[Elecraft] Lightning season is on the way in New Mexico.

[Don Wilhelm]

  Bob,

A ground fault is either an open ground wire in the AC wiring system, or 
it is more commonly a short of the hot wire to ground (could be just 
leakage, like leakage from a capacitor from the hot wire to the chassis).

The separate grounds do not have the same resistance back to the AC 
mains ground, and will cause the equipment chassis to elevate above the 
potential of the grounded AC mains safety ground wire.  How much depends 
on how much resistance difference there is between the two ground rods 
(soil does not conduct very well in many areas).

I refer you to section 28.1.9 of the ARRL Handbook for 2010, especially 
figures 28.6 and 28.7 which clearly illustrate the situation.  This 
information was not in the 2005 edition of the ARRL Handbook, and I 
don't know when it was first included, but I am very glad to see it covered.

Don't have the ARRL Handbook?  Get one, it is worth the price.

73,
Don W3FPR

On 3/28/2011 6:45 PM, w5ov at w5ov.com wrote:
> Don,
>
> I often see this warning and I have some questions.
>
> You said:
>
>> First, it is required by National Electric Code, and 2nd because it is
>> dangerous without it.  Should you have a ground fault in your house
>> wiring,
> Please define a "ground fault" as you are using the term here.
>
>> everything connected to that isolated ground rod can carry the
>> ground current - touching anything within the area that is connected to
>> the house wiring, but not to the ground rod at the same time as touching
>> those items which are connected to the ground rod can cause
>> electrocution.
> How would everything in your home suddenly become hot?
>
> Thanks,
>
> Bob
>
>
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