Wire size question

Guys,

Two questions:

Question 1: What size wire to use? Copper or Aluminum?

Installing an "external tap of unlimited length" from a 320amp meter base to the 100amp main disconnect panel in the detached garage other lug will connect to the 200amp panel in the house. Garage is approximately 150' away.

Question 2: What size wire to use? (I'm thinking copper 8/3 with ground)

From the 100amp panel in the garage, we will connect to the barn (approximately 250' away). The barn will be a subpanel and have a 30amp main breaker.

I am concerned about voltage drop over these distances. All will be buried at depth specified by local code and in conduit.

And if you know anyone in or around Abingdon, Virginia qualified to do this, holler back.

Thanks in advance,
Scott

How much load do you want to put on this panel? If I really wanted 100A it would be number 1 alum, limiting the ampacity to 60 or so you could get by with number 2 at 150 ft and the number 2 would be good at 250 ft @ 30A. There is only sifnificant V drop when there is load, you running 1 light bulb it might not make much difference, hook up a 50A stick welder and its different.

Personally, I'd use copper and not aluminum. If you do use aluminum, make sure the lugs at the meter base and at the panel are rated for use with aluminum wire.

To feed a 100 amp panel, for residential use you have to go with #4 copper or #2 aluminum, minimum. Then, you have to look at the voltage drop. There is a handy voltage drop calculator at http://www.electrician.com/vd_calculator.html. Voltage drop should be kept to 3% or less; plugging in 100 amps, 240 volts single phase and 150 feet, you need to upsize to #2 copper or #1/0 aluminum.

The 30 amp subpanel in the barn will need a minimum of #10 in either copper or aluminum, but when you add 250 feet from the garage to the barn it has to be upsized to #4 copper or #3 aluminum.

Now, these are worst case values...for instance, you can probably reasonably assume you'll never draw a full 100 amps in the garage. If, say, the biggest load you'll ever see will be 75 amps, you could go back to #4 copper from the meter base to the garage panel.

i wasnt aware aluminum was still an option, here in canada it was banned in the 70's i believe..was known for causing fires due to bad connections. has to do with the hich expansion rate when heated, which eventually loosens the connection making more heat causing more expansion/retraction....u get the idea!

In the US, it's only used for large-gauge feeder lines. typically, from the meter to the main panel, or from main to sub-panels. I don't think it's banned anywhere else, it's just not used for residental branch circuit wiring anymore.
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Honda GL500I

yup, 95% of the worlds power thru alum wire. I dont use copper on feeders. Alum is so much cheaper and the difference in cost makes it worth upsizing. I would determine on what I wanted to run, you can run a lot from 60A but if I was going to be working regular in this garage with a little welding maybe or a decent air comp in use frequently I would opt to up to number 1 al. I know number 2 is the limit for most 60A breakers, I am sure 1 would fit in a 100.