On 7/26/16 22:54, Jim Brown wrote:
> On Tue,7/26/2016 10:30 PM, Christopher Brown wrote:
>> If you dig a bit there is language about supplemental and supplementary
>> grounding electrodes. I forget which is which, but one is bonded to the
>> GES via #6 or larger bonding run, the other is not.
>
> NEC places very little importance on the quality of the connection to
> earth. It calls for some maximum value of resistance to earth (25
> ohms?), and if a single rod does not provide it, a second rod must be
> driven. That's ALL it says! What matters, and what is says a LOT about,
> is BONDING -- that is, how grounded equipment and earth electrodes and
> parts of the system are connected together.
That and maintaining the seperation of the grounded (neutral) and
grounding (green wire) conductors at ALL places except the designated
bond location at the "source" of a SDS (seperately derived system).
Also critical is detecting the prior work of idiots that swap the two
conductors or think that connecting the ground lug of a 3 prong outlet
to the neutral in a faux 2 prong to 2 prong conversion is OK... A swap
or extra bond + a neutral break is a serious safety hazard.
> And using only a driven rod at the equipment with NO ground conductor
> from the panel to the load is CRAZY unsafe, because the earth is
> basically a big resistor, and doesn't conduct enough current to blow the
> breaker. In my life in pro audio, we ran into dumbos who insisted on a
> separate "clean audio ground," not connected to the building ground.
> Mondo unsafe, for the reasons stated, and it does nothing to make audio
> systems cleaner.
>
> 73, Jim K9YC
Agreed, absolute safety hazard, totally breaks the function. Seen that
one many times myself with clueless installers of communications
hardware...Almost as common as using bare copper wire on tin
electroplated wire-wrap posts instead of wire-wrap wire that is itself
electroplated. Works well enough for audio-band stuff, but BER
nightmare for anything else after 1 - 5 years depending on humidity.
I have seen a few cases where a _DEEP_ driven (20+ foot rod) bonded to
the grounding conductor was useful, but think LONG runs in an unusual
environment (repair facility with both monster conventional and RF
welding systems), and the key there, _not separate_, in addition to the
long grounding conduction that ran with the phase and neutral conductors
all the way back to the panel.
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