UL 1449 Rated Surge Protection

UL 1449 is a standard that covers transient voltage surge suppressors (TVSS) intended for permanently connected, cord-connected and direct plug-in applications. UL Standard 1449 established various values for Suppressed Voltage Ratings (SVR). This specification includes a requirement that surge suppression devices be marked with the surge let-through voltage for a specific UL test. By assigning a UL voltage rating for a particular mode (i.e. N-G), it can be inferred that this mode is protected against surges.

For the three-wire, single-phase branch circuit commonly used in the U.S. and Canada), the power transfer potential, L-N, is called the Normal Mode. Sometimes this mode is also called the Transverse Mode. Any voltage measurement taken with respect to Ground (N-G and L-G) represents Common Mode potentials. These are sometimes abbreviated L=N-G.
Keep in mind that measured limiting voltages are rounded up to the nearest UL rating (i.e., a SVR of 380 Volts, would be classified as a UL 1449 400 rating), so please consult the manufacturer for the actual suppressed voltage rating.