Somebody had it right.
Mike Marlow maybe.
A sub panel requires an insulated ground buss as well as an
insulated neutral buss.
In addition, a sub panel must be able to disconnect all power
under it's control in a maximum of six (6) motions of the hand;
otherwise known as the six (6) hand rule.
If more than (6) motions are required to disconnect all branches,
then a main c'bkr is required.
SFWIW, a branch c'bkr located in the main panel and feeding the
sub panel is also required.
The bonding strap located in the sub panel shall be connected to
the insulated ground buss.
The sub panel shall be fed by four (4) conductors (L1, L2, N and G)
from the main panel.
The neutral buss and ground buss in the main panel do not have
to be insulated but often are.
The bonding strap located in the main panel shall be connected to
the ground buss.
The neutral buss and ground buss in the main panel are tied together
as well as the earth ground conductor which connects to the earth
ground rod driven into the earth at the service point.
The above meets code or did when I was in the business.
Nothing else is required.
I'm confused by all this, but assuming your feeding your sub panel
with three conductors and a ground sized for the OCD then the only
reason I can think of for the #6 is that its a separate building and
he wants a grounding system which varies from jurisdiction to
jurisdiction. #6 being the largest size required to a grounding rod.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.