Shocking grounding problem

[NobeyamaGP]

We installed our satellite system ourselves back in 1994. This last week, while I was away at college, my parents suffered an intense wind storm and subsequently, 3 days without power. When I got home this weekend, my parents told me that they were missing some of their channels. I checked it out and noticed that some channels had "Searching for satellite signal (771)" on them, so I went outside to see if I could see anything wrong at the dish. I reached down to where the coax runs to the signal splitter and the metal connections shocked me. It wasn't anything major, just surprising. I went and got the multimeter, stuck one lead directly into the ground and the other on the connector. I was getting a pulsing signal back and forth from 0 all the way up to nearly 6V. I then discovered that the ground wire also had this voltage on it, so I traced it back to the ground rod and tried it there. The result was a constant 2.5-3V. I then tried checking the resistance between the ground and the ground rod and the it was almost unmeasurably large. This makes me think that the ground is bad. What do you think?

Also, any idea what could be causing the buildup of charge? As far as I know, there's no wiring running back there except the coax and the phone line which is grounded to the same ground rod. My only idea is it is an inductive current from somewhere. Any thoughts? Thanks.

[joe diamond]

Seen this once.
First unplug all your receivers and retest. IF that controls the current, dump the receiver(s), but I doubt that will be the case. That pulsing is a characteristic of the receiver & multiswitch. They could have been damaged and will also need checking after this is resolved.

Then.......start turning off breakers and testing until you find the breaker that controls the short. That interior line has a problem that is not blowing a fuse or flipping the breaker.

The one time I found this it was the ground wire inside a wall box shorting to a screw that had crushed the hot wire inside the wall nearby. The insulation had melted without starting a fire.

Most places require a licensed electrician to open the panel & rerun the wire.

Report back what fixes this........always interesting.

Joe

[Racer88]

You can't really test a ground rod with a multimeter. It takes very expensive earth/ground test equipment to do that properly.

What you most likely have is a ground loop somewhere in your house. The most likely source of that being a piece of electronics gear plugged in somewhere that had a power supply damaged when the power was acting up.

Like was said above, set up your meter and start turning off breakers one at a time until the offending voltage goes away. Then proceed from there.

If that doesn't clear the problem then you should consider getting a qualified electrician and/or the power company involved.

[houskamp]

put your phone line on a separate ground rod.. thats where the power is coming from.. your ground isn't good enough..

[joe diamond]

put your phone line on a separate ground rod.. thats where the power is coming from.. your ground isn't good enough..

Good one !

I have seen black iron pipe ground rods that were pounded in around 1940 that have vanished over time. Still, new, "heavy up" work had added miles of romex and huge main power cables without anybody inspecting the ground rod.

I'd like to know more about the phone thing.



Joe

[NobeyamaGP]

Thanks for the replies. I'll try some of these out and report back.:)

[NobeyamaGP]

Ok, reporting back about this from yesterday. I first went and made sure the electricity was still flowing on the ground cable before I tried anything. Since it was, I started by unplugging the coax from my parents D11-500 receiver and went to check if the current was gone. I started with it since it was the one acting up and I left my Tivo connected since it was working fine. I went back outside and tested the ground wire the old fashioned way (grab it and see) and the current was gone! I then went back inside to reconnect their receiver and noticed arcing when I touched the coax to the terminal! I told my parents to call it in and get someone to come out and look at the receiver. Thanks for your help!

[Mike500]

You have a floating or "bootleg" ground. This is a very dangerous situation. A 120 VAC circuit, one which your satellite receiver is connected, comprises one side of a "full phase" 220 VAC circuit and a "neutral" conductor, which is really not neutral, bit is a "circuit refurn" conductor.

If the "neutral" is connected to a grounding conductor or connected to the "grounding lug," somewhere away from the service panel, current flow can occur through the grounding conductor.

The codes, since 2002, has required a 25 ohm grounding conductor resistance standard for system grounds. The codes also state that two grounding rods bonded by a #6 or better copper conductor spaced 8 feet apart satisfies this requirement, without a validation test.

Quite possibly, also, if a water pipe was used originally as a system ground, plumbing repairs as well as corrosion has degraded or destroyed the continuity of the ground.

You need an experienced and competent electrician.