"Zack" wrote:

I just recently bought a house that was made in the 1950's. I would
like to add a hot tub to the house (220V). Protection to the house's
electrical system is provided by a fuse box - which is full. My
question is, how do I add a sub panel to the fuse box assuming that the
electrical system can handle the load? I am assuming that I branch the
wire directly off (in parallel) of where it comes into the fuse box.

You have to disconnect an existing 220v circuit, connect up the subpanel
to where this circuit was, and then reconnect the existing circuit(s) up
to the new sub-panel.

By the time one does this much fiddling around, replacing the fuse box
with a new service is usually not that much more expensive, since your
already doing most of the work anyway.