Since there is a reduced cooling effect at high altitudes, the continuous current rating of a fuse will need to be derated for applications above 2000m. The following equation can be used to determine the adjusted current rating: IA = I * XA XA = 1 – (A – 2000)/20000 IA = Altitude Adjusted Current Rating of the Fuse I = Current Rating of the Fuse A = Altitude of the Application XA = Altitude Derating Factor Example For a 30A fuse at 3000m XA = 1 - (3000-2000)/20000 = 1 – 0.05 = 0.95 IA = 30 * 0.95 = 28.5A