What happens when electric neutral cut/disconnected? (2025 Update)

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I was replying to the poster that said he had never seen a transformer ground and asked if houses have 4 wires now. Did I say the service entrance neutral did not carry a load? No, I didn't.

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I was that poster, and yes you did.

"But the earth rod and the transformer ground are not going to carry enough current to stabilize the load. "

then you said, in response to my post

"Transformers are usually grounded. Houses still have 3 wires. 2 hots and a grounded neutral."

I didn't start off to bust your balls, but now I feel obligated to because at this point I haven't a clue whether you know what you're talking about or not.

In short, if you are using "transformer ground" and "neutral" interchangeably, then you did make an incorrect statement.

nate

Seems to me this is fine but would "a neutral that is grounded" work better?

I thought james was clear and correct.

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I didn't. I made 2 statements. In response to your 2 sentences. First you said you had not seen transformer grounds. Then later you asked if houses had 3 or 4 wire service.

1. Yes, transformers are usually grounded.
2. Houses have 3 service wires.

I didn't say there was a relationship between those 2 statements. I didn't say anything about the grounds being able to carry the load. I didn't comment on what happens if the neutral service line is broken. You're reading a lot of things into two simple statements. All I did was tell you that transformers are typically grounded and that houses have 3 service wires. Quit trying to read things into a post that are not there. I didn't try to say anything else. You've jumped to half a dozen other assumptions from my simple comments. If I'd wanted to say something else I would have said it.

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Still not seeing how your initial statement was correct. You stated that the xformer ground would not carry the unbalanced neutral current. Isn't that exactly what it is designed to do? I'm not aware that it is common practice to provide a neutral in transmission lines, only distribution ones.

nate

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Not what I heard him say - but even what I heard didn't make a whole lot of sense.

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It's my understanding the distribution, usually 3 phase, feeds 3 transformers - but be that true or not, each transformer gets 2 power wires to the primary, and the center tapped secondary has 3 wires, L1, N, and L2.

Inmany areas it is common practice to run one bare and 2 oinsulated wires from transformer to service stack when using overhead wire. The bare wire is sometimes a steel cable and it supports the other 2 (live) wires, and is grounded at the pole and at the service panel.

This is obviously not the only way to do it, but it is fairly common.

Look at inspectopedia.com/electric/Electrical_Ground_Required.htm for all you ever wanted to know about grounding, bonding, and neutral conductors.

The "bare" is probably ACSR cable. Aluminum Conductor- Steel Reinforced. The center strand or strands will be steel for strength and the outer strands are the aluminum conductor. You may actually see the strands separated with the steel wire/s attached to a support and the aluminum strands crimped to an entrance cable neutral.

Thanks for pointing that out. When I added new circuits to the kitchen, I was sorely disappointed that light on that circuit still dimmed when the microwave started up. I thought something must be wrong somewhere but rechecking everything to the point of overloading the circuit with two space heaters to see if it indeed carried 20A and popped at 25A and it did, so I forgot about it. Nice to know that it's just what happens. I suppose when the microwave starts dimming lights on unrelated circuits that you have to worry . . .

-- Bobby G.

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Now you're arguing about my earlier post. If you cut the neutral coming into your entrance panel and leave the house ground rod(s) connected, the ground rod(s) will not handle the load originally carried by the neutral. Ground resistance is too high. Go pound a ground rod into your yard somewhere and measure the current when you connect a hot to it.

This is an interesting thread that I've pruned of >>>>>> and "chatter" to reach these 13 statements. Which are true, if any, which are false, if any? Which have "not enough info to decide:"

Question: What exactly would happen if a residential electric service (3 wire 240/120 with neutral) lost just the electric company neutral connection but had a good ground to the neutral bar in the main panel? We've had a couple of lifted neutrals at the service entrance that I recall. Maybe a little Googling is in order because it seems it would be a very good idea to QUICKLY recognize the signs of an open neutral. IIRC, it can be both hazardous and costly in a worst case scenario.

I can't count the times when I've stopped to think "Gee, that motor never sounded that loud" or sensed a number of clues to an impending disaster but didn't react in time to prevent it. There's a current Army program that tries to find soldiers who have that special gift to know when something doesn't look, sound or feel right. It feels badlies. (-: Anyway, I want to know what to look for when a neutral fails.

So onto to T/F survey:

2) In a three wire (bi-phase) service, most current entering on one hot wire leaves on the other. Only current that flows in a neutral is due to imbalance in the load. [You get the idea]

4) In one house, the earth ground was completely missing. A neutral wire broke inside the street transformer. So current took a return path via the gas meter. When insulators finally broke down, the house exploded. [ ]

6) The neutral is only used where 120 is required. [ ]

8) The earth rod and the transformer ground are not going to carry enough current to stabilize the load. [ ]

10) If the ground connection is completely lost, that unbalanced neutral current will try to find any path it can to ground, which will likely be either a water or gas line (or both) [ ]

12) If you cut the neutral coming into your entrance panel and leave the house ground rod(s) connected, the ground rod(s) will not handle the load originally carried by the neutral. Ground resistance is too high. [ ]

What is the range you'd expect to see in soil resistance. Why do worms come up when you electrify the ground? Is the ground literally holding an electrical charge like some giant wet electrolyte capacitor?

I'm bored waiting for the doctor's office to open at 9AM. I know they are there, but they absolutely NEVER pick up before nine. Wassup mit dat?

-- Bobby G.

A confused question.

"Gounding" has an "earthing" function and a "bonding" function. The language in the NEC has been changing over the last couple versions to make the difference clearer.

The earth connection is to keep the electrical system at approximately earth potential. It can also sink surges and helps with crossed primary power lines. This is the "earthing" function. The earth is not a reliable neutral path, and not intended to be

The earth is also not a reliable "grounding" connection for electrical equipment, like a parking lot light. There must be a metal ground return path. This is the "bonding" function.

As someone already said, the building "ground" system and the neutral are *required* to be connected at the service disconnect. This is a critical connection. Without it fuses/circuit breakers would probably not open on a hot-to-ground short. It requires a metal path from the ground wire back to the utility transformer (via the service neutral). This is the "bonding" function..

If the utility system has a neutral it must be brought to the building and connected to the building ground system ("bonding" function) and earthing system ("earthing" function). You are not likely to ever see an ungrounded power system. (They exist for rather specialized industrial uses.)

Virtually all building electrical systems have a utility grounded neutral (it will be earthed at the transformer). The utility neutral to the building is necessary for the "bonding" function. It also helps to "earth" the utility system.

The resistance of the connection to earth is too high.

For a ground rod the NEC wants the resistance to earth to be 25 ohms or less. If you connect the hot wire to a 25 ohm ground rod you get 5A. To avoid measuring the resistance to earth 2 ground rods are usually used. Then resistance to earth could then be anything.

A metal municipal water pipe system might be 5 ohms or less to earth.

Here's my answers;

1. True
2. I'm calling this an urban legend until someone comes up with something more definitive. Even if you used a metal gas line as an earth ground there's not a lot of reasons for it to explode. The gas inside the line has no oxygen. What "insulators" and why would they break down? If it's a conductive path to ground that is because it is metal and buried. If it has an isolator coupling then it's not a path. An isolator coupling is not going to "break down". It's designed to isolate electrically. If there is not an isolator then the pipe will carry far more current than the ground resistance will allow. Again why would it explode? You need a gas leak and a loose connection in proximity to each other to get an explosion.
3. False, at the entrance box the house side grounds and neutrals are tied together.
4. True.
5. True.
6. True.
7. True.
8. Not necessarily. The system doesn't care if the load is unbalanced. It's perfectly happy to run that way. What happens is that there is now potential (voltage) between the house neutral and the earth ground. This causes some amount of current to flow to the ground. How much depends on the ground resistance and the potential.
9. True
10. True.

replying to S. Barker, Jesse C. wrote: That's very common with direct burial. I know, I've dug a lot of holes and busted a lot of concrete in my day making splices.

Short answer, yes, it's possible.

If you had both hots still connected to the panel but only lost the neutral, It can cause some 120volt devices in your house to get 240 instead. While some others will get less than 120volts if this happens. I believe (I'm sure one of the old timers will correct me if i'm wrong) whichever has the most resistance on one leg when this happens is going to get the least amount of power while the ones with less resistance on the other leg will get far more than they expect.

The old timers (I mean no disrespect with the comment) can explain in greater detail if the two short videos above are confusing.

replying to RBM, TE W wrote: The neutral on my Daughter's house was cut by AT&T. That burned every wall socket that was in use in the house and burned off the driven ground. It may not be noticeable at first but as the ground rode caroades from cathodic effect. BE CAREFUL

replying to Bill, Zahidul Haque Nayem Shikdder, from Bangladesh wrote: All are bogus 100% practical skilled is when neutral is cut from the load then the black wire will be variated as phase current.

replying to N8N, Smitty wrote: Transformer grounds sole purpose is to ground the can should it become engerized. It is to protect anyone servicing the equipment. However the X2 bushing that the neutral uses running to the house is bonded internally to the transformer case also. You could technically use just the neutral wire as your ground for the transformer too but it's just added protection. Because the two are technically connected, yes it would help carry your unbalanced load, but your transformer ground should still be connected to the same pole ground and main line neutral as the service neutral so it does help, but not that is not the transformer grounds purpose.