Powerwalls and fire codes
We’re in the process of designing a new home for a client on Martha’s Vineyard. We’ve been told by the solar panel provider that under present fire codes only a single powerwall (generically known as an Electric Storage System ESS) can be installed in a dwelling without triggering various provisions that would be onerous to meet in a dwelling. They say that for systems over 20Kwh (a single power wall is rated at 13.5kwh), the ESS must be enclosed with two hour construction, have a sprinkler system, ventilation, fire alarm, and battery arrays must be mounted 3′ off of walls and 3′ apart.
For any but the smallest home, a single powerwall is not sufficient for backup power except for relatively short period of time, and certainly not for a larger home in the dead of winter. Tesla has been extremely unhelpful regarding any limitations in the number of powerwalls that can be installed together. They say talk to their permitting division, but then indicate that you can’t talk to the permitting people without already having placed an order.
My research has found that under NFPA 855 , Chapter 15 , a stationary ESS of aggregating not more than 50KWh in a basement or 80KWh is allowable without special measures. But this is part of the electric code, not the fire code. See attachment.
We would appreciate any guidance regarding building and fire code requirements relating to stationary ESS systems exceeding 20KWh (i.e. multiple powerwalls).
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