electricalgrounding-and-bonding
I've got a circuit in the basement carrying a handful of outlets. This circuit has no ground wire. I want to add a couple of outlets and want them to be grounded. I may even want gfci outlets on them in the future. I have no reasonable way of getting a ground wire to the panel but I do have easy access to another circuit that does have a ground wire. Is it acceptable to borrow or share a ground wire between circuits? If not, why not?
Both circuits are 20A with 12 AWG wire.
National Electrical Code 2014
Chapter 3 Wiring Methods
Article 300 Wiring Methods and Materials
I. General
300.3 Conductors
(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment-grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
The hot and neutral wires should be in the same raceway to reduce Inductive Coupling. You'll see using the Right-hand rule, that the magnetic fields created by the hot and neutral wires tend to cancel each other out. Thereby reducing the affects of inductive coupling.
I = current flow direction. B = direction of the magnetic field.
The ground wire was required to run in the same raceway, to provide a safe path for electricity to travel in the event of a short. If one of the wires sheathing becomes damaged, it's likely the exposed wire would have come in contact with the ground. The same way an equipment ground provides protection at a consumer, running the ground in the same raceway provides similar protection the entire length of the circuit.
I would avoid using the baseboard ground for the outlets since the baseboard is on a different breaker (circuit). Per NEC:
NEC 300.3(B) All conductors of the same circuit, including grounding and bonding conductors shall be contained in the same raceway, cable, or trench.
You can certianly replace the home run and associated branches with 3/12 (20 A) or 3/14 (15 A) depending on the circuit breaker size.
Best Answer
Yes, in most jurisdictions.
NEC 2014
The 2014 version of NEC has made a change to 250.130(C), which now allows you to connect to the equipment grounding conductor of another branch circuit, as long as it originates from the same enclosure. The new text reads as follows:
So if your area has adopted NEC 2014, you can connect a grounding conductor to the grounding conductor from another branch circuit, as long as both circuits originate from the same panel.
NEC 2011
Depending on what code has been adopted in your area, you may not be able to borrow the grounding conductor from another circuit.
Here is what NEC 2011 has to say about replacing receptacles with no equipment ground.
Which means you can add a grounding conductor, but only at or before the service panel.
NOTE:
The grounding electrode system (of which the grounding electrode is a part), dose NOT include branch circuit equipment grounding conductors. The grounding electrode system is a collection of conductors used to connect the service equipment to earth, and is typically located at or near the service entrance only.
More from the NEC
There's a good YouTube video, where Mike Holt explains the options for Replacing two-wire receptacles
Consult your local government and/or a licensed electrician, to determine which version of code is used in your area. Codes do change, and you'll always have to follow the code adopted in your area.