This post was written by Josh Weiner, Solar Expert Witness & Solar Engineering Expert. Mr. Weiner has been at the forefront of the solar energy industry for over 20 years and is an industry leader on solar-plus-storage engineering & design. Josh’s expertise spans both in-front of and behind-the-meter initiatives including residential, commercial, utility, grid-scale, and ev charging solar and storage applications. 

Ok, let’s cut to the chase. Here are the new Code sections that Bill Brooks and team have implemented as part of the new 2017 cycle and why they’re awesome:

NEC 691 – Large-Scale Photovoltaic (PV) Electric Power Production Facility

We finally have a section that addresses large-scale PV! Before this, all we had was 690.80 for systems over 1000 V, which just redirects us to generic ol’ NEC 490, which is for any equipment over 1000 V, not just photovoltaic (PV). Ok, we also had 705.12(C), but, admit it, that was a fairly useless section. Now, at least, we have a dedicated section for large-scale PV that will undoubtedly grow and evolve over time.

This section was not overdone. When introducing a new chapter, it’s very easy for the authors to go a bit nuts and add a lot of rules from the get-go without understanding how the article will be adopted, enforced, and exercised in the real world. I applaud the balance that the CMP crew brought to this particular section.

NEC 705 – Interconnected Electric Power Production Sources

New definitions! We now have definitions for microgrid systems and microgrid interconnects! The common message with the new 2017 NEC is definitions, definitions, and definitions. Even with old language (like grounding, where the phrase “functional grounding” is now being used), this NEC version is making a clear directive to be clear in how we talk and address these things. I, for one, am really thankful for the clarity this Code cycle brings to our industry.

120% rule on center fed panels. Remember how painful it was when 690.64(B), which later became 705.12(D), revised their rules to eliminate the 120% allowance for center-fed panels? Then, remember how Code officials allowed us to use the 120% rule but only if detailed busbar load calculations were provided? As much as I like to earn solar engineering business, I definitely do not believe in arbitrarily creating additional engineering and design work for industry professionals. The name of the game is to lower costs and accelerate system installations, without sacrificing safety. Well, let’s give a big shout out to the CMP panel because all those rules are now gone, and we can go back to the good ol’ days of using the 120% rule for center-fed panels. Be sure to check out the new 705.12(B)(2)(3)(d).

Available fault current and busbar load calculations remain. Sometimes when Code officials revert or “undo” certain code sections like the one above about the 120% rule for center-fed panels, they also undo some of the new code requirements that came along with those. Not this time. If you want to venture outside the industry standard and work on more complex interconnections, we still can perform detailed busbar calculations and fault current analysis to ensure that your (complex, unique) system is designed to Code.

NEC 706 – Energy Storage Systems

It’s finally here! I’m just so glad we finally have a section dedicated to energy storage. Sometimes I almost don’t even care what’s in it, just as long as it’s there, but this section goes above-and-beyond my wildest expectations for a great release of the first generation of an energy storage system-dedicated code section.

Definitions. Just read the definitions section. It’s a great read. Let’s all use this language to create clarity in an otherwise young, unclear, and ever-developing marketplace. Be sure to read the 3 italicized definitions in particular:

• Energy Storage System, Self-Contained
• Energy Storage System, Pre-Engineered of Matched Components
• Energy Storage System, Other

It’s really important to understand the differences between these, since battery systems come together in the field in a variety of different ways, and if you want to fly through permitting and inspection processes, I suggest using the correct language for the correct system to help push projects through more quickly. For instance, UL 9540 is a standard now, let’s use it! Be sure to work with manufacturers that have this certification as it makes the entire process easier. Yes, UL 1642, 1973, and 1741 SA are all great standards to refer to, but nothing is quite as nice as having a full wrap of 9540 on all components.

Battery locations, terminations, and types, oh my! I think what I like most about this section is the care that the CMP took to address as many technology types and unique requirements as possible. For instance, the worst thing that can happen to a lead-acid or lithium battery is that it could explode or catch fire under short-circuit conditions. However, the worst thing that can happen to a flow battery is that it will leak and cause rusting of metal components. This code section attempts to address these unique concerns differently, for each technology, which is to say the Code officials are considering the uniqueness and specific applicability of these types of technologies and products. I like detail work!

NEC 710 – Stand-Alone Systems

I wouldn’t necessarily call this section revolutionary, but it is nice to finally have a standard. We’ve been designing and installing off-grid PV and energy storage systems for decades, and this is the first time there is a dedicated section to address those installations with some basic standards. This is a quick read, and it ought to confirm to anyone who’s designed or installed an off-grid system that this is how it ought to be done (at a minimum). I’m curious to see how this section develops and evolves over time. For instance, the PV must not be sized to handle 100% of load, batteries need not be included, etc. These are just some of the nice things to have in a Code that we can fall back on in the presence of inspectors or plan checkers.

Don’t worry, 690.56(A) and 706.11(B) still apply.

NEC 712 – Direct Current Microgrids

Again, read the definitions. I know I’m starting to sound like a broken record, but before we can agree on rules, costs, and benefits of these systems, we really need to understand how to talk about them. Here’s to assimilating code language in everyday work life!

Finally, we have a definition of system voltage. With DC micro-grids, it’s not uncommon to have 5 different voltages: low-voltage controls / sensing, high voltage power, DC-to-AC inversion, auxiliary loads, etc. Now we have a definition of what the entire system voltage ought to be. Read 712.30 to learn more. Same goes for available DC short-circuit current (712.65), OCPD (712.70), so I highly recommend reading this section. It’s only 2 pages, so it’ll be a breeze.

Thank you for reading, and as always, don’t hesitate to reach out to SepiSolar if you’d like to learn more about how to integrate these types of systems that can involve PV, energy storage, generators and grid interconnections, or for information about our solar consulting services. There are NEC codes coming out, UL standards, new product configurations, and new technologies entering the market, and as an independent, 3rd party technical consulting firm, we can provide unique perspectives on the state of these products, technologies, and applications to help ensure that your customers get the best experience and solutions possible. We’re here to help!

Visit this link for information about our solar consulting services for both residential and commercial projects.