I will be running 220 to my pole barn which is about 70’ away from the house main panel. <!—-><!—-> <!—->
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My questions is how many wires should be run from the main house panel to the pole barn panel? <!—-><!—->
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My brother, who works at one of the larger electrical supply houses, says four wires; two for the 110’s, one for neutral and one for ground. I on the other hand, was figuring only three, eliminating a ground wire and using a grounding rod at the barn’s box instead.
Help!
Replies
3-wire usually does it, bond the neutral and ground in the barn panel and install two ground rods..........UNLESS you've got a continuous buried metal waterpipe or something else conductive like that from the house to the barn. THEN you run a 4-wire service out there. and keep the grounds and neutrals separate in the panel.
Ed
you need four, and a ground rod at the barn.
As I write this, there is some poor grammar in the code book that allows for multiple "correct" readings of the code. In the next edition, a large part of this confusion will be resolved.
You need 4 wires. AND a ground rod. The ground wire and the ground rod are there for different reasons.
Indeed, there are enough details that you really ought to leave this to an electrical contractor. Wire size, wiring method, disconnect location, trench depth ...
Now ... my advice ... may not be the "minimum" according to some, but it will save you much heartache down the road.
First, dig DEEP. The top of your pipe should be at least two feet under the surface ... which means you start with a ditch at least 30" deep. Line it with sand. Cover the pipe with sand.
Did I say pipe? I sure did. Schedule 80 PVC, with transitions to rigid, tape-wrapped steel sweeps at the sharp bends. The pipe should be at least one, preferably two, sizes larger than the "code minimum" for your wire. While you're at it, run a second pipe, at least 1", in the same ditch for any future phone or cable lines.
The idea is to make sure that you never need dig again.
Run the pipe to a disconnect on the outside of the barn. Then feed your panel inside the barn.
At the panel, add a ground buss. DO NOT use the little green screw to bond the panel to the neutral buss.
The ground wire, and the wire from the ground rod, both connect to the ground buss. Only neutral wires connect to the neutral buss.
Your wire feed should be no smaller than #4 (for a 60 amp feed). Do not use aluminum wire.
one word of advice, I have been there. If you can afford irun a three or four inch pipe. I would say 4 and get a couple quarts of that pulling soap
Brown and reno are both wrong in the sense that 3-wire is allowed. I'm really surprised that this question is still being debated after all the threads about it in the past.
Please look at 250.32(B)(2).
"250.32 Buildings or Structures Supplied by Feeders or Branch Circuits".
250.32(B)(2) Grounded Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building, (2) there are no continuous metallic paths bonded to the grounding system in each building involved, and (3) gfi protection of the equipment has not been installed on the supply side of the feeder(s), the grounded (i.e.neutral) conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means and to the grouding electrode(s) and shall be used for grounding or bonding of equipment , structures or frames required to be grounded or bonded."
This doesn't disallow running a 4-wire, rather it allows the neutral to be used in the same way it is used where the utility drop comes to your house. As the others said, if you use 4-wire then you still need to ground the building with rods or something similiar. It may be common practice in some areas to run 4-wire everywhere (not in mine though) but it doesn 't make it required.
This section is pretty clearly written and was slightly improved from the 2002 edition. If you guys disagree, please quote relevant code sections, otherwise you're just wasting time.
Ed
Thank you.
I know that my 3 wire system works just fine over my 700'. Wasn't a problem for the inspector at the time. I did screw up by not planning for enough current (wire size). Bought larger tooling than I ever dreamed. And I found out why you don't want to run aluminum wire without conduit. Wish somebody had warned me. Number of wires is no issue for function. PAHS Designer/Builder- Bury it!
I am glad that you find this part of the NEC clear. A few years ago, the IAEI ... the electrical inspectors' trade group ... asked some of its' experts this exact question. Three experts, four answers! I'm not about to get into the debate ... I simply described how I would do it (four wire), and noted that the sections of the NEC that have been used to justify 3-wire are in the process of being edited. I also noted that a ground rod was required, no matter how the panel was fed.
The rewrite has already happened, as far as I can tell.
Before 2005 , Section 250.32 was titled "Two or More Buildings or Structures Supplied from a Common Service". There was some ambiguity as to whether or not 250.32 (B) applied to branch circuits or direct service connections only even though 250.32(A) clearly applied to feeders and branch circuits from a common service. Thus all the debates.
So in 2005 the title of 250.32 was changed to "Buildings or Structures Supplied by Feeders or Branch Circuits".
This resolved the ambiguity and made it clear that 250.32(B)(2) applies to the OP’s question.
IMHO the section I quoted in my previous post is pretty easy to understand, for codespeak anyway. Have you read it?
Ed
Edited 5/20/2007 8:18 pm ET by edlee