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Old 12-20-2008, 07:49 PM   #16
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Confused About Grounding?


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Originally Posted by nprranch View Post
Does anyone know if I have 1/0 aluminum wire coming into my first service panel, what would be the copper equivalent for grounding it?

Thanks

Are you talking about the cable that actually lands on the main breaker or the overhead cable? For a 200 A service, 4/0 aluminum is the minimum size allowed. This doesn't apply to the power company feed, only the wire that lands on your main. I ask because 1/0 is awful small. For 200 A 4/0 is the minimum. You should verify the size just to be sure.

At any rate, if it is 1/0 then #8 copper is all that is needed.

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Old 12-20-2008, 09:13 PM   #17
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Are you talking about the cable that actually lands on the main breaker or the overhead cable? For a 200 A service, 4/0 aluminum is the minimum size allowed. This doesn't apply to the power company feed, only the wire that lands on your main. I ask because 1/0 is awful small. For 200 A 4/0 is the minimum. You should verify the size just to be sure.

At any rate, if it is 1/0 then #8 copper is all that is needed.

The cable going to this first panel in the arena is 1/0 buried cable from the pole to a 100-amp breaker in the first service panel. The buried cable to the house is 4/0 and it goes to a 200-amp breaker in the house. I think the buried line to the arena was added on after the house was done. Not sure exactly how it is hooked up at the pole. Should this be another area of concern??
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Old 12-20-2008, 10:18 PM   #18
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Confused About Grounding?


Quote:
Originally Posted by nprranch View Post
The cable going to this first panel in the arena is 1/0 buried cable from the pole to a 100-amp breaker in the first service panel. The buried cable to the house is 4/0 and it goes to a 200-amp breaker in the house. I think the buried line to the arena was added on after the house was done. Not sure exactly how it is hooked up at the pole. Should this be another area of concern??
I had to go back and re-read your first post. I missed it the first time. You said:
Quote:
I have a 200amp service coming off the pole which is switched at the pole.
Then you said:
Quote:
From here I have 3 wires running into a building which is a steel pole barn combo riding arena/horse stall barn to a 100-amp service panel (in the riding arena section).
You didn't mention a house! How does the house come into the circuit? Is the panel at the barn a subpanel from the house panel?
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Old 12-21-2008, 12:27 AM   #19
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Quote:
The cable going to this first panel in the arena is 1/0 buried cable from the pole to a 100-amp breaker in the first service panel. The buried cable to the house is 4/0 and it goes to a 200-amp breaker in the house. I think the buried line to the arena was added on after the house was done. Not sure exactly how it is hooked up at the pole. Should this be another area of concern??
Ok were getting close now. Your feeding multiple buildings from a farm pole. If you only have a single disconnect out there at the pole this is your site isolation device not your service equipment with service conductors ran to your house and horse barn. This is covered in NEC 547.2 and subsequent sub sections.

Your service equipment is located at each building IE you have more than one panel that is your service equipment..in other words each building has its own service equipment. The barn is fed from the pole underground and the ampacity of these service conductors falls under table 310.16. 1/0 aluminum is good for 120 amps for 75C insulated wires or 100 amps for 60C insulated wires so your good serving a 100 amp service rated panel with main breaker at the barn and that panel is your service equipment. You run all your grounding electrode conductors from the neutral bar in that panel. You do not install ground rods at the barn sub-panel.

So here is what I would do. I'd just get a length of #4 bare copper connect it to the neutral bar of the 100 amp panel and run it to the structural steel. Attach two ground lugs like shown below to the steel. Connect the #4 from the panel to one lug. Then connect another #4 to the second lug and run it to a ground rod either inside the building if the floor is dirt or outside your choice. Use a ground rod clamp to connect it. If you drive two ground rods then add a second clamp to the first rod and run a length of number 4 to the second rod and clamp it. I would use #4 bare copper grounding electrode conductor because it is commonly available at the big boxes keeps things simple and it doesn't require physical protection and it covers all the bases for your situation.

ground rod clamp

water pipe clamp


ground lug



From the 100 amp panel in the barn run a 4 wire feeder using the below diagram as your guide. This is to supplement what inphase277 has already told you but the graphics will make it more clear for you. You may or may not have a metal water pipe at the barn if you do you must run a #4 bare copper to it from the neutral bar of the 100 amp panel. Use an approved pipe clamp. Word of caution every panel comes with a bonding means screw or jumper or metal wire or strap to bond the neutral bar to the metal of the panel....you do not install that bonding means to the neutral bar. The ground bar is the only bar that bonds to the metal of the panel.

Last edited by Stubbie; 12-21-2008 at 12:59 AM.
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Old 12-21-2008, 01:26 AM   #20
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If you can find a grounding lug like this then you can use just one of these on the structural steel and not cut the #4 as you continue on to the ground rod. You can do the same with the other type lug but it is a bit more of a PITA.

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Old 12-21-2008, 07:27 AM   #21
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You didn't mention a house! How does the house come into the circuit? Is the panel at the barn a subpanel from the house panel?
Both the barn service and the house service comes off the pole. One is east of the pole the other is west.
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Old 12-21-2008, 01:11 PM   #22
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Ok, the barn has its own service, and is not a subfeed from the house. This clarifies it for me.

Anyway, the bottom line is this:

Drive a ground rod.
Run a wire to the building steel.
Run a wire to any metal water lines that may enter the structure.

These can all be the same wire if you like, looping from one thing to the next. Stubbie suggests #4, which is readily available, but to keep costs down, you don't need any bigger than a #8 for all of them. Look at Stubbie's last post to see the kinds of clamps and hardware you need for the various items to be grounded.

I personally like the single wire method if it is applicable to your physical setup. Come from the main panel neutral bar, and hit the first point (steel, ground rod, etc), then continue to the next.

And since you have taken care of the second panel, you're all done!

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