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I've been helping my son rebuild a house (tear down, new construction) and I'm doing most of the electrical. He also has a pole barn that had it's own 200 amp service (believe it or not) with it's own meter. He wanted to consolidate that into one service.

At first, I suggested we just feed the pole barn off a breaker in the new panel in the new house. But an electrician friend of mine said then it would be treated like a sub-panel, requiring a 4 wire feed. I called an inspector and also said that it would need a 4 wire service, even though the pole barn already had it's own grounding system. I've never understood that logic if the neutral was floated (not bonded to the grounding system).

The reason for not wanting to convert to a 4 wire service for the pole barn is it would have required trenching in a difficult area and the service conductors were direct bury, not in conduit.

Others here have said outbuildings require their own grounding electrode system. I'm interested in hearing from other parts of the country how this is handled.

We did solve the problem by going with a class 320 service, which of course treats the panel in the pole barn as a main service panel.

  • First you have more than one question and maybe 4 or 6 so please ask one or a vote to close is required. – Ed Beal Jan 21 at 3:40
  • Ed Beal, Thank you for the comment, but In re-reading my post, I believe I just described our situation and asked only one question: "do outbuildings require 4 wire service". If you disagree, please let me know why so I can be a better contributor. – George Anderson Jan 21 at 3:51
  • George, since 1999 in my state we have had to have to have 4 wire , I remember. – Ed Beal Jan 21 at 4:21
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In every part of the country, any subpanel requires a 4-wire feed. That's been code for well over a decade.

Additionally, any outbuilding (not connected by a breezeway) requires a Grounding Electrode System of its very own.

The reason is because the wire takes human-made current back to source, but the ground rod takes nature-made current back to source. Dirt doesn't conduct well enough to do both.

Retrofitting ground isn't that big a deal

In a 3-wire outdoor subpanel feed, you can just add the ground wire. It needs to get from A to B, it is not required to run the same route or lay in the same trench.

Rigid Metal Conduit or IMC only needs a 6" burial depth (but it's expensive), and it qualifies as the ground path. Lay a 1/2" steel pipe and yer done. Use it for comms later :)

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    Thank you for the response. When I contacted the electrical inspector here and described my problem, he was actually the one that said, why don't you just go with a class 320 service? I also advised my son to contact the project manager at the power company to ensure we could do a class 320 (IE, large enough conductors from the transformer to the 320 meter base). They came out and said we were good to go. I thought that would be the case because both 200 amp services (old house & pole barn) were serviced by the same feed from the transformer. – George Anderson Jan 21 at 3:48
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    @GeorgeAnderson can't get better than that, the idea coming from the inspector. That's the horse's mouth. Edited. – Harper - Reinstate Monica Jan 21 at 3:53
  • Funny some parts of the U.S have not adopted the NEC as far back – Ed Beal Jan 21 at 4:12
  • @EdBeal Yeah, the People's Republic is already on 2020 NEC (they needed a special color for it). But 43 states are on 2014+. Some of the "NEC 2008" states actually have municipalities endorsing newer NEC. I personally have my opinions of what NFPA can do with all those arc-fault breakers. – Harper - Reinstate Monica Jan 21 at 4:43
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    @GeorgeAnderson I think Ed is telling me to tighten up my first section... I do have a tendency to ramble... It,s like Mark Twain said, "forgive the long letter, I did not have time to write a short one..." – Harper - Reinstate Monica Jan 21 at 8:32

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