Adding a circuit in existing raceway

[Jradatti]

I have been studying for the CO exam and while looking at conductor ampacities it got me thinking.... when you are adding an additional circuit in an existing raceway that would bump you up another wire size due to derating for # of current carrying conductors are you only required to increse the wire size for the new circuit or are you now responsible for all wires contained in that raceway?

 

[iwire]

Yes, if you add conductors to an existing conduit you must take derating into consideration of both the added and existing conductors.