Can anyone help me understand why a fusible link would be installed between the main distribution buss and the alternator side of the master switch, even when a circuit breaker is already installed in this same circuit? For the most part Bob Nuckols does a great job of explaining the where's and why's of circuit protection, but this one escapes me. Some of his electrical diagrams (Z11 & Z13) include a fusible link in this circuit but others (Z12) do not. Hoping to understand why and when a fusible link in this circuit should be considered.