30 AMP home wiring Question

Dutch Oven Man wrote:
The previous owners of our home installed a 8/3 wire from the breaker box to the garage. I assume they intended to install a welder or something, but never did. The wire terminates in the breaker box and is not hooked up to anything, and the wires are loose in the metal outlet box.

I was hoping to install a 50 amp service, but realized I don't have a ground wire. I have a red, white and black wire only.

My question is, can I use the red wire as my ground for a 30 amp service? I'm thinking I would connect my hot and neutral as usual to a 30 amp single pole, and the red to the ground buss bar in the breaker box.

I found several people on here refer to www.myrv.us that has very good instructions about wiring a 30 amp service, but it doesn't address my question.

#8 wire is good for 50 amps. If the wiring has been installed in a metal conduit or metal jacketed flex that is the ground as long as the conduit (or flex) goes all the way back to the main panal and the main panel has been grounded or sometimes called earthened. This is done by a (most often) #6 bare copper wire connected to 1) a copper ground rod, 2) connnected to the incoming water line (not done vary often anymore, or 3) connected to a Ufer ground (a 30 foot long bare copper wire embedded in the concrete foundation.

The black wire is phase A, red wire is phase B, and the white wire is the neutral or sometimes refered to as the common wire.

Hope this helps