What is CLT wire and why can it with stand higher amperages and voltages than other wires types of the same size?

Answer 1

I researched CLT wire and found 2 possibilities. One is a heat trace cable and the other is a current limiting FLAT 2 conductor cable for 12 and 24 volt systems. I can only guess since your question involves "higher amperages" than other conductors that you are referring to the heat trace cable.

In either case, however, I believe the answer is the same. Different types of insulation can handle different amounts of current. The ampacity of a conductor is limited mostly by its insulation. This is to say that any BARE conductor in a certain application can carry more amps than it can with insulation. In most any case, the insulation melts and burns at temperatures below when the conductor itself melts. Glass or porcelain may be exceptions, as in fuses, but these insulators are not in contact with the conductors they protect.

The voltage limit of a conductor is the maximum safe voltage an insulation can handle before the voltage breaches it, regardless of how many amps are flowing. The most common conductors in use today are rated for 600 volts. This rating means that applying more than 600 volts on the conductor could result in the voltage breaching (coming through) the insulation and allowing current to flow to any nearby conducting material, such as conduit or a panel enclosure. In other words it may be as if there is no insulation at all. This rating is mostly determined by insulation thickness, though material also plays a role.