Square D B3.30 Thermal Unit Brand: Square D. Part Number: B3.30. Square D, B3.30, Thermal Unit, Melting Alloy, 600 V AC, 2.15 to 978 A Full Load, Class 63/Standard Trip, 4.8 in L x 3.5 in W x 0.8 in H Size, Plug-In Mounting, 40 deg C. Additional Description: SQD -B3.30 THERMAL UNIT. Catalog Description: Thermal Unit, Type S, Type B, melting alloy, Class 20..