Telecom ground to lightning protection

[Electromatic]

I was working on a service the other day and noticed that the communication (coax) demarc box ground wire was attached to the braided "down" conductor of the house's lightning protection system. At first blush, this seemed like a horrible idea. Thinking about it, though, these systems are supposed to be bonded to the GES, so does it really matter if the coax ground is attached to the lightning protection conductor or the IBT?

I know lightning protection systems aren't covered by the NEC except to say that they be bonded to the GES. I'm not going to fool with the LPS, but moving the telecom ground would be easy. Is it worth even bothering, though?

 

[LarryFine]

I would be hesitant to use it.

 

[petersonra]

I would be hesitant to use it.

the down wire is eventually connected to whatever the telecom ground is connected to. I don't see how it matters much where the connection is made.

how would it be any worse than connecting the down wire and the telecom ground to the same ground rod?

the question is whether it is code legal. I would say no based on what 250.94 (A) says and yes if going by what (B) says.

 

[K8MHZ]

I have been led to believe that the little #10 wire connected to the knitting needle jammed in the ground by the telco's isn't a ground, it's a static drain. We are bound by law to install an IBT, but the telcos never use it. I was also told it was a no-no for an electrician to move the drain/ground or whatever it is and connect it in a different manner than the telco did.

 

[hbiss]

I was also told it was a no-no for an electrician to move the drain/ground or whatever it is and connect it in a different manner than the telco did.

I do it all the time. I also remove the cable company grounds from PVC service masts.

Sue me...

-Hal

 

[winnie]

My _guess_ is that connecting the telco 'ground' to the lightning down conductor would be similar to connecting the telco 'ground' to a random neutral wire.

These conductors are all joined at some point and are joined to the ground electrode system, and thus at approximately the same (ground) potential...except for current flowing in the actual connected wire. In the event of an actual lightning strike on one of the air terminals, the voltage on that down conductor will be rather different than 'ground'.

My rough understanding is that the lightning system down conductors should go to their own grounding electrodes, and that the lightning ground electrodes should be bonded to the other grounding electrode system at one (and only one) point. However I am not a lighting protection professional, so this information should be taken with a large grain of salt...

-Jon

 

[hbiss]

However I am not a lighting protection professional, so this information should be taken with a large grain of salt...

And that is who you should be asking.

-Hal