What gauge wire would be needed to carry 100 amps 200 ft underground

Question

running wire to outbuilding; 210 volts

Answer 1

At minimum, 4 gauge.  I assume that the length of the run is 200 feet, not that it is to be buried 200 feet deep.  (Code requires that it be 18 inches down.)  

Answer 2

You will want to be running 240volts.  That means you will run 5 wires.  2 hot,(black, red) 2 grounded connector (neutral)(white), and one grounding wire(green)#8.   The voltage drop should be about 0 volts.  Using #1 would give sound service.   This would run in a 2" conduit  so as to not exceed 40% fill. NEC Chapter 9 Table C2.  NEC 310.16.  This is what is called a 200 Amp service.  The phase of each of the 2 wires is the same.

Answer 3

It depends on the insulation type:

You can go as low as 3 gauge copper or 1 gauge aluminum for types FEPW, RH, RHW, RUH, THW, THWN, XHWN, USE, and ZW (but I would use 0 gauge copper or 000 gauge aluminum for that long of a run).

In general, for all wire types listed in the NEC tables, 0 gauge will suffice except for aluminum types RUW, T, TW, and UF -- in which case 0 gauge is rated for exactly 100 Amps and I wouldn't do that.

No more than 3 of these can be placed in the conduit though, and you'll have to get your local ordinance 'code' for the proper conduit size and type.

Home Depot and Lowes usually sell THHN.  I would recommend copper (1 gauge) or aluminum (00 gauge).

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Answer 4

I did 214 feet with 2 number 4 and 1 number 6, really heavy as I run a welder, air compressor and other power tools.

Answer 5

For 100 amps you should use #3AWG THHN (copper) or #2 for aluminum.  

Do not reduce the size of the neutral.  

Include a grounding wire with the pull, #8 copper, or #6 aluminum.

Definately run PVC pipe the whole way, by code you could get by with smaller, but I'd put in  

1 1/2" (inch and a half) minimum for an easy pull.  18" deep is right.

200 feet isn't enough distance to worry about voltage drop, and spending the extra money increasing the wire sizes.   I'd be surprised if it was a drop of more than one volt.