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ESS group size clarification NFPA855

Question asked by lane.young on Sep 22, 2019

I am looking for clarification on the maximum stored energy group size within a outdoor ESS installation near exposures (less than 100 feet but greater than 10 feet away from the exposure). My application is potentially one were an exterior enclosure (a modified 20 foot long steel shipping sea container/enclosure) with multiple doors would be dedicated for less than 600kwh of Li batteries along with all the needed DC - AC equipment, HVAC, and fire suppression system. The enclosure would not have any rooms for an occupant to enter. Access to a single piece of equipment would be via an exterior door. based on section 4.6.2 the max group size is limited to 50kwh and per section 4.8 (2) and table 4.8.3 the total max system size is limited to 600kwh. My question, based on the description of my proposed system above does the 600kwh system size need to be separated into the 50kwh groups?


My thoughts are if the modified steel shipping container is a complete and dedicated piece of equipment where no personnel can enter unless for repair or maintenance and the system has a sufficient fire suppression system then the Li batteries capacity of 600kwh would not need to be separated within the 20 foot shipping container/enclosure into 50kwh groups by the 3 foot spacing or a fire barrier. 


I look forward to replies.