Ground Rod Required But Not Desirable?

[ewdudley]

Stumbled on to some of MH's videos on YT today and came away convinced by his good-hearted rants that auxiliary ground rods should be avoided in a good design, due to the need to avoid a low resistance path from the point of a lightning strike from a rod closer to the strike to a rod further from the strike.

Yet I read here over and over that "250.52" requires (as of 2008) that four wires be run to outbuildings and that "EGC" must be connected to a suitable "GES" at the main outbuilding panel. (And that neutral, as always, stays separate.)

So are auxiliary ground rods required but not desirable for (residential) outbuildings?

 

[starbolin]

So are auxiliary ground rods required but not desirable for (residential) outbuildings?

The case has been argued that 'Remote' auxiliary rods on a service entrance my not provide any additional protection. On remote sructures however a rod provides an essential protection against induced voltages. In many cases they are required by code and supported by testing, case reports and engineering.

I have heard Mr Holt's and others arguments against multiple rods used in an installation, in fact the arguements have changed little in my 35 years, unless good engineering was used and an alternate system was specified for a particular installation I would feel comfortable installing auxilary ground rods in any place required by code.

 

[don_resqcapt19]

I don't think the required grounding electrode system at a second building is what Mike is talking about. They are required electrodes and are not "auxiliary rods" as covered by 250.54. The rods that he is talking about are the ones that some CNC machine manufacturer's require in their instructions, or other non-code required grounding electrodes that are connected to the EGC.

 

[GoldDigger]

And perhaps more to the point they are not required to be metallically connected to the other electrodes that are mandatory parts of the GES.

 

[ewdudley]

And perhaps more to the point they are not required to be metallically connected to the other electrodes that are mandatory parts of the GES.

He was also objecting to ground rods on exterior gensets, for instance, where the ground rod is connected to the EGC bonding conductor. Schematically, how is this different from connecting EGC to a grounding rod by an outbuilding?