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Cable issue or wiring issue?

13K views 57 replies 15 participants last post by  jrclen 
#1 ·
I've been having an issue with my coaxi cable giving off strong electrical shocks. In fact, it's fried two cable boxes, my TV and three cable techs:eek:.

I had out an electrician and he told me that it's probably the coaxi ground (grounded to the junction box by the meter) and said the the only wires running thru there are a hot and a neutral and that it could get getting back feed. He went on to test the outlets with a plug in meter and they all read "correct", so he claimed that it's not the wiring and that I should have them ground the cable to a water pipe.
SO, the cable company sent out two more techs who I briefed on everything I had been told by the electrician. They said that the ground is not the problem and that "company policy" states that they cannot ground to water, so they replaced all the cable in the apartment and outside. When they tried to hook up the tv they got the predictable shock.

They left telling me that they were sending out a supervisor this week. In the mean time, I started to do a little trouble shooting of my own. Here's what I found.
I took a look at all of the components that I have hooked up to my entertainment center and all of them with the exception of my PS3 are two prong plugs, the PS3 on the other hand is a three prong. I grabbed an old DVD player and hooked it up like normal to the television, the PS3 was also connected to the tv via HDMI. When I touched the coaxi to the back of the dvd player it shocked like hell. I then unplugged the HDMI from the PS3 to the tv and repeated the process,,,no shock at all. SO, I'm thinking that the PS3 must have a short of some type, but just to confirm I decided to pull the only other three prong source in my apartment, my pc. I ran the pc into the tv via S-video and had the hook up the same way to the dvd player. Touched the coaxi to the dvd and boom!,, unhooked the S-video from the pc and nothing.
So, I've concluded that the coaxi only gives off a shock when a grounded plug piece of equipment is hooked up. Does this sound like a wiring issue or could it really be a bad ground on the coaxi?
 
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#2 ·
Sounds VERY much to me that its a bad ground on the coaxial line. What you are experiencing is a difference in potential from the equipment ground on your PS3 (or your computer) and the coaxial ground. Ground the coax line to the electrical supply ground and everything should be fine. It surprises me that the cable company couldn't figure that out, they install a ground block on the outside of the house for a reason, its to ground the cable line to the electrical ground! Though its nice that they replaced all the coax cable for you!
 
#4 ·
I agree that the coax should be bonded to the house grounding electrode system, but there is still the issue of where the current coming from.

One cause could be a loose service neutral. The neutral current is trying to find a path back to the transformer. The cable can provide a path, in some cases.

Is your electrical service overhead or underground?
Is your water service (incoming) metal or plastic?
How does the coax run? Is it overhead or underground?
 
#10 · (Edited)
I agree that the coax should be bonded to the house grounding electrode system, but there is still the issue of where the current coming from.

One cause could be a loose service neutral. The neutral current is trying to find a path back to the transformer. The cable can provide a path, in some cases.

Is your electrical service overhead or underground?
Is your water service (incoming) metal or plastic?
How does the coax run? Is it overhead or underground?
Electrical is overhead.
Water service is metal, but it's grounded to an outside water heater.
Coax is ran straight from the power pole then into the house(no more than 25feet from the pole to the house). The ground on the other hand is running about thirty feet or so.

"Sending an engineer on a service call? Leaves a meter with you? And says "not to let the techs leave until it reads zero"? They will never read zero unless the engineer left you an analog meter."

Well he was doing it as a favor to my LL, but they joked around about charging the rental company for a service call. And I understand about not getting an absolute zero, but it shouldnt be reading 120v should it? Do you still think this could be a wiring problem or is it pretty much nailed down to the coaxi?

I don't know if it makes a difference or not, but the PS3, computer and anything else with a ground plug all function normaly, no shocks or anything as long as the coaxi is not hooked up. Don't know if that tells you anything or not.
 
#6 ·
Well, I'm getting it taken care of tomorrow. The cable company is sending out a Supervisor to "take care of the problem" and the electrician said he could come out anytime, so I'm gonna try to get them both here at the same time and let them duke it out.
The cable company at least put in a damage claim for the TV, but I'm wondering what, if any, action I could take against them for having a hot line ran into my apartment for the past four years? I should at lest get free HBO out of it!:laughing:
 
#8 ·
Wow, this story just wont end. So I finaly get the cable company to send out a few guy's to fix the grounding problem. I decided as a precaution to unhook any components with a ground plug (three prong) before they try to hook up the box just incase it turns out to be a wiring problem. They run the ground over to the cold water pipe on a water heater, bring in a new cable box and hook it up with no problems. After they left I decided to test out the system to see what would happen if I hooked up the PS3. Sure enough, once the ground plug comes in to play it causes a shock (mind you I used a broken old VCR for this test so no PS3 was hurt:)).
Well, I instantly call up the LL thinking that it MUST be a wiring problem now. The LL is by this time sick of hearing from me, so he pulls out all the stops and gets an electrical engineer to come out. The guy spends two hours testing everything from the breaker to the main box and checking every component for a short. Finally he ends up finding a "dirty" signal from the cable box. He unhooks the coaxi cable, plugs in a three prong plug in to the outlet, puts one end of the multimeter into the ground hole of the ground plug and touches the other end to the outer shiled of the coaxi,,, he gets a reading of 120v on the meter:(. He goes on to test the coaxi at every point till we get to the power line and he cant go any higher. He told me that it's got to be a bad connection from the cable company either at the source or at the ground.
Before he left he gave me his multimeter and showed me how to test the cable like he did. He told me not to let the cable guy's leave till that meter read zero.
 
#9 ·
Sending an engineer on a service call? Leaves a meter with you? And says "not to let the techs leave until it reads zero"? They will never read zero unless the engineer left you an analog meter.
I agree with John regarding the loose neutral or another grounding issue in your electrical system. 120 volts is a serious issue and could potentially be lethal, if the circumstance warrants.

Keep us posted. I would like to know what happens. Thanks John
 
#11 ·
Duchey, Okay, lemme see if I got this right... Ground to ground (coax to house) and you get 120V, the "EE" says it's the cable Co.. Disconnect the cable where it comes into the house/apartment and remeasure the coax ground to house ground. If there's no 120v, then it's outside the house, if there is, then it's inside.
I had a similar problem in a neighbor's house. Turned out to be a missing/energized ground on the circuit the TV/cable box was plugged into. He had 120v on the ground (which obviously wasn't connected right). The circuit started out at a convenience outlet next to the panel (right near the water ground) and ran all over the house (basement, bedrooms, attic, etc...). I pointed out that on the outlet ground to water ground was 120v. He said, "Oh yeah. I remember one time I touched the outside of the metal box and the shutoff valve and I got a helluva shock."
Do you have 120V ground (coax) to ground on any other circuits? (an extension cord will help here). Turn off the breaker on the circuit that the TV/cable box is on (I'm assuming for argument’ s sake that this is where the problem lies. This will eliminate false positives in case you plug into another outlet on the same circuit) and measure your voltage (should be zero) on the ground of the extension cord to the coax ground. If it's zero, I'd start (or have the LL's electrician) to trace the circuit back to its origin (or work from the panel outwards) and check the ground/neutral at every point along the way. Best of luck and let us know what the fix is. pete
 
#12 · (Edited)
Well, he (the EE) measured the coaxi all the way up to the wall outlet inside of the house and got the 120v reading the whole way and said that it was coming from outside. So what your saying is that I need to test the cable outside the house with a house ground and if I get 120v then it's coming from the cable? We also measured it in two different rooms from three separate outlets that I belive are on two different circuits (will test when I get home).
I'll try to do what you posted when I get home, but my question is why do I only get a shock when the coaxi comes into the picture? Why dont I get shocked when hooking up the computer or PS3 normaly if it's a ground problem? Things only get nasty once the coaxi enters the picture.

AH,, I do have another cable connection in the bedroom and I'm almost certin that the outlets are on a separate circuit. So, if I test the house ground to coaxi ground in the bedroom and it comes up 120V then I've got a problem with the coaxi?
 
#13 ·
The ground is not the problem. The problem is whatever is putting 120 volts on the cable shield. Your biggest problem at this point is an electrician who checks outlets with a plug in tester rather than trouble shooting the actual problem with a volt meter. I think you need a real electrician before someone gets hurt or graveyard dead.
 
#14 ·
Well, he (the EE) measured the coaxi all the way up to the wall outlet inside of the house and got the 120v reading the whole way and said that it was coming from outside. So what your saying is that I need to test the cable outside the house with a house ground and if I get 120v then it's coming from the cable? You can check it at the same place you tested it before. You just have to disconnect the coax input from where it enters the house. Usually they have a barrel type connector with two water proof "boots." Slide one of the boots out of the way and disconnect the coax from the connector, then make your measurement.

We also measured it in two different rooms from three separate outlets that I belive are on two different circuits (will test when I get home).
I'll try to do what you posted when I get home, but my question is why do I only get a shock when the coaxi comes into the picture? Why dont I get shocked when hooking up the computer or PS3 normaly if it's a ground problem? Things only get nasty once the coaxi enters the picture.


What type of plugs do the PS3 and computer use? If they aren't grounded plugs (3 prong) 120V on the ground would have no effect on them.

AH,, I do have another cable connection in the bedroom and I'm almost certin that the outlets are on a separate circuit. So, if I test the house ground to coaxi ground in the bedroom and it comes up 120V then I've got a problem with the coaxi?
If it is on a separate circuit you may be correct. Disconnecting the coax outside should narrow down the possibilities.
 
#16 ·
Well, cable guy just left after replacing the outside cable and ran a new line straight thru the wall. He was laughing at me about the 120v thru the coaxi cable and said that it's got to be the wiring.
So I just checked with the MM and it's still reading 120V, I cycled thru the breaker and killed the circuit that all of the components are running on and plugged an extension cord into the furthest circuit away. Took another reading and it shows 120V again.. Tried this with every circuit in the house and it shows the same.
I'm tempted to go ask my neighbor to plug in the extension cord to her outlet and then test it with her power.. What do you think?
 
#19 ·
I'm tempted to go ask my neighbor to plug in the extension cord to her outlet and then test it with her power.. What do you think?
Give it try. Disconnect your cable outside first, like suggested before. That will isolate the inside cable from the outside. Did you turn all of your breakers off and ever get to zero volts ?? (not one at a time...but all of them off). I know this may sound silly, but obviously this isn't being a quick diagnosis.
 
#17 ·
Haha, who's going to be laughing when its determined that its the cable company's problem?

I would do like has been mentioned and simply disconnect the cable line where it connects on the outside of the house. Check with the MM from house electrical ground to coax ground on both the cable entering the house, and the cable going up to the pole.

If you get 0 volts on the cable entering the house, and 120 volts on the cable going up to the pole, then you know for sure its the cable company's problem.

Just because they ran a new cable, doesn't mean they sheared the jacket on the cable somewhere along the line in the process. Also might want to check and see if its the ground barrel on the outside of the house that has the 120 volts on it. Disconnect both cables from the barrel and check electrical ground to just the barrel (no cables attached).
 
#21 ·
Yes, disconnect the new cable at the splitter and check that. As for the 25 volts to your neighbors ground, could mean something, but what you are really worried about is the difference in potential to the ground in your place. You won't be plugging your grounded equipment into your's neighbors power.
 
#22 ·
I'm actually throwing this question out there to the other electricians looking into this problem for Duchey. If this house had a main service disconnect, say outside, and a separate branch circuit panelboard, that had a neutral to case connection...do you think this might be a cause??
 
#23 ·
It really could be alot of different reasons, he needs to forget about the CATV and start looking into the electrical, start by hiring a competent electrician. You need to first off, find where the current is coming from, so I would turn breakers off one by one till the current went away, they tear that circuit apart till I found the problem.
 
#28 ·
First, put new batteries in your meter and test it on a known live source.



Turn off ALL of your power and see if the issue goes away.

If it does not, the 120V is coming from an outside source.

If it DOES go away, turn the circuits on and off one at a time and check voltage.

If the voltage reurns on one circuit, you have begun to isolate the problem.

If the voltage returns when ANY of the breakers are turned on, you have isolated the problem to the service.
 
#31 ·
Tell me if I did this right.
I killed all the power from the breaker box (flipped all the breakers off), then tested it from house ground to the coaxi and still got 120v.
Do I need to cut the main power at the fuse box or is this test good enough?
 
#36 ·
If you are getting the 120v from coax to house ground with breakers off, I'd say highly likely it is the cable system somehow.
Have you checked, with all breakers off, to test one or more outlets in your apt to see if you get any voltage from the ground slot to either the white or black terminals (slots) of your outlets. If so (highly unlikely), then there would be an issue inside your house.
b
 
#46 ·
Right, I was thinking when the power is on. It would probably be a good idea to check that to make sure the ground really is a ground at zero potential along with the neutral. If there is power between the neutral (wide blade on outlet) and ground, then theres a problem in the electrical system.

Try checking the voltage between the neutral and the coax and see what you get.
 
#41 ·
Yes John...that was the article I thought of. Thank you for finding it.

Duchey, you may want to bookmark that article for your electrician to look at if one comes back out.

http://ecmweb.com/grounding/electric_shocking_truth_grounding/

As far as proving who's fault it is...I think that will have to be taken care of after the problem has been found.
 
#42 · (Edited)
Bookmarked!
Well, I don't know why I didnt think about it before, but I work with some of the best engineers in the world, so I cornered one of them before I left work and told him all the symptoms and testing that's been done thus far.
After half an hour of detailed drawings on a dry erase board he told me that his conclusion would be a floating or open neutral.
So I guess I'll have the guy check that as well.

Oh, forgot to mention. This may have nothing to do with the problem, but when I touch the exposed screws on the top of my refrigerator and the steel of my kitchen sink at the same time I get a little shock. I checked it with the VM and it showed 102v.
 
#43 ·
MAN...quit touching things!! Especially metal...:eek:

I'm going to guess your 'fridge has a 3 prong plug (all do that I know of) and you have a garbage disposal (which has a 3 pronger). It is sounding more and more like a loose/missing neutral somewhere. I wonder if you plugged an extention cord into your neighbors, and test your water meter bonding jumper (don't touch it !!) to both the ground hole and the wide (neutral slot) of the ext cord if you'ld get a reading. Just curiousity on my part.
 
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