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Old 06-11-2010, 09:06 AM   #1
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Another Subpanel Grounding Question


I built a pole barn, ran (if I remember correctly) 1/0,1/0,2 aluminium Triplex to it with a 125A breaker. Bought the triplex for <$1/ft from our coop electric company. I made two significant errors though. The first is I used a subpanel without a main breaker. I bought a GE retrofit kit from the local electrical supply house yesterday. The second error was that I drove ground rods and grounded to them without running a discrete ground to the panel. This originally wasn't an issue however now that I want to run phone and satelite TV out there, I need to lay a ground wire (I think). All circuits (including lighting) are on GFIs. I have 2 extra runs of conduit that I can pull the ground through. The run is about 250' back to my main panel. What is the minimum size ground wire do I need for this run or do I even need it if everything is GFI protected? Also, what type of wire is recommended, THHN? Does it sound like I am missing anything else. Thanks!

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Old 06-11-2010, 09:17 AM   #2
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Another Subpanel Grounding Question


I think code requires all the wires to be in the same conduit. Also, your 125A breaker may not be correct for 1/0 aluminum.
If there are six or fewer disconnects at the pole barn you are really OK, but a building disconnect is nice to have.


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Old 06-11-2010, 10:49 AM   #3
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Another Subpanel Grounding Question


You cannot run a separate ground wire to the panel. It must be in the same conduit or cable.
If you are on the 2005 code cycle or earlier you can use the 3 wire feeder. If you are on the 2008 cycle, you can start digging or pulling the wire out. The bonding wires from the rods go directly to the sub panel and land on the grounding bar.

See what code cycle you are on. We can address the rest once you get back with an answer.

PS......The 125 amp breaker is fine in the sub panel, as it is only a switch. You must use the correct size breaker in the main panel for the size and type of wire you are using.

Last edited by J. V.; 06-11-2010 at 10:54 AM.
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Old 06-11-2010, 11:46 AM   #4
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Another Subpanel Grounding Question


JV, I think he is saying the 125 breaker is in the main service and the sub is a main lug.
Quote:
The first is I used a subpanel without a main breaker.
Isn't the 1/0 AL only good for 100 amps at 60C?
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Old 06-11-2010, 11:57 AM   #5
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Another Subpanel Grounding Question


Quote:
Originally Posted by a7ecorsair View Post
JV, I think he is saying the 125 breaker is in the main service and the sub is a main lug.
Quote:
The first is I used a subpanel without a main breaker.
Isn't the 1/0 AL only good for 100 amps at 60C?

Yes but then
Quote:
I bought a GE retrofit kit from the local electrical supply house yesterday.
It doesn't matter what code cycle he is on. He now wants to run phone lines. Either code cycles requires four wire feed with phone lines.
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Last edited by joed; 06-11-2010 at 12:00 PM.
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Old 06-11-2010, 12:49 PM   #6
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Another Subpanel Grounding Question


I am under the 2003 code. I'll check on the triplex, i can't remember if it is 1/0 or 2/0. Thanks.

The more I think about it, doesn't sound like it is worth the effort to be bothered by some telemarketer anyhow. If I ran satellite TV or ethernet out there, would I have to add the 4th wire for those as well?
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Old 06-11-2010, 12:55 PM   #7
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I am under the 2003 code. I'll check on the triplex, i can't remember if it is 1/0 or 2/0. Thanks.

The more I think about it, doesn't sound like it is worth the effort to be bothered by some telemarketer anyhow. If I ran satellite TV or ethernet out there, would I have to add the 4th wire for those as well?
Any additional metal path between the buildings requires the 4th wire
You could run fiber optic
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Old 06-11-2010, 01:21 PM   #8
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Another Subpanel Grounding Question


Quote:
Originally Posted by a7ecorsair View Post
JV, I think he is saying the 125 breaker is in the main service and the sub is a main lug.

Isn't the 1/0 AL only good for 100 amps at 60C?
I believe the ampacity of directly buried URD is not governed by the 60 deg C. rating. It is not SE , SER or NM cable. Southwire lists one of theirs at 215 amps.

Last edited by brric; 06-11-2010 at 01:27 PM.
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Old 06-11-2010, 01:30 PM   #9
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So if I dug up the trench and added the 4th wire, what kind of wire and gauge would be appropriate? Thanks.
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Old 06-11-2010, 01:41 PM   #10
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So if I dug up the trench and added the 4th wire, what kind of wire and gauge would be appropriate? Thanks.
#8 Cu or #6 Al.
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Old 06-13-2010, 10:08 AM   #11
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Another Subpanel Grounding Question


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So if I dug up the trench and added the 4th wire, what kind of wire and gauge would be appropriate? Thanks.
You can't add another wire. You need to replace the cable or pull in a ground if you have conduit.
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Old 06-13-2010, 10:22 AM   #12
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Another Subpanel Grounding Question


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Originally Posted by Scuba_Dave View Post
Any additional metal path between the buildings requires the 4th wire
You coud run fiber optic
Just to add to this, I would really recommend using fiber if you run ethernet over this distance. My previous employer had a 100' or so ethernet run between two buildings, and about once a month during summer storm season the switch on one end or the other would fry. We pulled in a length of fiber with a media converter on each end and that was the end of it.

You can get the media converters from Ebay pretty cheap, they're just a little box with a network jack on one end and fiber connectors on the other.

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