Sub Panel assistance - ~225ft run

[mooseracing]

I think I have read myself into confusion.

I upgraded the house to a 200 amp main panel and ran 2" conduit out to my barn. The main panel has a 100amp 240v breaker I plan to feed the barn panel with.

I am confused on ground sizing. Looking at voltage drop tables I plan to use #1 copper for the hots and neutral. I can't determine what is needed for the ground wiring going back to the main panel.

I think due to changes a few years ago as far as sizing I am getting conflicted information.

Is a #4 thhn green okay or does it have to be the same size as the feeder wires?

I am planning on ground rods as well, its just the size going back to the main I am confused on.

Thanks

 

[AntonLargiader]

Table 250.122 says #8 copper or #6 aluminum for 100A. Some notes I have say that's the reference to use.

 

[pattenp]

When upsizing the ungrounded conductors for voltage drop the equipment ground conductor needs to be up sized by the same percentage of mil area size. NEC 250.122(B)


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[wyliesdiesels]

Using aluminum will save you a good chunk of money...

And EGC needs to be upsized above what 250.122(B) as pattenp stated above.

 

[sberry]

6 copper.

 

[Jlarson]

Should be a #4 cu (if you do the math) but going with a #6 isn't gonna end the world.

 

[pattenp]

Should be a #4 cu (if you do the math) but going with a #6 isn't gonna end the world.

Yep.. #6 it's only under by a very small fraction.

 

[Sevenhills1952]

My 2 cents is I'm betting wire cost is only going to go up in the future. So if you run larger gauge now as moose said you're way ahead. If down the road you need more power the larger buried wire is there to handle it.

 

[mooseracing]

When upsizing the ungrounded conductors for voltage drop the equipment ground conductor needs to be up sized by the same percentage of mil area size. NEC 250.122(B)


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Thats what I needed. Thanks

Using aluminum will save you a good chunk of money...

I'm worried its going to be a rough pull. There will be 2 90 sweeps to pull through before the panels on each end. When looking at up sizing the aluminum, the conduit fill was making me nervous.

I'm wishing I would have just dumped 3" in like I had to run for the supply form the pole to the house.

 

[theoldwizard1]

Just because the "main" in the barn is 100A, does NOT mean the breaker feeding it from the house has to be 100A !

What kind of loads do you have ? Have you really adding them up ? For "Joe average", 60A is plenty.

Using aluminum will save you a good chunk of money...

BIG TIME !

2-2-2-4 Al MHF is about $1.25/foot. Four #6 THWN is over $2.25/foot !

 

[wyliesdiesels]

Just because the "main" in the barn is 100A, does NOT mean the breaker feeding it from the house has to be 100A !

What kind of loads do you have ? Have you really adding them up ? For "Joe average", 60A is plenty.



BIG TIME !

2-2-2-4 Al MHF is about $1.25/foot. Four #6 THWN is over $2.25/foot !

The problem in this case is the length of the run. If he wanted even 90a, #2 is too small to keep the VD 3%...

 

[Sevenhills1952]

That was my point...it may cost a few hundred $ now to run the heavier gauge wire but from a safety standpoint and possibly needing more power in the future it's money well spent. Better over than undersized.

 

[mooseracing]

J

What kind of loads do you have ? Have you really adding them up ? For "Joe average", 60A is plenty.

This isn't your average setup. If I had a choice there would be at least 200 amp service going out there.

 

[tapout187]

I was completely in the same spot you are in now. Although my run was shorter at 165’ I also went with #1 copper, I used xhhw-2. I used #4 for my ground back to house panel. For my ground rods I already had #6 copper xhhw left over from when my friend did my house panel so I just used that.