probably the size of the box vs amount of conductors in it. Box may be
too small.

If you are not running 300 amps at a time, why not a 100 amp breaker and
a sub panel? still one shutoff, and now you can shut just the sub off if
you want

Terry Mayhugh wrote:
I built a detached backyard garage several years ago with a 200 amp service
entrance fed from its own pole and transformer. There is a disconnect switch
located on the exterior wall that is wired in between the meter and the
inside service panel. I'm now adding an additional workshop area and I want
to power it with its own 100 amp panel. I would like to feed this new panel
through exterior conduit run from the bottom of the existing disconnect
switch so that I will have a common disconnect switch at the meter for the
entire garage. But this means that I will somehow have to splice the wiring
for the new panel to the wiring already leading from the disconnect switch
to the existing 200 amp panel. I've looked in the National Electrical Code
but can't seem to find where this is addressed. Does anyone know if what I
want to do is legal? If not, is there a better way? I no longer have easy
access to add a sub panel inside fed from the existing 200 amp panel. TIA.