Dedicated Line, Surge and Safety

Timo - 10/2 is the standard designation for 2 insulated 10ga wires in combination with an uninsulated ground wire. It's a three-wire cable.

Subaruguru - I'm interested in reading your explanation as to how two dedicated lines somehow isolate components from each other. If you put both lines on the same power leg to avoid ground potential problems, you're riding on the same big bus. Any noise or AC distortion is going to ride that bus, and every circuit on it will be affected. Neither the wire nor the circuit breaker have filters in them, and they flow current both ways.

So can you tell me how this constitutes isolation? If there's something I'm missing, please enlighten me.

As Ez2hear said, 12ga is the minimum gauge for a 20A circuit. It's preferred by electricians over 10ga precisely because it's thinner. Thinner is easier to install. If you've ever worked with 10ga NMS, you know it is a major PITA - it makes any job take about twice as long.

12ga works fine for most 20A circuit applications. The only REAL reason to use it (i.e. besides tweaky weird audiophile reasons) is if you have to go a long distance. There's a maximum length spec for 12ga on a 20A circuit, and if you exceed that you need to use 10ga. BTW there's not too many residential situations that would cause you to exceed the max length. An almost sane reason to use 10ga is if you're going from one side of your house all the way to the other and it's a long way, 10ga will cause a little bit less voltage drop than the 12ga. That's one to use on more imaginative electricians.

If you've got one who just stares at you like you've lost your mind when you say you want a 12ft run of 10ga for your 20A circuit, tell him you may need to upgrade it to 30A at some point because your next hobby will be arc-welding! :)