Parallel connection of conductors

[thinker]

Can anybody explain why NEC allows to parallel conductors larger than AWG 1/0 (aside from all exceptions to this rule)? Why this specific size 1/0 is a magic number?

 

[dpc]

Smaller sizes are more likely to have differing contact resistance at the terminations and less likely to share current equally and more likely to fail due to high current.

And there is generally little need to parallel the smaller sizes if the system is properly designed.

#1/0 AWG is not a magic number, but they had to draw the line somewhere.

 

[thinker]

Thank you, dpc. I just thought that other than "more likely/less likely" approach might exist. The line could be drawn at AWG #2 (for example) as well.

 

[dpc]

Yes, I'm sure it was somewhat arbitrary.