SURGE-GARD™ NTC Inrush Current Limiters Ametherm SURGE-GARD™ NTC Inrush Current Limiting devices are manufactured using specially formulated metal oxide ceramic materials and certified to UL 1434 for single- and three-phase input voltages to 480VAC. SURGE-GARD devices are capable of handling high steady-state currents to 36A and input energy to 250J. Available with various options in multiple leaded package styles, the components offer resistance at +25°C (R25) from 0.4Ω to 220Ω with tolerances down to ±10%, maximum operating voltage to 265VRMS, and beta from 3000°K to 3965°K.