2/0 and 2 AWG?

Old 10-11-04, 06:54 PM
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2/0 and 2 AWG?

Hello I'm not an electrician but, have some residential experience. It's mostly been with inside stuff. I am looking at upgrading the service entrance on an old home and saw requirements of 200 amp - 2/0 150 amp - 1 AWG 100 amp - 4 AWG. I'm assuming since there is a 1 and 4 AWG there must also be a 2 AWG? If so what is the difference between 2/0 and 2 AWG? Is it strictly size difference? Also when asking for 2/0 wire at a store does it have a name or would you just tell them I need 2/0?
Additionally do I use the same size wire from the meter to weatherhead as meter to breaker panel? Could 6 AWG be used for a 100 amp service safely? Thanks in advance for any help. I'd like to learn this area a little better.
Old 10-11-04, 08:42 PM
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2/0 is called "two-ott" (phonetically) from the British pronunciation of zero as "aught". Pronounced the same as "you aught to be in pictures". In American Wire gauge, sizes run from the smallest of 40 gauge, which is 3.1 thousandths of an inch, (.0031") diameter, getting larger until they reach 1 gauge which is 289 thousandths (.289") diameter.

To designate larger diameters, there being no number smaller than 1 the next logical number was 0, or "one aught", .325", then 00, generally designated 2/0, two aught, .365", then 000, threee aught, .410, and 0000, 4/0, four aught.

The designation AWG refers to American Wire Gauge, which was formerly referred to as Brown and Sharp.
Old 10-12-04, 09:48 AM
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Your questions pertaining to copper conductors suggests you are using a "raceway" for the Service Wiring Method-- the W-M could be steel or non-metallic conduit, or steel tubing.

The NEC has a "exception" for the ampacity of copper conductors when used as Service-Conductors for residential services. #4 copper for example has a "higher" ampacity rating--- 100 amps--- when so used, then for other applications, and would be the minimum size for a 100 amp service.

Sizes larger than #4 have permissible "higher" ampacity ratings then "normal" IF the use complies with the requirements of the "exception."

Good Luck & Enjoy the Experience!!!!!!!!!!!
Old 10-12-04, 02:12 PM
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Ahh I have actually heard the term 2 aught and thought that might be what 2/0 was but, I wasn't sure. Your post has really cleared things up for me especially given that you posted the sizes. That gives me a picture of what we are talking about so I thank you for such an informative post.
Is there anyway to tell what size in amps the existing service is? Its an older home and pretty small so I'm thinking it's probably like a 60 amp service but, not sure how to tell. Thanks again.

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