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 dry contact and auible alarm, internal mountin in P1, P2 panels (requires TPS0IKITP1 or TPS0IKITP2, extended indicator light, mounts internal to P1 panelboards and busway