I recently rebuilt a shed that had electricity run to it in the past. There are wires run from the main panel to the shed underground. The old shed used 12 gauge black, white and green wires. There are also 10 gauge black and green where there was an old RV outlet. I have 3 - 12 gauge wires (blk, white, and grn) to a 20 amp breaker in the house and 2-10 gauge wires (black and green) on a 30amp breaker in the house, run to the shed. I installed a subpanel in the shed and am trying to figure out what is the best way to wire it up. Id like to have the 10awg wires because I could use more amperage (30Amps).
Can I use the black and green 10g wires for the hot and neutral (Jump the 10g hot to the other hot bus)? Also can I use the 12g ground from the main panel to the subpanel ground bar? (which is separate from the neutrals) I have a grounding rod also that will be tied to the ground bus.
The wires are in liquid tight and are individual thhn stranded wires. The rv outlet was a three pin outlet. I'll look up that 250.122 rule.
Today I opened the junction box that is halfway between the run of these wires and opened the main box to check. I noted that there is a white 10g that runs from main to junction box, then ties to the green 10g that runs to the shed. Im not sure why the person that ran these didn't continue with white. Can I use this green for neutral, or do I need to run a white and pull out the green?