Electrical Problem With Home

 
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Old 10-30-2017, 06:20 PM   #1
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Electrical Problem With Home


So there was a bunch of wind last night in the northeast. My sisters house had some issues. At some point last night, the lights started dimming and over brightening randomly throughout the house. This was accompanied by a heavy electrical burning smell.
Fire department came and checked the place out. She told me they said, the neutral at the pole came unattached and they had random voltage running through the house. She is still without power at the moment. Her electrician said that most likely anything that was plugged in while this was happening is toast appliance wise. He canít assess, until the PC hooks neutral back up.
She said that one of her fixtures was actually glowing when the fire department was there. They shot it with a laser thermometer or something and said it was 250 degrees hot.
My question is, wtf happened? And is there any chance all the wiring in her house is shot? Thanks, Nick.
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Old 10-30-2017, 06:43 PM   #2
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Re: Electrical Problem With Home


Basically, the house is fed with 240V. Neutral sits halfway between, so to get 120V you connect your outlets to one side or the other and to neutral.

If the house loses that neutral connection, a heavy load (like an air conditioner for instance) will "pull" the neutral wiring electrically close to the hot leg it's connected to.

Devices that are connected to neutral and the other leg suddenly see much more than 120V. So more current flows, lights get brighter and things start to get hot because of that extra current. That's where the burning smell comes from, and devices on that leg are likely to be damaged.

Conversely, devices connected to the heavy load leg will see a much lower voltage. Lights on that leg will get dimmer and pull less current. Generally, anything connected to that leg won't suffer damage unless it has a motor--and then it's a maybe.

The house wiring itself is probably okay, but the electrician is going to have to verify that with some physical examination.

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Old 10-30-2017, 06:48 PM   #3
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Re: Electrical Problem With Home


I get it now. Well, sounds bad regardless. She needs a new kitchen anyway. Time to renovate.
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Old 10-30-2017, 06:57 PM   #4
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Re: Electrical Problem With Home


When is the poco coming out? They should come as soon as it is reported .
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Old 10-30-2017, 07:27 PM   #5
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Re: Electrical Problem With Home


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When is the poco coming out? They should come as soon as it is reported .


There are multiple outages statewide, so no idea. They have a lot of work to do. Iíd assume theyíll be there sometime tomorrow.
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Old 11-02-2017, 01:26 PM   #6
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I get it now. Well, sounds bad regardless. She needs a new kitchen anyway. Time to renovate.


I lied. I donít get it at all.
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Old 11-02-2017, 05:14 PM   #7
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Re: Electrical Problem With Home


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Originally Posted by Tinstaafl View Post
Basically, the house is fed with 240V. Neutral sits halfway between, so to get 120V you connect your outlets to one side or the other and to neutral.

If the house loses that neutral connection, a heavy load (like an air conditioner for instance) will "pull" the neutral wiring electrically close to the hot leg it's connected to.

Devices that are connected to neutral and the other leg suddenly see much more than 120V. So more current flows, lights get brighter and things start to get hot because of that extra current. That's where the burning smell comes from, and devices on that leg are likely to be damaged.

Conversely, devices connected to the heavy load leg will see a much lower voltage. Lights on that leg will get dimmer and pull less current. Generally, anything connected to that leg won't suffer damage unless it has a motor--and then it's a maybe.

The house wiring itself is probably okay, but the electrician is going to have to verify that with some physical examination.
Tying to learn something here!! So if the neutral from the pole is broken then the other legs go up or down? BUT if there is a good ground rod, should that not step in to assist?? Sorry if this is wrong, just a thought with what I know.
Thanks, Dave
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Old 11-02-2017, 06:36 PM   #8
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Re: Electrical Problem With Home


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BUT if there is a good ground rod, should that not step in to assist??
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.
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Old 11-04-2017, 05:03 PM   #9
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Re: Electrical Problem With Home


Here is a good diagram that shows what happens when a neutral is opened (2nd pic) First pic shows normal situation.

The voltage can be very different depending on the resistance on the lines. In every case the voltage total will add up to 240.

So if one side reads 100V then the other leg will be 140V or if one side has 40V then the other leg will get 200V


Electrical problem with Home-open-neutral-part-.jpg

Electrical problem with Home-open-neutral-part-b.jpg
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Old 11-14-2017, 10:58 PM   #10
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Re: Electrical Problem With Home


Was talking with one of my electricians today telling him about my sisters. He immediately asked if the appliances were all fried. He said they went to a house once where an excavator had ripped up the supply line to the house and had somehow energized the neutral wire in the process. He said it was scary. The whole house was filled with smoke and everything appliance wise was totally Gonzo.
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Old 11-14-2017, 11:04 PM   #11
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Re: Electrical Problem With Home


Been waiting for the shoe to drop. How'd she make out?
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Old 11-20-2017, 06:33 PM   #12
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Re: Electrical Problem With Home


Quote:
Originally Posted by Dave in Pa View Post
Tying to learn something here!! So if the neutral from the pole is broken then the other legs go up or down? BUT if there is a good ground rod, should that not step in to assist?? Sorry if this is wrong, just a thought with what I know.
Thanks, Dave
I second this question. I'm not an electrician, but I'm pretty sure a house's neutral wiring is tied to earth ground at the main panel (i.e. white wires and green wires both tied to ground lugs inside the panel). So if there's a decent earth ground - by way of a ground rod connecting to the panel's ground lugs, the neutral shouldn't float. In an ideal world, of course.

But maybe I'm missing something. Any chance the ground rod connection was bad/non-existent and this contributed to the problem?

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Old 11-20-2017, 06:57 PM   #13
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So if there's a decent earth ground - by way of a ground rod connecting to the panel's ground lugs, the neutral shouldn't float.
The bit you're missing is that the chunk of ground your rod is driven into is quite likely at a different potential than the chunk of ground at the pole.

Say it's 20V higher. Then the house would be seeing 100V on one leg and 140V on the other.

Drive two ground rods into the earth anywhere on the planet, and unless they're very close to each other, you'll be able to measure a voltage difference between them.
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Old 11-20-2017, 08:05 PM   #14
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Re: Electrical Problem With Home


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Been waiting for the shoe to drop. How'd she make out?
Fridge was running but not working right. But so far, other than the light fixture that was glowing and the fridge that has been it. She had to replace a few power strips with surge protectors. And a circulator pump was toast on the heating system as well. Her electrician seems to think that in the next few months more stuff will croak.
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Old 11-20-2017, 08:39 PM   #15
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Re: Electrical Problem With Home


She got off easy then, at least for now. Yeah, sometimes it takes a while for the weakened devices to give up the ghost--and you can never be absolutely positive it's due to that incident, or they just died a natural death.
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Old 11-21-2017, 12:43 AM   #16
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Re: Electrical Problem With Home


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The bit you're missing is that the chunk of ground your rod is driven into is quite likely at a different potential than the chunk of ground at the pole.
Totally with you on that – don’t disagree at all.

But strictly speaking I think the problem here isn’t that the neutral is getting pulled high or low at the house - the ground rod should still be keeping it stable. I also don't think it's because earth ground is at a different potential at the pole vs. the house.

I'm thinkin' the problem is that when the neutral at the pole is lost, the output of the pole’s transformer no longer has an earth ground reference. This allows the “high” and “low” phases coming into the home to float with respect to ground. They do stay 240V apart, but they’re no longer +120V and -120V because nothing is forcing them to “split evenly” (i.e. stay centered around 0 V). They will shift based on the loads in the home.

After a closer look at post #9, I realized that's what the circuit diagram was saying. The lower circuit gives an example of how the voltages could shift to 60 & 180 if the different loads on the phases were 10 Ohms vs 30 Ohms.

Keeping with this example, the lights on the 60 v side would go dim, and the bigscreen that’s inevitably attached to the 180 V side would get fried.

Again, unless I missed something.

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Old 11-21-2017, 07:24 AM   #17
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Re: Electrical Problem With Home


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I'm thinkin' the problem is that when the neutral at the pole is lost, the output of the poleís transformer no longer has an earth ground reference.
It's irrelevant where the neutral is lost. The house is grounded, the pole is grounded. The neutral wire serves to ensure that both of those grounds are at the same potential.
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Old 11-21-2017, 11:57 PM   #18
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Re: Electrical Problem With Home


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Fridge was running but not working right. ......
An electrical surge would probably ruin the refrigerator relay overload capacitor which protects the compressor. It usually is an easy (fifteen minute) fix, since it often is just a matter of locating the compressor (an obvious item) and looking for an electrical item attached to it. That is the relay, which needs to be replaced. When you remove it, it will probably have burnt terminals and it will rattle when shaken. The part might cost anywhere from $18. to over $30. depending where you buy it from and what model the refrigerator is.
A refrigerator with a busted relay might sound like it is working, but that might only be the fans and lights. The compressor will not be working.
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Old 11-22-2017, 12:11 AM   #19
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Re: Electrical Problem With Home


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I'm thinkin' the problem is that when the neutral at the pole is lost, the output of the poleís transformer no longer has an earth ground reference.
First off, error on my part. Losing the neutral at the pole wouldn't break the earth ground connection, assuming the transformer is somehow grounded at the pole. Again not an electrician, so I don't know the details there.

Tinstaafl, thanks for bearing with me on this one. While I understood that two points on earth aren't necessarily at the same potential, there was a point I was still missing, and it was your point about how poor of a conductor dirt really is.

As an example, consider the bottom circuit in post #9 again. In a scenario like this, the 60 V shift that has occurred at the house must be made up by a 60 V drop across the sides of the open neutral. Assuming both the pole and the house have ground rods stuck in the dirt, this means the two rods also have a potential difference of 60 V between them.

I realize the numbers aren't etched in stone - it was just an example. But it does demonstrate Tinstaafl's point: in order for the house voltages to be "pulled" in a certain direction, there has to be a potential difference between earth grounds at the pole and the house.

Again, thanks for bearing with me.

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Old 11-22-2017, 01:23 AM   #20
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Re: Electrical Problem With Home


"Her electrician seems to think that in the next few months more stuff will croak."

That is due to what is termed "latent damage". The extreme over-voltage and/or under-voltage reduces the "mean time between failure" of components, especially electronics on circuitboards.

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