alarmguy
Thread starter
Im not sure what code other than the NEC which all states do not follow. I thought that was rescinded but all I know in our brand new 2023 home in North Carolina, inspected and C/O of the year 2023 does not have one.While whole home SPDs are required by code now, I haven't really found any authoritative sources on how to properly size SPDs other than guidance from manufacturers themselves. Siemens sizes their whole home SPDs based on regions, starting at 60 kA:
SO just installed was one on my HVAC system and small breaker one soon this week on my panel buss.