I am having problems calculating RCA. I know how to calculate Ri for the insulation but cannot seem to arrive at the same current value as per NEC table. The example given atampacity of No 2 conductor uses RCA = Ri + Rsd + Re and is 120A but that is for conductor in conduit. I need to calculate RCA for a conductor in air which should be 190A at 90degC conductor and 30degC ambient.
Can you shine some light on the subject.