feeder to sub panelshi

[Toros]

Hi,
Do i havt to use 310_15(6) to derate for service entrance cond. And sub panel throughout the single family resident?
I have single family house receiving 400A ,single phase service with sub panels in every floor

 

[augie47]

310.15(B)(6) {'08 Code} has a few stipulations.
In reference to your question, one of the stipulations is that the conductor be a service or "main power feeder" that supplies all loads that are part or associated with the dwelling unit.
In the case of a sub-panel, unless that sub-panel carries ALL loads associated with the dwelling unit, you can not use 310.15(B)(6)

 

[suemarkp]

You never have to use 310.15(B)(6), but you can if you meet the rules (dwelling, wire types, etc). You can't use it for the subpanels, since each panel is not serving an entire dwelling unit. But you can use it on the conductors from the meter to the main panel.