SPD · Surge protective device
A surge-diverting device coordinated in stages from service entrance to equipment, keeping lightning and switching transients off sensitive electronics.
Current numbers
UL 1449 5th Ed.current North American SPD listing basis, ANSI-approved 2025; NEC mandates UL 1449 listing
10/350 µsType 1 / Class I SPD test waveform (direct-lightning current); Type 2 / Class II uses 8/20 µs