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Old 10-26-2008, 12:34 AM   #1
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wire size?


I need to run a underground line(in conduit) from my main box to a building approximately 150 feet away.
I planned on putting a 75 amp breaker in my main box and running the wire from it.
What size copper wire would be required?

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Old 10-26-2008, 08:27 AM   #2
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wire size?


I am curious about something. Why are you choosing a "75 amp" breaker???
There is not even such a thing as a 75 amp breaker.

Answer this and we can answer your wire size question.

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Old 10-26-2008, 11:29 PM   #3
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wire size?


Speedy...
If I knew anything about breakers, I wouldn't be asking about wire size...grin.

I "googled" 75 amp breaker and got dozens of references to 75 amp breaker:

Here's one:

ITE Pushmatic Circuit Breaker 75 AMP double pole
ITE Pushmatic Circuit Breaker 75 AMP double pole See more about 'ITE Pushmatic Circuit Breaker 75 AMP double pole'

Anyway, I will be using about 45-50 amps on the circuit(welder) plus some lights so I thought 75 should be good....

What would you suggest?
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Old 10-26-2008, 11:46 PM   #4
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wire size?


This was from another forum:

I can give you what the National Electric Code Says;


14 ga 15 amp breaker
12 ga 20 amp breaker
10 ga 30 amp breaker
8 ga 40 amp breaker
6 ga 50 or 60 amp breaker
4 ga 75 amp breaker
3 ga 100 amp breaker


So if they really don't make a 75 amp breaker for my use, what do they make between 60 and 100?
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Old 10-27-2008, 12:30 AM   #5
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wire size?


Quote:
Originally Posted by LipCa View Post
This was from another forum:

I can give you what the National Electric Code Says;


14 ga 15 amp breaker
12 ga 20 amp breaker
10 ga 30 amp breaker
8 ga 40 amp breaker
6 ga 50 or 60 amp breaker
4 ga 75 amp breaker
3 ga 100 amp breaker


So if they really don't make a 75 amp breaker for my use, what do they make between 60 and 100?
Usually 70,90 and then 100
(That chart is talking about copper, not aluminum. Thats a different story.)
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Old 10-27-2008, 12:34 AM   #6
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wire size?


http://www.cerrowire.com/default.aspx?id=46
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Old 10-27-2008, 05:56 AM   #7
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wire size?


Ampacity charts are one thing. Breaker sizes are another.

According to the NEC 75a is NOT a standard breaker size. I was just curious as to how you came to the decision to use that particular size. That was my point.

I agree. 70, 80, 90 or 100 amps. This fact dictates that you will need at least #4cu or #2al. The distance pretty much rules out 100a, so I would recommend a 70 or 80 amp feeder breaker.

Are you doing conduit the whole way or direct burial cable?
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Old 10-27-2008, 11:40 AM   #8
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wire size?


If I had known 75 was not a common breaker, I would have selected 70 or 80.
I was just trying to select something above my uses.

It is 1.5" conduit all the way with correct number of sweeps.

Thanks for the info

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