# Wire Size



## sparks134 (Jan 30, 2009)

welcome to the forum:thumbsup:


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## Bob Badger (Apr 19, 2009)

tjvaughan said:


> Hello,
> Just stumbled across this awesome web site. Im an apprentice electrician working on a job where we are replacing a 200amp single phase service with a 300amp three phase service service in an old gas station building. Its an overhead service and out of the meter socket we come into a gutter where we tap on to the feeders to feed one 100amp single phase panel and one 200amp three phase panel. My question is what size feeder wire is required and what size grounding electrode conductor is required? Thanks!



First from your description you have no feeders.

Are you asking about copper or aluminum?

What are the calculated loads?

What size do you think they should be?

What does the licensed guy say? 


Welcome to the forum.


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## MDShunk (Jan 7, 2007)

TJ, the best approach might be for you to tell us what you think it should be, and why. We can help you from there. Surely the JM on the job is going to put the right stuff in, but it wouldn't be very helpful to you in your learning stage if we just gave you the answer, would it?


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## tjvaughan (Mar 10, 2010)

The journeyman is saying 300kcmil copper. He is basing it off of the 90 degree celsius column in table 310.16. I always thought that that coulumn is for deration so i think it should be 350kcmil. Im just confused on which column to use. For the grounding electrode conductor you base it off of the largest service entrance conductors so it sould be 2awg copper right? Thanks alot! This is a very helpful website that im sure ill use throughout my career.


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## MDShunk (Jan 7, 2007)

TJ, is your electrode a driven electrode or something like the water line/building steel?


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## Dennis Alwon (May 9, 2009)

tjvaughan said:


> The journeyman is saying 300kcmil copper.


If we are talking copper than yes the 300 kcm is good for 300 amps as long as the calculated load is not greater than 285 amps (300 KCM at 75C)
Article 240.4 (B) allows us to do this


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## Dennis Alwon (May 9, 2009)

tjvaughan said:


> For the grounding electrode conductor you base it off of the largest service entrance conductors so it should be 2awg copper right? Thanks alot! This is a very helpful website that im sure ill use throughout my career.


That is correct for building steel and water pipes. Article 250.66 Can you tell us what size is required for the ground rods?


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## jwjrw (Jan 14, 2010)

Are you asking about copper or aluminum?

What are the calculated loads?

What size do you think they should be?

What does the licensed guy say? 


Welcome to the forum. [/quote]





Bob Badger said:


> First from your description you have no feeders.
> 
> Ok im not thinking clearly and I dont have alot of experience with taps. Maybe I dont understand what the op said or meant... but what does he have?


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## Dennis Alwon (May 9, 2009)

Bob Badger said:


> First from your description you have no feeders.





jwjrw said:


> Ok im not thinking clearly and I dont have alot of experience with taps. Maybe I dont understand what the op said or meant... but what does he have?


The OP is asking about service conductors not feeders.


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## tjvaughan (Mar 10, 2010)

There is an existing conductor that is already ran to the water main im not sure of the size but i know we will be replacing it with the 2awg copper. We drove a ground rod outside. 250.66(A) says the conductor shall not be required to be larger than 6awg copper? If you wanted to use the 300amp service to its full potential (if the calculated load was 300amps) you would have to pull in 350kcmill wouldnt you? Im full of questions arent i? Just trying to learn as much as i can.

Sorry, they are service conductors. I just looked up the definitions of each...didnt know there was a difference.


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## Dennis Alwon (May 9, 2009)

tjvaughan said:


> There is an existing conductor that is already ran to the water main im not sure of the size but i know we will be replacing it with the 2awg copper. We drove a ground rod outside. 250.66(A) says the conductor shall not be required to be larger than 6awg copper? If you wanted to use the 300amp service to its full potential (if the calculated load was 300amps) you would have to pull in 350kcmill wouldnt you? Im full of questions arent i? Just trying to learn as much as i can.


It's good to hear you thinking and learning. Yes, if you want the full 300 amp load then you would need 350kcm.


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## jwjrw (Jan 14, 2010)

Dennis Alwon said:


> The OP is asking about service conductors not feeders.


So the service is not the gutter in this case (or could it be?)
Maybe Im picturing something else in my mind. 
I assume you are saying by tapping (out of a gutter fed by a meter) to a panel .HMMMM i THINK i know where I went wrong. The op wanted to know about the wire size to feed the gutter. Wow I knew I was missing something:whistling2::laughing:


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## tjvaughan (Mar 10, 2010)

The way it is set up is we come out of the back of the meter socket into the back of the gutter. On one side of the gutter is one 100amp single phase panel and on the other side is one 200amp three phase panel. The service conductors are taped onto in the gutter to feed each panel. Since each panel is basically the service disconnecting means we need a main bonding jumper in each panel right?


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