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Old 03-29-2012, 11:17 AM   #1
JWithers2005
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Default What size wire needed to feed 100amp sub-panel

Im having the power company upgrade my service to a 320amp main panel so I will be able to pull 100amps from it to power all the goodies in my new garage. My question is, What size wire will be required to handle the 100amp feed to the garage sub-panel? Copper or aluminum? Im just trying to get an idea what it will cost to run the 75' or so of wire to power the new garage. Hopefully I will be able to use aluminum from the main panel to the sub. I know it's going to be costly if it requires a copper wire so hopefully aluminum is an option..Thanks for any help..

-Joey
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Old 03-29-2012, 11:29 AM   #2
cj7365
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Default Re: What size wire needed to feed 100amp sub-panel

Not sure of the wire size, but my electric guy ran aluminum for my 100 amp panel that was about 125ft away
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Old 03-29-2012, 11:45 AM   #3
JWithers2005
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Default Re: What size wire needed to feed 100amp sub-panel

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Originally Posted by cj7365 View Post
Not sure of the wire size, but my electric guy ran aluminum for my 100 amp panel that was about 125ft away
That's good to know. I can only imagine what it would cost in copper. Do you remember what it cost you for the wire?
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Old 03-29-2012, 12:24 PM   #4
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Default Re: What size wire needed to feed 100amp sub-panel

For 100A you need at a minimum #1 AL or #3 CU. Aluminum is a third or less than the cost of copper. Go with AL. Note: This is based on 75C temp rating, if 60C is used then the next size larger wire is needed.

Last edited by pattenp; 03-29-2012 at 12:26 PM.
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Old 03-29-2012, 01:55 PM   #5
JWithers2005
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Default Re: What size wire needed to feed 100amp sub-panel

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For 100A you need at a minimum #1 AL or #3 CU. Aluminum is a third or less than the cost of copper. Go with AL. Note: This is based on 75C temp rating, if 60C is used then the next size larger wire is needed.
Ok thanks for ur reply..do u know of a website that has what you are talking about? so I can check pricing? a link would be great if it isn't too much trouble. thanks again
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Old 03-29-2012, 02:21 PM   #6
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Default Re: What size wire needed to feed 100amp sub-panel

For those sizes, you'll probably want to call a local electrical supply. You don't usually or always find those in home stores. Especially #3 CU. Now if you scale back to 75A or 90A (ask your local inspector what's allowed), you could use 2-2-2-4 aluminum mobile home feeder, which runs about $1.6x a foot more or less.
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Old 03-29-2012, 02:38 PM   #7
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Default Re: What size wire needed to feed 100amp sub-panel

I never have found trying to price wire on the web a worth while effort. I just go to my local Lowes or Home Depot. For the larger wire such as the mobile home feeder I go to my local electrical supply. The last 2-2-2-4 AL MHF I purchased was around $1.20US per foot.

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Ok thanks for ur reply..do u know of a website that has what you are talking about? so I can check pricing? a link would be great if it isn't too much trouble. thanks again
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Old 03-29-2012, 08:06 PM   #8
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Default Re: What size wire needed to feed 100amp sub-panel

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Originally Posted by JWithers2005 View Post
Im having the power company upgrade my service to a 320amp main panel so I will be able to pull 100amps from it to power all the goodies in my new garage.
Is this a meter base or panel or a combo of both. That'll dictate how many wires to run to the garage....

A "320" is slang for a 400 amp meterbase is why I ask.
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Old 03-29-2012, 09:16 PM   #9
JWithers2005
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Default Re: What size wire needed to feed 100amp sub-panel

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Is this a meter base or panel or a combo of both. That'll dictate how many wires to run to the garage....

A "320" is slang for a 400 amp meterbase is why I ask.
just a meter socket and a service panel from what i understand..im green when it comes to electrical so I can't exactly talk intelligently about the subject..i spoke with the electrician today and he suggests a 200amp panel and a 70 or 90amp breaker to power the panel in the garage. he wants a thousands bucks just to upgrade the panel on the house!! I was blown away by that price but maybe that is the going rate??
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Old 03-30-2012, 09:37 AM   #10
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Default Re: What size wire needed to feed 100amp sub-panel

$1000 sounds good to me. Parts aren't the expense, it's the labor/time.
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