100 Amp Sub Panel 250'

[wimpy525]

Ok I have been doing a lot of reading here before I posted up so I may have this some what figured out just want someone to check my thinking.
I want to run 100 amp service out to my pole barn I have 200 amp service at the house with room in the panel. I have 2" PVC run under ground with long radius sweeps. Run is about 250 ft
So from what I can tell I need to use 2/0-2/0-2/0-1 AL Mobile Home Feeder Wire.
I from what I can calculate this will give me voltage drop 6.6284 for a 2.7618% voltage drop. I believe I need to stay under 3% so I am good here.
I have a 100 amp panel from a friend who upgraded his service, so I just need to make sure the neutral bar is un-bonded.
I need to drive 2 ground rods connected by #6 bare copper.

So what have a missed or am I way off base.

 

[Slowgsr]

How are you going to connect a 2/0 to your main 200a panel?
I doubt a 2/0 cable is going to fit in a 100a breaker lug.

Otherwise it looks fine. Slightly different then how we do our grounding/bonding up here. Clean installations are important, proper terminating, strapping, expansion joints. Etc.

 

[theoldwizard1]

How are you going to connect a 2/0 to your main 200a panel?
I doubt a 2/0 cable is going to fit in a 100a breaker lug.

I guess you could run smaller copper cable (2 ?) off of the breaker to a nearby junction box and splice your Al cable in there.

 

[pattenp]

100A breaker will take 2/0.

 

[wimpy525]

How are you going to connect a 2/0 to your main 200a panel?
I doubt a 2/0 cable is going to fit in a 100a breaker lug.

Otherwise it looks fine. Slightly different then how we do our grounding/bonding up here. Clean installations are important, proper terminating, strapping, expansion joints. Etc.

This is a good point not sure it will fit I will check today. Like the wizard says I could run #2 to a J-box an splice.

 

[Slowgsr]

Voltage drop is taken too seriously.
Considering measured source voltage will range easily 5-7% depending on the time of day, most devices have a pretty reasonable input range, and the sizes/length of runs the utility companies use. They have their own rules anyways.

I would much rather see you install a 100a isolation switch (non fused) when your 2/0 al comes into the dwelling, then you can run from this to your panel with #3 cu.

2/0 will fit in a 100a isolation switch. You can swap proper size lugs in if you need. Use the proper compound when you terminate AL, and not have to deal with proper methods for splicing Al to cu of different sizes. Unless you make the joint in a splitter. If you go the disconnect route make sure it has an isolated block for the neutral.

Most 100a breakers will not accept a 2/0 at least for single phase applications. Plus depending on your panel, routing 2/0 isnt always fun. What brand/model is your house panel?

 

[pattenp]

I know Square-D 100A Homeline and QO will take 2/0. I was thinking other brands of 100A did too.

 

[theoldwizard1]

Voltage drop is taken too seriously.

IANAE - Kind of my gut feel also. If I was calculating voltage drop for an out building, I would use 7% of the rated breaker feeding the wire, knowing that it is highly unlikely that breaker will ever be tripped.

And as stated, most "modern" equipment is more voltage "tolerant".

 

[theoldwizard1]

I know Square-D 100A Homeline and QO will take 2/0. I was thinking others did too.

From the Square D catalog

 

[2000xpsd]

I have Siemens qp's, had 260', 2" conduit...ran #1 copper into a 100a breaker. Cu wasn't that much more and that was the biggest the breaker could take without lugging it. Had 2 90s and 1 long sweep 90...pulled it by hand ok, got scary once but it went...alum would of ready sucked.

 

[Slowgsr]

I know Square-D 100A Homeline and QO will take 2/0. I was thinking other brands of 100A did too.

Thanks for that, I guess I was wrong!
Looks like the OP will have an easier time.

Just respect the 360 degree rule with regards to pulling that cable

 

[pattenp]

Thanks for that, I guess I was wrong!
Looks like the OP will have an easier time.

Just respect the 360 degree rule with regards to pulling that cable

We're both part right. Looks like Eaton and Siemens 100A is maxed at 1/0.

 

[wyliesdiesels]

Ok I have been doing a lot of reading here before I posted up so I may have this some what figured out just want someone to check my thinking.
I want to run 100 amp service out to my pole barn I have 200 amp service at the house with room in the panel. I have 2" PVC run under ground with long radius sweeps. Run is about 250 ft
So from what I can tell I need to use 2/0-2/0-2/0-1 AL Mobile Home Feeder Wire.
I from what I can calculate this will give me voltage drop 6.6284 for a 2.7618% voltage drop. I believe I need to stay under 3% so I am good here.
I have a 100 amp panel from a friend who upgraded his service, so I just need to make sure the neutral bar is un-bonded.
I need to drive 2 ground rods connected by #6 bare copper.

So what have a missed or am I way off base.

My voltage drop calcs were higher than yours.

21.2 * 2 * 250' * 100a= 1060000 / 133072 cir mils = 7.96v.

Either way u will be fine.

For that subpanel u may need a ground bar kit.

 

[wimpy525]

Well thanks for the replies been busy running wire. A friend that is an electrician stop by and gave me some guidance. He said I was way over thinking this. He had some #1 copper and said that this would be fine for what I am going to be doing in the shop and I could have the wire. (I get him a lot of work in some of the plants I am in) So we pulled the wire and will be making connections this week. I off to go spend sometime riding dirt bikes in the woods.
Thanks for the help.

 

[wyliesdiesels]

Yeah #1 cu will give u about 7.7v drop at max load.