Steve McDonald wrote:

No, it should go to the ground connection. If your 220V outlet does
not have a ground wire, then make the 110V outlet a GFCI type.

I forgot, leave the green wire unconnected if you don't have a
real ground connection. Do not connect it to the neutral wire.

What are the ramifications of putting them together?

Could I just screw the green wire to the 220v outlet's grounded case since
there is no availible prong to use for this?

First, it's a code requirement that neutral and ground
only be connected a *one* place, generally at the service
entrance. The practical reason is that connecting them
together in other places can cause ground loops and this
can put voltages onto grounded metal cases. Not good.

If your 220V outlet case is truly grounded, then yes
you would connect the ground lead to the metal
case. This might be the situation if you have metal
conduit leading to the 220V outlet. You could do
that and also use a GFCI, then if the case isn't
grounded you are still OK.

Bill Ranck
Blacksburg, Va.