Radio Tower

[eddie-king]

I am having some difference of opinion concerning grounding at 180' radio tower at our plant. I would like to see the the tower grounded to the plant electrical system grounding grid. The tower installer's are wanting there tower seperately grounded, not connected to our system. The ground reading on our system is 18 ohms. The soil in our area is sand. River bottoms. Please your thoughts.

 

[don_resqcapt19]

I assume that there will be conductive connections of some type between the plant and the tower. If that is the case, the lack of a bonding connection between the tower and plant grounding systems may result in catastrophic failure in the event of a nearby lighting strike.
Don

 

[tom baker]

My thoughts are that I argee with Don 100% and the NEC in art 810 requires the tower to be bonded to the building electrical ground system, Art 820 are the rules for coax, it also requires bonding of the impulse supressor to the building grounding system. In a lighting strike, if all is bonded together, then there is little difference of potential and no currrent flow. The radio industry uses a term called single point grounding. A good technical reference is by Times Microwave " The grounds for lighting and EMF protection". The cellular industry knows that a properly bonded and grounded tower can withstand a direct lightning strike.
Isolating as your tower installers want goes against all standards such as Motorola and the NEC. Whats their basis for isolation?

 

[dereckbc]

Eddie your tower crews do not know fully what they are talking about.

Yes your building has it own GES, as your tower has it own. However they are bonded with a made connection (as many as you can afford). What Don said is 100% true. Put one coax and the two are bonded together.

Now let me ask you this question. If the tower is struck, and it is highly likely it will be, do you want the equalizing current to go through your coax and electronics, or to the made connection(s) underground bonding the two together? Ask the tower crew that question and watch their eyes glaze over with that “Deer in the Headlights” look.

 

[mdshunk]

If the tower is struck, and it will be, do you want the equalizing current to go through your coax and electronics, or to the made connection underground bonding the two together?

"Well... since you put it like that..."

 

[charlie tuna]

we had a customer that had this same installation with the tower grounding system separate from the building's electrical grounding system. they had all kinds of problems with their electronics since they were in the electric meter calibration and recondition business! strange happenings like "dancing sparks" in the bar joists??? computer failures and outside light fixture damage. once we bonded the two systems together these problems went away!!