ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Recent Posts
Question on power to 4 Nema 6-50 & 5 Nema 5-15.
by TrickedoutTech. 10/22/17 11:36 PM
VFD MotorFeeders
by Yoopersup. 10/22/17 07:52 PM
Generator Cable Sizing
by brsele. 10/18/17 07:39 PM
What do you do?
by gfretwell. 10/17/17 01:08 AM
Good ol' copper pipe in the fuse holder trick
by HotLine1. 10/16/17 07:16 PM
New in the Gallery:
Gallery Test
Popular Topics(Views)
241,457 Are you busy
177,441 Re: Forum
169,024 Need opinion
Who's Online Now
0 registered members (), 12 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#179204 - 07/01/08 09:07 AM CATV Shield to GEC voltage  
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
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.

Work Gear for Electricians and the Trades

#179211 - 07/01/08 11:17 AM Re: CATV Shield to GEC voltage [Re: Tom]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,124
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

#179295 - 07/05/08 07:17 AM Re: CATV Shield to GEC voltage [Re: gfretwell]  
drum  Offline
Member
Joined: Sep 2007
Posts: 14
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


#179298 - 07/05/08 01:00 PM Re: CATV Shield to GEC voltage [Re: drum]  
SolarPowered  Offline
Member
Joined: Jul 2004
Posts: 625
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.



Member Spotlight
sparky66wv
sparky66wv
West Virginia
Posts: 2,236
Joined: November 2000
Show All Member Profiles 
Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.012s Queries: 15 (0.003s) Memory: 0.7622 MB (Peak: 0.8957 MB) Zlib enabled. Server Time: 2017-10-23 09:52:29 UTC