10v on gnd

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Shaneyj

Shaneyj

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Location
Katy, Texas
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Project Engineer
Checking out a friend's house with flickering lights. This only happens under load. Fridge, dryer, ac, etc.
Get to his house, main breaker panel with back to back meter. Check panel and service conductors in panel are fine.
Go outside and find that ground wire is disconnected from ground rod. Same with the neighbor 20 feet away.
Neighbors house has 12v ground rod to hose spigot, my friends house has 5v gnd rod to spigot.
These readings are with gec disconnected, so measuring straight to earth.
Did the neighbor lose a neutral? transformer lose a neutral?
Both homes are fed from the same transformer.

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It looks like 4 homes may share the same tranny. Friends house has 2 to 5v. Immediate neighbor had 10 volts. Furthest neighbor like 1/2 a volt. Rear neighbor 15 volts.

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The light in his laundry room also burns brighter with the dryer running...

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Sounds like a lost neutral on the pole. 12 volts is VERY high for stray voltage. I'd call the power company.
 
Concur: neutral at a point common to multiple houses.

Good forensics testing to the water piping*. :thumbsup:

* There should have been bonding and zero volts, though.
 
LarryFine said:
Concur: neutral at a point common to multiple houses.

Good forensics testing to the water piping*.

* There should have been bonding and zero volts, though.
Click to expand...
Good point... but the bond clamp was on the actual spigot. So I was testing between that and earth.
Any thoughts about the potential difference between those two points?

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Shaneyj said:
Good point... but the bond clamp was on the actual spigot. So I was testing between that and earth.
Click to expand...
Ohhhhhhh. I thought you were measuring between the electrical ground and the spigot.

Any thoughts about the potential difference between those two points?
Click to expand...
Yes, either the water piping or the earth is energized; I'm betting it's not the earth. ;)
 
Poco showed up. Verified the info I had gathered, pulled the meter, then drove around the block to check the transformer (in the backyard neighbors backyard)
We hear their truck stop, we can see them over the fence. They're at the transformer for about 5 minutes. Hear them slam the vault door closed. Hear the truck drive away.
They show up at my friends house 1/2 hour later.
One says they tightened the neutral but it wasn't lose (weird). Then the other one says they didn't find anything.
But the stray voltage is gone and no more flickering lights.
Are lineman instructed to withhold information?
Because their 1/2 hour absence and strange comments made it seem so.

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Shaneyj said:
Poco showed up. Verified the info I had gathered, pulled the meter, then drove around the block to check the transformer (in the backyard neighbors backyard)
We hear their truck stop, we can see them over the fence. They're at the transformer for about 5 minutes. Hear them slam the vault door closed. Hear the truck drive away.
They show up at my friends house 1/2 hour later.
One says they tightened the neutral but it wasn't lose (weird). Then the other one says they didn't find anything.
But the stray voltage is gone and no more flickering lights.
Are lineman instructed to withhold information?
Because their 1/2 hour absence and strange comments made it seem so.

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Click to expand...

They fixed something- thats for sure.
 
Shaneyj said:
Poco showed up. . . . pulled the meter . . .
Click to expand...
I once went a service call where the issue was clearly an open neutral. A couple of items had caught fire due to over-voltage, so I left the two mains open and called the POCO myself so there'd be no question about the problem.

The customer called me an hour or so later and said the POCO guys shower up, told the customer that they measured equal voltages in both panels, said there was absolutely no problem, turned the mains back on, and left. :rant:

I asked whether they tested with the mains on or off. You can guess the answer. I told them to turn the mains back off, and I called the POCO again. I spoke to a supervisor and explained why the breaker had to be on to test.

They returned and tested again under load, then dug up and replaced the underground feed. You'd think that the POCO technicians would be the last guys you would have to explain open-neutral symptoms and testing to. :roll:
 
LarryFine said:
I once went a service call where the issue was clearly an open neutral. A couple of items had caught fire due to over-voltage, so I left the two mains open and called the POCO myself so there'd be no question about the problem.

The customer called me an hour or so later and said the POCO guys shower up, told the customer that they measured equal voltages in both panels, said there was absolutely no problem, turned the mains back on, and left. :rant:

I asked whether they tested with the mains on or off. You can guess the answer. I told them to turn the mains back off, and I called the POCO again. I spoke to a supervisor and explained why the breaker had to be on to test.

They returned and tested again under load, then dug up and replaced the underground feed. You'd think that the POCO technicians would be the last guys you would have to explain open-neutral symptoms and testing to. :roll:
Click to expand...

Some POCO guys are as dumb as a box of rocks when it comes to electrical theory. But still, they should bring this on every LV service call:

Super-Beast-Pulse-1024x1024.jpg
 
I used a floor fan once, it was enough to show the open neutral.

On another, the Customer had had two other ECs out and they both blamed the aluminum wiring in the house for the burned out computers and video games. Wound up being an open neutral from the transformer.
 
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When I was a little bitty helper, I remember electricians being called 'mechanics.' It was years later that I realized how appropriate the term was. I knew more electrical theory than the guys I worked under. But then, I was "into" electronics ever since building a "foxhole" radio from a book I found in the school library.
 
LarryFine said:
When I was a little bitty helper, I remember electricians being called 'mechanics.' It was years later that I realized how appropriate the term was. I knew more electrical theory than the guys I worked under.
Click to expand...

Yep, there are electricians and there are electrical mechanics.

(One of my go-to books at the library when I was maybe 12 or 13 was Richter's Practical Electrical Wiring, maybe the 7th or 8th edition :lol:. And the Radio Amateur's Handbook, of course.).
 
Shaneyj said:
Checking out a friend's house with flickering lights. This only happens under load. Fridge, dryer, ac, etc.
Get to his house, main breaker panel with back to back meter. Check panel and service conductors in panel are fine.
Go outside and find that ground wire is disconnected from ground rod. Same with the neighbor 20 feet away.
Neighbors house has 12v ground rod to hose spigot, my friends house has 5v gnd rod to spigot.
These readings are with gec disconnected, so measuring straight to earth.
Did the neighbor lose a neutral? transformer lose a neutral?
Both homes are fed from the same transformer.

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Click to expand...



Check the grounding clamps on the ground rods as well, my mother-in-law's house had the same scenario the grounding clamps had just deteriorated and disconnected from the rods and yes there is an open neutral on the Utility side as well. Although in her scenario we got to watch the cable guy get zinged off his coax twice and then his manager come in and get hit a third time, was kind of funny.
 
Just a word of warning to wrap up the story. If there is a compromised neutral, repairing or improving the earth ground connection may reduce the offset of neutral from earth. But that is only masking the problem, which can only get worse over time.

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