Thought I'd throw this out to the gurus here for a final answer....first the detail of the install:

200amp meter/main panel located at pump house. Two ground rods and well casing tied to ground bus in this main panel. Passed inspection no problems.

100 amp feeder to subpanel, with ground wire, all THHW/THHN, in PVC conduit to said subpanel in main house. Ground bus and neutral bus isolated at subpanel as per Code. Run of about 110 feet.

We do have telco and (most likely not to be used) CATV run from the pumphouse to the main house. Again in PVC conduit.

Inspector wants us to drive a ground rod at the subpanel location in the main house.

I feel that it would not be required, as the grounding of the system is established at the main service. If, for example, we had only a meter socket/can at the pump house, with the main panel being at the house (where the EGCs and neutral would be bonded, right?) would we require another ground rod. Adding the rod is not a problem, the walls are unfinished at this stage.

I am also concerned about creating a separate ground fault path...something rattles in the back of my mind about this rod being necessary only if another grounding path exists between the buildings...

Not too sure of what Code section (art. 250 of course) this would fall under, inspector did NOT give a Code reference.

This is in So. Cali., (up in the fire zone) and we're under the 2005 Code.

Thanks!!

You need a Grounding Electroid system per 250.32 installed in accordance with 250.50 even if you run a equipment ground. If the buildings are not tied together.(one Building).
The NFPA nec Code handbook spells this out quite well in. 250.32
Neutral floats in SubPanel. Grounds Equipment and Electroid system tie together.

The inspector is just a bit ahead of his time ....

If there are no metal paths between the two buildings, the code can be read to say that no ground rod is required. This ambiguity, though, will go away in the 08 code .... where it is said to make clear that detached buildings do need ground rods.

Code finesse aside, though ... that ground rod is there for lightning (more than anything else). It's sure not there to clear faults. It seems only sensible that anything that might make a separate 'target' for lightning have its' own rod.

EVEN WITH a rod, though, I'd keep the neutral and ground separated at this panel. Can't say why ... it just seems right that way.

NOTE: I'M WRONG .... corrected post later on ... OOPS!!!

A grounding electroid system IS required whether or Not you bring 3 or 4 wires even in 2005 code. Neutrals and Ground are required to be bonded together if by code you are allowed to run 3 (no equipment gr.)Required to be seperate if you run four.
Theres only one Exception 250.32 A exception

Ernie- You've never been more right in your life. See Ya in Rochester, you can buy me an adult beverage:)

(Bold emphasis in the following quote added by me..)



Thanks, Reno. That confirms what I had thought, i.e. the '05 and earlier Codes are not too clear on this requirement. That was what gave me pause when we got this notification.

And being as this is a remote area somewhat, I agree that lightning protection is a good reason for that extra rod.

I intend to keep the neutrals and grounds separate at the subpanel....now if that inspector had instructed us to bond the neutrals and grounds at the subpanel that would have brought out my claws.

And to be clear, I will be adding the rod, it wasn't an issue of doing it (I'm all for going above what Code asks for) but I was concerned about the duplicate grounding paths possibly being an issue.

Oh yeah, this cabin is being built by my friend (who's an inspector himself) and wired by both of us. He was as surprised as I was by this request from the local AHJ.

Yooupersup, thanks for the Code article references too. Are those from '05 or the upcoming '08?

Reno is mistaken and your inspector is correct. 2005 NEC article 250.50, "Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(6)that are present at each building or structure served shall be bonded together to form the grounding electrode system. WHERE NONE OF THESE GROUNDING ELECTRODES EXIST, ONE OR MORE OF THE GROUNDING ELECTRODES SPECIFIED IN 250.52(A)(4) THROUGH (A)(7)SHALL BE INSTALLED AND USED." I believe that is quite clear. 250.52(A)(4) through (A)(7) does not list the 4th wire(EGC) of the feeder as a grounding electrode.

The section 250.32 I quoted is from the 2005. Its the same in the 2008 except they added in the exception: (including a multi wire banch circuit)instead of as in 2005(for the purpose of this section, a multiwire branch circuit shall be considered as a single branch circuit).

The question that gets asked is if the telco is a "metal path" and the question becomes, did you reground the telco at the second building? That still only refers to the 3 wire feeder (regrounded neutral) vs 4 wire feeder (separated neutral). Our buddy Ryan made that moot with his proposal to the 2008.
I am going to be curious to see how this works out in lightning country. There is going to be a significant difference between grounds and neutrals in interconnected equipment at the far end. This may require different thinking in the surge protection of some equipment.

The coax sheild is a path connecting both buildings so a four wire feeder would be necessary.

Regardless of a four wire or three wire feeder, Ernie is correct.

If a three wire feeder is used, the sub-panel rod will be connected as if it were a service GE, and if a four wire feeder were used, the GE would connect only to the sub-panel enclosure and EGC in the feeder.

Roger

MX ... I did you wrong ... I must have been inhaling kitty litter fumes last night!

I managed to mangle the question in my mind something awful, confusing 'separating the neutral and ground' with 'driving a ground rod.' Two completely different issues.

If you're feeding a panel, you no longer have a 'single circuit,' you have 'feeders.' A detached building requires an additional ground rod (or other grounding electrode).

And, yes, I'd keep the neutrals and grounds apart

Thanks everyone for the input on this one.. I knew there was some missing info in what I thought and what the inspector is asking for. So a rod it shall be, attached to the ground bus in the subpanel.

Fred, thank you for taking the time to type in that Code reference, that was what I was looking for....

Yoopersup, thank you too. (I really need to spring for an '05 Code book.)

Greg, yeah, that was what I was thinking too, is the telco considered a "metal path" as defined by Code. But I don't quite follow what you mean by this: By "equipment" are you referring to the panel(s) or actual utilization devices?

Roger is of course correct that the coax woukld be a significant path as well. A four wire feeder was in the mix regardless of anything else. Like I'd mentioned, since we have a meter/main where the EGC and neutral is already bonded, it would definately make the panel in the house a subpanel. Offhand, I can't think of any way that one could use a three-wire feeder to the house in this situation. Now if the pumphouse only had a meter pan, then a three-wire feed could be used, with the EGC and neutral bond at the main house, right?

Reno: LOL No problem. I had lost that distinction between a circuit and feeders as used for a detached building.

OT: I'm currently teaching my cat, Gizmo, how to use the toilet. There is a device that makes it easy. After an intitial rebellion (Gizmo hates any kinds of changes) he's doing really good. May be able to throw out litter completely by the end of November.

This is why I love coming here, you guys are all great at helping out!!

When you don't reground the neutral at a remote site you not only see the voltage drop across the neutral feeder you also see the local ground shift between ground and neutral.
If you have something like a PC that uses the EGC as DC ground, connected to something that has a reference to neutral like a TV you will get a lot of hum and you might even let the magic smoke out.

Looking at a job that we have to finish... There is a combination meter socket/disconnect at one end of the lawn that had a 160 foot pipe run that we had to relocate for an addition. It had three lengths of 4/0 that I felt to be too small for the distance and no seperate ground, assuming the meter disconnect to be the actual service. I stepped it up to 3 250's AL and one #3 copper. Would I need rods at the house, and considering what was just said in the previous post, are they going to have that kind of problem if I don't bond the neutral and ground at the panel?

This thread brings up a question I've been pondering for a while.
Assuming no other metal paths between buildings, what method is better. 3 wire or 4 wire feeders? Obviously not paying for or pulling the 4th wire makes sense money wise, but in light of Greg's response it seems better for the end user as well.

And if you didn't reground phone and cable could you still use 3 wire feeders?

If there SEPERATE buildings weither you run 3 or 4 wires a grounding electroide system (Unless) ones there already per code is required.250.32 & 250.50 If 3 wires is allowed bond Neutral if 4 wires required Float the neutral .

I was referring to a separate building with no metal between situation. With grounding electrode systems at each building of course. Or even a remote power pole serving as the service entrance with a sub in the house.
As I understand it you would have the choice NOT to pull the ground with the feeders as long as you reground the neutral at the sub.

My question is what do the people on the forum think is the better system?

I like the four wire system . Then you lose the Neutral ever you still have a equipment ground to trip any hots to ground. Sometimes it becomes a cost issue if your talking long distances with the price of wire now.Going overhead I've never had a problem with 3 wires ,Just the way I look at it I guess.

With no metalic paths I think you are better going 3 wire and regrounding the neutral ... for all the same reasons we ground the neutral at the service in the first place.
Sorry Ryan

Maybe we should go to ground rods at each pole then instead of a equipment ground! Kinda the same thing right!Then bond the neutrals to the poles on 120 volt. ( Just making a point)

There usually is a ground rod at each pole, certainly any pole with a transformer on it. I find little difference electrically between the service drops and a feeder to a separate building. I suspect that is why 230 and 225 have so much similar language. The only significant difference is the lack of overcurrent protection of service conductors and that really doesn't affect the point and method of grounding that much IMHO, only the grounding conductor size (250.66 vs 250.122).
From a lightning and surge standpoint, separating the neutral and ground at a remote site is troublesome. The only way to "stabilize the voltage to earth" is via your TVSS equipment and that will have a significant "let through" voltage before it triggers.

So in my case, with wires coming from a remote meter disconnect, I would be better off leaving out the ground wire and driving a couple of rods? I was going to drive the two rods anyway. This would allow me to not have to rewire the panel (seperate the grounds and neutrals to seperate bars). The only things coming to the house are phone and cable, directly from the pole. Sounds like a better way to go. One less wire to pull, I'll use the #3 elsewhere.

You need to drive the rods in either case. You must have a local connection to the earth for anything but a single branch circuit. I think 3 wire vs 4 is better for your electronics but that might just be me