Cable TV Question 1

[bluealhunter]

I've installed all sorts of comm cable (STP, Thinnet, Fiber) but never TV cable. When my brother had an addition added to his house, the TV cable they ran to his existing cable splitter (outside) had a copper cable running (but attached) along the outside of the cable (also covered in plastic). Is this some sort of ground?

 

[franklin97355]

Yes it's a ground wire.

 

[hbiss]

NO it's not a ground and it isn't copper. It's a steel messenger wire and it's purpose is simply to support the cable between the pole and the house. It is grounded at the pole but that's just for safety reasons, the wire should not be used for a ground.

Cable with a messenger wire should be used only for overhead runs, not within a building where it would serve no purpose. If you have an overhead messengered run and want to continue it into a building you would strip the messenger wire off and discard it after the point where the overhead part attaches to the building.

-Hal

 

[daronwilson]

Let's not be quite so absolute. There are figure 8 style cables and dual coax w/ground cables. SO, it could be a steel or aluminum messenger, or it could be a copper covered steel ground wire.

http://www.x10.com/electronics/allc...ringracksystems/_vextra_V2621GW-500BLACK.html

Here is an example of coax with a ground wire.

Good Luck!

Daron J. Wilson, RCDD

 

[daronwilson]

Here is another link that is more applicable:

http://www.vextratech.com/pdfs/V60GW.pdf

Daron J. Wilson, RCDD

 

[hbiss]

Who the heck is Vextra? You really must have done some digging for that one Daron.

Bigger question is why they would even make a fig 8 RG-6 with a copperweld "ground" wire. The clue here is that the cable is swept to 2200Mhz and the ground wire is 17 AWG. That would indicate that the use for this cable is for the run from a rooftop DBS dish along with the ground wire for the dish. The 17 AWG copperweld wire is the minimum allowable by the NEC to be used to ground the dish. There would be no other reason to use a ground wire with coax otherwise since the shield itself provides a suitable ground path.

There are some dish installers who have been using messengered RG-6 type cable, utilizing the messenger wire to ground the dish. This is against the NEC because the messenger is galvanized steel. I guess Vextra decided to market an NEC compliant product with a copper plated messenger and call it a ground wire, but I question the use of a cable with an attached ground wire for this purpose. Apparently the major cable manufacturers do also since Vextra seems to be the only one making this stuff.

The ground wire from the dish must be connected to the electrical service ground outside the building or within 5 feet of where it enters the building. I would say that most times the coax and ground wire leaving the dish location must go in different directions if you are going to do things right. My opinion is a product like this just encourages the dish installer (who is restricted on the time to do the job and underpaid) to cheat on where the ground is connected if it ever gets connected at all.

But I digress.

So, back to the original question, apparently there is a cable with a ground wire or at least marketed as such and we know where it came from. It's not clear from the original question who "they" are who installed this cable and where it comes from. If it was the cable company I don't know why they would be using a cable with a copperweld messenger, they don't need a ground. Maybe they got a bunch of it cheap from Vextra? If it was just run around the outside of the house perhaps it was installed by a dish guy or an electrician who bummed a reel of it off one of them?


-Hal

 

[Servamatic]

Hal

Please quote the code where it states a dish ground must be connected at the electroical service ground or within 5'.

Richard S. Anderson, RCDD

http://www.servamatic.net

 

[ISDNman]

Hal,

Excellent points (star for you).

I have yet to see a cable TV or satellite installation that is up to code (mine comes closer than any "pro" installation and I know that mine does nto comply to the letter.

Richard, see the section on "TV antennas" (sorry code book is at home).

Both TV antenna and phone sysems must tie their grounding to the building ground system. The concept of isolated grounds is long dead.

 

[Servamatic]

Thanks ISDNman, but I would like specific codes cited as I have questions about some of the statements made. I would like to know exactly which sections are being interpreted before I ask my questions.

Anytime the code is cited effort should be made to list the exact section so as to eliminate confusion. Also which revision of the code as there have been many changes to Chapter 8 in the 2 most recent revisions.



Richard S. Anderson, RCDD

http://www.servamatic.net

 

[hbiss]

From the 2002 edition, Article 810.21(F). This section gives you your choices for grounds.

You are right though (I think) in that 810.21(F)(1)(b) states that the ground may be connected to "The grounded interior metal piping system (water line) within 1.52m (5 feet) from its point of entrance to the building". I'm now taking that to mean that they are refering to 5 feet of pipe not ground wire which is the same requirement for where the electrical service ground clamp on the water line must be installed.

810.21(G)states that the ground wire may be run either inside or outside of the building.

The NEC is a minimum requirement that takes into account a great many installation situations and tries to make as many of them as safe as practical without seeing every job. So, with it as a guide you then have to design your particular installation to comply with the code and add any additional measures beyond whats required so as to provide a safe and properly functioning installation.

With that said I don't think anybody who knows what they are doing would want to invite lightning into a house by running a long length of ground wire from the dish on the roof through the house. That may be a different matter with a steel framed commercial building. This is where you must have the knowledge to not take the code literally and apply it according to the circumstances.

-Hal

 

[daronwilson]

Hal,

Thanks for some of the explanation. I guess I just get a bit frustrated with real absoulute answers when the question lacks the details to discern the correct answer. Who or Why it was done is not really the issue, my concern was that there are in fact figure 8 style cables with a ground wire as well as those with just a messenger.

I'll have to dig my codebook out now too and look, thanks.


Daron J. Wilson, RCDD

 

[daronwilson]

The NEC is a minimum requirement that takes into account a great many installation situations and tries to make as many of them as safe as practical without seeing every job.

Interestingly enough, Article 90 explains the purpose of the code, which has nothing to do with function or practicality, but only safety.

90.1(B) "Adequacy. This Code contains provisions that are considered necesary for safety. Compliance therewith and proper maintenance will result in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use."

In short, if you follow the code you get safety with no guarentee of fucntion.



Daron J. Wilson, RCDD

 

[fz6yamaha]

Just a pointer, Being a cable guy, I've been taught that my grounding has to be the shorest copper wire posible, electricity needs to travel the shortest distance to the ground to be discharged, so if you use a coax with the messenger and your run to the 1st (tv)outlet is shorter than the source distance most likely you will end up burning a TV (I have seen slacky grounding and in GA after storm season we see a lot of burned out tvs).
We (cable company)must ground to a metal water pipe or the electrical meter box, if we happen to ground to the water meter (not usual) we must create sort kind of jump between the 2 pipes(feed-house pipe)