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120/240v residential home, owner installed a barn and needs a sub panel installed for some water heaters/lights for the animals. The contractor that installed the barn put the PVC in for me, 1 1/2 PVC 425 feet long. I want to install a 100amp sub panel but dont know if its passable. So far the best I can figure is 1/0 aluminum, and # 6 for the ground. What do you think? Do I need to drive a ground rod?, Will this even pull, its a straight shot with one 90 and thats it. Should I put this on a 60a over current device? Copper wire is out of the question due to the cost. Also the electric fence requires two ground rods so I'm a little Leary about driving a third for the panel. Can you guys give me some ideas? Keep in mind that the 1 1/2 PVC was already installed and I need to work around it. Thanks for any help that you can give me. SO 425ft long, 100a, 1 1/2 PVC, and what to do about the grounding???
 

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Master Of Disaster
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I didn't do the math but my app says 250mcm copper for 3.5 percent vd , length is going to be a basterd with 1.5
 

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So far the best I can figure is 1/0 alumnium, and # 6 for the ground. What do you think?
I think, actully I know, the 6 AWG 'ground' is too small and is a code violtion.

250.122 requires the equipment grounding conductor to be increased in size when the other conductors are.


Do I need to drive a ground rod?,
Likely.

The code requires a grounding electrode system at the building.


Also the electric fence requires two ground rods so Im a little leary about driving a third for the panel.
:blink:

Leary of what?:001_huh:


Can you guys give me some ideas? Keep in mind that the 1 1/2 pvc was allready installed and I need to wotk around it. Thanks for any help that you can give me. SO 425ft long, 100a, 1 1/2 pvc, and what to do about the grounding???
First thing you have to do is decide how much current is really going to be needed.

You need to know this to do a voltage drop calculation. It would be foolish to figure a full 100 amps of load if there is only going to be 40 amps of full load.
 

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Discussion Starter #10 (Edited)
well

2xkxIxd divided by cmill = 2x21.20x100x425 divide by 105600=17.1
2xkxIxd divided by VD = 2x21.20x100x425 divide by 17.1= 105380cmill
and the cmill of 1/0 is 105600
With out derating is this ok so far?
the barn will draw 58 amps max as far as i can guess pending on what we go with for water heaters.
I'm Leary of creating an potential between three rods, thats what, also why cant I just bond the fence transformer to the rod I drive for the panel???
 

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Master Of Disaster
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I think, actully I know, the 6 AWG 'ground' is too small and is a code violtion.

250.122 requires the equipment grounding conductor to be increased in size when the other conductors are.

Likely.

The code requires a grounding electrode system at the building.

:blink:

Leary of what?:001_huh:

First thing you have to do is decide how much current is really going to be needed.

You need to know this to do a voltage drop calculation. It would be foolish to figure a full 100 amps of load if there is only going to be 40 amps of full load.
Load may change in time too may as well do it right the first time
 

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Scotchkote Installer
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For a few dollars more the barn builder could of run 2" PVC instead.. :no::no:

It sucks these guys don't ask the guy who has to fix their mess and get it to work properly...

Running 2" is a no brainer for that length of a run....

The phone company has up running 4" conduit with large sweeps to pull in a 1/2" cable..
 

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Scotchkote Installer
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The pipe is 1 1/2 and thats what I have to work with. I told the dude to install two 2in runs and thats not what was done.
I would run CU.. instead of AL.. now for an :rolleyes::rolleyes: from BBQ and MTW...

But it is the only way I can see this working for what you need...
 

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Master Of Disaster
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I would run CU.. instead of AL.. now for an :rolleyes::rolleyes: from BBQ and MTW...

But it is the only way I can see this working for what you need...
He still hasn't stated a load , he said 100 amp before but I doubt he can make that work with 1.5 PVC
 

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Discussion Starter #17 (Edited)
omg

Let me rephrase the question, I have a 1 1/2 PVC pipe run that is 425 ft long. The voltage is 120/240. What is the largest circuit that can be run in that pipe.​
 

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Load may change in time too may as well do it right the first time
If it costs to much it might not get done at all.


If I was pricing this I might give the customer a couple of price options.

One for the known load at this time and one for a 'full 100 amps'

At this point we don't know if the customer asked for a 100 amp panel or just wants their stuff powered up.
 
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