BackInTheHabit
Senior Member
- Location
- Lexington, Kentucky
Do you have voltage at the ground wire in the CATV box as shown in your photos?
I just don't know...
- Thread starter 1793
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1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
There is NO ground at the CATV main connection. I'm not sure if I can explain this next part that I forgot to mention in my last post.
With the TV on, on the ungrounded circuit, when I disconnected the cable going to the TV still holding onto the splitter I could feel that tingle you get with some electronics this tingle does go away after a few moments.
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aftershock
Senior Member
- Location
- Memphis, TN
There is NO ground at the CATV main connection. I'm not sure if I can explain this next part that I forgot to mention in my last post.
With the TV on, on the ungrounded circuit, when I disconnected the cable going to the TV still holding onto the splitter I could feel that tingle you get with some electronics this tingle does go away after a few moments.
Would it be possible to go ahead and ground the first splitter and see what happens?
I have been on a few calls where the cable was causing problems and ofcourse the cable guys blamed the electrical but I always found that the lead splitter was not grounded.
1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
Since your suggestion I've done that, heat gun, and the voltage dropped from 122v to ~115v. The heat gun has a grounded cord and when turned on nothing else seemed to be affected.
...and remember this could be the same as breaking a conductive path, creating a potentially lethal voltage differential.
The posted pictures of demarcation indicate the coaxial cables are grounded... i.e. the first splitters on each of the two services appear to be grounded. Having an energized run would indicate that the grounding has failed somewhere.[Edit to add] ...or it may not have been grounded properly to begin with.
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1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
I thought the same thing about the grounding at the CATV but when I went into the basement I found the other end of the ground lying on the dirt floor.
The Cable folks are to come back on Tuesday. I'm not sure if I want to be there when they show up.
I thought it looked as if the cable ground might not be truly connected. How many apt. in the building ? What type of wiring method is the building wired with K&T,NM,BX,etc.?
I would start by opening the coax splitters at the main/demark "BE CAREFUL" then test each of those to ground, My guess is you are going to find one that is "Live" while all the rest are not. This would be why the ground was cut (someone didn't know what else to do, so they cut the ground and there issue stopped.) Some where the coax is getting energized now the easy way to find it is open all of the cables and check one by one. Once all the coaxes are disconnected re-connect the bonding jumper to the demark, as you test each coax reconnect them to the now bonded system. When you find the energized one you will be able to start tracing where it goes, you need to find where it is getting energized from,so no one gets hurt. You will most likely get a call that "Joe in unit #4" has no TV and is complaining up a storm.Then you get to see what "Joe" has done to the cable.
I am going to guess one of three things has happened here, 1) the coax has gotten nailed to a phase conductor and accidentally energized. 2) someone has intentionally energized the shield of a coax to make some sort of "bastard circuit" using the shield as the grounded conductor. 3) there is a hot neutral reverse on the circuit somewhere that has energized the coax.
1793
Senior Member
- Location
- Louisville, Kentucky
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- Inspector
There is a combination of all three methods you posted. I think there are three units in this building. Sounds like a plan to break everything apart and start from scratch.
e57
Senior Member
- Location
- San Francisco, CA
And to add to that for the benifit of the OP - from the sounds of it, all of those interconnected grounds have one path back to the main and bond - the RG-6 from the cable.....
I can also assume that most of the outlets on the devices are 2-prong, or served by an ungrounded power supply - with the exception of the TV equipment.
Anyway.... 1793 I hope you realize that you can't just walk away from this one, the problem is a shock or fire hazard. It sounds like a multi-unit building, and if you need permission to kill power to other units - GET IT.
NOW:
I was however, after re-reading this, was starting to suspect that there coud be a miss-read of the voltages at the original electrical outlet, and that the ground there is energized - and maybe not the coaxial. (Cant tell from the comfort of the comfy chair.....)
BUT: And now after this post:
If you're reading from any phase conductor to the 'supposedly' grounded shield of the coaxial - you should get a voltage reading from any hot to the shield - unless that 'supposedly' grounded shield is energized by the same leg.... Much like what you are getting from the original outlet - you should be getting the same or simular from the "non-grounded circuit". What is different at that circuit, is that it lacks a path back via the grounded conductor, and a connection for the enegized coaxial.
Once again not sure of what meter type you are using? But have you done any ohmmeter readings and if so was there a 'beeping' noise from your meter?????? If so this would normally indicate voltage present. But that said, I would avoid doing any continuity readings untill you have located the source of the voltage and removed it....
To find this, assuming you can't physically follow the path of the coaxial, I would shut off circuits to eleminate voltage on the coaxial, then go from there.
- Find out which leg is enegizing it, by locating the circuit it the first outlet is on. If it is on "A" in the unit you're working in, it should be "A" the same for the whole building. Or if "B" - "B" for the whole building. (Unless the building is 3 phase...)
- Drag an extention cord from the effected outlet to the demark of the CATV to see if you get the same there. If you do, this means all of the shield is energized. If you don't, a portion within the building may have blown/burned open leaving on side ground, the other energized.
- Shut off every cicuit on that leg in the unit panel until the voltage on the shield disappears. The one that makes it go away is your baby. You'll need to disconnect it, find and fix (isolate) the connection between the two before you can restore power to it.
- If none of the circuits make the voltage on the shield go away, shut off the feeder to the unit, then each of the units, repeat from step #1 for the unit that is/may be effected.
- If all of the units are off, and you still have voltage - shut off the main. If shutting of the main does not make it go away - this does NOT completely mean the problem is outside the building... You still have the grounding of the coaxial to check, and a concerted effort needs to be taken to get any outside source of the problem corrected. But I would not leave the building until it is.
e57
Senior Member
- Location
- San Francisco, CA
I hope you have a DMM, as a wiggy carries voltage and current to the sheild of the CATV everytime you test anything hot....
1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
I have been using both DMM and a WIGGY. i don't always like the readings from the DMM but I have been able to see specific volt readings with it.
I hope to get back there tomorrow. This has become a personal challenge and I would like to get it figured out. I really do appreciate all of the help and I'll continue to look for more and of course report back all findings.
One other thought I had is, if you can check the coax shield against BOTH phase conductors A & B, if against "A" there is zero voltage difference, "B" will have a difference/potential of 240 volt, then you DO have an energized coax shield. Could be a signal booster in one of the units.
1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
I've been thinking about this for some time as I'm sure you can tell. One of the first questions to the HO was to see if any work has been done in the Apt just prior to the problems. I was told "no".
Just pouring over my notes I noticed that the receptacle that allows the system to work is not only ungrounded it has reversed polarity.
First thing I 'm going to do is correct that problem and start testing again.
I've been doing most of the testing in the Apt. on the second floor and since the panel(s) are outside and about 100' awayI'm going to install my temp. power outlet at the panel and run my cord to the demark. This way I'll be able to change between the "phases" as needed and I'm going to go a head and ground the main CATV blocks.
Wish me luck.
Just pouring over my notes I noticed that the receptacle that allows the system to work is not only ungrounded it has reversed polarity.
First thing I 'm going to do is correct that problem and start testing again.
I've been doing most of the testing in the Apt. on the second floor and since the panel(s) are outside and about 100' awayI'm going to install my temp. power outlet at the panel and run my cord to the demark. This way I'll be able to change between the "phases" as needed and I'm going to go a head and ground the main CATV blocks.
Wish me luck.
e57
Senior Member
- Location
- San Francisco, CA
Since you already know you have an energized one - take care not to make any corrections to the ground while energized - you don't know what it is energized by yet - it could even be a transformer lead out at the street.....
Also for what its worth - there may be another point at which the gounding of this could be energized - depending on the configuration - the Telco grounding.
Anyway, I often make line diagrams, even schematics of situations like this to help visualize the problem.... It helps.
Since you already know you have an energized one - take care not to make any corrections to the ground while energized - you don't know what it is energized by yet - it could even be a transformer lead out at the street.....
Also for what its worth - there may be another point at which the gounding of this could be energized - depending on the configuration - the Telco grounding.
Anyway, I often make line diagrams, even schematics of situations like this to help visualize the problem.... It helps.[/QUOTE]
Bring an easel and a pointy stick also, so you can explain to the tenants what is going on.
e57
Senior Member
- Location
- San Francisco, CA
Thats for my own benifit - not theirs.... To them I just say "Please remember to reset your clocks...."Bring an easel and a pointy stick also, so you can explain to the tenants what is going on.
1793
Senior Member
- Location
- Louisville, Kentucky
- Occupation
- Inspector
Problem solved:
I went back today and after more testing I found the problem.
The suspect receptacle had a "bootlegged" ground formed by a jumper from the neutral to the EGC. I found this the first day, after I removed the jumper I still had a ground and a neutral, so I thought.
I kept testing from line to neutral and line to ground and got voltage so I thought I had correct polarity as well as I had voltage from neutral to coax shield.
After more searching, I found another jumper form the neutral to ECG at another receptacle. When I removed that jumper I found that the neutral was actually the "HOT".
When I corrected the reverse polarity the problem went away.
During all of the testing from receptacles to coax shield I was using the neutral "HOT" and getting voltage on the shield when in reality I was getting the ground from the coax.
It took using the extension cord method coupled with other results from testing that led me to solving this problem.
Thanks to everyone for your insight and willingness to help. I could not have done this with all of you.
Again, thank you to everyone.
I went back today and after more testing I found the problem.
The suspect receptacle had a "bootlegged" ground formed by a jumper from the neutral to the EGC. I found this the first day, after I removed the jumper I still had a ground and a neutral, so I thought.
I kept testing from line to neutral and line to ground and got voltage so I thought I had correct polarity as well as I had voltage from neutral to coax shield.
After more searching, I found another jumper form the neutral to ECG at another receptacle. When I removed that jumper I found that the neutral was actually the "HOT".
When I corrected the reverse polarity the problem went away.
During all of the testing from receptacles to coax shield I was using the neutral "HOT" and getting voltage on the shield when in reality I was getting the ground from the coax.
It took using the extension cord method coupled with other results from testing that led me to solving this problem.
Thanks to everyone for your insight and willingness to help. I could not have done this with all of you.
Again, thank you to everyone.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
Cool.:smile:
I love hearing how it turns out!
I love hearing how it turns out!
quogueelectric
Senior Member
- Location
- new york
Bravo young pirate!!
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