Square D B17.5 Thermal Unit Brand: Square D. Part Number: B17.5. Square D Thermal Unit, Melting Alloy, 600 VAC, 10 to 14.3 A Full Load, Class 54/Standard Trip, 5 in L x 3.5 in W x 0.8 in H, Plug-In Mount, 40 deg C. Additional Description: SQD -B17.5 THERMAL UNIT. Catalog Description: Thermal Unit, Type S, Type B, melting alloy, Class 20..