I installed an new 200 amp breaker box to the right of my existing box. A few wire runs coming from the left side will need to be extended in order to reach the new box. They are ungrounded. 2 of these runs are accessable in my basement so I plan to rewire the basement circuits immediately with 12/2 romex. However, 2 are not easily accessible and travel to an upstairs bedroom through an outside wall. They will be very difficult to run new wires. In the meantime I'd like to use a junction box next to my breaker and extend the wires to the new box. My question is what is the acceptable way to lengthen these ungrounded wires? Do I use the 12/2 romex and just cap off the ground on both ends? Do I pull the ground wire out of the romex and wire into the new box without a ground? Do I use Romex and ground the junction box? Each of the runs will need to be lengthened by 3'-4'.
I could use the older ungrounded wire that I replace in the basement to extend these runs. But I'd prefer not to.
Aside from running a new wire upstairs whats the best option here?