I have a 2 wire system in my garage and need to update to a 3 wire grounded plug. Can I leave my existed 2 conductor and just run a single 12 gauge insulated ground in the same conduit back to the panel/grounding rod. Or do I need to pull out the 2 wore replace with 3 wire ?
By the N E C the ground wire is part of the cable, just adding a ground will not do what the code requires, unless there is a local variance.
It will could be tough to pull if there are existing wires in there. You may need to tie a line to what you remove, then lube a new set of wires, and pull the new line and wire back through.
What you propose to do (inserting an earth wire) is just fine as is removing the existing and replacing with twin and earth.
Which ever you do, the ground goes to the panel not the grounding rod.
You can just add a wire. If you have metal conduit and metal j-boxes all you have to do is connect a ground to the box. NEC 250.118 Types of Equipment Grounding Conductors. The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following: (1) A copper, aluminum, or copper-clad aluminum conductor. This conductor shall be solid or stranded; insulated, covered, or bare; and in the form of a wire or a busbar of any shape. (2) Rigid metal conduit. (3) Intermediate metal conduit. (4) Electrical metallic tubing... But if not in metal conduit then you can connect it to the first 5 feet of metal water pipe, the ground rod, the wire leading to the ground rod/metal water pipe, or the ground bar in the source electrical panel. NEC 250.130(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions. The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following: (1) Any accessible point on the grounding electrode system as described in 250.50 (2) Any accessible point on the grounding electrode conductor (3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates (4) For grounded systems, the grounded service conductor within the service equipment enclosure
