Schneider Electric one-piece thermal unit construction provides overload protection for the majority of motors. Repeated tripping does not affect the original calibration. Melting alloy thermal units are available in three designs: Standard Trip (Class 20), Slow Trip (Class 30) and Quick Trip (Class 10). This is a Type B, Class 20 thermal unit. This thermal unit shall be installed such that its catalog number is visible. Thermal unit selection charts are provided with all devices that require the selection of thermal units. This thermal unit is UL and CSA rated.