The NEC (National Electric Code) published by the NFPA (National Fire Protection Association) receives major updates every three years and is in effect across the United States, but local and state bodies dictate and enforce different versions of the code.
As of July 1, 2020, the 2020 NEC is in effect in four states, the 2017 NEC is in effect in 31 states, the 2014 NEC is in effect in 9 states and the 2008 NEC is in effect in three states.
Fig. 1. The 2020 NEC is in effect in Colorado, Massachusetts, South Dakota, & Wyoming.
The 2019 California Electrical Code, California Code of Regulations Title 24, Part 3 is based on the 2017 edition of NFPA 70®, National Electrical Code®.
The 2011 New York City Electrical Code is based on the 2008 edition of NFPA 70®, National Electrical Code®.
The NFPA website also includes a helpful table showing the different dates each state has switched or will switch between versions of the NEC. With over a third of the states on their way to enforcing 2020’s code, it’s a good idea to become well-versed in applicable changes, as these will impact your permitting processes, your installation crews, and ultimately your bottom line.
In the 2020 NEC, changes have affected overcurrent protection devices (OCPD), conductor sizing, grounding requirements, labeling, rapid shutdown, and more. We will highlight major changes, but this is by no means a comprehensive list of all the updates that have been made. There are two articles of the NEC that directly impact the installation of solar photovoltaic systems, and we’ll briefly summarize the modifications to each section separately.
Changes to Article 690, Solar Photovoltaic (PV) Systems (2020 NEC)
690.1: Removed “panel” from list of formal nomenclature; no longer refers to a “cluster of modules.” The terms “solar module” and “solar panel” can now be used interchangeably without starting a war over semantics! 690.8: Updated calculations for conductor/OCPD sizing on the DC side. The maximum circuit current for a PV circuit can be derived from the rated input current of the inverter, rather than the cumulative circuit current of each string. Conductors must be protected by an OCPD whose rating cannot exceed the ampacity of the circuit conductor. Overall, this change has the potential to reduce conductor sizes by one or two increments, which could result in substantial savings for larger systems. 690.9: Added restrictions to OCPD installation under certain conditions. When installers have the option of placing OCPD at the supply end or the load end of the circuit, new limitations on distance have been implemented. Additionally, when installed inside a building, physical protection such as metal raceways or cable armor shall be provided. Please refer to the NEC directly as this will only apply to a subset of installations. 690.12: Added “Hazard Control” systems per UL 3741 as a third option for meeting rapid shutdown requirements. We have written extensively about rapid shutdown in the 2017 NEC, and we will soon have an article out for rapid shutdown in the 2020 NEC. Section 690.12(B)(2) now refers to UL 3741-compliant “Hazard Control” systems, which shall be UL-listed to meet requirements inside the 1-foot array boundary. As UL 3741 itself is still being finalized, for now, most non-BIPV systems will need to comply with the familiar <80V/30s requirement as before. 690.13: Added lock-out requirements to PV system disconnects. If a disconnecting means is located where unqualified personnel can access it, the disconnecting device must have the ability to be locked to prevent unintended operation. 690.31(A): Updated correction factor tables for temperature correction for conductors. In some cases, this will need to be supplemented with the manufacturer’s datasheet and/or guidance. 690.31(B): Mandated a consistent labeling or color-coding schematic for PV system conductors. To avoid any confusion, the positive conductor(s) are labeled with “+,” “POSITIVE,” or “POS” while the negative conductor(s) are labeled with “-,” “NEGATIVE,” or “NEG.” 690.31(C): Revised miscellaneous cable requirements. Added Type DG cable as a recognized wiring method. Updated requirements for Sunlight Resistant cable to align more closely with UL 4703. Recognized a 2-ft (24”) distance between single-conductor cable supports as sufficient. 690.33(C): Added terminology addressing compatibility of PV mating connectors. The text reads “Where mating connectors are not of the identical type and brand, they shall be listed and identified for intermateability, as described in the manufacturer’s instructions.” This could mean that manufacturer Stäubli (original manufacturer of Multi-Contact mating connectors, better known as MC4) could have a case against any equipment using “MC4-compatible” connectors, which are not Stäubli products. 690.41(B): Mentioned concerns with ground-fault protection in systems where DC to DC converters are being used. These DC to DC converters may block recognition of ground faults, and the manufacturer will need to provide a solution. 690.56(C): Modified rapid shutdown labeling requirements. Label now reads: “SOLAR PV SYSTEM IS EQUIPPED WITH RAPID SHUTDOWN. TURN RAPID SHUTDOWN SWITCH TO THE ‘OFF’ POSITION TO SHUT DOWN PV SYSTEM AND REDUCE SHOCK HAZARD IN ARRAY.” Placarding and diagram are to be placed at each service equipment location when a building has more than one type of system.
Now let’s take a brief look at requirements for interconnected production sources in general…
Changes to Article 705, Interconnected Electric Power Production Sources (2020 NEC)
705.2: Defined “Power Source Output Circuit” as the conductors between power production equipment or a power source and the service or distribution equipment. 705.11: Defined supply-side requirements in more detail. This update includes but is not limited to disconnecting means, conductor sizing/wiring methods, and grounding/bonding requirements. For example, 705.11(B) and (C) introduce minimum conductor sizes and length limitations, respectively. 705.13: Defined installation requirements for “Power Control Systems.” These systems monitor and control multiple power sources while preventing overloading from these sources. 705.20: Consolidated requirements for disconnects. This section encompasses disconnecting types, requirements, labeling, and more in one section.
In conclusion, with Massachusetts leading the way, and another 16 states in the process of implementing the 2020 NEC, now is the time to become well-versed in any applicable changes. Creating your team’s plan for meeting these new requirements will ensure a smooth transition to the 2020 NEC. Be sure to talk to your local AHJ/utility regarding any upcoming projects, to ensure that you and your team are proactively developing code-compliant solutions.