Ground wire size

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  #1  
Old 02-02-12, 12:56 PM
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Ground wire size

Hi all

I have a 100 amp service in barn but main disconnect is outside
about 15 feet away. What size THHN ground wire should be run with the conductors inside the PVC pipe from the main disconnect to the 100 amp panel?
 
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Old 02-02-12, 01:13 PM
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#8 copper and #6 aluminum. Ground must be green or bare. You also need a ground rod.
 
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Old 02-02-12, 11:52 PM
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Thanks for reply ray. But I have the ground rod in place and the number 4awg
from rod to disconnect. Can you tell me size of ground wire to run with the feeder conductors to the breaker panel?

Thank you for your time Ray
 
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Old 02-03-12, 06:39 AM
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As I said from the ground bar of the disconnect run #8 copper or #6 aluminum bare or green to the ground bar of the subpanel..
 
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Old 02-03-12, 09:17 AM
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With respect to size EGC, Ray is correct. But, if you have some #4conductor left over [ I’m assuming you used bare copper. If you used anything other than bare, please post back with the type], you can use it to ground your equipment.
Note: Conduit fill shall be observed
Note 2: THHN is not rated for outdoor use—even if conduit is used. [With no emphasis on the equipment grounding conductor]
 
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Old 02-03-12, 03:23 PM
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Most, if not all, THHN wire is duel rated THHN/THWN and is fine for outdoor use.
 
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Old 02-03-12, 03:51 PM
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Most, if not all, THHN wire is duel rated THHN/THWN and is fine for outdoor use.
The dual type is available, but If you was to tell me you was going to buy a roll of THHN to install in outdoor conduit, I would immediately correct you. Regardless of the dual rating, we “must” use the correct trade name to indicate it’s application. This ensures proper understanding of electrical equipment.
 
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Old 02-09-12, 12:49 PM
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Thanks guys

The main disconnect is mounted to the side of the building.
A 4awg copper ground wire is attached to two ground rods and then to the main disconnect on the side of the building and is bonded to the neutral at that point.. A 4 inch length of pipe goes out the top of the disconnect directly into the meter socket.
Out the bottom of the disconnect, is another 4 inch piece of conduit
connected to an LB which goes directly into the basement. The
pipe in the basement then runs 20 feet through a crawl space, directly into my 100amp breaker panel.
I just need to run a properly sized ground wire in the pipe with the 3 feeder conductors from the disconnect to the breaker panel. I think the feeder conductors are number 3awg. But not sure yet.

What size grounding conductor should go in the pipe with the feeders to the breaker panel?
 
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Old 02-09-12, 04:50 PM
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#8 copper or #6 aluminum bare or green.
 
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