Does the sub panel have to have a ground rod if in a detached garage?
What condition need to be met to make it OK?
I often find this on farm properties that run overhead service drops out to sub panels in out buildings. I thought it was OK if it had a separate ground rod. Just looking for more clarification.
ANY detached structure feed with a feeder requires a ground rod (or two).
I’m not sure how long this has been in place. I too see many really old settings with feeders run all over the place and not a ground rod in sight except for the service.
You can use a 3-wire feeder if there are NO other metallic paths between structures, such as a copper water line or phone and cable wires.
The NEC refrence is 250.32(B)(2)
Yes. A remote panel in a separate/detached building requires its own grounding electrode.
It should also have a four wire feed to the panel from the service or a distribution panel.
As HI’s, it’s well beyond our scope to make this determination. It’s better left to the experts.
The three wire feed also requires a fused or switched neutral at the disconnect for the detached bldg or structure (based on strict interpretation of the reference).
So for the HI - look for a four wire feed. If is not present, defer it.
For Canadians .
You can only have one ground in a system .
You must carry four wires to all pony panels 1 grnd 1 neutral and two hot wires .( All must be identified one Green or bare one white and two coloured ( black or a black and red ) )( If metal conduit is used then the ground is not required but it must have two metal lock nuts.0
The pony panel must also be isolated from the neutral ( do not put in the screw from the neutral block to the panel )
Roy Cooke … Royshomeinspection.com…
This seems so strange to me that you can have a fused neutral.
with a secondary ground at the out building every thing could still operate if a person was to remove the fuse at the source of supply with the ground carring the unbalanced load .
Roy Cooke
Basically, if allowed, a switched/fused neutral in this situation would require a “three-pole” breaker with an internal switch (no handle tie).
Jeff, I’m going to have to disagree with you here.
The section you “bolded” does not mean the grounded conductor must be broken or switched. If it did it would have stated so.
What that sentence is implying is that the grounded conductor must be bonded to the disconnect. Just as with a main disconnect.
If you bolded a bit further you would have highlighted the rest which is: *“the grounded circuit conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means **and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded.”.
The intent of this is not to switch the neutral, but to make sure it is bonded o the equipment and the grounding electrode system.
I will agree that a H-I should note a 3-wire feeder as a possible issue.
Different you then can not feed the Pony panel from the main panel you must feed a three pole breaker/disconect then go to the pony panel.
Roy Cooke
I would expect that you would disagree, and if you were asked to come to the property to verify the installation (after my recommendation to do so), I would submit to your expertise.
However 
, (don’t you just love that), you are stating what is implied by the code, whereas I am stating was is directed by the code.
“shall be connected to the. . . disconnecting means”
There are additional requirements as to “what else” it is connected to, but this is clear (at least to me).
I understand the theory of the “three-wire feed and no other metallic path,” and I used to take that into consideration. It was just recently that I was challenged on this issue.
I simply recommend “verification” of the installation of a three-wire feed to a detached structure. The expert can determine that there is no other bonding issue and/or if the neutral should be switched.
If you dont mind ( and I certainly don’t want to step into your debate…but )at what point did that reference call for a switched or fused neutral if you don’t mind. I would be interested in this…
As for the debate…I am here to educate and not to puff up my “Electrical Feathers”…so I will say this…
You are allowed under the NEC ( Currently anyway ) to run a 3 wire setup to a detached garage…IF their is no potential between them…in my opinion something as simple as a telephone line, structured wire and concrete walkway or fence is something that could cause a potential between the two structures and thus would not allow the 3 wire setup.
However it would still require it’s own GEC and i guess my basic opinion is the HI should not TRY to determine the “Potential” of the buildings as part of their scope…as their scope is VERY clear…so if the HI runs up on this situation they can most certainly defer it…before stepping over their boundaries into “Specialists” on the subject and getting into potential trouble.
But in the end…yes the NEC allows for it…IF it mets the listed items that are associated with it.
Welcome aboard Paul. FWIW - This is not "our" debate, it is "a" debate, and all opinions are welcome.
As I have stated before, electrical professionals have much more latitude than the HI when interpreting the codes. It is best (IMHO) for the HI to side with the strictest legitimate interpretation. The electrical professional and/or the AHJ can make the final determination.
Here it is posted. . .
It is (IMHO) a legitimate interpretation that this means the neutral will be switched or fused, based on the NEC definition of “disconnecting means.”
**Disconnecting Means. **A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply.
I am Retired from the trade do not have a code book I stay away from the code .
If I think it is wrong I defer it to a qualified person .
Looks wrong not my decision on if they do or do not get it fixed I have marked it up as requiring immediate repair or replacement by qualified person .
If I made a mistake at least the worst thing can happen is I have to pay for the trades man to come out on a not required trip .
I want to stay out of court CRA all the way. (Cover Roys A$$)
Roy Cooke
Yes but I always feel I have to be able to explain why it is wrong to the client ,who have little knowledge of electric, in terms they can understand. Yet many clients decide not to upgrade panels, grounded outlets, GFCI’s, etc…even though the issue is fairly clear and not code interpretation.
I guess I would not call out a 3 wire in a detached if it met the requirements.
Nor would I. But how would you verify that it does meet all of the requirements?
AND. . .
Would you consider a switched/fused neutral to be one of those requirements? Why or why not?
I guess because i cannot understand or explain why it would be necessary. I don’t profess to be an expert on electrical code, far from it, but the majority of the code based requirements are understandable in real world circumstances and this one just doesn’t make sense as you interpreted it. I never tried to interpret it myself but I have never seen a four wire to a detached yet. If that is the way it is done in your area or??? then i would like a explanation why it is necessary. Wisconsin hasn’t adopted AFCI yet but that is one code that makes sense and I recommend as an upgrade!
So would you pass right by a 3-wire installation and say “I don’t know if it’s right, but it looks okay to me”?
Or would you defer it to someone who could make that determination?
If I saw the 3 wire sub and a good ground, no other pathway as described and everthing in each panel was OK then I would say it is OK. I only call out things I know are wrong.
I understand what you are getting at but have you always called out every thing you interpreted from code. I think the way code is written you could make an argument for your case by citing something similar to our laws and the way judges and juries interpret them.
As long as it is mostly right, it’s okay. Is that what you’re saying?
There is a list of specific requirements for a “3-wire” installation. Will you pick and choose which ones will be in place before you give it your blessing?
Mind you, I don’t know when this section was cycled in, so it may not have been required until recently. So I’ll stick with new(er) construction.
This was not my interpretation. It was that of someone with much more experience than I. But as a matter of rule, yes, our recommendations are based strongly on model codes and their interpretation.
I’m really just throwing this out there. I would love to hear (read) a compelling argument against this interpretation. One with some “substance” that I can take to the table 
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Jeff,
Here is the quoted section again:
***"…, the grounded conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded."
***Look at the two times the word "and" is used. By your interpretation the GEC should also be broken by the service disconnect.
Since they use “and” you cannot exclued one part and include the others.