ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

Topic Options
Rate This Topic
#179204 - 07/01/08 06:07 AM CATV Shield to GEC voltage
Tom Offline
Member
Registered: 01/01/01
Posts: 1044
Loc: Shinnston, WV USA
After a recent storm, the CATV drop to a customers house was replaced. Customer told me the installer did not hook up the required bonding conductor (shield to GEC) because it arced when he touched it to the grounding electrode conductor.

I stopped by this morning, no arc or spark when I touched the jumper to the GEC. Voltage measurement from shield to GEC varied from .5 volts to 1.1 volts as I had the customer turn on lights in the house. I suspect this reading is the voltage drop in the neutral. House is connect to transformer by about 100 feet of triplex & single conductor and there are four other houses on the same transformer.

I measured my own house & had about .3 volts, but I'm the only load on the transformer and have a very short drop.

Are the readings reasonable or is further investigation needed?
_________________________
Few things are harder to put up with than the annoyance of a good example.
Top
Work Gear for Electricians and the Trades
#179211 - 07/01/08 08:17 AM Re: CATV Shield to GEC voltage [Re: Tom]
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9038
Loc: Estero,Fl,usa
There is no better example of the "all paths" parable than in neutral current. It really becomes complicated when you have wye distribution. The only answer is bonding, lots of bonding. Back in the olden days when the metal water system was a city wide bonding grid this was minimized but these days every house is it's own "earth". Ground ain't "ground" in any practical sense.
I measured the pole ground current on every pole on my street and got from less than an amp to over 8. My GEC is carrying about 3 with the main breaker off, about the same as the pole in front of my house. I may have the best ground electrode on the street tho (in ground pool). I do make sure I bond everything I can, every chance I get.
_________________________
Greg Fretwell
Top
#179295 - 07/05/08 04:17 AM Re: CATV Shield to GEC voltage [Re: gfretwell]
drum Offline
Member
Registered: 09/29/07
Posts: 14
Loc: USA
Have seen this voltage on ground problem many times with catv. Most times it has turned out to be a bad underground neutral. Had an entire street all underground fed with the cable drops melting due to this. Power company had to send out " power quality " troublshooters to find the problem and sometimes it takes several visits and can be a real pain because these problems like to be intermittant. Sometimes you will see voltage issues when you do a load test. Good luck
Top
#179298 - 07/05/08 10:00 AM Re: CATV Shield to GEC voltage [Re: drum]
SolarPowered Offline
Member
Registered: 07/05/04
Posts: 625
Loc: Palo Alto, CA, USA
There are CATV isolation transformers available to mitigate this problem. Jensen sells one ($$$). This is a decent solution if ground differences between your TV and stereo system are causing hum.
Top

Member Spotlight
Member Since: 02/23/13
Posts: 204
New in the Gallery:
SE cable question
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box


Who's Online
0 registered (), 59 Guests and 9 Spiders online.
Key: Admin, Global Mod, Mod
 
New in the Gallery:
SE cable question
 
Top Posters (30 Days)
Admin 51
HotLine1 43
gfretwell 17
Trumpy 16
Ruben Rocha 13
 
Newest Members
clee512, Jdscott2005, FAIZAN, Regitest2, sureshazhagai

ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals