Bonded ground wires vs. earth ground wire

Page 2 of 2  

Eigenvector wrote:

If your house is more then eight feet from the water line the metal service lateral will be longer then eight feet. Since it's entire length is installed below the frost depth it is at least likely to be a better electrode than the two eight foot long driven rods.
Be advised that many larger diameters of underground piping can be purchased with plastic linings and coatings. What appears to be plastic piping may be coated steal.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Does NEC do engineering studies like this? I see #4/0 and 250MCM bonded to ground rods and loops designed by system power engineers. Commercial or industrial facilities may have a grounded fault of 200,000A or more so do you really want to use #6?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
# Fred # wrote:

Do you really want to ground such a system with just a ground rod? Such systems usually use building steel and underground metal water pipes as the primary grounding electrode(s). Yes, as you stated, such systems do require the primary grounding electrode conductor to be larger, as do _houses_ when the primary grounding electrode is an undergound metal water pipe. However, even on those large systems, the sole connection to a ground rod is still only required to be a #6 copper, per (2002) NEC 250.66(A). You can connect a 250 MCM to a ground rod on such systems if you want, even Cadweld it, but it still won't dissipate any more electrons to ground than a #6 because of the limitations of the ground rod itself, as determined by engineering studies. IMHO, that's why ground rods suck, while they are better than nothing. Driving them deeper helps too.
For residential, 200 amps and below, IMO, it's easier to install bare #4 for the entire system ground, even for ground rods, because it avoids confusion and mostly because #4 doesn't require physical protection.
The OP wanted to know why a _smaller_ wire was ran to the ground rod. Sorry for not being clear.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.