Yes, it means you can use 30A fuses in it. However, you don't just go willy nilly changing fuses just because that box allows larger ones. The size of the fuse is determined by the ampacity of the circuit which not only includes that box but also the wiring involved.

Fuses are only necessary at the point the branch circuit originates. The exterior disconnect typically doesn't need it. It's just a way for the guy who's servicing the unit to be able to assure the power is off.

Thanks Ron. I have an electrician coming to look at changing my panel. I was just curious about the fuses. It's always worked with the 2 15A fuses, so I was in no hurry to try larger ones. I'm going to take a look at the wires going from the box. 15A seems too low to be running a central AC unit, but I'm not going to over-fuse it.

Thanks again.