I'm setting up a battery system with an inverter (EG4 18k and EG4 280AH) and recently submitted my diagram to the electrical inspector. He asked for proof of certification concerning whether the battery can be housed indoors. Is that something like UL 1973? I'm finding that EG4's support isn't helpful in answering this. Additionally, he mentioned needing double drywall around the installation, but I couldn't find specific references in the NEC about that. Can anyone clarify the relevant regulations?
3 Answers
You should check the NEC cycle your AHJ follows; they might be referencing changes in NEC 706. The IRC has fire resistance info, and NFPA 855 discusses details like your drywall query. UL 1973 does cover battery cells, but the inspector might really want to see documentation proving compliance with NEC and NFPA standards. Having the UL listings on cut sheets can make your case stronger. Also, planning departments can give you the exact requirements you need. It's a bit of a maze right now with all the updates to energy storage regulations, particularly with systems over 20kWh.
It really depends on what the Authority Having Jurisdiction (AHJ) dictates. If you're up against it, sometimes it's better to comply than to contest things in court. Fire codes like NFPA will be a major concern, not just the NEC.
The double drywall situation usually relates to fire resistance. I can't say for sure if it's required, but using 5/8" fire-resistant sheetrock could offer you a 1- or 2-hour wall rating, which would definitely add a layer of safety. Personal opinion: I wouldn’t want lithium batteries inside my actual living space if I could help it, mainly due to smoke risk if something were to go wrong. I've set up my batteries in a separate shed for peace of mind.