How it is calculated: For a PV string, the minimum fuse rating is estimated as 1.56 × panel Isc and then rounded up to the next common fuse size. The selected PV fuse must not exceed the module manufacturer’s maximum series fuse rating. For a general continuous DC circuit, the calculator uses 125% of continuous current and rounds up to the next common fuse size. The fuse must also be DC-rated for the system voltage and must not exceed the allowable current of the protected cable or equipment. Always follow the equipment manufacturer’s specified fuse rating where one is provided.