AWG code for 100amp subpanel

[hardworker]

What does code say about using #3 awg copper for the hots, #3 awg copper for neutral and # 8 awg copper for ground on a 135 ft run between the main and this 100 amp subpanel?

 

[Cow]

Sounds fine to me.

 

[Volta]

As long as you satisfy 110.10, and the terminations are rated 75 deg C, all voltage drop considerations aside, it sounds ok to me.

 

[ActionDave]

Sounds ok. What are your concerns?

 

[infinity]

What does code say about using #3 awg copper for the hots, #3 awg copper for neutral and # 8 awg copper for ground on a 135 ft run between the main and this 100 amp subpanel?

With 75? C terminations the NEC says that your installation is code compliant. Is someone saying otherwise?

 

[augie47]

I will note that, although it is not a NEC violation, at 50 amps or greater you will be exceeding the recommended voltage drop with a #3.

 

[petersonra]

What does code say about using #3 awg copper for the hots, #3 awg copper for neutral and # 8 awg copper for ground on a 135 ft run between the main and this 100 amp subpanel?

can't say there is anything "wrong" with it code wise.

might have VD issues at high usage times.

presumably you have done a load calculation and this installation is adequate to support that.

is the main 100A as well?

 

[don_resqcapt19]

I will note that, although it is not a NEC violation, at 50 amps or greater you will be exceeding the recommended voltage drop with a #3.

That would be the case assuming a 100% unbalanced load. With a balanced load and or line to line loads the current can go up will out exceeding the voltage drop recommendations.

 

[hardworker]

The main is a 200amp panel. The building owner was worried about voltage drop on the 135 run. The 100amp sub will never pull more than 70amp.

 

[augie47]

You can go here and play with the numbers....

http://www.mikeholt.com/documents/freestuff/other/VoltageDropCalculator.xls