Mayfield Renewables Code Corner: 2020 NEC 706.15 Disconnecting Means 

Which manufacturer are you talking about here? SMA?

Not necessarily. See my comment above for additional info as the 2023 Code gave us good clarification.

The scope of Article 706 includes all energy storage systems with capacities greater than 1 kWh, regardless of where the system is installed. You will always need a means to disconnect your ESS from the rest of the system. Some specific requirements will only apply to residential, namely: “For one-family and two-family dwellings, a disconnecting means or its remote control shall be located at a readily accessible location outside the building.” This is from the 2020 NEC, 2023 clarified the language but kept the specific location for one and two-family dwellings.

The 706.15(A) requirement for an emergency disconnect outdoors in a readily accessible location for one and two-family dwellings was not very clear in 2020 and was clarified in the 2023 Code. I realize that the 2023 language may not be enforceable for you immediately, but the clarification is often welcomed by both installers and AHJs and accepted when it helps all involved, which I believe it does in this case. In short, 2023 calls for an "an emergency shutdown function to cease the export of power from the ESS to premises wiring of other systems." The commentary in the 2020 Handbook also refers to emergency disconnects in 230.85 immediately after the 706.15 language. Therefore, I would say the intent in 2020 is for exactly that, an emergency disconnect to cease the production of power from the ESS system. To meet that requirement, as Justine discusses, we need a way to turn the ESS inverter off. But Code does not dictate in 706 that this is done on either the ac or dc side specifically. As she points out, if the disconnect were the one that connects the inverter to the utility, that would only initiate the off-grid mode of the inverter. I would say you would need a way to "cease the export of power" from that inverter entirely. This may mean a disconnect on both the input and output of the inverter. In an emergency situation, the utility power would be removed from the building anyway. So one could argue the outdoor emergency disconnect for the utility connection would not be required. The inverter output would need to cease power production though. You could use a disconnect for that output circuit in that scenario. I believe a better solution would be to use an inverter's relay capabilities (it's been so long since I've installed a Sunny Island that I can't remember the specifics for that one). This way, you don't route any power conductors unnecessarily and use an exterior switch to send a signal to the inverter to shut down. One could argue this is safer. If you route the inverter output circuits outside and then back into the load center, the line side of that disconnect would still have voltage (presuming the batteries are still connected), and therefore that section of the circuit would be energized and a hazard to firefighters. Of course, this emergency disconnect could also be accomplished by disconnecting the dc conductors from the batteries, but as for the reasons stated, this may not be the best answer. To answer the question directly, yes I believe a disconnect between the inverter and backup load center would meet the requirements. To be compliant, you do need to consider the utility input connection too.

@@ryanmayfield2728 Thank you for clarifying. As soon as I heard her say the disconnect has to be on the DC side and how complicated that was, I stopped watching the video as I didn't understand why she didn't even mention one on the output of the system.

It doesn't have to be. I added additional commentary to the comment from Dan that should be helpful.

We cover all of these topics in more detail in our solar-plus-storage workshops, which you can find here: www.mayfield.energy/workshops

I added some additional commentary in the comment above too.