Question: Does this table in the 2008 NEC permit a 4 AWG Copper to be used for 100 ampere service entrance conductors if the insulation is over 40 years old?
That is always a good question. Does a U/L listing expire when newer products come along? If I found a roll of old 60c asphalt/paper jacket NM in my basement, could I use it in new construction?
The Table mentioned was not in the NEC when some older installations of 4 AWG were installed, and they were probably Type R, my point was that we cannot make new rules fit older installations, and that an unidentified Type wire sized at 4 AWG is not rated for 100 A in accccordance with Table 310-12 in earlier codes.