I’ve seen many discussions on this subject in general, but have one more (hopefully final) question… If there is a sub-panel in a remote building, where there is no other conducting path connecting the two, a 3-wire service was acceptable under earlier code editions. My question is - if all the conditions are present to qualify for that exception, should a ground rod be driven at the remote location and be connected to the neutral / ground bus in the sub-panel? TIA
Jeff, I understand that to be required for detached buildings for lightning protection. Is that correct?
Yes, that’s correct. I would add one thing, a ground rod is not required but a grounding electrode is. It could be something other than a rod. Here’s what the NEC has to say about why things are grounded:
Not approved In Canada .
The system ground must be carried with the two hot wires and the neutral.
The neutral is then complete isolated from the ground through out the rest of the system.
A secondary ground in out buildings frequently causes Eddie currents
One more for you that I heard today from an electrician on the job.
The newest NEC code requires that there be two ground rods 6’ apart and a grounding conductor goes to the panel and a #6 ground wire has to go from the water service piping back to the meter and not the panel as it is now.
Is that the way it is now?
The requirement for two 8’ ground rods has been around for a while, sort of. The old requirement was for a single rod to have a resistance or 25 ohms or less. So on a service you could buy expensive testing equipment and prove 25 ohms or less or you could simply install two rods a minimum of 6’ apart (we always just install two rods). The 2011 simply reverses the requirement, now you must install two rods or prove that a single rod has a resistance of 25 ohms or less. IMO this makes more sense.
I have not heard this for 2011. Under the 2008 and earlier code editions you need to connect all of the electrodes together to form a grounding electrode system (GES). You’re permitted to connect one electrode to another with a bonding jumper or a GEC back to the neutral bus at the service disconnect.
Here’s a nice GES graphic from Mike Holt:
Thanks Robert, that is a good illustration, I will print it out.
I gave a simple answer, but you are certainly correct. The requirement is for an effective GE.