SDSA1175 SPDs are designed and listed for indoor or outdoor installation and surge suppression for single-phase three-wire 120/240 VACor two-wire 120 VAC60 Hz electrical services. This product is ideal for residential applications for single phase power systems. SDSAs work together with surge protection plug strips to provide surge suppression for sensitive electronics. Two SDSA1175 surge protection devices can be installed to provide suppression for 208Y/120 VACthree-phase four-wire services.