beeron
OBAMA 2008
Premium
join:2000-06-06
Downingtown, PA
clubs: 
 ·Comcast
 ·Verizon FIOS
edit:
May 10th, @03:21PM
| Need tech help from Cable tech, current coming from coax
This is not directly HSI related but I have a technical question for the Comcast techs. We were discussing ground currents in the electronics forum »Re: Voltage in earth near ground-stake. when out of curiosity I checked my house. I found a 2 amps coming from the drop to our house to ground. Today, it’s down to 0.5 amps. It’s on the shield of the RG6 to ground. It had been raining so that may have had some effect.
It appears to be caused by a 60Hz triangle wave, see scope picture.
I’m assuming that it is not suppose to be there.
Any idea what it is and how to get it fixed? I can’t imagine calling customer service and explaining this one. 
BTW - I did switch all the electricity to the house off and still had the current. It only occurs when connected to cable.
--
"Facts do not cease to exist because they are ignored." - Aldous Huxley
"The difference between stupidity and genius is that genius has its limits." - Albert Einstein |
|
beerbum
Premium
join:2000-05-06
Reading
·Comcast
| Re: Need tech help from Comcast tech, current coming from coax
let me be clear.. you are getting voltage from the drop feeding your house, and you did this with the drop disconnected from the house?
call comcast and tell them your electrician found a ground fault coming off the drop from the pole - mention that the drop was disconnected from the house, it shouldn't be a problem getting a tech out - hopefully one experienced with ground fault troubleshooting.. it could be either a problem with the main ground at the pole (which then the electric co would have to fix) or a faulty tap feeding power to the drop.. |
|
beeron
OBAMA 2008
Premium
join:2000-06-06
Downingtown, PA
clubs:
·Comcast
·Verizon FIOS
| said by beerbum  :let me be clear.. you are getting voltage from the drop feeding your house, and you did this with the drop disconnected from the house? Correct, all you need is the coax and a good ground. Our feed is underground here. I believe each connection box has a ground rod. They are the old small metal ones, 4 houses to a box.
I like the electrician idea. That might work. 
--
"Facts do not cease to exist because they are ignored." - Aldous Huxley
"The difference between stupidity and genius is that genius has its limits." - Albert Einstein |
|
Splitpair
Premium
join:2000-07-29
Cow Towne
 ·T-Mobile US
·T-Mobile US
 ·AT&T Southeast
| reply to beeron
To me that looks like a shield problem in Comcast's OSP. CATV is powered over the coax center hot shield return if a shield gets a partial open that return current will find its way back over the power company's Multi grounded neutral via the common grounds and bonds your ground being one of them. As for varying day to day hey it's a partial open and it involves aluminum need I say more?
As for Comcast finding the problem and making a repair all I can say from my experience is if it’s busted when they get out there the chances are good they will clear it however if all is well when they show up then it will be what the folks in my business call a re-visit.
As for the waveform I’m willing to bet that is what the power looks like coming out of the power supply they don’t just use transformers anymore.
Wayne
--
If you cannot fix it with a buttset and some bennies you ain't a technician.
|
|
SolarPup
Cable Dawg
Premium
join:2002-03-07
The Pound
clubs:
 ·Osiris Communicati..
·FRII Front Range I..
·Comcast
| reply to beeron
Re: Need tech help from Cable tech, current coming from coax
You may be best to go to your local office to explain that then to try and explain it over the phone. Also, is your drop connected to a ground block at your house with a good ground? If so, it shouldn't come back to the house if you're grounded where the drop connects to the house.
--
...I don't have a 8mb speedy connection, I fly through the net at low altitudes! |
|
beeron
OBAMA 2008
Premium
join:2000-06-06
Downingtown, PA
clubs:
·Comcast
·Verizon FIOS
| said by SolarPup :Also, is your drop connected to a ground block at your house with a good ground? If so, it shouldn't come back to the house if you're grounded where the drop connects to the house. It's grounded via a ground block connected to the water pipe. The point is (IMO), there shouldn't be 2 amps of 60 Hz flowing on the shield, regardless of where it is grounded.
--
"Facts do not cease to exist because they are ignored." - Aldous Huxley
"The difference between stupidity and genius is that genius has its limits." - Albert Einstein |
|
tshirt
Premium
join:2004-07-11
Snohomish, WA
| reply to beeron
BTW ~ A ground to a water pipe is not legal or safe, In most cases the pipe is plastic from the house to the watermain, and even if it's metal is not a reliable ground.
It sounds like the ground at the tap is incorrect or failed also.
2 amps is enough to damage any electronics attached to the cable.
I would leave it disconnected, and imedietely call comcast, insist on an emergency call as this is a life safety issue (mentioning that it is a safety issue in your call should get a pretty quick response). |
|
NormanS
Premium,MVM
join:2001-02-14
San Jose, CA
·Pacific Bell - SBC
| said by tshirt :BTW ~ A ground to a water pipe is not legal or safe, In most cases the pipe is plastic from the house to the watermain, and even if it's metal is not a reliable ground. Per an electrician, who upgraded our premises from 100 A service to 200 A service, at the time the cold water grounding bond was installed on our premises, it was legal, and perfectly safe because the cold water feed was buried, galvanized steel.
It wasn't up to current code so he installed a proper ground rod. Still, the cold water ground remains in place; as a backup.
It isn't clear, to me, that bringing an outdated grounding arrangement up to current code would fix this issue.
--
Norman
~Oh Lord, why have you come
~To Konnyu, with the Lion and the Drum |
|
tshirt
Premium
join:2004-07-11
Snohomish, WA
edit:
May 12th, @12:48PM
| said by NormanS :said by tshirt :BTW ~ A ground to a water pipe is not legal or safe, In most cases the pipe is plastic from the house to the watermain, and even if it's metal is not a reliable ground. It wasn't up to current code so he installed a proper ground rod. Still, the cold water ground remains in place; as a backup. It is legal until you do some upgrade (such as you did)then the liecensed electrician is REQUIRED to bring it up to current code (most areas "grandfather" older buildings, until they are worked on.
However, given the frequentcy of lightning in the greater Philadelphia area. (where the OP lives, and very old homes commonly have ancient mechanicals)it is advisable to upgrade this ASAP.
said by NormanS :It isn't clear, to me, that bringing an outdated grounding arrangement up to current code would fix this issue. It won't solve the problem , the A/C is from/being passed through the ComCast plant, however the ground could save the OP's electronics/ from a potential fire/ perhaps his life. The point being CC should prompt repair the fault on their system, and the OP should protect himself from future faults/errors/accidents. |
|
beeron
OBAMA 2008
Premium
join:2000-06-06
Downingtown, PA
clubs:
·Comcast
·Verizon FIOS
| said by tshirt : However, given the frequentcy of lightning in the greater Philadelphia area. (where the OP lives, and very old homes commonly have ancient mechanicals)it is advisable to upgrade this ASAP. We don't all live in Independence Hall
The system is about 30 years old the water pipe is bonded to the the electrical neutral and ground which is bonded to 2 ground rods. In this case the water pipe would not work anyway since it is plastic to the street.
The ground is fine the problem is CC but what?
--
"Facts do not cease to exist because they are ignored." - Aldous Huxley
"The difference between stupidity and genius is that genius has its limits." - Albert Einstein |
|
tshirt
Premium
join:2004-07-11
Snohomish, WA
edit:
May 12th, @04:35PM
| said by beeron :said by tshirt : However, given the frequentcy of lightning in the greater Philadelphia area. (where the OP lives, and very old homes commonly have ancient mechanicals)it is advisable to upgrade this ASAP. We don't all live in Independence Hall The ground is fine the problem is CC but what? It could be a miss wired power supply or more likely voltage being feed back from one of your neighbors electronics (QC of discount tv's/VCR's/etc. manufactered in the third/2.5 world is terrible, and this is becoming a common problem)or perhaps they have a defective ground.
A tech should be able to trackdown and repair/disconnect the problem very quickly.
BTW with the million$ the park service spent on refurbishing and protecting Independence Hall it probably has among the safest lightning protection and electrical systems ............But Ben Franklin always said the internet service sucked 
also BTW My parents lived in the Philadelphia area (Swarthmore) until 2000, in the '90's a PECO contractor dropped a live 15KV line on a cable run near their house which cooked alot of TV's/etc. and started several house fires. (my parents were spared because they were to cheap to have cable) some of the neighbors were in court for several years in order to recieve full compansation.
Your pipe really should not be within the ground system, in a major short/lightning event the surge will follow ALL paths to ground, so if you are touching say a fauct and also touching an independant ground like a drain pipe/metal sink you may become a fuse in the ground path even though it is not the shortest, most direct, lowest resistance path to ground. |
|
beeron
OBAMA 2008
Premium
join:2000-06-06
Downingtown, PA
clubs:
·Comcast
·Verizon FIOS
| said by tshirt :also BTW My parents lived in the Philadelphia area (Swarthmore) until 2000, in the '90's a PECO contractor dropped a live 15KV line on a cable run near their house which cooked alot of TV's/etc. and started several house fires. (my parents were spared because they were to cheap to have cable) some of the neighbors were in court for several years in order to recieve full compansation. totally off topic but my parents probably lived a mile from yours I spent the early 60's hanging around Swarthmore being cool 
--
"Facts do not cease to exist because they are ignored." - Aldous Huxley
"The difference between stupidity and genius is that genius has its limits." - Albert Einstein |
|
EG
CLINK
Premium
join:2006-11-18
Union, NJ
| reply to beeron
I'm curious as to what type of Ammeter / Multimeter you are using. Digital, analog ? And how are you connecting it, in series ?, with what ? From the coax shield/coupling to where ?
Many digital meters are overly sensitive and the test leads will read stray RF which may actually be a false positive.
Just my .02 |
|
tech8
join:2008-03-06
Bishop, CA
|  reply to beeron
This is a common problem usually caused by a incorrectly
wired house nearby. This issue should be referred to a cable tech and your local power company ASAP. This can be hazardous
to all concerned. Check for voltage differentials between the
tap, strand, phone strand and power ground. The last time I
found this, it was an incorrectly wired arc welder half a block away, before that it was a badly wired hot tub, again
a half block away. This can damage your drop, damage your
equipment and cause some weird internet issues on the return
path. |
|
EG
CLINK
Premium
join:2006-11-18
Union, NJ
| said by tech8 : The last time I found this, it was an incorrectly wired arc welder half a block away, before that it was a badly wired hot tub, again a half block away. Not to be argumentitive or combative here, and I'm just curious, but can you elaborate on exactly what is meant by "incorrectly" and "badly" ?, as this almost sounds like a bit of a stretch, especially being a "half a block away" |
|
jplove71
IBEW 292 MPLS, MN
Premium
join:2001-03-16
Twin Cities
| reply to tshirt
said by tshirt :BTW ~ A ground to a water pipe is not legal or safe, In most cases the pipe is plastic from the house to the watermain, and even if it's metal is not a reliable ground. Per the NEC 2005 (NFPA 70), it is allowed to be used provided that the connection is within 5' of the entrance to the building/facility.
Article 250.52(A)(1) - Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0m (10ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52m (5ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.
Article 800.100(B)(1)(2) - The grounded interior metal water piping system, within 1.5m (5ft) from its point of entrance to the building, as covered in 250.52
--
Rakkasan! |
|
beavercable
join:2008-05-11
Beaverton, OR
| reply to beeron
Well dont know how they do things back east but out here in oregon possible reasons for 2 amps coming through coax. Old at&t power coming from the tap, underground electrical conduit moved or coax moved and the 2 are in contact, faulty amp. Speaking of can you see where the dog house is in relation to your house? |
|
beeron
OBAMA 2008
Premium
join:2000-06-06
Downingtown, PA
clubs:
·Comcast
·Verizon FIOS
| reply to EG
said by EG :I'm curious as to what type of Ammeter / Multimeter you are using. Digital, analog ? And how are you connecting it, in series ?, with what ? From the coax shield/coupling to where ? Many digital meters are overly sensitive and the test leads will read stray RF which may actually be a false positive. A Fluke 8060, Fluke 77, Westward 33II clamp-on and a Tektronix TDS 1012. I've measure the current with the clamp meter, a series current reading with a multimeter and with the scope across a 0.1 ohm resistor. They all correlate, so I think I took measurement questions out of the test. I can assure you the current is real and is a 60Hz triangle wave.
said by beavercable :Well dont know how they do things back east but out here in oregon possible reasons for 2 amps coming through coax. Old at&t power coming from the tap, underground electrical conduit moved or coax moved and the 2 are in contact, faulty amp. Speaking of can you see where the dog house is in relation to your house? The electrical utilities are coming from the front and the cable from the back, so they don't get near each other.
Ummm, dog house? If that mean where it connects to the cable system yes, about 120' away, opposite of any other utilities.
--
"Facts do not cease to exist because they are ignored." - Aldous Huxley
"The difference between stupidity and genius is that genius has its limits." - Albert Einstein |
|
NormanS
Premium,MVM
join:2001-02-14
San Jose, CA
·Pacific Bell - SBC
| reply to beavercable
said by beavercable :Well dont know how they do things back east but out here in oregon possible reasons for 2 amps coming through coax. Old at&t power coming from the tap... "Old at&t power"? Wouldn't that just be Comcast?
--
Norman
~Oh Lord, why have you come
~To Konnyu, with the Lion and the Drum |
|
TechnoScott
Premium
join:2003-03-25
00000
| reply to beeron
OK, not taking the time to read every post in the thread, I hope this isn't a repeat. Take a VOM out to the house box on the side of your home. Meter AC voltage from each cable shield to the ground wire in the box. Chances are you have voltage on the shield. Often times it comes from crappy TVs and sometimes from the DCTs. It usually gets dissipated in the cable ground and is not a problem. |
|
