Electrical Questions... Lots of them!

[LD1]

I don't think copper and aluminum have the same current carrying characteristics. Usually have to upsize for aluminum.

Let me start by saying I am NOT an electrician so I may be wrong BUT

I do believe you are correct and grsthegreat is wrong here.

When I built by barn, I used what the local COOP uses for their 100 Amp service, which is 1/0 underground. Which has 1/0 AL wire for the conductors and #2 AL forthe neutral. My choices were either this 1/0, 1/0, #2 Aluminum wire OR 2/2/4 copper wire. obviously the copper was ore expensive.

For 200A installs with aluminum wire they use 4/0 with 2/0 for the Neutral.

#2 aluminum xhhw is only rated @ 90A. I personally would not want to use that for 100A service. #2 copper would be okay though.

Again, I am no electrician, but I can read a chart Ampacity Charts

 

[LarryD]

You can actually get 100A through #2 aluminum if you use the 90ｺC table but then all terminations/equipment must be rated here as well.

If you stick to the 60ｺC table you'll be fine.

 

[grsthegreat]

Let me start by saying I am NOT an electrician so I may be wrong BUT

I do believe you are correct and grsthegreat is wrong here.

When I built by barn, I used what the local COOP uses for their 100 Amp service, which is 1/0 underground. Which has 1/0 AL wire for the conductors and #2 AL forthe neutral. My choices were either this 1/0, 1/0, #2 Aluminum wire OR 2/2/4 copper wire. obviously the copper was ore expensive.

For 200A installs with aluminum wire they use 4/0 with 2/0 for the Neutral.

#2 aluminum xhhw is only rated @ 90A. I personally would not want to use that for 100A service. #2 copper would be okay though.

Again, I am no electrician, but I can read a chart Ampacity Charts

nope...not wrong....do it every day and totally legal. IF ITS UNDERGROUND. remember services require different rated levels than branch circuits. #2 copper is actually rated at 125 amps, and #2 alum is rated 100 amp for service use. as long as its underground.
its very confusing. these are the absolute minimums for the 50 foot run. personally i would use a 2/0 alum if it was my place just cause im always doing stuff overdone. but thats just me. and anyways it may be a mute point cause i still think that you wont be allowed to take anymore than 50 amps off of that existing panel legally. we usually upgrade the main service to 400 amps to run a dedicated shop circuit, then run 4/0 alum feeders to a 200 amp shop panel.