Exterior Battery Disconnect Requirement

[PWDickerson]

I have been having an email discussion with a colleague that works for an inverter manufacturer about how NEC 2020 706.15 should be interpreted. This code section requires a disconnect for ungrounded conductors derived from an Energy Storage System, and further requires that one and two family dwellings must have an ESS disconnect, or it's remote control, outside the building. 706.2 defines Energy Storage Systems, and it has an Informational Note that says an ESS can include an inverter or a DC-DC converter. When I first read that, I assumed that the informational note would apply to products like the Tesla Powerwall (built-in inverter) or the LG 16H Prime (built in DC-DC converter), but my colleague is arguing for a broader interpretation. Is it reasonable to consider, for example, a Sol-Ark inverter connected to several Fortress eFlex batteries to be an ESS and have the Sol-Ark emergency disconnect circuit with an exterior mushroom switch be the ESS disconnect. In this example, hitting the ESS disconnect would shut off power to the backup loads, but would leave the batteries connected to the inverter. Of course I understand that it will up to the AHJ to render the opinion that counts, but I would like to know how others would interpret this. Thanks.

 

[jaggedben]

I think it could depend on the exact configuration and listing. For example the Fortress e-Flex batteries are sold as batteries, but the Flex Tower is sold as an ESS. But is the latter actually listed differently? And even so, which are they really, according to the NEC? The e-Flex have a BMS, so they seem to be more than Article 480 storage batteries which are defined as cells (vs. 'multiple components' in 706). It seems to me that your colleague is probably right, but I'm sure we'll be discussing this a lot more going forward.