Wire size for 125 amp service

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  #1  
Old 11-20-11, 07:11 PM
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Wire size for 125 amp service

I want to run from a meter pole 140' underground to a 125 service panel box. What size aluminum wire size do I need. Also if I change my mind about the 125 amp and make it a 200 amp service what wire size would that take?
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Old 11-20-11, 09:28 PM
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I think I'd use 1/0 AL for 125 amp service or 4/0 AL for 200amp service.
 
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Old 11-21-11, 08:47 PM
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If I go ahead and run the 4/0 AL and still go with the 125 amp panel box, does that create any problems as the wire would be oversized for the 125 amps.
 
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Old 11-21-11, 10:15 PM
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The larger wire may not fit the lugs or circuit breaker on the smaller panel. You would have to splice short pieces of smaller wire to the 4/0 using proper procedures and materials and then have the smaller wires connect to the panel lugs or main circuit breaker. It may be necessary to make these splices in a separate enclosure as the smaller panel will not have sufficient room.
 
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Old 11-22-11, 02:11 PM
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There will probably be no problem running the #4/0 aluminum, however if you do there's no reason not to install a 200A / 40 space panel. The difference in panel price is almost nothing compared to the price of the wire and the time and effort to install it.
 
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Old 11-22-11, 06:28 PM
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The reason I was going to use the 125 amp panel is I've got one thats been collecting dust in my shop for 7 years. I even have some breakers for it.
I want to put in a disconnect ahead of the panel box if I use the 125 amp panel. Do I have to use a 125 amp disconnect or can it be less amperage?
Thanks for the advice!
 
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Old 11-22-11, 07:14 PM
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I want to put in a disconnect ahead of the panel box if I use the 125 amp panel. Do I have to use a 125 amp disconnect or can it be less amperage?
Is there a disconnect at the meter pole?
 
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Old 11-23-11, 10:04 AM
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Originally Posted by Slip Joint View Post
Do I have to use a 125 amp disconnect or can it be less amperage?
The disconnect has to be the same or larger amps as the main breaker panel. You could install a 200A disconnect to terminate the #4/0 wire and continue on to the 125A main panel with 1/0. In my opinion though this is a convoluted design just to use up spare parts.
 
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Old 11-23-11, 04:40 PM
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There is no disconnect at the meter, it's not required. If I use a disconnect ahead of the breaker panel I would be able to cut the electricity off at any time I wanted to change to a larger panel. I am going to figure the difference in cost before I get in to buying anything for the 125 amp service panel.
 
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