Derating wires in conduit ?

[wrestless]

Guys could someone explain this or clarify. Does the size conduit change the derating factor at all and if so where is it the NEC ? Secondly does it have to do with heat ? if so and size of conduit does not matter wouldnt a larger conduit mean more dissapation of heat. I have always derated just not sure anymore if it is truely necessary if you up the conduit size. Any help much appreciated Thanks Rich

 

[augie47]

The size of the conduit has no bearing on 310.15(B)(2).
I have been taught that a wire, surrounded by other wires, for all practical purposes, attains the same temperature regardless of the conduit size.

 

[iwire]

Guys could someone explain this or clarify. Does the size conduit change the derating factor at all

No

Secondly does it have to do with heat ?

Yes

if so and size of conduit does not matter wouldnt a larger conduit mean more dissapation of heat.

The size of the conduit likely does make an actual difference but it does not make a difference to the NEC or our calculations.

I have always derated just not sure anymore if it is truly necessary if you up the conduit size.

We cannot avoid derating by up sizing.

Six 14 AWGs get the same derating in 6" RMC as they would in 1/2"PVC.