[flybouy]

Plain and simple, somebody screwed up. A fuse or a circuit breaker serve the same function, it's an overcurrent device to interrupt the circuit and prevent a fire. Now, if the 30 amp was protecting branch circuits downstream, then you msy have several circuits, each protected by the 30 amp as the main circuit is wire sized to handle 30 amps. That could be one 30 amp load, or two 15 amp circcuits, or three 10 amp loads. There is no way that Keystone would purpously waste the money to place a 30 amp breaker and wire to match just to step it down to 15 with no other circuits connected.