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I ran 2 4/0 lines to a new horse barn from our shop to a sub-panel. The sub-panel has a ground rod.

When the breakers are off the volt meter on each 4/0 line reads 120 but as soon as you turn any breaker on that load side drops to 90 and the other hot side jumps to 150 with no breakers on on that side.

The main panel has a double 60 GE breaker running to an Eaton subpanel.

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  • Is there a legally required ground equipment ground from the shop to barn (4 wires are required)? Are you reading to ground or neutral? Commented Dec 31, 2020 at 19:49
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    I may be crazy and really missing something, but it seems like you don't even have a neutral!!! You said you ran 2 4/0 lines from your panel to a sub-panel in the barn. Two hots, no ground and no neutral. If that's the case, that's really really bad. Normally a sub-panel requires a 4 wire service (2 hots, a neutral and a ground), ground rods that service the sub-panel as well as circuits connected with the neutral isolated from the ground. Commented Dec 31, 2020 at 20:56
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    @GeorgeAnderson I read & interpreted the same way. If there was ground-but-no-neutral and ground/neutral bonded in the subpanel then the neutral would effectively be piggybacked on the ground. But in this case it doesn't look like the ground is there. So aside from the grounding issue, this sounds like a job for a transformer to turn straight 240 into 240/120, except that with 4/0 you'd need a pretty big transformer to handle the possibly very large total load. Commented Dec 31, 2020 at 21:17
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    @GeorgeAnderson The electric company brought power to the shop on a service drop with 2 insulated wires and 1 bare carrier. OP extended to the barn basically copying the technique (and modifying it) without understanding it (or caring). Commented Jan 1, 2021 at 2:06
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    @Harper-ReinstateMonica Yeah, this whole setup is ridiculously stupid and dangerous. Like Will Rogers said, "what you don't know that you don't know will get you into trouble. " Commented Jan 1, 2021 at 3:41

2 Answers 2

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Nope, you blew it. There is no way to save this.

Your only option is to totally redo the job with the correct wires. You'll need a third 4/0 neutral (well, it has to match the 2 hots) and a #2 insulated aluminum ground wire. Sorry!

This didn't work because you tried to "seat of the pants" this job. You didn't do anywhere near sufficient research before you dove in. And now you're paying the tuition for learning "the hard way". Of course here you are, so that's a major turn in the right direction.

Now listen to what we say. We're NOT interested in wasting your money, much the opposite. We'll save you money.

Dirt does not work as a conductor

What you did was drive ground rods. Even though you know grounds are important, you didn't run a ground wire because you figured "hey, there are ground rods".

And then, you didn't run a netural because you ate of the fruit of the Tree of Knowledge (by seeing the inside of a main panel's neutrals connected to grounds)... and ever since, you have believed they are the same thing. So you figured "took care of ground, that handles neutral".

Actually, safety ground only carries current during fault conditions. However neutral the regular everyday current return. The two are tied together exactly one place in the entire system - at the main breaker. If other breakers are in that same box, then yeah, they get to be

Now, grounds have 2 reasons. For lightning, we have ground rods. For human-generated electricity, which is high current but very low voltage (compared to lightning), we have ground wires.

Dirt, you see, isn't a very good conductor at all. And driving it 8 feet into the ground doesn't make it any better of a conductor. Your scheme relies on using the dirt as the normal current return. And you can see for yourself, this happens when you have a defective neutral. That's why it's displaying "lost neutral" behavior.

I need to save this, and I'm willing to violate Code

I'm very reluctant to advise this, because this was a huge, forehead-slapping blunder - which tells me there are dozens of other dangerous blunders in your work. If you really want to "turn over a new leaf" and get serious about hitting the how-to books and actually learn what you're doing, that's awesome. You're in the right place. I'll touch on your available options from here, but you really need to learn way more than we can hand-hold you through in this Q&A format.

*And you should note, getting this stuff right on a farm is important, because animals can detect and really do not like stray current. Generally grounding on a farm must be pristine, or you'll have the same effects as having predators nearby - the animals will be stressed, and won't grow or behave properly.

"Yeah, but I gotta make this work". OK, you'll need to downgrade to 120V-only, and convert one of your hot wires into the neutral. This will still be a Code violation because you need to have separate neutral and ground WIRES. But if you talk to you local licensing authority, they may give you a waiver to

  • wire it on the 1980s rules which allow you to bond them. It's dangerous because if the neutral breaks, it can electrify all your grounds. That's why it was outlawed.

  • Or, you could fit a GFCI type breaker at the supply end (shop) - however large GFCIs are 2-pole, expensive, and limited to 60A (50A for HOMeline). And you'll be wasting most of the wire capacity.

I need to save this cable run, and follow Code, and support 240V

Your best bet in this case is to fit a supply transformer which provides isolation. The isolated secondary allows you to make the barn an entire service of its own, deriving neutral from the transformer itself, and bonding it to ground locally at the supply. and locally source its neutral from the transformer and ground from the rods. Transformers are not cheap, and you'll have to consider that versus the cost of re-running the wire.

This is overhead line, though. It's 2 insulated wires + bare, just like the service.

No, not like the service. On the service wires, bare was neutral, which the power company can do, but you can't for reasons discussed above.

In that case you'll need to re-wire 120V it like my cottage: Bare is safety ground, one wire is neutral and the other is hot.

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  • 3rd para after "dirt does not work as a conductor" heading is incom
    – FreeMan
    Commented Jan 1, 2021 at 16:12
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You clearly have a floating neutral line. This can cause destruction of equipment or fire.

Normally, there should be 120 VAC between each hot wire and the neutral, which should also be connected to ground at the breaker panel. The neutral is connected to the center-tape of the pole transformer. Somewhere between your electric utility's pole (or underground) transformer and the horse barn, there's a break in that neutral wire. It might not have been connected at the shop, the wire could be broken, or it might not be connected at the barn.

The reason for the uneven split of 240 VAC is that there are different loads on each of the hot wires. For example, if you have a 60 W lamp on on line and 100 W on the other, the side with the 60 W load would be about 150 VAC, and the other about 90 VAC (since tungsten lamp resistance drops when hot, the imbalance would actually be worse). Low voltage can destroy motors and power supplies, high voltage can damage almost any equipment. A ballast for a discharge lamp, and the surface it's mounted to, could easily go up in smoke. Don't burn down the barn!

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  • Based on the OP, it seems like there isn't even a neutral there. Commented Dec 31, 2020 at 21:00
  • There is a line in the barn, nominally called "neutral", but it ain't. Commented Dec 31, 2020 at 21:56

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