject to more extensive requirements that are more typical to utility companies. These include supervision, installation, engineering, documentation, and safeguards that are all laid out in Article 691. These are not typically in the scope of the NEC, but are needed to provide the proper safeguard on a large scale system on a case-by-case basis.
On the other hand, the NEC allows small scale Photovoltaic systems to refer to the standard sections of the code when it comes to wiring, grounding, disconnecting means, overprotection, etc. Specific considerations to small systems are laid out in Article 690.
INTERACTION WITH UTILITY POWER GRIDS
The simplest power supply from a utility grid is at a single point of connection to the end user, supplying continuous power interrupted by a disconnecting means. The NEC makes special provisions for how alternative power systems can interact with utility power grids. Article 705 covers such systems as interactive inverters and interconnected micro-grids. In some cases alternative sources supplement utility grid power. In other cases they disconnect utility grid power and supply full power. Still in other cases they feed power back into the utility power grid. Additionally, Article 710 covers Stand Alone Systems, which have no interaction to a larger utility power grid.
These are just a few examples of safeguards provided by the NEC regarding alternate energy sources. The principal purpose of the National Electrical Code is to save lives and protect property. The codes are constantly working to stay up-to-date with new electrical systems and changing user requirements. Alternative energy systems provide unique and often times a beneficial electrical power source. However like with any new technology, these systems require the proper testing and oversite. In addition, alternative energy systems are becoming more and more custom designed to the specific facility and end user that they serve. The design professional needs to understand the adopted codes and standards to effectively navigate the various options to satisfying the requirements of the NEC. Lastly, the plan reviewer and inspector must equally understand the codes and standards to verify the proposed designs will be safe structures.
International Building Code are copywritten codes of the International Code Council.
NEC 2014 and NEC 2017 are copywritten standards of the National Fire Protection Association
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