ECN Forum Forums Code Related Discussion NEC & other Code issues Grounding rod for outbuilding branch circuit?

Steve, although not exactly like your vault, i have a similar situation with my house. The service disconnect is in the garage (200a panel) with a 150a feeder to the house 13' away. My ground electrode system is between the two. It is really only one system but one of the rods is under the meter base at the garage and the other (2) are under the LB where the feeder enters the house. They are tied together underground with a bare #2 (in the same 24" trench as the raceway). One might argue I only have one ground electrode system for 2 buildings. I don't see the problem.

If the 2 buildings are tied together with a common foundation I think they are considered to be one building. On the other hand if the two buildings only had a roof or car port type connection, my understanding they would be considered two buildings. This becomes an issue sometimes and a building inspector explained it to me this way. Makes sense to me.

Coming up in the 2008 code ,equipment grounding conductor will be required to be ran with the circuit conductors

I am confused. I dont do residential. But I helped a buddy out whou built a three car grage with a second story (game room)about 75' from the house. I ran conduit from the house service, to a 100a panel in the garage. Ran #2 SER in the conduit.

I than drove a ground rod, right outside the garage where the conduit came up, and bonded my garage panel (like a service) and ran a #6 grounding conductor to my electrode.

The inspector told me to disconnect the ground rod and use the grounding conductor in the SER for the ground only.

I did what he said, but do not agree.

Whom is right?

Not the inspector. Plus I find it hard to believe he allowed SER in conduit. Not listed for use in conduit.

If you read this thread you can see how inspector and contractor alike will say that your grounding electrode at the second building was accurate. You should have floated the neutral and fastened the wire from the grounding buss to the rod(s).

The neutral must be floated at the garage. NEC normally requires a grounding electrode for a detached garage, but the exceptions do allow you to use the main building's grounding electrode if the ground wire is continuous and spliced in the right way.

So, I don't think what the inspector told you is illegal, but there's no reason he should have had you disconnect the ground rod.

In either case, the neutral bus should be isolated & ungrounded in the garage panel, lest you couple current onto the ground wire connecting the garage subpanel to the main panel in the house.

Steve I need some code references here. When I read in the NEC 250.32 I don't see any exceptions allowing a second building to be without a Grounding Electrode unless it is a branch circuit and not a feeder supplying the second building. And I'm not reading anything in the NEC allowing the use of the Grounding Electrode at the Main building becoming the Grounding Electrode at the second building if it's "spliced in the right way" what am I missing?

I have a question about the 12' X 12' shed scenario. Isn't the minimum allowable feeder size #10? Since it was mentioned that it's feeding TWO overcurrent devices, doesn't that make the branch circuit feeding the shed become a feeder, thus rules for feeders and sub panels would apply? Hey, I am just asking.

I did the same thing with my shed, well sort of. I ran a 1" PVC with four THWN #6, to a 12 circuit sub panel with a 60 amp main breaker (kit). There was a ground rod lying on the ground that I just happened to have sitting there. The first thing the inspector said to me was "what's that rod for?" I explained that it had nothing to do with my sub panel and that I understood that the sub panel had to be fed with a separate EGC. He made me promise that I wouldn't come back and drive/connect it later as he signed off on the job.

In a recent continuing education course I took to maintain my license, we learned that a separate EGC must be provided for sub panels IF there is any chance that any form of other metallic connection between the buildings exists (water, gas, telephone, CATV), etc. If there is no metallic connection, then the sub panel may be wired like a service, with a bonded neutral to rods, etc.

I still stick with the separate EGC since you can't control someone coming in after the fact and adding a metal water line thus turning your installation into a violation.

On another note, SER in a pipe underground is a definite no-no. I don't know how that one passed inspection.


[This message has been edited by EV607797 (edited 11-28-2006).]

George, if you read up this thread a little ways, you'll see that even though a GEC is required for the garage, it doesn't need to be located at the garage, and can share the house rod.

250.64(C)(3) permits connections to busbar to be used vice a single continuous conductor. The grounding conductor run between the house and garage, and house's GEC thus satisfy 250.32.

EV607797,

I ran a 20A GFCI-protected circuit to my shed, which let me run it just 12" deep in PVC, so as to avoid trenching deeply into my septic field. Really, it should only be a single branch circuit for what I need (lights and receptacles), but I had previously wired it up with a panel which I had installed about 5 years ago with the intent of putting in a 240V 30A circuit for heat, AC and a bunch of shop tools. Of course, I never got around to actually running the feeder, and instead just spliced on a 3-prong plug into a backfed 15A breaker and plugged it into an extension cord... So, it's WAY better now!

NEC allows 20A feeders, but it can only have 2 circuits on it. So, I rewired it for 2 circuits.

I know I'm in violation of NEC as I did not drive a grounding rod, and the ground conductor is spliced in the GFCI box, violating 250.64(C). But the AHJ here didn't so much as bother to open the shed door when he inspected my addition, letalone look that hard at it, so I get the feeling they just don't care.