Table 310.15(B)(6) Conductor Types and Sizes

[size=3]Table 310.15(B)(6) Conductor Types and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders.

[size=3]Conductor Types RHH, RHW, RHW-2, THHN, THHW, THW, THW-2, THWN, THWN-2, XHHW, XHHW-2, SE, USE, USE-2

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?

For both Joe and Greg

If the conductor type matches the table list, I would say yes.

The older cable you mention does not have conductors rated at 90C, so you have to “sneak” it in and just say it is an “old” installation. :wink:

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.