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Electrical Problem With Home

 
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Old 11-22-2017, 07:54 AM   #21
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Re: Electrical Problem With Home


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Originally Posted by Tinstaafl View Post
Sorta kinda, in a perfect world. But in real life, the ground point at the pole can be at a significantly different potential from the ground point at your house--unless you happen to have a good conductor (the neutral) tying the two points together.

Dirt isn't nearly as good a conductor as copper or aluminum.
So I guess the obvious followup question is this: aside from any damage done to the home's electrical system and/or loads, does this mean there's also a shock hazard in the home while the neutral is broken?

If the ground potential is different at the pole vs. the home, then one of them (or both), isn't at zero potential. So the broken neutral may have allowed the house loads to pull the house's neutral wiring higher. Since the neutral is tied to earth ground at the panel, the house's "green-wire ground" is no longer at zero volts. That would mean the metal enclosures of my furnace, washing machine, table saw, etc. - anything with a 3-prong power cord - are no longer at zero.

Am I looking at this right, or am I missing something? Again.

Or maybe there IS NO shock hazard.

In a normal situation, if I'm standing barefoot in a puddle of water touching the black "hot" lead (because that's what I do for fun), I get shocked because there's a potential difference across me. I've got earth ground at my feet and 120 V at my hand.

But in the broken-neutral scenario, even though the earth ground and the neutral at the home may be a little high, if I touch the case of my table saw there's still no potential difference across me. There's earth ground on the case and earth ground at my feet. So I happily stand there safe and sound. Oblivious to the fact that my big screen is getting fried.

Any thoughts?

Thanks,

Steve
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Last edited by svankirk; 11-22-2017 at 08:34 AM.
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Old 11-22-2017, 12:39 PM   #22
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Re: Electrical Problem With Home


Remove the neutral wire and the house ground. Now you have the two sets of circuits - one set per leg - in series. Motor runs, lights dim, motor stops, lights get 240 and brighten right up. It all depends on load imbalance between the two legs.

Transformer and house grounds aren't intended to take the place of a neutral conductor, the systems aren't built that way most places.

There is no telling if you'd get shocked or not touching an electronic chassis.
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Old 11-22-2017, 12:43 PM   #23
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Re: Electrical Problem With Home


Thinking out loud: A registered letter to the util co. Stating what happened, damage discovered so far, & req a util rep to inspect/test the home & electrical grounds, etc.
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Old 11-22-2017, 06:30 PM   #24
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Re: Electrical Problem With Home


Quote:
Originally Posted by svankirk View Post
So I guess the obvious followup question is this: aside from any damage done to the home's electrical system and/or loads, does this mean there's also a shock hazard in the home while the neutral is broken?

If the ground potential is different at the pole vs. the home, then one of them (or both), isn't at zero potential.
Second part first: Virtually nothing is at zero potential in any absolute sense. It's only zero (or not) relative to some other point. If the transformer was in the house rather than way out there on the pole, a 500V difference in the two earth grounds wouldn't mean diddly.

Of course, then there would be no point in having a ground at the pole. Confused yet?

As for a shock hazard, probably not with any device having a three-prong plug. But as hdavis points out, some devices with only a two-prong plug may have the chassis connected to neutral (though they shouldn't). In that case, probably a good idea to wear your rubber boots.
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Old 11-22-2017, 10:16 PM   #25
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Re: Electrical Problem With Home


I was good when that diagram was posted, and now just getting more and more confused.
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Old 11-22-2017, 10:39 PM   #26
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Re: Electrical Problem With Home


It's a confusing subject, even if you have the background for it. I spent 30 years as an electronics tech, and that got me down to only about a gazillion aspects of electrical theory I don't have a good grasp on.
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Old 11-23-2017, 12:19 AM   #27
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Re: Electrical Problem With Home


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I was good when that diagram was posted, and now just getting more and more confused.
The diagram is what I'm going over. This case isn't exactly the same, but the diagram still covers it on a simple level..
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Old 11-23-2017, 06:01 AM   #28
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Re: Electrical Problem With Home


Quote:
Originally Posted by Tinstaafl View Post
It's a confusing subject, even if you have the background for it. I spent 30 years as an electronics tech, and that got me down to only about a gazillion aspects of electrical theory I don't have a good grasp on.
electron holes, covalent bonds...
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Old 11-23-2017, 07:24 AM   #29
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Re: Electrical Problem With Home


That’s what I like about the diagram. It’s simple and being simple minded I feel I get it. Then grounding rods come in and screw it all up for me.
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Old 11-23-2017, 07:36 AM   #30
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Re: Electrical Problem With Home


Look at the wire gauge feeding the panel, then look at the wire gauge to a ground rod, and keep in mind the ground rod isn't huge. It isn't a single wire earth return system, where grounds are built to handle all the current. There s significant resistance in the average home ground system.
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Old 11-23-2017, 11:53 AM   #31
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Re: Electrical Problem With Home


Seems to be a lot of confusion about ground rods. The only thing you need to remember is that they do nothing. They are only required because they can offer some degree of mitigation against lightning. That's because soil resistance is much too high to conduct much current, certainly not what it would take to substitute for an open neutral. To prove it, drive an 8' ground rod and connect a 100w light bulb between it and the hot of an extension cord. See how bright it is.

What is important is the ground bond to the water service coming into the house. Assuming municipal water and no plastic pipe, your ground is connected to every other house and consequently their neutral conductors also. So many times if you lose your neutral you won't even know it.

But if you have a well or a plastic service line you will have the problem the OP is experiencing.

-Hal

Last edited by ComRemodel; 11-23-2017 at 11:55 AM.
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Old 11-23-2017, 12:39 PM   #32
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Re: Electrical Problem With Home


"...does this mean there's also a shock hazard in the home while the neutral is broken?"

When I rented the upstairs of an old house with a loose neutral at the pole, I measured 30 or 50 volts on the metal chasis of an old 220v electric space heater. I can't remember if that was voltage measured relative to another circuit's neutral or ground. This house had all sorts of electrical nightmares, as well as the noted dimming and excessive brightening of lightbulbs. Possibly due to the home's problems, the power company refused to believe the loose neutral was on their side (per my testing) but when they finished the second recrimp at the pole the problem mysteriously went away.
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Old 11-24-2017, 12:07 AM   #33
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Re: Electrical Problem With Home


Remember that the grounds on all your receptacles and the water piping originate in the main panel by being connected to the neutral. So if you have an open neutral and you notice lights dimming and flaring you are going to have some voltage on the grounds with respect to a ground that does not rely on the building ground or neutral. So it is possible to feel some current for instance when touching an item like washer or dryer while standing on a bare concrete floor (depending on your shoes, dampness and the voltage).

-Hal
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Old 11-27-2017, 10:27 PM   #34
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Re: Electrical Problem With Home


Quote:
Originally Posted by Tinstaafl View Post
It's a confusing subject, even if you have the background for it. I spent 30 years as an electronics tech, and that got me down to only about a gazillion aspects of electrical theory I don't have a good grasp on.
I second that.

I've spent over 20 years as an electrical engineer (EMI & signal integrity, not power distribution & utilities). If I've learned anything, it's this: the list of things I know is a lot shorter than the list of things I don't know.

Sorry if any of my questions have created confusion. I was only hoping to learn something. I was hoping there would be a trained professional (e.g. lineman, electrician, etc.) who could clear this up.

So Hal, I think what you're saying is that the ground rod itself does very little to provide a protective earth ground reference for the house wiring - the water pipes do a much better job of this?

Steve
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Old 11-28-2017, 07:43 AM   #35
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Re: Electrical Problem With Home


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Originally Posted by svankirk View Post

So Hal, I think what you're saying is that the ground rod itself does very little to provide a protective earth ground reference for the house wiring - the water pipes do a much better job of this?

Steve
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What if you have a plastic water system?

Tom
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Old 11-28-2017, 08:21 AM   #36
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Re: Electrical Problem With Home


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What if you have a plastic water system?

Tom
Hi Tom,


Check out Hal's final sentence in post #31. Plastic pipes would be a problem, as he describes it.

Honestly - and I mean no offense to anyone - but I'm skeptical that the ground rod is only useful for lightning protection. Plastic service pipes are an example of why. Something has to provide a "safety" ground for any metallic chassis in the house (appliances, etc.). If the ground rod was useless for this - and if the house was fed with a plastic service pipe - a safety ground wouldn't exist. In theory.

And by "safety ground" I'm not referring to a neutral-like conductor intended to carry the normal operational currents of the house loads. I'm referring to something that gives an earth ground reference to the house wiring for safety purposes. In fact, it does not carry current under normal circumstances. It's there so that if the hot shorts to the case of my toaster, the breaker will trip - regardless of whether the neutral at the pole is broken.

Again, utilities/power distribution isn't my area of expertise so I'm treading lightly here. There may be practical, hands-on things I'm unaware of. But some of my EMI background relates to understanding the different uses of "ground" (i.e. circuit board return paths vs. safety ground, etc.).

No offense intended. Still looking to learn from the experts. Thanks for your input.

Steve
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Old 11-28-2017, 08:52 AM   #37
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Re: Electrical Problem With Home


Quote:
Originally Posted by tjbnwi View Post
What if you have a plastic water system?

Tom

A single ground rod installed per NEC would be no better than 25 ohms in most locations. A 10A current through it will pull your house neutral right up to line voltage. In most cases, it would take substantially less than 10A.

They're really only there to keep the house electrical from floating with respect to the local earth potential, and the pole transformer ground is similar, but also allows safety devices to work if the high voltage line gets shorted to the line supplying a customer.
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Old 11-28-2017, 09:04 AM   #38
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Re: Electrical Problem With Home


Safety devices like breakers and GFCIs work on the individual batch circuit ground and neutral integrity. They should work correctly even with no ground rod.
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Old 11-28-2017, 09:16 PM   #39
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Re: Electrical Problem With Home


My sister has a well
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Old 11-28-2017, 09:27 PM   #40
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Re: Electrical Problem With Home


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My sister has a well
ok...

thought this was about electricity, not water?

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