Sub-Panel Feeder Sizing

[Gshell82]

70A breaker in main panel protects a 125A MLO sub-panel. Size the feeder for 70A or 125?

Thanks

 

[infinity]

The ampacity of the sub-panel is irrelevant as long as it's greater than or equal to the feeder size which is 70 amps due to the OCPD ahead of it.

 

[kwired]

What he said - plus do a load calculation for what you will have for loads.

You should only match your gear and conductors to what you have when it is more then what load calculation says is the minimum.

If you came up with a calculation of 137 amps - neither the 70 amp breaker or the 125 amp panel really do you any good.

 

[publicgood]

As kwired said, follow the code and do a calculation to properly size the feeder. Consider the continuous and non, also demand factors.

 

[publicgood]

As kwired said, follow the code and do a calculation to properly size the feeder. Consider the continuous and non, also demand factors.

If 70A meets the code load calc, 70A and not 125A would be the feeder.