[TowerTalk] Challenging Grounding/Bonding Situation ?

[Jim Brown]

On Fri,9/12/2014 5:42 PM, Gary Schafer wrote:
> The whole purpose of the 4 wire system is to keep neutral current off of the
> ground wire.

Right.

> With a 3 wire system, if the neutral/ground should open there could be 120
> volts on cabinets that are connected to the green wire ground.

Neutral and ground are separate conductors. They are bonded together at 
the service entrance, but they remain separate after that.

> There will also be a voltage difference between grounds due to voltage drop
> on the common neutral/ground.

So what?  By your logic, the power company would have to bring us four 
conductors. They do not -- they give us two hots and a neutral, which is 
the transformer center-tap.

As to bonding a tower to premises grounds -- if the tower is close to 
the house, certainly yes. If it is distant from the house, it can cause 
as many problems as it solves. Remember that lightning is an RF event, 
not a DC event. Remember also that coax shield is properly bonded to the 
tower top and bottom.And remember that the impedance between the tower 
and the shack is dominated by the inductance, not the resistance.

And if you re-read my description, you'll see that everything in both of 
my buildings are, indeed, bonded not only per code, but far more 
robustly than code.

73, Jim K9YC