I have an old house with a detached garage. There is power to the detached garage through a 3-conductor cable that is routed above ground. Power from my house comes from the power pole, to my house. To get to the garage power from my main panel the cable routing goes back up to the power pole and down to the garage because the power pole is right by my garage.

My understanding is that 3 conductor power (hot, hot, neutral) to a subpanel is not code anymore but was used quite a bit back in the day. In the case of 3 conductors to a subpanel you do actually bond the neutral and ground at the subpanel and then have a separate ground rod at the garage. As long as their is no ground conductor that can get back to the main panel. Correct?

I was planning on making the necessary fixes to make it that way: install ground rod at garage, bond neutral and ground (grounds are currently not connected to anything!), and ground it to the ground rod.

I opened my panels to go over my plan again but then realized the neutral to my garage is a bare wire! That seems unsafe to me. Is this a big problem or not so much and I can continue with my plan? If it is a big problem do I need to get an electrician to replace that bare neutral, and at that point just replace it with a 4 conductor cable? Or is there some other option?

  • Can you draw a diagram of this situation? That'd help us understand it better...also, how far is it from the house to the garage, and is digging a trench between the two practical? – ThreePhaseEel Oct 11 '20 at 19:35
  • Unfortunately, digging a trench is not feasible. There is about 20 ft of concrete between the garage and the house. – mck Oct 12 '20 at 4:03

The Power Company did that, didn't they? :) They gave us a very similar setup; thru lugs off the bottom of the main panel, back up the pole to another pole to another panel. They're installing that according to NESC, which is their electrical code. Not ours.

Yes, in that case, you need to install the garage exactly like a whole separate service -- neutral-ground bond in the panel, 2 grounding rods etc. (assuming the concrete guys weren't kind enough to give you an Ufer ground). And this also counts on this being old enough to be "grandfathered".

The bare neutral is not a big concern; that's just how pole line is done under NESC.

If you want or need to modernize that, yes, you'll need to go 4-wire, and if you ask the PoCo to do it, they'll look at you funny. They do have 4-wire; they're just not used to putting it on the truck for residential jobs. It's used to serve 3-phase to businesses.

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