5 of NFPA 855, we learn that individual ESS units shall be separated from each other by a minimum of three feet unless smaller separation distances are documented to be adequate and approved by the authority having jurisdiction (AHJ) based on large-scale fire testing. Powerwall 3 requires adequate clearance for installation, cabling, and airflow. Therefore, if. The diagram shows that each ESS unit can have a maximum rating of 20 kWh, and if you're going to install two units, let's say outside on your wall, you need to have the appropriate spacing between those units and three-feet separation from doors and windows per NFPA 855 15. How can a battery. sted to UL 9540. According to UL 9540 the separation between batteries should e 3ft (91. UL 9540 also provides that equipment evaluated to UL 9540A with a written report from a nationally recognized testing laboratory (NRTL), such as ETL, can be permitted to be installed with less than 3ft. Wärtsilä, a global leader in innovative technologies for energy markets, recommends approximately 10 feet between containers for ease of maintenance and to ensure workers and firefighters can move around safely. Although the 20 kWh storage unit limit is similar to the 20 kWh lithium-ion size when the IFC starts to be en or ividual ESS units are installed are separated by 36” or are installe ” apart.