Grounding Problem

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  #1  
Old 02-11-10, 03:40 PM
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Grounding Problem

Yesterday I came home to find cable tv wasn't working . The cable co. sent out a rep who informed me that over time their grounding lug had overheated and failed and so thats why the cable went out. He told me the reason for that was that they ground their equipment to the electrical service ground and that I had about 20 Volts coming through the ground from a living room circuit and 10 Volts from another. When he touched their cable ground wire to their lug there, was a spark and the basement lights would dim . We have called an electrician. but I'm curious what this might be.(Trying to do some of the leg work for him since he is a friend and learn something along the way . Perhaps the panel itself isn't grounded adequately? To me it doesn't look like the panel itself is grounded to the copper water line. We have the our Electric meter inside the house with the Main Panel right next to it. The 2 Hot feeds and a ground coming from the meter to the panel but then another smaller ground wire coming from the meter to the copper pipe above the hot water tank (approx. 4 ft away from meter)and then to the jumper at the water main ......Does that seem right?........Perhaps its the 2 circuits causing the problem.. I have checked the neutrals/ ground in panel and all are tight. I have also changed out several plugs as well as tighten all the grounds in the boxes and the lights no longer dim but there is still a small amount of spark at the cable ground. Would be curious to know how many volts are still coming through cable ground but I'm not sure how to get that value. Can it be measured with with a Volt / Ohm meter? Thanks for your imput
 

Last edited by Wouldy; 02-11-10 at 06:37 PM.
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  #2  
Old 02-11-10, 08:18 PM
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Your service may have met code at one time, but not today. You should have 2 hot legs and a neutral leg coming from the meter to your panel. The neutral IS NOT a ground. Today you are required to have 2 grounds, one to a ground rod and another to the cold water line where it enters the home. It should be looped through water pipe ground clamps to jump around the water meter and pressure reducing valve, if you have one. The grounding conductors should terminate at the neutral bar either in the meter socket or at the first disconnect which is probably your panel since it is adjacent to the meter. It is possible you could have a leakage to ground that won't trip a branch breaker. You can find it by turning off one breaker at a time till you find which one when turned off doesn't give you the arcing at the cable ground.


"He told me the reason for that was that they ground their equipment to the electrical service ground and that I had about 20 Volts coming through the ground from a living room circuit and 10 Volts from another."


How would the cable guy know this?
 
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Old 02-11-10, 09:46 PM
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You are correct. I misspoke. I do have 2 Hots and a Neutral and I am grounded from the electric meter and then clamped to the copper pipe above the hot water tank and then over at water meter also with the ground clamps but thats the only place that I can see.Will take another look and see if there's any evidence of a ground going to a grounding rod........ I 've already tried turning off one breaker at a time but I get just a little bit of sparking on every one which is what made me think maybe the panel itself is n't grounded properly.(Nothing that has tripped a breaker) The cable guy with the use of a volt meter was able to tell which circuits were the biggest problems. That's part of the reason I wrote in, was wondering how he could determine that.Thanks so much for your input. A
 
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Old 02-12-10, 02:44 PM
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Just wanted to follow up:An electrician took a look at my panel and said the problem with the ground wire sparking is because there is no ground from the main panel to a grounding rod which is required by code. Grounding to the water meter is not enough.. He will be installing one at the end of the week.
 
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Old 02-12-10, 09:05 PM
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In my opinion, a ground to the cold water pipe is a better ground than you'll ever get from a ground rod. I'd be interested in what happens after he connects your ground to a driven rod.
 
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Old 02-13-10, 11:44 AM
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Originally Posted by CasualJoe View Post
In my opinion, a ground to the cold water pipe is a better ground than you'll ever get from a ground rod. I'd be interested in what happens after he connects your ground to a driven rod.

I agree except in the case of my parents house the water line is plastic coming into the house and the box is grounded to the copper water line. Good thing they have high iron in there water
 
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Old 02-13-10, 08:08 PM
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Originally Posted by braether3 View Post
I agree except in the case of my parents house the water line is plastic coming into the house and the box is grounded to the copper water line. Good thing they have high iron in there water
That's a perfect example of why code now requires 2 grounds; one to a ground rod and one to where the cold water line enters the house. In your parents case, it would just be a bond to the water pipe and not a ground.
 
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Old 02-15-10, 06:58 PM
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I'll let the pros chime in on this one, but I'm not convinced that ground rods will help your situation much. Ground rods typically have a rather high impedance to ground since they are just in contact with dirt, which while moist dirt does conduct electricity, it doesn't all that well. Ground rods are generally considered more help in terms of lightning protection and for large surges. That said, it's certainly a good thing that you're having them installed regardless. They weren't always required, but any new installations require 2 ground rods plus the water piping bond.

When the electrician comes back, I would ask him to also tighten down the neutral connections in your main panel. You also want to make doubly sure that there is a good bond between your cable tv ground and electrical ground (and telephone ground while you're at it). As long as everything is well bonded together, you shouldn't have any problems.

As for how he figured out what was 'leaking' to ground, I believe that's a pretty complex process to figure out. I have a feeling unless he opened up your breaker panel and started disconnecting ground wires, there's no real way he could tell where the 'leak' is coming from. (again, if I'm incorrect, I'm sure someone will jump in).

Good luck!
 
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Old 02-15-10, 07:04 PM
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I'll let the pros chime in on this one, but I'm not convinced that ground rods will help your situation much. Ground rods typically have a rather high impedance to ground since they are just in contact with dirt, which while moist dirt does conduct electricity, it doesn't all that well. Ground rods are generally considered more help in terms of lightning protection and for large surges. That said, it's certainly a good thing that you're having them installed regardless. They weren't always required, but any new installations require 2 ground rods plus the water piping bond.

When the electrician comes back, I would ask him to also tighten down the neutral connections in your main panel. You also want to make doubly sure that there is a good bond between your cable tv ground and electrical ground (and telephone ground while you're at it). As long as everything is well bonded together, you shouldn't have any problems.

As for how he figured out what was 'leaking' to ground, I believe that's a pretty complex process to figure out. I have a feeling unless he opened up your breaker panel and started disconnecting ground wires, there's no real way he could tell where the 'leak' is coming from. (again, if I'm incorrect, I'm sure someone will jump in).

Good luck!
 
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Old 02-20-10, 01:07 PM
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I'm curious as to how those ground rods are workin' for you and if the "electrician" was gonna take another whack at it.
 
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