Can I run a ground wire of a single circuit to the panel outside the house?

Question

This is a follow-up to this question.

I am adding (outlets) on to a 2-wire 12AWG (no ground) circuit and I want the new outlets grounded. Can I run a ground wire to the panel along the outside of the house? Obviously it is at greater risk of corrosion and damage than a wire run internally, but this is my only choice (other than leaving the outlets ungrounded). It seems like most ground wires I have seen from the panel to the ground rod are usually un-shielded and un-armored, but are heavy gauge and short runs.

I am thinking maybe a 10- or 8-AWG bare wire run under the eaves would be the easiest/best (however ugly) solution. Total run would be about 30 feet. All suggestions, warnings, or scoldings are welcome.

Answer 1

NEC Article 300: Wiring Methods

300.3(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 is 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 will 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.

Answer 2

by code, this is not allowed. the ground must be run in parallel for the entire run.

Answer 3

While I agree with all of the above, the direct answer to your question is, "Yes."

If you can get a ground wire to your new outlets, then they'll be grounded. The currently installed wires will not have the protection of the parallel ground wire, but the the new outlets themselves will be normally grounded.

In practical use, your ground wire will not be affected by inductive coupling, since it will carry no current.

Your installation will not meet code, so a licensed electrician is prohibited from installing it that way. But it would have met code 40 years ago, when many homes were retroactively grounded. It was considered at that time to be a perfectly safe/normal option. Only you can decide if that's good enough for your purposes.