# Thread: Circuit Size

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## Circuit Size

Doe sthi make sense to have a 3P-20A breaker with 4 #6's and a disconnect switch fused at 15amps? That's wrong I think.

2. What's the purpose of the disconnect switch? On the surface it doesn't make much sense but we could be missing some details.

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The #6 is above and beyond what the NEC requires for ampacity reasons, unless there is a serious factor like high ambient temperature, or extreme conductor bundling, or both.

#12 is what the NEC requires for a 20A circuit. The 15A fused disconnect downstream doesn't override this, until you get downstream of it.

That being said, if you run #6 for voltage drop or any reason unrelated to ampacity, you have to proportionally upsize the EGC. In this case, it means it would be the same size as the rest of the conductors.

4. Originally Posted by Carultch
That being said, if you run #6 for voltage drop or any reason unrelated to ampacity, you have to proportionally upsize the EGC. In this case, it means it would be the same size as the rest of the conductors.
Good point the #10 EGC with the #6's is possibly a violation.

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Originally Posted by Carultch
The #6 is above and beyond what the NEC requires for ampacity reasons, unless there is a serious factor like high ambient temperature, or extreme conductor bundling, or both.

#12 is what the NEC requires for a 20A circuit. The 15A fused disconnect downstream doesn't override this, until you get downstream of it.

That being said, if you run #6 for voltage drop or any reason unrelated to ampacity, you have to proportionally upsize the EGC. In this case, it means it would be the same size as the rest of the conductors.
Y would you say a #6 is needed if you upsize for voltage drop do you not use 250.122 table to size the egc

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6. Originally Posted by nickelec
Y would you say a #6 is needed if you upsize for voltage drop do you not use 250.122 table to size the egc

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Table 250.122 is the general rule. 250.122(B) would apply if upsizing for voltage drop, and it would require 6 AWG EGC in OP's situation if conductors are sized like they are because of voltage drop.

Put a 60 amp breaker on it and then 10 AWG EGC is fine though.

Makes sense yet it doesn't, right?

7. I don't believe the OP provides enough information to derive an accurate response to the question.
What is the load served?
Why #6?
What is the distances involved?

Otherwise it's all speculation.

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