conductor sizing

[rsovercool]

I am fairly new to the trade, and while taking some training courses and working in the field I am often asked question to which I am unsure of the answers.

The latest question asked of me is "can I install a 1/0 wire from a 50 amp breaker to a 240 volt outlet that will supply my shed?" Where the code only requires an 8 guage copper conductor at 75 degrees C, can the conductor be oversized without any issues of clearing ground faults or voltage drop coming up?

 

[roger]

I am fairly new to the trade, and while taking some training courses and working in the field I am often asked question to which I am unsure of the answers.

The latest question asked of me is "can I install a 1/0 wire from a 50 amp breaker to a 240 volt outlet that will supply my shed?" Where the code only requires an 8 guage copper conductor at 75 degrees C, can the conductor be oversized without any issues of clearing ground faults or voltage drop coming up?

The answer to your question is yes you can but, you need to be aware of article 250.122(B) for sizing the EGC.

Roger

 

[charlie b]

. . . can the conductor be oversized without any issues of clearing ground faults or voltage drop coming up?

In fact, oversizing the wire makes it easier to clear a fault and gives you a lower voltage drop. So it is better, from those two perspectives.

However, the question is placing the tasks out of order.

. . . "can I install a 1/0 wire from a 50 amp breaker to a 240 volt outlet that will supply my shed?"

My answer is, ?I don?t know, because you didn?t give me enough information.? I agree with Roger, in that it is acceptable to use a 1/0 and a 50 amp breaker together, so long as you pay attention to the requirements for the EGC, and so long as you can actually fit that large a wire onto the breaker lugs. But that is not the whole story. If you were to learn that the total calculated load within the shed was 75 amps, then you would have a code violation on your hands.

The proper sequence for selecting and sizing is as follows:
1. Determine the total load, usually by performing a load calculation.
2. Select a wire that has an ampacity at least as high as the calculated load.
3. Select a breaker that will protect the selected wire at its ampacity value.
The question you were handed seems to have ignored step 1.

Welcome to the forum.

 

[petersonra]

can you actually terminate a 1/0 wire on a 50A outlet?