Generator feed to outbuilding - oops!

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ramdiesel3500

ramdiesel3500

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Bloomington IN
Well I have goofed again. A friend asked me advise on a new installation and I gave him a bad suggestion. Heres the story: He currently has an existing pole building on his property with a 400A single phase service. He wanted to install an additional 200A service beside the 400A service and feed his new house 100 feet away. I told him he needs a 200A meter base, a 200A disconnect, and a 200A panel for the house. He is a close friend, so we are gonna do this one together (gratis labor on my part) and he is purchasing his own supplies. Sooo, he gets himself a 200A MCB load center for the house (oops should have be MLO, not MCB). I tell him this will be okay, we will just run a 4/0, 4/0, 2/0 URD aluminum feeder and drive a ground rod at the house. We will bond at both ends with no grounding conductor. That was the plan! Then, as an afterthought, he decides he wants to run a separate set of conductors for a generator feed and put one of those switch prohibiting devices in his house panel for a generator. (I know this could have been accomplished cheaper with a transfer switch at the pole building, but he wanted to do it this way) I say, "okay, get yourself a 2,2,2,4 URD AL. cable and put it in the ditch with the main feed. Well, today I get to thinking about it and I re-read 250.32(B)(2). That grounding conductor sure screwed up my plan. So, now I believe I have only two choices. #1- since we ran both cables together in the ditch, I can just pull the #4 grounding conductor into the main service disconnect at the meter location. This will require me to remove the bonding bar in the panel and separate all of the grounded conductors and grounding conductors for all the branch circuits (I normally do this anyway:)). Or, #2 -I can just NOT land the #4 Al. grounding conductor. I am strongly considering option #2 since this will allow him to use his generator in its currently bonded configuration.
Do you all see any problem with either option? Have I missed anthing? (sure wish he had not buried the conductors already!!!)
Thanks in advance!
 
To respond in some semblance of order:

The panel in the house should have a main breaker, since it's a separate structure, so that was a good mistake. The disco at the pole barn is optional, if I'm not mistaken.

Even if you clip the smaller feeder's EGC (and believing your transfer switch will not switch the neutral), you will still have both neutrals (the service's and the generator's) bonded at both ends.

If I'm correct, each feeder's neutral would qualify as a parallel metallic pathway to the other, disallowing omitting a separate EGC. I'd like opinions on this from others, please.

It seems to me that the only solution is to place the generator and transfer switch at the pole barn, intercepting the service feeder, and abandon (for now, at least) the 2-2-2-4.
 
You have 7 conductors in the trench, all aluminium, 1 of 4ga, 3 of 2ga, 1 of 2/0 ga and 2 of 4/0ga.
That would seem to be enough to provide 2 feeders with a large enough EGC for the larger one.

Hell, you could use a 'common neutral' and do this with only 6 conductors :)

230.30(A)(4) would seem to permit the second feeder.

This leaves open the question of the allowed ampacity of these feeders; I can make arguments that 310.15(B)(6) applies to the larger, to both, or to neither :)

-Jon
 
Thanks for your replies!!
Well, one thing's for sure! This is not an easy problem to solve. I'm gonna cap off that grounding conductor (the #4 Al.) so as to avoid any parallel path for neutral current. Then I am gonna discuss it with the inspector. Hopefully he won't throw the book at me! Wish me luck!!!
Thanks again everyone!
 
winnie said:
You have 7 conductors in the trench, all aluminium, 1 of 4ga, 3 of 2ga, 1 of 2/0 ga and 2 of 4/0ga.
That would seem to be enough to provide 2 feeders with a large enough EGC for the larger one.
Click to expand...
He's correct. Table 250.122 allows a #4 for a 200a OCPD.
 
Larry and others
After reading and re-reading your great responses to this thread I have reconsidered my approach to this fine mess I have gotten myself into. Thanks to all your responses, I am now considering doing the following:

1) Pull the #4 green ground wire from the 4-conductor (2,2,2,4) Aluminum URD cable assembly into the 200A main disconnect at the meter. (both cables are run together from the service disconnect to the house anyway)

2) I will, then, remove the bonding bar at the house panel and separate the grounded conductors from the grounding conductors. (this will be easy since we have yet to land any branch circuit conductors anyway)

3) Next, I will utilize the (3) #2 conductors from the 2,2,2,4 URD for the generator feed. This is where it gets tricky again. I plan to install a recessed power inlet for the generator feed. It will be a 4-wire 125/250V twist-locking device matched to the generator. There will be no grounding conductor leaving this box except the generator ground wire. When the generator is connected to this box via a 4-wire extension cord, there will be no grounding conductor path between the house and the generator inlet. The inlet and box will be grounded via grounding conductor in the cord set to the neutral/ground bond at the generator.

I feel compelled to do this installation as such since my friend uses his generator for many different applications that require the internal bond to be in place. I cannot trust that he will always dis-assemble his generator and remove the bond prior to using it for back-up power.

Comments? I'm looking for other ideas and views. I especially would like to know if any violations exist with this proposed installation. What have I gotten myself into???? :) :)
 
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