Siemens Low Voltage s Surge Protection Devices Line of TPS309 as part of the External (Remote Mounted) Group. Type 1 SPD. Dimensions (L x W x H) 8.3 x 3.6 x 3.0. 3-Phase 4-Wire Rated 120/208 V surge current 100 kA per phase. Special features extended indicator light, mounts internal to P1 panelboards and busway