Feeding from my main to my panel

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Old 12-06-16, 12:22 AM
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Feeding from my main to my panel

I need to feed from my 200 amp main breaker at the meter (which is on an out-building) to the breaker panel at my house. It's a fifty-foot run, and I'm planning to use 4/0 Aluminum rated for 200 amps. Voltage drop should be about .65%, so that's all good.

Question#1: What size ground wire do I need for this application? (I know it can be smaller ... just don't know how much)

and

Question#2: I assume the neutral wire needs to be 4/0 just like the two hots. Is that correct, or can it also be smaller?
 
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Old 12-06-16, 12:48 AM
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4/0 Al for the two hots.
2/0 Al for the neutral.
#4 Al for the ground.

#6 copper to the ground rod.

Will this be in conduit ?
If not.... there are cables sized for the job.
 
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Old 12-06-16, 01:21 AM
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Thanks.

Yes, thinking 2" conduit should fit everything comfortably. Sound OK?
 
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Old 12-06-16, 01:29 AM
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That will work. A 2" conduit can handle four 4/0 wires.
 
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Old 12-06-16, 10:03 AM
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Technically the service stops at the first disconnect, so the 4/0 is good for 200A from meter to the first 200A breaker under NEC 310.15(B)(7). After the first disconnect it's a feeder and 4/0 is limited to 180A under NEC 310.15(B)(16). One of those crazy NEC things.
 
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Old 12-06-16, 10:37 AM
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Those NEC codes references are correct.


But I have a personal question:

How is that, that if for example you use a #4AWG for a 100Amps Service, then you cannot use same #4AWG for feeders but need to use a higher ampacity like a #2AWG for same 100Amps as feeders conductors... thing is if you hypothetically are pulling 100Amps through all the devices in your house, aren't you pulling all that current all the way back from the SERVICE in first instance, not only from the feeders, so if the #4AWG can handle those 100Amps at the Service, of course it can at the feeders too, same wire ampacity, same ampacity capacity, it seems logical and simple... so any clues why NEC states those ''crazy'' things for Services vs. Feeders ampacity limitations of same size conductors???
 
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Old 12-06-16, 10:58 AM
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I really don't have a clue why the NEC is that way on service conductors vs. branch circuits and feeders. It doesn't make sense to me either.
 
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Old 12-06-16, 12:15 PM
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The round up would allow the 4/0 to be used for a feeder also.

The NEC also says the feeders never need to be larger than the service conductors.
 
 

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