Melting Coax cable and warm grnd wire
Follow me here on this one. This is sorta complicated but I need answers to something I’ve not seen before, and maybe no one here has either.
Got a call today to investigate why the owners Cable Network Interface box keeps melting the connections inside the box. It has happened twice. Once about a month ago, and then today. In each case the owner lost their cable TV, Internet and phone (the 3 are bundled by the cable company). In each case the cable company had to run a new drop, the coax had melted quite signicantly inside the Interface box.
In the first instance the cable company was contacted and came out. The ground wire was arcing inside the cable interface box where it grounds the splitter. The cable guy called the electric company, PPL. PPL comes out says they can’t find a problem, they inspected the line drop, said all their stuff looked good. PPL said, according to the owner, “Must’ve been some built up current in the grouind wire that was discharging.” When I heard that I’m like I can’t believe the utility would say that. There should always be zero volts and no current in the ground, ever, unless there is a problem.
Today, when it happened again I was called to investigate. Here is what I found.
I placed my hand on the coax drop from the cable company. it was VERY warm. They had just replaced it not even a half hour before I arrived. None of the branch coax cable connections coming out of the box were hot, only the drop. I next felt the ground wire coming out of the cable interface box. It, too, was quite warm. I went into the basement to inspect the ground wire from inside. Inside I found that it was wire nutted to a #20 ga bare copper wire, which in turn was “bonded” to the cold water pipe. The entire ground wire (about 10ft in all) was quite warm when touched. There is also a bare copper jumper wire to jump the meter.
I next inspected the elec panel. It is a 100amp Siemens Panel. I inspected teh ground wire that runs from panel to ground rod. I found the ground rod to be quite loose in the ground and was not no 8ft into the ground, appeared to have been cut off at some point then attached the ground via grounding clamp. I then inspected for bonding of the elec panel to the cold water pipe where it enters the fouindation. I foiund NO ground wire at all
I had an Ah ha moment. My theory is there is electricity leaking somewhere onto the cold water pipe and its’ finding its way back to ground by going true the cable company grouind wire that’s attached to the water pipe, up to the utility pole and jumping onto the ground from the transformer then going down the ground wire that goes into the groiund at the base of the pole. To prove it I ran a #2 Alum ground wire from the panel to 75ft away to beyond the water meter where it enters the house. After some time, the coax began to cool down. It was still quite warm, but not hot, and seemed to be coolilng. Seems as if my theory were correct. Or not?
I believe there is current leakingonto the cold water pipe. Would you agree? If so what is a good way of trying to find it? Couldn’t it also be that a neighbor may be leaking the current and it’s just attacking this woman?
THoughts, ideas, I”m listeing.
Replies
There should be some along that has more knowlege and experience but it sounds like the water pipe is hot.
Check the garbage disposal or some other equiptment.
About all you can do is to be sure the neutral connections are sound and that everything is bonded together.
The idea that there is never any current on the ground violates Ohms law. (current doesn't just take the path of least resistance, it takes all available paths)
Back in the olden days a solid metal water system equalized "ground" everywhere.
If you are in a place without a metal water distribution system and wye distribution on the primaries there are lots of places to get significant voltage deltas the grounds. The TV cable is probably a better path than the dirt around the ground rod so that may have am amp or 2 of current on it.
I went up my street measuring the current on the ground wires at each pole. It went from over 3 amps down to about a half amp on the best pole. The highest reading was on the pole with the TV cable distribution amps.
I have a satellite dish. The installer grounded it to my hose bib. Problem being, most underground water lines are plastic since, mid 70's? You can't ground to a water pipe when it's not grounded.
Beat it to fit / Paint it to match
I discovered this yesterday. The previous owner of our home had a 200 amp panel installed along with the sub panel for the spa, and they grounded the new panel to a 3/4" gas line in the attic.ML
Based on your description, sounds like water lines are picking up some juice.
Because the ground rod is not likely well grounded, it can create mayham with a system as well.
The copper lines could be picking up flux from wires running parallel to them also. I cant imagine it would be enough to heat up a ground wire, but with a bad house ground and a good cable wire ground, I recon it is possible. (I did not do so well in my electrical engineering class)
I would definitely get everything grounded properly and my best guess is that you will resolve the problem. If you start blowing breakers, then re-start the diagnosis.
Call the Po Co guys back. You've almost certainly got an open neutral connection somewhere between transformer and service entrance. If the Po Co guys find nothing you need a sparky to check out the main panel.
This is a very dangerous situation.
Dan, when you say you believe there is most likely an open neutrual between the transformer and the service entrance, I'm confused. There is a utility drop directly from the transformer to the house. How could there be an open neutral between the two? It's one continuous drop from the transformer to the SE. I wasn't sure I was understanding you correctly. Also, maybe dumb question. But Power company was out the first time this happened and found nothing wrong according to them. So if it were the case you believe it to be, an open neutral, wouldn't they have fouind that. Or would I be safet to assume that all linemen are not well educated?If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
All that's required for a open neutral is a cable clamp that isn't tight enough.I don't know how well the linemen are trained to trouble-shoot this sort of thing.But whatever the problem, it's a real hazard, and simply tightening some ground clamps and adding a bonding wire isn't enough to fix it. For some reason there's more ground current than there should be and the cause of this needs to be determined and fixed.
It is an ironic habit of human beings to run faster when we have lost our way. --Rollo May
"Dan, when you say you believe there is most likely an open neutrual between the transformer and the service entrance, I'm confused. There is a utility drop directly from the transformer to the house. How could there be an open neutral between the two? It's one continuous drop from the transformer to the SE. I wasn't sure I was understanding you correctly."No there are a number of pieces.You have the connection to the panel, then the wire to the meter, then the wire on the poCO side of the meter where it sticks out the weather head, then it is clamped to the POCO triplex, Then at the the other end it is clamped to a clamped to the PCOO 120/240 feeder (if the transformer is not that that pole), then the feeder to the transformer bushing, then to the transformer winding.Lots of places to go bad.However an OPEN neutral would be unusally and there would be much worse problems than you described for this setup.More likely problem is a (relatively) high resistance connection. With the splice out in the weahter and wind that is the most likely problem point.But if you described it correctly;Only ground wire from the panel was a short ground rod. That the panel was not bonded to the water line,Then, unless there where some gotcha's such as wire underground from the rod to clamp on the waterline underground on the outside, or that some wiring had been added that used cold water pipe in the house for a ground (and/or neutral) that the problem can't have anything to do with the house wiring or drop.I am also assuming that the cable box either had a 2 wire plug or a wallwart (IE, was not grounded).Then the cable/water pipe system is fairly well isolated from the house. Still is slight possibility of a problem with a computer/TV that connects to the cable. But that would take several different failure modes.But that can be eliminated by disconnecting all of the outputs from the cable box.Also, as I said pulling the main breaker at the house would eliminate that as a source of the problems..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The easiest way to check for an open neutral is to measure the voltage of both phases to the neutral in the panel. If the path back to the XO is bad there will be a significant difference in the voltages measured.
Depends on what the load(S) are.But that is not necessary. If he had an open neutral there would be exploding light bulbs and MW that don't work or burn out.And the symptoms don't relate to a neutral problem AT THAT HOUSE..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 7/23/2008 9:54 pm by BillHartmann
I just think, if you are in a place with no metal water pipes between houses, you will have stray currents everywhere and lots of current on grounding connections, particularly if they have wye distribution on the primary. All that voltage drop on the wires on the poles has to show up somewhere. You might find the TV cable is as good a conductor as the ground wire between transformers.
You are not the right track.
It is most likely a NEUTRAL problem.
It might be your side/service. Any place between where it is bonded to the ground in your panel through to the transformer.
But it could be in neigbhors service.
It might be in the POCO high voltage side.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
But how could it be a neutral problem when the elec panel wasn't even bonded to the cold water pipe? It is now because I remedied that yesterday, but prior to it wasn't even connected tothe plumbing system.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
In that case it probably not a neutral problem on YOUR side.But it could still be a neighbors or POCO primary, or it could be at the cable companies "service" they power the amplifiers.What you need is a clamp on amp meter and measure the current in the different "grounds".And measure it with your main in the off position..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I have a clamp on Multimeter that will let me clamp around a wire and measure amperage on the wire. So you're saying turn the main breaker off and go around measuring ground connections to see if any of them are pulling off any current on them. There is a neighbor, as this is a halfhouse. I did suspect there could be a prob in their panel. Then I thought, it could be ANY of their neighbors in theory. I wouldn't think I'm to go around house to house checking everyones panels :)If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
If you measure current with the main off that means that it is coming from some other source.Call the POCO and tell them to fix it. And talking to some one in the engineering department. .
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
If the panel were bonded to the pipe then there would be (virtually) no heating of the coax, because the current would flow through the bonding wire instead. The problem is that there is a high ground current and much of it is flowing through the coax.There should be essentially zero ground current, so something's wrong with the AC wiring. Most likely an open neutral connection between house and transformer is causing what would otherwise be neutral current to flow through the ground. The situation is exacerbated by the bad ground connection.I'm guessing the lights flicker a lot, and sometimes get brighter when, say, the microwave runs.
It is an ironic habit of human beings to run faster when we have lost our way. --Rollo May
I'lll have to ask about the lights if they flicker. My big question is, why don't I get shocked when I touch the cold water pipe? If there is that much current to overheat the coax then you'd think there is enough that I'd get a jolt. Sidenote: The first time this happened when the cable guy showed up and attempted to touch the splitter he got a very nasty shock. This was when he also reported that the cable ground wire going to the cold water pipe was arcing where it jointed the splitter. So at least on THAT day there was enough to shock you. But yesterday I received no shock at all.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
You don't get shocked because the cable is "shorting out" the voltage. Loosen the ground clamp and (as the cable guy found out) the voltage differential increases.
It is an ironic habit of human beings to run faster when we have lost our way. --Rollo May
that makes sense. Still....I was standing on a dirt floor in the basement. Wouldn't I be the path of least resistance and therefore get jolted? Electricity always seems weird and funny, especially on wierd cases like this.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Since the current is getting shunted through the cable there's only a few volts present. Open the ground and the cable would get "hot" in the other sense.
It is an ironic habit of human beings to run faster when we have lost our way. --Rollo May
Now that you bonded everything properly on the cold, I would not expect you to get a shock, correct?
If you took your service panel bond wire off then I am guessing you would get a shock. (not the way I would test it though because you dont know how much current is running thru it but sounds like enough to wake you up (hopefully)
This was an awesome explanation Dan! I totally got it which is not very common for me.
Thanks
Jeff
107347.14 in reply to 107347.8
"If the panel were bonded to the pipe then there would be (virtually) no heating of the coax, because the current would flow through the bonding wire instead. The problem is that there is a high ground current and much of it is flowing through the coax.
There should be essentially zero ground current, so something's wrong with the AC wiring. Most likely an open neutral connection between house and transformer is causing what would otherwise be neutral current to flow through the ground. The situation is exacerbated by the bad ground connection.
I'm guessing the lights flicker a lot, and sometimes get brighter when, say, the microwave runs."
Hey Bill...
Curious about your take on one aspect of this that had me scratching my head... the coax is very warm? What scenario do you see where it's carrying enough current to generate a lot of heat?PaulB
Heating up?
Any chance they’ve been ordering an inordinate number of “adult” pay-per-view movies?
"Preach the Gospel at all times; if necessary, use words." - St. Francis of Assisi
Yeah well, the lady of the house is incredibly hot. So hot it was like I couldn't stand it. She has a boyfriend of another race, though. Dang.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Any update?
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
None yet, Bill...coax hasn't melted yet and it's beena week. I told the owners when I'm done with this other job I'm on, about a week from now, I'll then go over and try and find the stray currents plus sink in the new ground rod. It appears all is working fine for the moment and I have some time to finish my current project.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
When your there try measuring voltage between the coax and ground. The fault could be in the cable systems stuff, and coming down line to your ground because it is the best one available.
Ok, that's worth a shot also, checking for voltage from the cable company.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Hey Bill,Unbelievable.....I just got a call at this late hour. Guess what happened. The Coax melted AGAIN. Fried 'er crisp like bacon. So it lasted a mere 7 days. The tenant said what I did last week appeared to work fine and the coax remained cool for several days. But tonight, it did, for no real apparent reason. Now....here are some more clues.On Saturday the tenant was in their 3rd floor bathroom using a hair dryer. The tenant said when they turned on the dryer it was barely blowing air and it wasn't even warm air. Sorta running like an ultra low speed. About a minute later a breaker popped. They reset the breaker and the dryer behaved normally, blowing hot air as if there were no problem at all prior to. Next clue....the tenant has their phone service thru the cable company. Tenant said tonight that they were watching TV when the signal got fuzzier and fuzzier and started to "pause" a lot and get hercky jerky. Tenant then went up to check their internet connection and it was behaving abnormally also. Then the phone, internet, and cable went out totally just like last week when it fried. She said it took about 2 hrs between the time they noticed degradation of the TV signal til they lost everything. So that tells me that the overheating of the coax was not instant or immediate but slow. I suspect the heating of the coax, slowly, is what caused the signal to begin to degrade until the heating got so hot it finally fried the cable. I will go over in the AM and begin further in depth diagnosis based on suggestions from this thread. You have any other thoughts?If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
The breaker pop is odd, but the rest still sounds like a bad neutral.
It is an ironic habit of human beings to run faster when we have lost our way. --Rollo May
I thought the breaker pop odd also. However, I thought it may be a clue among all the clues I need to find this problem.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Where is the burned cable relative to the ground connection? Is it the house to grounding block link or the grounding block to pole link?
It is an ironic habit of human beings to run faster when we have lost our way. --Rollo May
I've lived through a loose neutral at the street, combined with a corroded (and therefore unconnected) panel ground. As I understand it, this was a very dangerous condition.
Make sure you get the POCO out to check this as I *suspect* this is your issue.
We were going through LOTS of light bulbs, lights flickering (irregular) and several pieces of equipment, including IIRC, a VCR, were fried. I had to work hard to convince our POCO that there was a real problem, which they found by installing a recording ammeter or similar.
Jeff
Edited 7/29/2008 10:15 am ET by Jeff_Clarke
Check the phase balance. Each phase to neutral should be virtually the same. Try it with a big 120v load on one side (like that hair dryer). If there is an imbalance go after the loose neutral idea farther
Edited 7/29/2008 10:31 am ET by gfretwell
Bill, I found an article on the net last night about possible AC current on the coax cable shielding. Apparently, if there is a ground fault, or otherwise improper grounding, or a failed grounding connection in the cable companies system it could send AC current thru the cables braided shielding. The article recommends putting a meter on the cable shielding in series to a ground connection and measuring for any current draw. If current is found then the cable company must fix the problem. I'm on my way over in a few mins to start further in depth troubleshooting of this issue. I will check the cable shielding as the article recommended as well. However, do you hve any opinion on what the article is suggesting could be possible?If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
That is one of the possibilities that I mentioned.Going back before you "fixed" it, if I understand correctly the panel was only connected to a short ground rod.And the cable was grounded to the water line via a small wire which burnt out the earlier go around.Thus, unless the ground rod was almost in phyiscal contact with the house is more or less isolated from the cable/water pipe.And as I said kill the power to the house will take the house out of the equation.The problem is it is not easy to tell if the water pipe is Hot and being grounded via the cable. Or if the cable is hot and being grounded via the water pipe.The hair dryer/breaker does add a wrinkle and I am not sure what it means.If there was a neutral problem to the house then the voltage at that time would be either low or high. By the sound of the dryer blower it was low. But most of the load is resistive and with resistive load the current goes down with load voltage.I wonder if they heard it speed up just before the breaker tripped?And if it is the house then selectively opening breakers will help isolated what circuit is causing the problem, if it is an individual circuit..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Bill, I have a whole ton of new info. I'll start a new thread called New Info on Melting Coax. Look for it in a few. VERY interesting new clues.
If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME