I would like to power a sub panel that is already in my house from my shop that has its own 200 amp service. It is currently supplied from my main panel with 6/3 romex. I will bury #6 Single stranded w/#10 G in conduit from the shop.
Since the shop is not attached to my house do i need to worry about anything special such as grounding in a particular way.
Article 225.30 NEC 2005.
Number of Supplies. Where more than one building
or other structure is on the same property and under
single management, each additional building or other structure
that is served by a branch circuit or feeder on the load
side of the service disconnecting means shall be supplied
by only one feeder or branch circuit unless permitted in
225.30(A) through (E). For the purpose of this section, a
multiwire branch circuit shall be considered a single circuit.
Your situation will not meet or satisfy using any of the exceptions discussed in this article. The answer is no. You cannot do what you propose.