[TowerTalk] CQ article error(?)

[Jim Lux]

At 07:35 AM 10/7/2005, Bill Aycock wrote:
>The regular article, "Math's Notes" in CQ in the October issue is on the
>subject of wiring safety, but appears to have a serious flaw concerning
>the concept of "single Point Ground" as currently used by most Hams, and
>as required by my local power company.


Let's not confuse things like "ground", "grounding conductor (green wire)", 
"grounded conductor (neutral/white wire)", RF ground, AC safety ground, 
etc.etc.

>In the article, the neutral and the earth ground are only connected
>through earth at the panel end and the transformer end of the service.

Yep.. NEC requires that neutral be grounded ONLY at the entrance.  That's 
because you don't want load current carried on the safety grounding 
network.  Imagine a scenario.. you have a subpanel 100 ft from the main 
panel, and at both panels, the neutral is connected to the greenwire 
ground.  Now, assume you have a 100 amp load fed off that subpanel.  The 
current flows through the "hot" wire from the main panel, through the sub, 
to the load, and then, the return flows from the load through the neutral, 
to the sub, then splits into two halves, part carried on the neutral (where 
it should be) and part on the green wire (where it shouldn't be) back to 
the main panel, where they join, and then back up to the feeder.

Not all utilities ground the neutral at the transformer, by the way.. it 
depends on the local practices, how many things are fed off that 
transformer, etc.  For instance, if you're the only load on the 
transformer, they may decide to make your service entrance ground "the 
ground" (although, I've only seen this on an industrial installation)


>Comment? Am I wrong, here?
>Bill-W4BSG
>
>--
>Bill Aycock W4BSG
>Woodville, Alabama
>
>
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