Is a Ground Rod Needed When Grounding Multiple Buildings?

1 year ago
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If we were roughing in multiple buildings on a project, are we required to install a ground rod at each one? Are we required to bond our neutral conductor and grounding conductor at each location as well? In this latest episode of Electrician U, Dustin takes a look into the requirements for each of these to shed some light on the subject.

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Article 250.32 of the 2020 NEC governs buildings or structures supplied by a Feeder or Branch circuits. Under the exceptions to 250.32(A), the code states that a Grounding Electrode is NOT required in a building supplied with a single branch circuit (including multiwire branch circuits) IF that branch circuit includes an equipment grounding conductor. So, if we were supplying a separate building from our main building with a circuit for a light or a receptacle or something like that, as long as we included an equipment grounding conductor with our run.
Feeders are slightly different. Again, article 250.32 covers this, but we will be using part (B) for feeders. If we are supplying this separate building with a PANEL that will provide power for things within it, then we are to install an equipment grounding conductor WITH our feeder, and it needs to also be connected to the Grounding Electrode. In addition, part A of 250.32 does require a grounding electrode system and conductor (we used the EXCEPTION when talking about branch circuits!) to be installed. So, if it’s going to be a brand-new slab, we will be required to install our grounding system just like a normal commercial building would (Ufer, Building Steel, Cold Water, Ground Rod, Etc.). The equipment ground carried in our feeder is used to BOND the parts and the grounding electrode system still must be established!
Article 250.32 (B) also states “Any installed GROUNDED CONDUCTOR (Neutral) shall NOT be connected to the equipment grounding conductor or to the grounding electrode(s). So, this tells us that our neutral and ground should NOT be bonded together at our new building, as it is already bonded together at our service. Remember from previous videos, that Dustin established the bond is needed at ONE point only to complete the loop so that the OCPD can sense a LARGE current flow and trip. But we do not want to establish that bonding point twice and creating a choke point. That complete loop for a ground fault needs to happen RAPIDLY and since there are no motors, panels etc. to give us any resistance or loads to go through, the resulting current flow is massive (but very short lived) allowing the breaker to do its job and trip.
So, to recap, if you are installing a new building from an existing one, you are NOT required to install a grounding electrode if it is fed from a Branch Circuit. We ARE required to install a grounding electrode if it is being fed with a Feeder. And we do NOT want to rebond our ground and neutral at the new building as this bond is already made at the source building.
We hope this has been helpful in understanding where we are to install grounding electrodes and Neutral/Ground bonds. Is there a topic you would like to see discussed here on Electrician U? Leave a comment in the comment section below and let us know! Please continue to follow Dustin and Electrician U as we are constantly adding new content to assist our followers in becoming the best electricians that they can be!

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