Do it correctly, to code. There are ample reasons why. I shudder when I read the description of what you propose to do.

Neither situation is even remotely safe. It's like asking whether it's safer to slit my wrists with a knife or shoot myself in the head. The answer is don't do either.

Turn the power off and don't use this circuit if you aren't going to fix it.

Please tone down your request. Nobody here is going to recommend you do something that's against the code. The code is there for a reason and that doesn't make us "Nazis."

You seem to have a mild grasp of the necessary skills. What you are proposing is illegal and unsafe and we're not going to recommend it. You can not turn the bare grounding conductors in cables into current-carrying wires just by "wrapping tape around them." Nor is it legal or safe to NOT run a proper grounding conductor to the structure even if it does have its own grounding system.

You've got conduit, pull the cables back and run properly sized current-carrying wires (times 3) and an appropriately sized grounding conductor. Install a subpanel at the shed and do what you want with the branch circuits there.

No. Just no.

If you've got a conduit in place (and it's big enough) just pull the proper wires and do it right. Neither expensive nor a big deal. If the conduit isn't big enough, spend the $100 to rent a ditchwitch for half a day and put in direct bury 10/3 with ground UF (or bigger if you need more than two 30A circuits) .

I never remember the exact rules for when a separate additional grounding rod is required in an outbuilding, for a single 240/120 MWBC I don't think you need one, but others will correct me.

I am not an electrician. I think what you're seeing is a method that was commonly used before codes changed. That's how my barns were connected before I upgraded: 2 hots and a bare ground. The major problem I see is that you have 10 gauge wire protected by 40 amp breaker. You could change the breaker at main panel to 30 amp. The ground rod is a good idea. Read up on 240 volt service.

Seabornman Thats a valid point I considered. According to this ampacity chart at 90c 40A is acceptable, only problem is it is not THHN, its NM which, as you say, is limited to 30A. I can definitely change the breaker, and probably will. Ampacity Chart

Rwiegand there is a concrete pad behind the house. I would have to bust the pad up in order to trench and lay new cable. Not a realistic option.

formulaross20 & Rwiegand I haven't heard any safety arguments. I've heard code arguments, which I specifically stated im not interested in. The Ground and Neutral are physically connected together at the main box. How will driving a new ground rod and providing a separate equipment ground make the situation less safe?

2 hots and a bare ground is fine if you are only using 240V.

A bare ground should NEVER be used as a current carrying conductor (ie. neutral). It was never acceptable. You should never use the bare ground as a means of providing 240V and 120V.

That doesn't mean that nobody has ever done that or that it won't technically work. It's just extremely unsafe.

Choose to either make this a 240v circuit or a 120v circuit. You can't have both.

Driving a new ground rod at the point of use and using it as a ground provides me a separate ground conductor to use. The only difference at that point is that the neutral wire is uninsulated once the outer jacket is stripped off.

The Ground and Neutral are physically connected together at the main box.

That's just at the main box. That doesn't mean that they are the same throughout your system. The ground wire doesn't carry current during the normal operation of your system.

Again, two separate conductors are provided. one bare one is used as ground the other bare one is used as neutral. Pay attention

The bare one should never be used as a neutral. I am paying attention. Are you?

It's unsafe to have an uninsulated wire carrying current. The outer jacket of a cable is not sufficient insulation. The individual wires need the insulation in order to be safe.

Honestly, it's a question of safety. It'll work. It's just not safe. If you don't care about that then there's nothing I can do to convince you of it and you probably don't want me to try.

To make it a little safer, I'd suggest using a GFCI breaker at the main panel. At least that should trip before someone gets electrocuted.

See, now you're offering suggestions that make sense. That's all i'm interested in.

What physically is realistically going to happen inside of the outer jacket inside of pvc conduit under 12" of earth that is going to shock someone? Seriously dude. If the hot conductor shorts to the bare conductor that couldve happened with 10/3 with ground as well. The only place a person could physically touch that neutral wire will be inside the box under tape and a wire nut. If theyre in there the circuit should be turned off.

You'd just discard any situation that I might propose that might show that it's unsafe. You don't actually want a discussion about it. You stated that in your original post. You know better than the experts (and I'm not claiming I'm an expert).

Code is there because situations arise that cause deaths. They might be unlikely situations but they happen and then they amend the code to try to prevent them from happening again. They are argued about by extremely knowledgeable people in the field before getting written down. They don't implement code for fun.

The good thing about following the code is that you don't need to spend multiple lifetimes of study to understand all of the reasons why the code is in place. And you don't need to learn the hard way why a certain code is in place.

But I guess I'm just a code nazi.

There's a lot to digest here but I'm not sure that a GFCI breaker used as above will operate correctly if it feeds an ungrounded sub-panel. Also, if the original installer was as hacky as you suggest then I would not be surprised to find that the pvc that you see is not conduit but is instead a sleeve. In other words, it disappears underground where it leaves the house and reappears at the shed, with no pipe at all for about 45 feet in between. This would be ok for UF cable but not for NM. I also think that property or appliance damage is likely at the shed end if you ever lose the neutral and have no ground while operating an appliance.

elltwo I agree about the GFCI breaker, but remember that i'm proposing to drive a new ground rod at the shed and connecting the shed box ground bar to that new ground rod, so there will be an equipment ground present in the shed if I do that, but it will be a separate ground from the house ground. So maybe I need to install the GFCI breaker in the shed box so it can utilize the same ground rod??? Also, on to your point about the sleeve issue. I had thought of that as well as i've seen it in the past frequently.. I excavated the conduit at the shed, which Is how I determined it's at 12" deep (at least at that point) and I went as far as to find a 90 degree sweep underground, which leads me to believe that the conduit does indeed continue the entire way. Obviously without attempting to pull wire or excavating the entire run there's no way to be sure.

GFCI doesn't need a ground to operate properly. It detects any imbalance between the hots and neutrals (which would indicate that the electricity is leaking somewhere unexpected).

You might find that the GFCI trips frequently (or maybe all the time).

I hope that isn't the case for you since you'd just go back to a regular breaker and an even more unsafe situation.

One issue with the uninsulated neutral is that it could have a ground fault somewhere along the length that's buried. Not enough to trip a regular breaker (ie. it isn't pulling massive amount of electricity and dumping it into the ground) but it could be enough to trip a GFCI. A little bit of moisture in that conduit (which is inevitable) and soaking through the outer sheath of the cable (because it's purpose is for physical damage prevention, not insulation) could cause the fault.

Is your cable really NM? Or are you just using that term to indicate wires bundled into a cable? Because NM isn't rated for wet areas and buried underground (even in conduit) is considered a wet area. But there I go citing code again. :)

I think that there could be a problem using a ground rod at the shed as your electric ground. It’s possible that this setup could result in voltage potential between ground and neutral which presents a potential dangerous situation.

Greg, its definitely NM, I opened the outside box and looked at it. Coming out of the conduit it is non UF cable. It's like typical romex wire where the outer jacket is not fully adhered to the inner insulators.

Steve, I'd be interested in learning more about that situation, but I would expect that scenario wouldn't really be applicable because the bare ground wire that would be used as a neutral wire would more than likely have connection to ground along it's buried length, plus the wire is literally coming from the same bus bar that my homes ground rod is on. I would think that the problem of ground fault would be a much more likely issue.

Thinking about it logically, the neutral wire eventually comes into contact with ground via the main panels bus bar. The ground circuit comes into contact with the equipment chassis, so both the neutral wire and the ground wire eventually go to ground, and the house is within 50' of the shed building, so the potential differences would probably be in the micro-volt ranges, probably less than what would even trip a GFCI.

I think the reason you want to keep sub panels ground wires and neutral wires isolated is because of ground fault issues, which tend to make GFCI's really "finicky." As Greg said, it might make the gfci's trip more frequently like when there's a thunderstorm nearby, but as long at the GFCI isn't tripping immediately as soon as it's reset it wouldn't be a really big deal. I'm not running sensitive equipment out there like refrigerators and such where losing power and not realizing it would damage the foodstuffs.

The issue with grounding can get pretty complicated, but here's my understanding (FYI, I understand electronics but I am not an electrician or NEC expert).

There are two separate grounds: The EGC, or Equipment Ground Conductor, that is the green wire in your circuits. The main purpose of the EGC is safety in the event of a defect or failure of an appliance or equipment. In the event of a fault, current will be shunted to ground and the circuit breaker will trip. The EGC should never carry current except in the case of a fault. Only the Neutral should carry current. The GEC, or Ground Electric Conductor, is the ground rod.

Normally the Neutral is bonded to the GEC and the voltage potential between them is zero, or very close to zero, at any point in the system. The potential of the GEC is not an absolute value... it depends upon the conductivity of the earth, the type and condition of the grounding rod, the moisture in the earth around the rod, and other factors. Because of this, the the voltage between the GEC and Neutral at the home's service entrance will be zero (assuming it functions properly) and can be higher at a second, remote GEC, between this new ground and Neutral. That difference is where things can get dangerous.

Imagine that you are using a device that develops a fault where HOT contacts the case. Normally this creates a ground fault and will trip the breaker since the HOT to GRONUD voltage wil be the full line voltage and the momentary current flow will trip the breaker. Now imagine that the GROUND is not the same as the rest of the electric system. Current will flow (perhaps at full line voltage, but likely at some other value) from HOT to the second GROUND. This will likely not trip the breaker since it does not see a full short. In this case, if you are touching the failed device, some of this voltage may pass through you with painful or deadly results.

Using this second GEC can also present fire risks and can present a problem in the event of nearby lightening induced voltages. Again, I am not an expert in the NEC, but I think most of the code is designed to protect users from electric shock and fire and even though compliance can be expensive it's likely cheap insurance in the long run. And speaking of insurance, if there is a fire and investigation shows non compliant wiring is the cause (or even COULD BE the cause) your claim may not be paid.

Good luck with your project and please stay safe.

Greg, I like your suggestion to install a GFCI breaker, and that's the type of input I'm looking for. I realize that the current situation does not meet code and I don't have the ability to bring the shed up to meet NEC, so that leaves me two options: 1. Disconnect the power entirely, which I would do if I felt there were safety concerns that justifiably warranted doing that. and 2. Try to mitigate the areas that don't meet code in some way. The reason I stated that i'm not looking for input from code nazis is because there are people in this world who have no ability to make rational common sense decisions. If it violates code, set it on fire. That mentality isn't going to fix my problem. These people fail to recognize the difference in letter and spirit. The letter states what it states and that's it. The spirit is the goal the law is trying to achieve. If I can attain that goal, but its methodology doesn't meet code, so be it.

Having looked at the situation first hand, I'm throwing option 1 out. I don't feel that the danger present rises to the level of needing to disconnect the power to that circuit BECAUSE I feel that installing a separate ground rod and providing a true dedicated equipment ground and using the bare wire returning to the main panel as a dedicated neutral, (it ALREADY is being used that way and has been for who knows how long) would successfully mitigate the realistic hazards present to human beings in using a bare ground wire as Both a conductor and ground. I'm not going to defend my stance on that in some fruitless code ethics debate over a shed that runs a couple lights and a handful outlets presently.

There are situations where bare wiring is used as a conductor. I'm looking at one right now out of my window. It's the 7400V Single Phase bare wire feeding the transformer on top of my power pole from the electric supplier. So there are situations where bare wire can be used as a conductor with minimal hazards. My proposal isn't perfect and certainly doesn't meet the letter of the code, but it will, in my opinion make the situation MORE safe for both people and equipment, and basically meets the spirit of the code without simply disconnecting my shed.

Steve, Thanks for your input. Im also not an NEC expert, but I do know that there are situations where the NEC requires additional ground rods to be installed in other locations, and I believe that these additional ground rods are also isolated from the main building ground rods and neutral wires. I don't know the specific scenarios, but they exist to my knowledge. The other thing I would mention is that the ground literally the Earth IS a conductor. The ground rods are still connected together by conduction through the Earth, which I'm sure you are aware of based on your background. And while the conduction through copper is better, the earth definitely works, especially on short runs in solid clay earth where i'm located. If the hot wire were ever to short to the chassis of the equipment it would trip the main breaker for sure. The neutral wire is at the main panels bus bar and the bus bar is connected to ground, so the main breaker would see that as a short and open the circuit. That resolves the fire issue right there, but not the death from electrocution aspect, lol. That would require a GFCI. I could derate the breaker in the main box to a 30A breaker when I install the GFCI breaker though. Probably cheaper to buy a 30A GFCI than a 50A one anyway.

Any time you have a structure that has more than one circuit (and a MWBC can count as only one in that context), you need a grounding system for that structure (e.g., rods).

Again, the code requires you to run a ground between the structures along with the proper insulated current carrying conductors. It used to be the case that you could avoid running the ground. You could NEVER avoid running the neutral. You could never just wrap tape around a bare wire and call it neutral.

The ground and neutral are connected at the SERVICE DISCONNECT and only there. In some places, that's the main panel. In some places it may be something else. For example, my house has a big honking service disconnect because there's a generator transfer switch between that and the main panel. The main panel and the transfer switch keep the grounds and neutrals separate.

I understand the code issue Ron. I can't afford to have the wires replaced right now and I'm not going to disconnect the circuit. Let's move on from the code.

If you have anything to add to this discussion that might make the situation more safe other than disconnecting the circuit, pulling new wire, only running 240V or 120V but not both, or setting the shed on fire and burning it to the ground I'd be interested in hearing it, but I suspect you're only here to reinforce the fact that my shed is in violation of code. Am I wrong?

Again. we can't recommend you dot things that are illegal and unsafe, no matter what your motivations are. The fact that you are broke doesn't make the dangerous things you want to do legitimate . You're right, I have nothing to contribute to you because you've made up your mind not to listen to those who are experts and know what the3y are doing, and only want to have your selfish views reinforced. I can't do that.

Good day, sir.

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People I would consider to be a code nazi are people who would willfully withhold information, even if that information would serve to lessen a hazardous condition, and even disrupt and subvert others in doing the same, all for the sake of making the point of giving laud and honor to the blessed NEC. Heil NEC! For this person, the NEC is more a God than a set of rules to follow. Do you know anyone like that Ron?